Merge 4bab898301d3e80bea6ab38f864a5a37fb2f2685 into 85e00b755b12821fb40dba0286c7231c2a6b611a

python/PyQt6/core/auto_additions/qgsprocessingoutputs.py

@@ -1,19 +1,19 @@
 # The following has been generated automatically from src/core/processing/qgsprocessingoutputs.h
 try:
     QgsProcessingOutputMapLayer.typeName = staticmethod(QgsProcessingOutputMapLayer.typeName)
-    QgsProcessingOutputMapLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputMapLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputMapLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputVectorLayer.typeName = staticmethod(QgsProcessingOutputVectorLayer.typeName)
-    QgsProcessingOutputVectorLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputVectorLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputVectorLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputRasterLayer.typeName = staticmethod(QgsProcessingOutputRasterLayer.typeName)
-    QgsProcessingOutputRasterLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputRasterLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputRasterLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -25,13 +25,13 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputMultipleLayers.typeName = staticmethod(QgsProcessingOutputMultipleLayers.typeName)
-    QgsProcessingOutputMultipleLayers.__overridden_methods__ = ['type', 'valueAsString']
+    QgsProcessingOutputMultipleLayers.__overridden_methods__ = ['type', 'modelColor', 'valueAsString']
     QgsProcessingOutputMultipleLayers.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputHtml.typeName = staticmethod(QgsProcessingOutputHtml.typeName)
-    QgsProcessingOutputHtml.__overridden_methods__ = ['type', 'valueAsFormattedString']
+    QgsProcessingOutputHtml.__overridden_methods__ = ['type', 'modelColor', 'valueAsFormattedString']
     QgsProcessingOutputHtml.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -43,31 +43,31 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputNumber.typeName = staticmethod(QgsProcessingOutputNumber.typeName)
-    QgsProcessingOutputNumber.__overridden_methods__ = ['type', 'valueAsString']
+    QgsProcessingOutputNumber.__overridden_methods__ = ['modelColor', 'type', 'valueAsString']
     QgsProcessingOutputNumber.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputString.typeName = staticmethod(QgsProcessingOutputString.typeName)
-    QgsProcessingOutputString.__overridden_methods__ = ['type']
+    QgsProcessingOutputString.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputString.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputBoolean.typeName = staticmethod(QgsProcessingOutputBoolean.typeName)
-    QgsProcessingOutputBoolean.__overridden_methods__ = ['type', 'valueAsString']
+    QgsProcessingOutputBoolean.__overridden_methods__ = ['modelColor', 'type', 'valueAsString']
     QgsProcessingOutputBoolean.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputFolder.typeName = staticmethod(QgsProcessingOutputFolder.typeName)
-    QgsProcessingOutputFolder.__overridden_methods__ = ['type', 'valueAsFormattedString']
+    QgsProcessingOutputFolder.__overridden_methods__ = ['type', 'modelColor', 'valueAsFormattedString']
     QgsProcessingOutputFolder.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputFile.typeName = staticmethod(QgsProcessingOutputFile.typeName)
-    QgsProcessingOutputFile.__overridden_methods__ = ['type', 'valueAsFormattedString']
+    QgsProcessingOutputFile.__overridden_methods__ = ['type', 'modelColor', 'valueAsFormattedString']
     QgsProcessingOutputFile.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -79,12 +79,12 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputVectorTileLayer.typeName = staticmethod(QgsProcessingOutputVectorTileLayer.typeName)
-    QgsProcessingOutputVectorTileLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputVectorTileLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputVectorTileLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
-    QgsProcessingOutputDefinition.__virtual_methods__ = ['valueAsString', 'valueAsFormattedString']
+    QgsProcessingOutputDefinition.__virtual_methods__ = ['modelColor', 'valueAsString', 'valueAsFormattedString']
     QgsProcessingOutputDefinition.__abstract_methods__ = ['type']
     QgsProcessingOutputDefinition.__group__ = ['processing']
 except (NameError, AttributeError):

python/PyQt6/core/auto_additions/qgsprocessingparameters.py

@@ -82,7 +82,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterCrs.typeName = staticmethod(QgsProcessingParameterCrs.typeName)
     QgsProcessingParameterCrs.fromScriptCode = staticmethod(QgsProcessingParameterCrs.fromScriptCode)
-    QgsProcessingParameterCrs.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsString', 'valueAsJsonObject']
+    QgsProcessingParameterCrs.__overridden_methods__ = ['userFriendlyString', 'clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsString', 'valueAsJsonObject']
     QgsProcessingParameterCrs.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -103,7 +103,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterGeometry.typeName = staticmethod(QgsProcessingParameterGeometry.typeName)
     QgsProcessingParameterGeometry.fromScriptCode = staticmethod(QgsProcessingParameterGeometry.fromScriptCode)
-    QgsProcessingParameterGeometry.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterGeometry.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterGeometry.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -137,25 +137,25 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterDistance.typeName = staticmethod(QgsProcessingParameterDistance.typeName)
-    QgsProcessingParameterDistance.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterDistance.__overridden_methods__ = ['userFriendlyString', 'clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
     QgsProcessingParameterDistance.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterArea.typeName = staticmethod(QgsProcessingParameterArea.typeName)
-    QgsProcessingParameterArea.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterArea.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterArea.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterVolume.typeName = staticmethod(QgsProcessingParameterVolume.typeName)
-    QgsProcessingParameterVolume.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterVolume.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterVolume.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterDuration.typeName = staticmethod(QgsProcessingParameterDuration.typeName)
-    QgsProcessingParameterDuration.__overridden_methods__ = ['clone', 'type', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterDuration.__overridden_methods__ = ['clone', 'type', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterDuration.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -183,7 +183,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterEnum.typeName = staticmethod(QgsProcessingParameterEnum.typeName)
     QgsProcessingParameterEnum.fromScriptCode = staticmethod(QgsProcessingParameterEnum.fromScriptCode)
-    QgsProcessingParameterEnum.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterEnum.__overridden_methods__ = ['userFriendlyString', 'clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap']
     QgsProcessingParameterEnum.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -326,7 +326,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterDateTime.typeName = staticmethod(QgsProcessingParameterDateTime.typeName)
     QgsProcessingParameterDateTime.fromScriptCode = staticmethod(QgsProcessingParameterDateTime.fromScriptCode)
-    QgsProcessingParameterDateTime.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'toolTip', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterDateTime.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'toolTip', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterDateTime.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -389,7 +389,7 @@ try:
 except (NameError, AttributeError):
     pass
 try:
-    QgsProcessingParameterDefinition.__virtual_methods__ = ['isDestination', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsJsonObject', 'valueAsString', 'valueAsStringList', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'dependsOnOtherParameters', 'toolTip']
+    QgsProcessingParameterDefinition.__virtual_methods__ = ['modelColor', 'userFriendlyString', 'isDestination', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsJsonObject', 'valueAsString', 'valueAsStringList', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'dependsOnOtherParameters', 'toolTip']
     QgsProcessingParameterDefinition.__abstract_methods__ = ['clone', 'type']
     QgsProcessingParameterDefinition.__group__ = ['processing']
 except (NameError, AttributeError):

python/PyQt6/core/auto_additions/qgsprocessingparametertype.py

@@ -1,6 +1,7 @@
 # The following has been generated automatically from src/core/processing/qgsprocessingparametertype.h
 try:
-    QgsProcessingParameterType.__virtual_methods__ = ['pythonImportString', 'className', 'flags', 'metadata', 'acceptedPythonTypes', 'acceptedStringValues', 'acceptedDataTypes']
+    QgsProcessingParameterType.defaultModelColor = staticmethod(QgsProcessingParameterType.defaultModelColor)
+    QgsProcessingParameterType.__virtual_methods__ = ['pythonImportString', 'className', 'flags', 'metadata', 'acceptedPythonTypes', 'acceptedStringValues', 'acceptedDataTypes', 'modelColor']
     QgsProcessingParameterType.__abstract_methods__ = ['create', 'description', 'name', 'id', 'acceptedParameterTypes', 'acceptedOutputTypes']
     QgsProcessingParameterType.__group__ = ['processing']
 except (NameError, AttributeError):

python/PyQt6/core/auto_generated/processing/qgsprocessingoutputs.sip.in

@@ -65,6 +65,13 @@ Constructor for QgsProcessingOutputDefinition.
 
     virtual ~QgsProcessingOutputDefinition();
 
+    virtual QColor modelColor() const;
+%Docstring
+Returns the color to use for the output in model designer windows.
+
+.. versionadded:: 4.0
+%End
+
     virtual QString type() const = 0;
 %Docstring
 Unique output type name.
@@ -189,6 +196,9 @@ raster), use :py:class:`QgsProcessingOutputVectorLayer` or
 Constructor for QgsProcessingOutputMapLayer.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -215,6 +225,9 @@ A vector layer output for processing algorithms.
 Constructor for QgsProcessingOutputVectorLayer.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -257,6 +270,9 @@ Constructor for QgsProcessingOutputRasterLayer.
 %Docstring
 Returns the type name for the output class.
 %End
+
+    virtual QColor modelColor() const;
+
     virtual QString type() const;
 };
 
@@ -316,8 +332,10 @@ Returns the type name for the output class.
 %End
     virtual QString type() const;
 
-    virtual QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
+    virtual QColor modelColor() const;
+
+    virtual QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
 
@@ -342,6 +360,9 @@ Constructor for QgsProcessingOutputHtml.
 Returns the type name for the output class.
 %End
     virtual QString type() const;
+
+    virtual QColor modelColor() const;
+
     virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
@@ -370,6 +391,7 @@ Constructor for QgsProcessingOutputVariant.
 %Docstring
 Returns the type name for the output class.
 %End
+
     virtual QString type() const;
 
     virtual QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
@@ -393,6 +415,9 @@ A numeric output for processing algorithms.
 Constructor for QgsProcessingOutputNumber.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -423,6 +448,9 @@ Constructor for QgsProcessingOutputString.
 %Docstring
 Returns the type name for the output class.
 %End
+
+    virtual QColor modelColor() const;
+
     virtual QString type() const;
 };
 
@@ -444,6 +472,9 @@ A boolean output for processing algorithms.
 Constructor for :py:class:`QgsProcessingOutputNumber`.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -475,8 +506,10 @@ Constructor for QgsProcessingOutputFolder.
 Returns the type name for the output class.
 %End
     virtual QString type() const;
-    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
+    virtual QColor modelColor() const;
+
+    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
 
@@ -501,8 +534,10 @@ Constructor for QgsProcessingOutputFile.
 Returns the type name for the output class.
 %End
     virtual QString type() const;
-    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
+    virtual QColor modelColor() const;
+
+    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
 
@@ -554,6 +589,9 @@ Constructor for QgsProcessingOutputVectorTileLayer.
 %Docstring
 Returns the type name for the output class.
 %End
+
+    virtual QColor modelColor() const;
+
     virtual QString type() const;
 };
 

python/PyQt6/core/auto_generated/processing/qgsprocessingparameters.sip.in

@@ -438,6 +438,27 @@ Constructor for QgsProcessingParameterDefinition.
 
     virtual ~QgsProcessingParameterDefinition();
 
+    virtual QColor modelColor() const;
+%Docstring
+Returns the color to use for the parameter in model designer windows.
+
+The default implementation retrieves the color from the parameter type,
+see :py:func:`QgsProcessingParameterType.modelColor()`.
+
+.. versionadded:: 4.0
+%End
+
+    virtual QString userFriendlyString( const QVariant &value ) const;
+%Docstring
+Returns a user-friendly string representation of the provided parameter
+``value``.
+
+The returned string is to be used for display purposes only, and should
+be translated as required.
+
+.. versionadded:: 4.0
+%End
+
     virtual QgsProcessingParameterDefinition *clone() const = 0 /Factory/;
 %Docstring
 Creates a clone of the parameter definition.
@@ -1994,6 +2015,9 @@ A coordinate reference system parameter for processing algorithms.
 Constructor for QgsProcessingParameterCrs.
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the parameter class.
@@ -2167,6 +2191,7 @@ Sets the allow multipart geometries
 .. seealso:: :py:func:`allowMultipart`
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
 
 
     static QgsProcessingParameterGeometry *fromScriptCode( const QString &name, const QString &description, bool isOptional, const QString &definition ) /Factory/;
@@ -2316,6 +2341,7 @@ Constructor for QgsProcessingParameterMatrix.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -2512,6 +2538,7 @@ Constructor for QgsProcessingParameterNumber.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -2620,6 +2647,9 @@ Constructor for QgsProcessingParameterDistance.
 Returns the type name for the parameter class.
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
+
     virtual QgsProcessingParameterDistance *clone() const /Factory/;
 
 
@@ -2758,6 +2788,8 @@ Sets the default area ``unit`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
 };
 
@@ -2848,6 +2880,8 @@ Sets the default volume ``unit`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
 };
 
@@ -2907,6 +2941,8 @@ Sets the default duration ``unit`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
 };
 
@@ -2977,6 +3013,7 @@ Constructor for QgsProcessingParameterRange.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -3106,6 +3143,9 @@ values.
 Constructor for QgsProcessingParameterEnum.
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the parameter class.
@@ -4523,6 +4563,7 @@ varying color opacity.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -4861,6 +4902,8 @@ Sets the acceptable data ``type`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
     static QgsProcessingParameterDateTime *fromScriptCode( const QString &name, const QString &description, bool isOptional, const QString &definition ) /Factory/;
 %Docstring

python/PyQt6/core/auto_generated/processing/qgsprocessingparametertype.sip.in

@@ -23,6 +23,13 @@ Makes metadata of processing parameters available.
 %End
   public:
 
+    static QColor defaultModelColor();
+%Docstring
+Returns the default color for a processing parameter.
+
+.. versionadded:: 4.0
+%End
+
     virtual QgsProcessingParameterDefinition *create( const QString &name ) const = 0 /Factory/;
 %Docstring
 Creates a new parameter of this type.
@@ -175,6 +182,16 @@ for the parameter.
 .. seealso:: :py:func:`acceptedOutputTypes`
 
 .. versionadded:: 3.44
+%End
+
+    virtual QColor modelColor() const;
+%Docstring
+Returns the color to use for the parameter in model designer windows.
+
+The default implementation returns
+:py:func:`~QgsProcessingParameterType.defaultModelColor`.
+
+.. versionadded:: 4.0
 %End
 
 };

python/PyQt6/gui/auto_additions/qgsmodelcomponentgraphicitem.py

@@ -16,7 +16,7 @@ QgsModelComponentGraphicItem.Flag.__and__ = lambda flag1, flag2: _force_int(flag
 QgsModelComponentGraphicItem.Flag.__or__ = lambda flag1, flag2: QgsModelComponentGraphicItem.Flag(_force_int(flag1) | _force_int(flag2))
 try:
     QgsModelComponentGraphicItem.__attribute_docs__ = {'requestModelRepaint': 'Emitted by the item to request a repaint of the parent model scene.\n', 'aboutToChange': 'Emitted when the definition of the associated component is about to be\nchanged by the item.\n\nThe ``text`` argument gives the translated text describing the change\nabout to occur, and the optional ``id`` can be used to group the\nassociated undo commands.\n', 'changed': 'Emitted when the definition of the associated component is changed by\nthe item.\n', 'repaintArrows': 'Emitted when item requests that all connected arrows are repainted.\n', 'updateArrowPaths': 'Emitted when item requires that all connected arrow paths are\nrecalculated.\n', 'sizePositionChanged': "Emitted when the item's size or position changes.\n"}
-    QgsModelComponentGraphicItem.__virtual_methods__ = ['flags', 'linkPointCount', 'linkPointText', 'editComment', 'canDeleteComponent', 'deleteComponent', 'editComponent', 'strokeStyle', 'titleAlignment', 'iconPicture', 'iconPixmap']
+    QgsModelComponentGraphicItem.__virtual_methods__ = ['flags', 'linkedParameterDataType', 'linkPointCount', 'linkPointText', 'editComment', 'canDeleteComponent', 'deleteComponent', 'editComponent', 'strokeStyle', 'titleAlignment', 'iconPicture', 'iconPixmap']
     QgsModelComponentGraphicItem.__abstract_methods__ = ['fillColor', 'strokeColor', 'textColor', 'updateStoredComponentPosition']
     QgsModelComponentGraphicItem.__overridden_methods__ = ['mouseDoubleClickEvent', 'hoverEnterEvent', 'hoverMoveEvent', 'hoverLeaveEvent', 'itemChange', 'boundingRect', 'contains', 'paint']
     QgsModelComponentGraphicItem.__signal_arguments__ = {'aboutToChange': ['text: str', 'id: int = 0']}
@@ -30,7 +30,7 @@ try:
 except (NameError, AttributeError):
     pass
 try:
-    QgsModelParameterGraphicItem.__overridden_methods__ = ['contextMenuEvent', 'canDeleteComponent', 'fillColor', 'strokeColor', 'textColor', 'iconPicture', 'linkPointCount', 'linkPointText', 'updateStoredComponentPosition', 'deleteComponent']
+    QgsModelParameterGraphicItem.__overridden_methods__ = ['contextMenuEvent', 'canDeleteComponent', 'linkedParameterDataType', 'linkColor', 'fillColor', 'strokeColor', 'textColor', 'iconPicture', 'linkPointCount', 'linkPointText', 'updateStoredComponentPosition', 'deleteComponent']
     QgsModelParameterGraphicItem.__group__ = ['processing', 'models']
 except (NameError, AttributeError):
     pass

python/PyQt6/gui/auto_generated/processing/models/qgsmodelcomponentgraphicitem.sip.in

@@ -112,6 +112,8 @@ Shows a preview of moving the item from its stored position by ``dx``,
 Sets a new scene ``rect`` for the item.
 %End
 
+    virtual QString linkedParameterDataType( Qt::Edge edge, int index ) const;
+
     virtual void mouseDoubleClickEvent( QGraphicsSceneMouseEvent *event );
 
     virtual void hoverEnterEvent( QGraphicsSceneHoverEvent *event );
@@ -324,6 +326,13 @@ comment
 Updates the item's button positions, based on the current item rect.
 %End
 
+    QColor fallbackColor() const;
+%Docstring
+Returns the fallback color if the parameter or output does not have a
+specific color.
+
+.. versionadded:: 4.0
+%End
 };
 QFlags<QgsModelComponentGraphicItem::Flag> operator|(QgsModelComponentGraphicItem::Flag f1, QFlags<QgsModelComponentGraphicItem::Flag> f2);
 
@@ -362,6 +371,12 @@ Ownership of ``parameter`` is transferred to the item.
     virtual bool canDeleteComponent();
 
 
+    virtual QString linkedParameterDataType( Qt::Edge /* unused in this implementation because parameters only have a bottom edge */, int index ) const;
+
+
+    virtual QColor linkColor( Qt::Edge edge, int index ) const;
+
+
   protected:
     virtual QColor fillColor( State state ) const;
 

python/PyQt6/gui/auto_generated/processing/models/qgsmodelgraphicitem.sip.in

@@ -182,6 +182,23 @@ Return the component associated to the socket.
 %Docstring
 Return the parent graphic item associated to the socket.
 %End
+    QColor socketColor() const;
+%Docstring
+Returns the color of the socket based on the type of data the param
+corresponds to.
+
+.. versionadded:: 4.0
+%End
+
+    bool isDefaultParameterValue() const;
+%Docstring
+Returns ``True`` if the parameter is set to the default parameter value.
+
+.. versionadded:: 4.0
+%End
+  signals:
+
+
 };
 
 

python/core/auto_additions/qgsprocessingoutputs.py

@@ -1,19 +1,19 @@
 # The following has been generated automatically from src/core/processing/qgsprocessingoutputs.h
 try:
     QgsProcessingOutputMapLayer.typeName = staticmethod(QgsProcessingOutputMapLayer.typeName)
-    QgsProcessingOutputMapLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputMapLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputMapLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputVectorLayer.typeName = staticmethod(QgsProcessingOutputVectorLayer.typeName)
-    QgsProcessingOutputVectorLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputVectorLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputVectorLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputRasterLayer.typeName = staticmethod(QgsProcessingOutputRasterLayer.typeName)
-    QgsProcessingOutputRasterLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputRasterLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputRasterLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -25,13 +25,13 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputMultipleLayers.typeName = staticmethod(QgsProcessingOutputMultipleLayers.typeName)
-    QgsProcessingOutputMultipleLayers.__overridden_methods__ = ['type', 'valueAsString']
+    QgsProcessingOutputMultipleLayers.__overridden_methods__ = ['type', 'modelColor', 'valueAsString']
     QgsProcessingOutputMultipleLayers.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputHtml.typeName = staticmethod(QgsProcessingOutputHtml.typeName)
-    QgsProcessingOutputHtml.__overridden_methods__ = ['type', 'valueAsFormattedString']
+    QgsProcessingOutputHtml.__overridden_methods__ = ['type', 'modelColor', 'valueAsFormattedString']
     QgsProcessingOutputHtml.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -43,31 +43,31 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputNumber.typeName = staticmethod(QgsProcessingOutputNumber.typeName)
-    QgsProcessingOutputNumber.__overridden_methods__ = ['type', 'valueAsString']
+    QgsProcessingOutputNumber.__overridden_methods__ = ['modelColor', 'type', 'valueAsString']
     QgsProcessingOutputNumber.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputString.typeName = staticmethod(QgsProcessingOutputString.typeName)
-    QgsProcessingOutputString.__overridden_methods__ = ['type']
+    QgsProcessingOutputString.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputString.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputBoolean.typeName = staticmethod(QgsProcessingOutputBoolean.typeName)
-    QgsProcessingOutputBoolean.__overridden_methods__ = ['type', 'valueAsString']
+    QgsProcessingOutputBoolean.__overridden_methods__ = ['modelColor', 'type', 'valueAsString']
     QgsProcessingOutputBoolean.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputFolder.typeName = staticmethod(QgsProcessingOutputFolder.typeName)
-    QgsProcessingOutputFolder.__overridden_methods__ = ['type', 'valueAsFormattedString']
+    QgsProcessingOutputFolder.__overridden_methods__ = ['type', 'modelColor', 'valueAsFormattedString']
     QgsProcessingOutputFolder.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputFile.typeName = staticmethod(QgsProcessingOutputFile.typeName)
-    QgsProcessingOutputFile.__overridden_methods__ = ['type', 'valueAsFormattedString']
+    QgsProcessingOutputFile.__overridden_methods__ = ['type', 'modelColor', 'valueAsFormattedString']
     QgsProcessingOutputFile.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -79,12 +79,12 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingOutputVectorTileLayer.typeName = staticmethod(QgsProcessingOutputVectorTileLayer.typeName)
-    QgsProcessingOutputVectorTileLayer.__overridden_methods__ = ['type']
+    QgsProcessingOutputVectorTileLayer.__overridden_methods__ = ['modelColor', 'type']
     QgsProcessingOutputVectorTileLayer.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
-    QgsProcessingOutputDefinition.__virtual_methods__ = ['valueAsString', 'valueAsFormattedString']
+    QgsProcessingOutputDefinition.__virtual_methods__ = ['modelColor', 'valueAsString', 'valueAsFormattedString']
     QgsProcessingOutputDefinition.__abstract_methods__ = ['type']
     QgsProcessingOutputDefinition.__group__ = ['processing']
 except (NameError, AttributeError):

python/core/auto_additions/qgsprocessingparameters.py

@@ -82,7 +82,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterCrs.typeName = staticmethod(QgsProcessingParameterCrs.typeName)
     QgsProcessingParameterCrs.fromScriptCode = staticmethod(QgsProcessingParameterCrs.fromScriptCode)
-    QgsProcessingParameterCrs.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsString', 'valueAsJsonObject']
+    QgsProcessingParameterCrs.__overridden_methods__ = ['userFriendlyString', 'clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsString', 'valueAsJsonObject']
     QgsProcessingParameterCrs.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -103,7 +103,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterGeometry.typeName = staticmethod(QgsProcessingParameterGeometry.typeName)
     QgsProcessingParameterGeometry.fromScriptCode = staticmethod(QgsProcessingParameterGeometry.fromScriptCode)
-    QgsProcessingParameterGeometry.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterGeometry.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterGeometry.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -137,25 +137,25 @@ except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterDistance.typeName = staticmethod(QgsProcessingParameterDistance.typeName)
-    QgsProcessingParameterDistance.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterDistance.__overridden_methods__ = ['userFriendlyString', 'clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
     QgsProcessingParameterDistance.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterArea.typeName = staticmethod(QgsProcessingParameterArea.typeName)
-    QgsProcessingParameterArea.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterArea.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterArea.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterVolume.typeName = staticmethod(QgsProcessingParameterVolume.typeName)
-    QgsProcessingParameterVolume.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterVolume.__overridden_methods__ = ['clone', 'type', 'dependsOnOtherParameters', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterVolume.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
 try:
     QgsProcessingParameterDuration.typeName = staticmethod(QgsProcessingParameterDuration.typeName)
-    QgsProcessingParameterDuration.__overridden_methods__ = ['clone', 'type', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterDuration.__overridden_methods__ = ['clone', 'type', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterDuration.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -183,7 +183,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterEnum.typeName = staticmethod(QgsProcessingParameterEnum.typeName)
     QgsProcessingParameterEnum.fromScriptCode = staticmethod(QgsProcessingParameterEnum.fromScriptCode)
-    QgsProcessingParameterEnum.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterEnum.__overridden_methods__ = ['userFriendlyString', 'clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap']
     QgsProcessingParameterEnum.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -326,7 +326,7 @@ except (NameError, AttributeError):
 try:
     QgsProcessingParameterDateTime.typeName = staticmethod(QgsProcessingParameterDateTime.typeName)
     QgsProcessingParameterDateTime.fromScriptCode = staticmethod(QgsProcessingParameterDateTime.fromScriptCode)
-    QgsProcessingParameterDateTime.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'toolTip', 'asPythonString', 'toVariantMap', 'fromVariantMap']
+    QgsProcessingParameterDateTime.__overridden_methods__ = ['clone', 'type', 'checkValueIsAcceptable', 'valueAsPythonString', 'toolTip', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'userFriendlyString']
     QgsProcessingParameterDateTime.__group__ = ['processing']
 except (NameError, AttributeError):
     pass
@@ -389,7 +389,7 @@ try:
 except (NameError, AttributeError):
     pass
 try:
-    QgsProcessingParameterDefinition.__virtual_methods__ = ['isDestination', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsJsonObject', 'valueAsString', 'valueAsStringList', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'dependsOnOtherParameters', 'toolTip']
+    QgsProcessingParameterDefinition.__virtual_methods__ = ['modelColor', 'userFriendlyString', 'isDestination', 'checkValueIsAcceptable', 'valueAsPythonString', 'valueAsJsonObject', 'valueAsString', 'valueAsStringList', 'valueAsPythonComment', 'asScriptCode', 'asPythonString', 'toVariantMap', 'fromVariantMap', 'dependsOnOtherParameters', 'toolTip']
     QgsProcessingParameterDefinition.__abstract_methods__ = ['clone', 'type']
     QgsProcessingParameterDefinition.__group__ = ['processing']
 except (NameError, AttributeError):

python/core/auto_additions/qgsprocessingparametertype.py

@@ -1,6 +1,7 @@
 # The following has been generated automatically from src/core/processing/qgsprocessingparametertype.h
 try:
-    QgsProcessingParameterType.__virtual_methods__ = ['pythonImportString', 'className', 'flags', 'metadata', 'acceptedPythonTypes', 'acceptedStringValues', 'acceptedDataTypes']
+    QgsProcessingParameterType.defaultModelColor = staticmethod(QgsProcessingParameterType.defaultModelColor)
+    QgsProcessingParameterType.__virtual_methods__ = ['pythonImportString', 'className', 'flags', 'metadata', 'acceptedPythonTypes', 'acceptedStringValues', 'acceptedDataTypes', 'modelColor']
     QgsProcessingParameterType.__abstract_methods__ = ['create', 'description', 'name', 'id', 'acceptedParameterTypes', 'acceptedOutputTypes']
     QgsProcessingParameterType.__group__ = ['processing']
 except (NameError, AttributeError):

python/core/auto_generated/processing/qgsprocessingoutputs.sip.in

@@ -65,6 +65,13 @@ Constructor for QgsProcessingOutputDefinition.
 
     virtual ~QgsProcessingOutputDefinition();
 
+    virtual QColor modelColor() const;
+%Docstring
+Returns the color to use for the output in model designer windows.
+
+.. versionadded:: 4.0
+%End
+
     virtual QString type() const = 0;
 %Docstring
 Unique output type name.
@@ -189,6 +196,9 @@ raster), use :py:class:`QgsProcessingOutputVectorLayer` or
 Constructor for QgsProcessingOutputMapLayer.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -215,6 +225,9 @@ A vector layer output for processing algorithms.
 Constructor for QgsProcessingOutputVectorLayer.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -257,6 +270,9 @@ Constructor for QgsProcessingOutputRasterLayer.
 %Docstring
 Returns the type name for the output class.
 %End
+
+    virtual QColor modelColor() const;
+
     virtual QString type() const;
 };
 
@@ -316,8 +332,10 @@ Returns the type name for the output class.
 %End
     virtual QString type() const;
 
-    virtual QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
+    virtual QColor modelColor() const;
+
+    virtual QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
 
@@ -342,6 +360,9 @@ Constructor for QgsProcessingOutputHtml.
 Returns the type name for the output class.
 %End
     virtual QString type() const;
+
+    virtual QColor modelColor() const;
+
     virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
@@ -370,6 +391,7 @@ Constructor for QgsProcessingOutputVariant.
 %Docstring
 Returns the type name for the output class.
 %End
+
     virtual QString type() const;
 
     virtual QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
@@ -393,6 +415,9 @@ A numeric output for processing algorithms.
 Constructor for QgsProcessingOutputNumber.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -423,6 +448,9 @@ Constructor for QgsProcessingOutputString.
 %Docstring
 Returns the type name for the output class.
 %End
+
+    virtual QColor modelColor() const;
+
     virtual QString type() const;
 };
 
@@ -444,6 +472,9 @@ A boolean output for processing algorithms.
 Constructor for :py:class:`QgsProcessingOutputNumber`.
 %End
 
+    virtual QColor modelColor() const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the output class.
@@ -475,8 +506,10 @@ Constructor for QgsProcessingOutputFolder.
 Returns the type name for the output class.
 %End
     virtual QString type() const;
-    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
+    virtual QColor modelColor() const;
+
+    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
 
@@ -501,8 +534,10 @@ Constructor for QgsProcessingOutputFile.
 Returns the type name for the output class.
 %End
     virtual QString type() const;
-    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
+    virtual QColor modelColor() const;
+
+    virtual QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok /Out/ ) const;
 
 };
 
@@ -554,6 +589,9 @@ Constructor for QgsProcessingOutputVectorTileLayer.
 %Docstring
 Returns the type name for the output class.
 %End
+
+    virtual QColor modelColor() const;
+
     virtual QString type() const;
 };
 

python/core/auto_generated/processing/qgsprocessingparameters.sip.in

@@ -438,6 +438,27 @@ Constructor for QgsProcessingParameterDefinition.
 
     virtual ~QgsProcessingParameterDefinition();
 
+    virtual QColor modelColor() const;
+%Docstring
+Returns the color to use for the parameter in model designer windows.
+
+The default implementation retrieves the color from the parameter type,
+see :py:func:`QgsProcessingParameterType.modelColor()`.
+
+.. versionadded:: 4.0
+%End
+
+    virtual QString userFriendlyString( const QVariant &value ) const;
+%Docstring
+Returns a user-friendly string representation of the provided parameter
+``value``.
+
+The returned string is to be used for display purposes only, and should
+be translated as required.
+
+.. versionadded:: 4.0
+%End
+
     virtual QgsProcessingParameterDefinition *clone() const = 0 /Factory/;
 %Docstring
 Creates a clone of the parameter definition.
@@ -1994,6 +2015,9 @@ A coordinate reference system parameter for processing algorithms.
 Constructor for QgsProcessingParameterCrs.
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the parameter class.
@@ -2167,6 +2191,7 @@ Sets the allow multipart geometries
 .. seealso:: :py:func:`allowMultipart`
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
 
 
     static QgsProcessingParameterGeometry *fromScriptCode( const QString &name, const QString &description, bool isOptional, const QString &definition ) /Factory/;
@@ -2316,6 +2341,7 @@ Constructor for QgsProcessingParameterMatrix.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -2512,6 +2538,7 @@ Constructor for QgsProcessingParameterNumber.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -2620,6 +2647,9 @@ Constructor for QgsProcessingParameterDistance.
 Returns the type name for the parameter class.
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
+
     virtual QgsProcessingParameterDistance *clone() const /Factory/;
 
 
@@ -2758,6 +2788,8 @@ Sets the default area ``unit`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
 };
 
@@ -2848,6 +2880,8 @@ Sets the default volume ``unit`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
 };
 
@@ -2907,6 +2941,8 @@ Sets the default duration ``unit`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
 };
 
@@ -2977,6 +3013,7 @@ Constructor for QgsProcessingParameterRange.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -3106,6 +3143,9 @@ values.
 Constructor for QgsProcessingParameterEnum.
 %End
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
+
     static QString typeName();
 %Docstring
 Returns the type name for the parameter class.
@@ -4523,6 +4563,7 @@ varying color opacity.
 %Docstring
 Returns the type name for the parameter class.
 %End
+
     virtual QgsProcessingParameterDefinition *clone() const /Factory/;
 
     virtual QString type() const;
@@ -4861,6 +4902,8 @@ Sets the acceptable data ``type`` for the parameter.
 
     virtual bool fromVariantMap( const QVariantMap &map );
 
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
 
     static QgsProcessingParameterDateTime *fromScriptCode( const QString &name, const QString &description, bool isOptional, const QString &definition ) /Factory/;
 %Docstring

python/core/auto_generated/processing/qgsprocessingparametertype.sip.in

@@ -23,6 +23,13 @@ Makes metadata of processing parameters available.
 %End
   public:
 
+    static QColor defaultModelColor();
+%Docstring
+Returns the default color for a processing parameter.
+
+.. versionadded:: 4.0
+%End
+
     virtual QgsProcessingParameterDefinition *create( const QString &name ) const = 0 /Factory/;
 %Docstring
 Creates a new parameter of this type.
@@ -175,6 +182,16 @@ for the parameter.
 .. seealso:: :py:func:`acceptedOutputTypes`
 
 .. versionadded:: 3.44
+%End
+
+    virtual QColor modelColor() const;
+%Docstring
+Returns the color to use for the parameter in model designer windows.
+
+The default implementation returns
+:py:func:`~QgsProcessingParameterType.defaultModelColor`.
+
+.. versionadded:: 4.0
 %End
 
 };

python/gui/auto_additions/qgsmodelcomponentgraphicitem.py

@@ -1,7 +1,7 @@
 # The following has been generated automatically from src/gui/processing/models/qgsmodelcomponentgraphicitem.h
 try:
     QgsModelComponentGraphicItem.__attribute_docs__ = {'requestModelRepaint': 'Emitted by the item to request a repaint of the parent model scene.\n', 'aboutToChange': 'Emitted when the definition of the associated component is about to be\nchanged by the item.\n\nThe ``text`` argument gives the translated text describing the change\nabout to occur, and the optional ``id`` can be used to group the\nassociated undo commands.\n', 'changed': 'Emitted when the definition of the associated component is changed by\nthe item.\n', 'repaintArrows': 'Emitted when item requests that all connected arrows are repainted.\n', 'updateArrowPaths': 'Emitted when item requires that all connected arrow paths are\nrecalculated.\n', 'sizePositionChanged': "Emitted when the item's size or position changes.\n"}
-    QgsModelComponentGraphicItem.__virtual_methods__ = ['flags', 'linkPointCount', 'linkPointText', 'editComment', 'canDeleteComponent', 'deleteComponent', 'editComponent', 'strokeStyle', 'titleAlignment', 'iconPicture', 'iconPixmap']
+    QgsModelComponentGraphicItem.__virtual_methods__ = ['flags', 'linkedParameterDataType', 'linkPointCount', 'linkPointText', 'editComment', 'canDeleteComponent', 'deleteComponent', 'editComponent', 'strokeStyle', 'titleAlignment', 'iconPicture', 'iconPixmap']
     QgsModelComponentGraphicItem.__abstract_methods__ = ['fillColor', 'strokeColor', 'textColor', 'updateStoredComponentPosition']
     QgsModelComponentGraphicItem.__overridden_methods__ = ['mouseDoubleClickEvent', 'hoverEnterEvent', 'hoverMoveEvent', 'hoverLeaveEvent', 'itemChange', 'boundingRect', 'contains', 'paint']
     QgsModelComponentGraphicItem.__signal_arguments__ = {'aboutToChange': ['text: str', 'id: int = 0']}
@@ -15,7 +15,7 @@ try:
 except (NameError, AttributeError):
     pass
 try:
-    QgsModelParameterGraphicItem.__overridden_methods__ = ['contextMenuEvent', 'canDeleteComponent', 'fillColor', 'strokeColor', 'textColor', 'iconPicture', 'linkPointCount', 'linkPointText', 'updateStoredComponentPosition', 'deleteComponent']
+    QgsModelParameterGraphicItem.__overridden_methods__ = ['contextMenuEvent', 'canDeleteComponent', 'linkedParameterDataType', 'linkColor', 'fillColor', 'strokeColor', 'textColor', 'iconPicture', 'linkPointCount', 'linkPointText', 'updateStoredComponentPosition', 'deleteComponent']
     QgsModelParameterGraphicItem.__group__ = ['processing', 'models']
 except (NameError, AttributeError):
     pass

python/gui/auto_generated/processing/models/qgsmodelcomponentgraphicitem.sip.in

@@ -112,6 +112,8 @@ Shows a preview of moving the item from its stored position by ``dx``,
 Sets a new scene ``rect`` for the item.
 %End
 
+    virtual QString linkedParameterDataType( Qt::Edge edge, int index ) const;
+
     virtual void mouseDoubleClickEvent( QGraphicsSceneMouseEvent *event );
 
     virtual void hoverEnterEvent( QGraphicsSceneHoverEvent *event );
@@ -324,6 +326,13 @@ comment
 Updates the item's button positions, based on the current item rect.
 %End
 
+    QColor fallbackColor() const;
+%Docstring
+Returns the fallback color if the parameter or output does not have a
+specific color.
+
+.. versionadded:: 4.0
+%End
 };
 QFlags<QgsModelComponentGraphicItem::Flag> operator|(QgsModelComponentGraphicItem::Flag f1, QFlags<QgsModelComponentGraphicItem::Flag> f2);
 
@@ -362,6 +371,12 @@ Ownership of ``parameter`` is transferred to the item.
     virtual bool canDeleteComponent();
 
 
+    virtual QString linkedParameterDataType( Qt::Edge /* unused in this implementation because parameters only have a bottom edge */, int index ) const;
+
+
+    virtual QColor linkColor( Qt::Edge edge, int index ) const;
+
+
   protected:
     virtual QColor fillColor( State state ) const;
 

python/gui/auto_generated/processing/models/qgsmodelgraphicitem.sip.in

@@ -182,6 +182,23 @@ Return the component associated to the socket.
 %Docstring
 Return the parent graphic item associated to the socket.
 %End
+    QColor socketColor() const;
+%Docstring
+Returns the color of the socket based on the type of data the param
+corresponds to.
+
+.. versionadded:: 4.0
+%End
+
+    bool isDefaultParameterValue() const;
+%Docstring
+Returns ``True`` if the parameter is set to the default parameter value.
+
+.. versionadded:: 4.0
+%End
+  signals:
+
+
 };
 
 

src/core/processing/models/qgsprocessingmodelchildparametersource.cpp

@@ -224,8 +224,21 @@ QString QgsProcessingModelChildParameterSource::friendlyIdentifier( QgsProcessin
   switch ( mSource )
   {
     case Qgis::ProcessingModelChildParameterSource::ModelParameter:
-      return model ? model->parameterDefinition( mParameterName )->description() : mParameterName;
+    {
 
+      if ( model )
+      {
+        const QgsProcessingParameterDefinition *paramDefinition = model->parameterDefinition( mParameterName );
+
+        // A model can be valid (non null) but we could be looking for a null parameter (if input if not set yet)
+        if ( paramDefinition )
+        {
+          return model->parameterDefinition( mParameterName )->description();
+        }
+      }
+
+      return mParameterName;
+    }
     case Qgis::ProcessingModelChildParameterSource::ChildOutput:
     {
       if ( model )
@@ -242,11 +255,11 @@ QString QgsProcessingModelChildParameterSource::friendlyIdentifier( QgsProcessin
             break;
           }
         }
-        return QObject::tr( "'%1' from algorithm '%2'" ).arg( outputName, alg.description() );
+        return QObject::tr( "<%1>" ).arg( alg.description() );
       }
       else
       {
-        return QObject::tr( "'%1' from algorithm '%2'" ).arg( mOutputName, mChildId );
+        return QObject::tr( "<%1>" ).arg( mChildId );
       }
     }
 

src/core/processing/qgsprocessingoutputs.cpp

@@ -48,6 +48,11 @@ QString QgsProcessingOutputDefinition::valueAsFormattedString( const QVariant &v
   return valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputDefinition::modelColor() const
+{
+  return QColor( 128, 128, 128 ); /* mid  gray */
+}
+
 QgsProcessingOutputVectorLayer::QgsProcessingOutputVectorLayer( const QString &name, const QString &description, Qgis::ProcessingSourceType type )
   : QgsProcessingOutputDefinition( name, description )
   , mDataType( type )
@@ -63,10 +68,20 @@ void QgsProcessingOutputVectorLayer::setDataType( Qgis::ProcessingSourceType typ
   mDataType = type;
 }
 
+QColor QgsProcessingOutputVectorLayer::modelColor() const
+{
+  return QColor( 122, 0, 47 ); /* burgundy */
+}
+
 QgsProcessingOutputRasterLayer::QgsProcessingOutputRasterLayer( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
 
+QColor QgsProcessingOutputRasterLayer::modelColor() const
+{
+  return QColor( 0, 180, 180 ); /* turquoise */
+}
+
 QgsProcessingOutputPointCloudLayer::QgsProcessingOutputPointCloudLayer( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -75,6 +90,11 @@ QgsProcessingOutputVectorTileLayer::QgsProcessingOutputVectorTileLayer( const QS
   : QgsProcessingOutputDefinition( name, description )
 {}
 
+QColor QgsProcessingOutputVectorTileLayer::modelColor() const
+{
+  return QColor( 137, 150, 171 ); /* cold gray */
+}
+
 QgsProcessingOutputHtml::QgsProcessingOutputHtml( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -90,6 +110,11 @@ QString QgsProcessingOutputHtml::valueAsFormattedString( const QVariant &value,
   return valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputHtml::modelColor() const
+{
+  return QColor( 255, 131, 23 ); /* orange */
+}
+
 QgsProcessingOutputNumber::QgsProcessingOutputNumber( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -112,10 +137,20 @@ QString QgsProcessingOutputNumber::valueAsString( const QVariant &value, QgsProc
   return QgsProcessingOutputDefinition::valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputNumber::modelColor() const
+{
+  return QColor( 34, 157, 214 ); /* blue */
+}
+
 QgsProcessingOutputString::QgsProcessingOutputString( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
 
+QColor QgsProcessingOutputString::modelColor() const
+{
+  return QColor( 255, 131, 23 ); /* orange */
+}
+
 QgsProcessingOutputBoolean::QgsProcessingOutputBoolean( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -131,6 +166,11 @@ QString QgsProcessingOutputBoolean::valueAsString( const QVariant &value, QgsPro
   return QgsProcessingOutputDefinition::valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputBoolean::modelColor() const
+{
+  return QColor( 51, 201, 28 ); /* green */
+}
+
 QgsProcessingOutputFolder::QgsProcessingOutputFolder( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -146,6 +186,11 @@ QString QgsProcessingOutputFolder::valueAsFormattedString( const QVariant &value
   return valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputFolder::modelColor() const
+{
+  return QColor( 80, 80, 80 ); /* dark gray */
+}
+
 QgsProcessingOutputFile::QgsProcessingOutputFile( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -161,6 +206,11 @@ QString QgsProcessingOutputFile::valueAsFormattedString( const QVariant &value,
   return valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputFile::modelColor() const
+{
+  return QColor( 80, 80, 80 ); /* dark gray */
+}
+
 QgsProcessingOutputMapLayer::QgsProcessingOutputMapLayer( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -170,6 +220,11 @@ QString QgsProcessingOutputMapLayer::type() const
   return typeName();
 }
 
+QColor QgsProcessingOutputMapLayer::modelColor() const
+{
+  return QColor( 137, 150, 171 ); /* cold gray */
+}
+
 QgsProcessingOutputMultipleLayers::QgsProcessingOutputMultipleLayers( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -210,6 +265,11 @@ QString QgsProcessingOutputMultipleLayers::valueAsString( const QVariant &value,
   return QgsProcessingOutputDefinition::valueAsString( value, context, ok );
 }
 
+QColor QgsProcessingOutputMultipleLayers::modelColor() const
+{
+  return QColor( 137, 150, 171 ); /* cold gray */
+}
+
 QgsProcessingOutputConditionalBranch::QgsProcessingOutputConditionalBranch( const QString &name, const QString &description )
   : QgsProcessingOutputDefinition( name, description )
 {}
@@ -266,3 +326,4 @@ QString QgsProcessingOutputVariant::valueAsString( const QVariant &value, QgsPro
   }
   return QgsProcessingOutputDefinition::valueAsString( value, context, ok );
 }
+

src/core/processing/qgsprocessingoutputs.h

@@ -18,6 +18,7 @@
 #ifndef QGSPROCESSINGOUTPUTS_H
 #define QGSPROCESSINGOUTPUTS_H
 
+#include <QColor>
 #include "qgis_core.h"
 #include "qgis.h"
 
@@ -85,6 +86,13 @@ class CORE_EXPORT QgsProcessingOutputDefinition
 
     virtual ~QgsProcessingOutputDefinition() = default;
 
+    /**
+    * Returns the color to use for the output in model designer windows.
+    *
+    * \since QGIS 4.0
+    */
+    virtual QColor modelColor() const;
+
     /**
      * Unique output type name.
      */
@@ -195,6 +203,8 @@ class CORE_EXPORT QgsProcessingOutputMapLayer : public QgsProcessingOutputDefini
      */
     QgsProcessingOutputMapLayer( const QString &name, const QString &description = QString() );
 
+    QColor modelColor() const override;
+
     /**
      * Returns the type name for the output class.
      */
@@ -218,6 +228,8 @@ class CORE_EXPORT QgsProcessingOutputVectorLayer : public QgsProcessingOutputDef
      */
     QgsProcessingOutputVectorLayer( const QString &name, const QString &description = QString(), Qgis::ProcessingSourceType type = Qgis::ProcessingSourceType::VectorAnyGeometry );
 
+    QColor modelColor() const override;
+
     /**
      * Returns the type name for the output class.
      */
@@ -259,6 +271,8 @@ class CORE_EXPORT QgsProcessingOutputRasterLayer : public QgsProcessingOutputDef
      * Returns the type name for the output class.
      */
     static QString typeName() { return QStringLiteral( "outputRaster" ); }
+
+    QColor modelColor() const override;
     QString type() const override { return typeName(); }
 };
 
@@ -310,8 +324,9 @@ class CORE_EXPORT QgsProcessingOutputMultipleLayers : public QgsProcessingOutput
      */
     static QString typeName() { return QStringLiteral( "outputMultilayer" ); }
     QString type() const override;
-    QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 
+    QColor modelColor() const override;
+    QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 };
 
 /**
@@ -333,6 +348,8 @@ class CORE_EXPORT QgsProcessingOutputHtml : public QgsProcessingOutputDefinition
      */
     static QString typeName() { return QStringLiteral( "outputHtml" ); }
     QString type() const override { return typeName(); }
+
+    QColor modelColor() const override;
     QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 };
 
@@ -356,6 +373,7 @@ class CORE_EXPORT QgsProcessingOutputVariant : public QgsProcessingOutputDefinit
      * Returns the type name for the output class.
      */
     static QString typeName() { return QStringLiteral( "outputVariant" ); }
+
     QString type() const override;
     QString valueAsString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 
@@ -375,6 +393,8 @@ class CORE_EXPORT QgsProcessingOutputNumber : public QgsProcessingOutputDefiniti
      */
     QgsProcessingOutputNumber( const QString &name, const QString &description = QString() );
 
+    QColor modelColor() const override;
+
     /**
      * Returns the type name for the output class.
      */
@@ -402,6 +422,8 @@ class CORE_EXPORT QgsProcessingOutputString : public QgsProcessingOutputDefiniti
      * Returns the type name for the output class.
      */
     static QString typeName() { return QStringLiteral( "outputString" ); }
+
+    QColor modelColor() const override;
     QString type() const override { return typeName(); }
 };
 
@@ -420,6 +442,8 @@ class CORE_EXPORT QgsProcessingOutputBoolean : public QgsProcessingOutputDefinit
      */
     QgsProcessingOutputBoolean( const QString &name, const QString &description = QString() );
 
+    QColor modelColor() const override ;
+
     /**
      * Returns the type name for the output class.
      */
@@ -448,8 +472,9 @@ class CORE_EXPORT QgsProcessingOutputFolder : public QgsProcessingOutputDefiniti
      */
     static QString typeName() { return QStringLiteral( "outputFolder" ); }
     QString type() const override { return typeName(); }
-    QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 
+    QColor modelColor() const override;
+    QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 };
 
 /**
@@ -471,8 +496,9 @@ class CORE_EXPORT QgsProcessingOutputFile : public QgsProcessingOutputDefinition
      */
     static QString typeName() { return QStringLiteral( "outputFile" ); }
     QString type() const override { return typeName(); }
-    QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 
+    QColor modelColor() const override;
+    QString valueAsFormattedString( const QVariant &value, QgsProcessingContext &context, bool &ok SIP_OUT ) const override;
 };
 
 /**
@@ -517,6 +543,8 @@ class CORE_EXPORT QgsProcessingOutputVectorTileLayer : public QgsProcessingOutpu
      * Returns the type name for the output class.
      */
     static QString typeName() { return QStringLiteral( "outputVectorTile" ); }
+
+    QColor modelColor() const override;
     QString type() const override { return typeName(); }
 };
 

src/core/processing/qgsprocessingparameters.cpp

@@ -39,6 +39,7 @@
 #include "qgsproviderregistry.h"
 #include "qgsvariantutils.h"
 #include "qgsmessagelog.h"
+#include "qgsunittypes.h"
 #include <functional>
 #include <QRegularExpression>
 
@@ -66,7 +67,6 @@ bool QgsProcessingFeatureSourceDefinition::loadVariant( const QVariantMap &map )
   return true;
 }
 
-
 //
 // QgsProcessingRasterLayerDefinition
 //
@@ -3061,6 +3061,73 @@ QgsProcessingParameterDefinition *QgsProcessingParameterBoolean::clone() const
   return new QgsProcessingParameterBoolean( *this );
 }
 
+QColor QgsProcessingParameterDefinition::modelColor() const
+{
+  QgsProcessingParameterType *paramType = QgsApplication::processingRegistry()->parameterType( type() );
+  if ( paramType )
+  {
+    return paramType->modelColor();
+  }
+
+  return QgsProcessingParameterType::defaultModelColor();
+}
+
+QString QgsProcessingParameterDefinition::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  if ( value.userType() == qMetaTypeId<QgsPointXY>() )
+  {
+    const QgsPointXY r = value.value<QgsPointXY>();
+    return QStringLiteral( "%1, %2" ).arg( qgsDoubleToString( r.x(), 4 ),
+                                           qgsDoubleToString( r.y(), 4 ) );
+  }
+
+  else if ( value.userType() == qMetaTypeId<QgsReferencedPointXY>() )
+  {
+    const QgsReferencedPointXY r = value.value<QgsReferencedPointXY>();
+    return QStringLiteral( "%1, %2 [%3]" ).arg(
+             qgsDoubleToString( r.x(), 4 ),
+             qgsDoubleToString( r.y(), 4 ),
+             r.crs().authid()
+           );
+  }
+
+  else if ( value.userType() == qMetaTypeId<QgsRectangle>() )
+  {
+    const QgsGeometry g = QgsGeometry::fromRect( value.value<QgsRectangle>() );
+    return QgsWkbTypes::geometryDisplayString( g.type() );
+  }
+
+  else if ( value.userType() == qMetaTypeId<QgsReferencedRectangle>() )
+  {
+    const QgsReferencedGeometry g = QgsReferencedGeometry::fromReferencedRect( value.value<QgsReferencedRectangle>() );
+    if ( !g.isNull() )
+    {
+
+      return QStringLiteral( "%1 [%2]" ).arg( QgsWkbTypes::geometryDisplayString( g.type() ), g.crs().userFriendlyIdentifier( Qgis::CrsIdentifierType::ShortString ) );
+    }
+    return QgsWkbTypes::geometryDisplayString( g.type() );
+  }
+
+  else if ( value.userType() == qMetaTypeId<QgsProcessingOutputLayerDefinition>() )
+  {
+    const QgsProcessingOutputLayerDefinition fromVar = qvariant_cast<QgsProcessingOutputLayerDefinition>( value );
+    if ( fromVar.sink.propertyType() == Qgis::PropertyType::Static )
+    {
+      return fromVar.sink.staticValue().toString();
+    }
+    else
+    {
+      return fromVar.sink.asExpression();
+    }
+  }
+
+  return value.toString();
+}
+
+
 QString QgsProcessingParameterBoolean::valueAsPythonString( const QVariant &val, QgsProcessingContext & ) const
 {
   if ( !val.isValid() )
@@ -3220,6 +3287,21 @@ QgsProcessingParameterCrs *QgsProcessingParameterCrs::fromScriptCode( const QStr
   return new QgsProcessingParameterCrs( name, description, definition.compare( QLatin1String( "none" ), Qt::CaseInsensitive ) == 0 ? QVariant() : definition, isOptional );
 }
 
+
+QString QgsProcessingParameterCrs::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  QgsCoordinateReferenceSystem crs( value.toString() );
+  if ( crs.isValid() )
+    return crs.userFriendlyIdentifier( Qgis::CrsIdentifierType::ShortString );
+
+  return QObject::tr( "Invalid CRS" );
+}
+
+
+
 QgsProcessingParameterMapLayer::QgsProcessingParameterMapLayer( const QString &name, const QString &description, const QVariant &defaultValue, bool optional, const QList<int> &types )
   : QgsProcessingParameterDefinition( name, description, defaultValue, optional )
   , QgsProcessingParameterLimitedDataTypes( types )
@@ -3652,7 +3734,8 @@ QString QgsProcessingParameterExtent::valueAsPythonString( const QVariant &value
     return QStringLiteral( "'%1, %3, %2, %4 [%5]'" ).arg( qgsDoubleToString( r.xMinimum() ),
            qgsDoubleToString( r.yMinimum() ),
            qgsDoubleToString( r.xMaximum() ),
-           qgsDoubleToString( r.yMaximum() ),                                                                                                                             r.crs().authid() );
+           qgsDoubleToString( r.yMaximum() ),
+           r.crs().authid() );
   }
   else if ( value.userType() == qMetaTypeId< QgsGeometry>() )
   {
@@ -3802,6 +3885,7 @@ QgsProcessingParameterPoint *QgsProcessingParameterPoint::fromScriptCode( const
   return new QgsProcessingParameterPoint( name, description, definition, isOptional );
 }
 
+
 QgsProcessingParameterGeometry::QgsProcessingParameterGeometry( const QString &name, const QString &description,
     const QVariant &defaultValue, bool optional, const QList<int> &geometryTypes, bool allowMultipart )
   : QgsProcessingParameterDefinition( name, description, defaultValue, optional ),
@@ -4073,6 +4157,45 @@ QgsProcessingParameterGeometry *QgsProcessingParameterGeometry::fromScriptCode(
   return new QgsProcessingParameterGeometry( name, description, definition, isOptional );
 }
 
+QString QgsProcessingParameterGeometry::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  if ( value.isValid() )
+  {
+
+    if ( value.userType() == qMetaTypeId< QgsGeometry>() )
+    {
+      const QgsGeometry g = value.value<QgsGeometry>();
+      return QgsWkbTypes::geometryDisplayString( g.type() );
+    }
+
+    else if ( value.userType() == qMetaTypeId<QgsReferencedGeometry>() )
+    {
+      const QgsReferencedGeometry g = value.value<QgsReferencedGeometry>();
+      if ( !g.isNull() )
+      {
+        return QStringLiteral( "%1 [%2]" ).arg( QgsWkbTypes::geometryDisplayString( g.type() ), g.crs().userFriendlyIdentifier( Qgis::CrsIdentifierType::ShortString ));
+      }
+      return QgsWkbTypes::geometryDisplayString( g.type() );
+    }
+
+    else if ( value.userType() == QMetaType::QString )
+    {
+      // In the case of a WKT-(string) encoded geometry, the type of geometry is going to be displayed
+      // rather than the possibly very long WKT payload
+      QgsGeometry g = QgsGeometry::fromWkt( value.toString() );
+      if ( !g.isNull() )
+      {
+        return QgsWkbTypes::geometryDisplayString( g.type() );
+      }
+    }
+  }
+
+  return QObject::tr( "Invalid geometry" );
+}
+
 QgsProcessingParameterFile::QgsProcessingParameterFile( const QString &name, const QString &description, Qgis::ProcessingFileParameterBehavior behavior, const QString &extension, const QVariant &defaultValue, bool optional, const QString &fileFilter )
   : QgsProcessingParameterDefinition( name, description, defaultValue, optional )
   , mBehavior( behavior )
@@ -5391,6 +5514,14 @@ QString QgsProcessingParameterEnum::asPythonString( const QgsProcessing::PythonO
   return QString();
 }
 
+QString QgsProcessingParameterEnum::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  return options().at( value.toInt() );
+}
+
 QStringList QgsProcessingParameterEnum::options() const
 {
   return mOptions;
@@ -7855,6 +7986,14 @@ bool QgsProcessingParameterDistance::fromVariantMap( const QVariantMap &map )
 }
 
 
+QString QgsProcessingParameterDistance::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  return QStringLiteral( "%1 %2" ).arg( value.toString(), QgsUnitTypes::toAbbreviatedString( defaultUnit() ) );
+}
+
 
 //
 // QgsProcessingParameterArea
@@ -7937,6 +8076,14 @@ bool QgsProcessingParameterArea::fromVariantMap( const QVariantMap &map )
 }
 
 
+QString QgsProcessingParameterArea::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  return QStringLiteral( "%1 %2" ).arg( value.toString(), QgsUnitTypes::toAbbreviatedString( defaultUnit() ) );
+}
+
 
 //
 // QgsProcessingParameterVolume
@@ -8018,6 +8165,13 @@ bool QgsProcessingParameterVolume::fromVariantMap( const QVariantMap &map )
   return true;
 }
 
+QString QgsProcessingParameterVolume::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  return QStringLiteral( "%1 %2" ).arg( value.toString(), QgsUnitTypes::toAbbreviatedString( defaultUnit() ) );
+}
 
 //
 // QgsProcessingParameterDuration
@@ -8075,6 +8229,14 @@ bool QgsProcessingParameterDuration::fromVariantMap( const QVariantMap &map )
   return true;
 }
 
+QString QgsProcessingParameterDuration::userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  return QStringLiteral( "%1 %2" ).arg( value.toString(), QgsUnitTypes::toAbbreviatedString( defaultUnit() ) );
+}
+
 
 //
 // QgsProcessingParameterScale
@@ -8932,6 +9094,40 @@ QgsProcessingParameterDateTime *QgsProcessingParameterDateTime::fromScriptCode(
 }
 
 
+QString QgsProcessingParameterDateTime:: userFriendlyString( const QVariant &value ) const
+{
+  if ( QgsVariantUtils::isNull( value ) )
+    return QString();
+
+  if ( value.userType() == QMetaType::Type::QDateTime )
+  {
+    const QDateTime dt = value.toDateTime();
+    if ( !dt.isValid() )
+      return QObject::tr( "Invalid datetime" );
+    else
+      return dt.toString( Qt::ISODate );
+  }
+
+  else if ( value.userType() == QMetaType::Type::QDate )
+  {
+    const QDate dt = value.toDate();
+    if ( !dt.isValid() )
+      return QObject::tr( "Invalid date" );
+    else
+      return dt.toString( Qt::ISODate );
+  }
+
+  else if ( value.userType() == QMetaType::Type::QTime )
+  {
+    const QTime dt = value.toTime();
+    if ( !dt.isValid() )
+      return QObject::tr( "Invalid time" );
+    else
+      return dt.toString( Qt::ISODate );
+  }
+
+  return value.toString();
+}
 
 //
 // QgsProcessingParameterProviderConnection

src/core/processing/qgsprocessingparameters.h

@@ -28,6 +28,7 @@
 #include "qgsremappingproxyfeaturesink.h"
 #include <QMap>
 #include <limits>
+#include <QColor>
 
 class QgsProcessingContext;
 class QgsProcessingAlgorithm;
@@ -554,6 +555,23 @@ class CORE_EXPORT QgsProcessingParameterDefinition
 
     virtual ~QgsProcessingParameterDefinition() = default;
 
+    /**
+     * Returns the color to use for the parameter in model designer windows.
+     *
+     * The default implementation retrieves the color from the parameter type, see QgsProcessingParameterType::modelColor().
+     *
+     * \since QGIS 4.0
+     */
+    virtual QColor modelColor() const;
+
+    /**
+     * Returns a user-friendly string representation of the provided parameter \a value.
+     *
+     * The returned string is to be used for display purposes only, and should be translated as required.
+     * \since QGIS 4.0
+     */
+    virtual QString userFriendlyString( const QVariant &value ) const;
+
     /**
      * Creates a clone of the parameter definition.
      */
@@ -1906,6 +1924,8 @@ class CORE_EXPORT QgsProcessingParameterCrs : public QgsProcessingParameterDefin
     QgsProcessingParameterCrs( const QString &name, const QString &description = QString(), const QVariant &defaultValue = QVariant(),
                                bool optional = false );
 
+    QString userFriendlyString( const QVariant &value ) const override;
+
     /**
      * Returns the type name for the parameter class.
      */
@@ -2054,7 +2074,7 @@ class CORE_EXPORT QgsProcessingParameterGeometry : public QgsProcessingParameter
      */
     void setAllowMultipart( bool allowMultipart ) { mAllowMultipart = allowMultipart; }
 
-
+    QString userFriendlyString( const QVariant &value ) const override;
 
     /**
      * Creates a new parameter using the definition from a script code.
@@ -2185,6 +2205,7 @@ class CORE_EXPORT QgsProcessingParameterMatrix : public QgsProcessingParameterDe
      * Returns the type name for the parameter class.
      */
     static QString typeName() { return QStringLiteral( "matrix" ); }
+
     QgsProcessingParameterDefinition *clone() const override SIP_FACTORY;
     QString type() const override { return typeName(); }
     bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = nullptr ) const override;
@@ -2356,6 +2377,7 @@ class CORE_EXPORT QgsProcessingParameterNumber : public QgsProcessingParameterDe
      * Returns the type name for the parameter class.
      */
     static QString typeName() { return QStringLiteral( "number" ); }
+
     QgsProcessingParameterDefinition *clone() const override SIP_FACTORY;
     QString type() const override { return typeName(); }
     bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = nullptr ) const override;
@@ -2454,6 +2476,8 @@ class CORE_EXPORT QgsProcessingParameterDistance : public QgsProcessingParameter
      */
     static QString typeName() { return QStringLiteral( "distance" ); } // cppcheck-suppress duplInheritedMember
 
+    QString userFriendlyString( const QVariant &value ) const override;
+
     QgsProcessingParameterDistance *clone() const override SIP_FACTORY;
 
     QString type() const override;
@@ -2573,6 +2597,7 @@ class CORE_EXPORT QgsProcessingParameterArea : public QgsProcessingParameterNumb
 
     QVariantMap toVariantMap() const override;
     bool fromVariantMap( const QVariantMap &map ) override;
+    QString userFriendlyString( const QVariant &value ) const override;
 
   private:
 
@@ -2656,6 +2681,7 @@ class CORE_EXPORT QgsProcessingParameterVolume : public QgsProcessingParameterNu
 
     QVariantMap toVariantMap() const override;
     bool fromVariantMap( const QVariantMap &map ) override;
+    QString userFriendlyString( const QVariant &value ) const override;
 
   private:
 
@@ -2712,6 +2738,7 @@ class CORE_EXPORT QgsProcessingParameterDuration : public QgsProcessingParameter
 
     QVariantMap toVariantMap() const override;
     bool fromVariantMap( const QVariantMap &map ) override;
+    QString userFriendlyString( const QVariant &value ) const override;
 
   private:
 
@@ -2778,6 +2805,7 @@ class CORE_EXPORT QgsProcessingParameterRange : public QgsProcessingParameterDef
      * Returns the type name for the parameter class.
      */
     static QString typeName() { return QStringLiteral( "range" ); }
+
     QgsProcessingParameterDefinition *clone() const override SIP_FACTORY;
     QString type() const override { return typeName(); }
     bool checkValueIsAcceptable( const QVariant &input, QgsProcessingContext *context = nullptr ) const override;
@@ -2889,6 +2917,8 @@ class CORE_EXPORT QgsProcessingParameterEnum : public QgsProcessingParameterDefi
                                 bool optional = false,
                                 bool usesStaticStrings = false );
 
+    QString userFriendlyString( const QVariant &value ) const override;
+
     /**
      * Returns the type name for the parameter class.
      */
@@ -4090,6 +4120,7 @@ class CORE_EXPORT QgsProcessingParameterColor : public QgsProcessingParameterDef
      * Returns the type name for the parameter class.
      */
     static QString typeName() { return QStringLiteral( "color" ); }
+
     QgsProcessingParameterDefinition *clone() const override SIP_FACTORY;
     QString type() const override { return typeName(); }
     QString valueAsPythonString( const QVariant &value, QgsProcessingContext &context ) const override;
@@ -4373,6 +4404,7 @@ class CORE_EXPORT QgsProcessingParameterDateTime : public QgsProcessingParameter
 
     QVariantMap toVariantMap() const override;
     bool fromVariantMap( const QVariantMap &map ) override;
+    QString userFriendlyString( const QVariant &value ) const override;
 
     /**
      * Creates a new parameter using the definition from a script code.

src/core/processing/qgsprocessingparametertype.cpp

@@ -17,6 +17,11 @@
 
 #include "qgsprocessingparametertype.h"
 
+QColor QgsProcessingParameterType::defaultModelColor()
+{
+  return QColor( 128, 128, 128 ); /* mid gray */
+}
+
 Qgis::ProcessingParameterTypeFlags QgsProcessingParameterType::flags() const
 {
   return Qgis::ProcessingParameterTypeFlag::ExposeToModeler;
@@ -51,3 +56,8 @@ QList<int> QgsProcessingParameterType::acceptedDataTypes( const QgsProcessingPar
 {
   return QList<int>();
 }
+
+QColor QgsProcessingParameterType::modelColor() const
+{
+  return defaultModelColor();
+}

src/core/processing/qgsprocessingparametertype.h

@@ -34,6 +34,13 @@ class CORE_EXPORT QgsProcessingParameterType
 {
   public:
 
+    /**
+     * Returns the default color for a processing parameter.
+     *
+     * \since QGIS 4.0
+     */
+    static QColor defaultModelColor();
+
     /**
      * Creates a new parameter of this type.
      */
@@ -171,6 +178,15 @@ class CORE_EXPORT QgsProcessingParameterType
      */
     virtual QList<int> acceptedDataTypes( const QgsProcessingParameterDefinition *parameter ) const;
 
+    /**
+     * Returns the color to use for the parameter in model designer windows.
+     *
+     * The default implementation returns defaultModelColor().
+     *
+     * \since QGIS 4.0
+     */
+    virtual QColor modelColor() const;
+
 };
 
 #endif // QGSPROCESSINGPARAMETERTYPE_H

src/core/processing/qgsprocessingparametertypeimpl.h

@@ -97,6 +97,8 @@ class CORE_EXPORT QgsProcessingParameterTypeRasterLayer : public QgsProcessingPa
              << QgsProcessingOutputFile::typeName()
              << QgsProcessingOutputFolder::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 0, 180, 180 ); /* turquoise */ };
 };
 
 /**
@@ -169,6 +171,8 @@ class CORE_EXPORT QgsProcessingParameterTypeMeshLayer : public QgsProcessingPara
              << QgsProcessingOutputFile::typeName()
              << QgsProcessingOutputFolder::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 137, 150, 171 ); /* cold gray */ };
 };
 
 /**
@@ -250,6 +254,8 @@ class CORE_EXPORT QgsProcessingParameterTypeVectorLayer : public QgsProcessingPa
       else
         return QList<int>();
     }
+
+    QColor modelColor() const override { return QColor( 122, 0, 47 ); /* burgundy */ };
 };
 
 /**
@@ -330,6 +336,8 @@ class CORE_EXPORT QgsProcessingParameterTypeMapLayer : public QgsProcessingParam
              << QgsProcessingOutputFile::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 137, 150, 171 ); /* cold gray */ };
 };
 
 /**
@@ -421,6 +429,8 @@ class CORE_EXPORT QgsProcessingParameterTypeBoolean : public QgsProcessingParame
              << QgsProcessingOutputVariant::typeName()
              << QgsProcessingOutputBoolean::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 51, 201, 28 ); /* green */ };
 };
 
 /**
@@ -493,6 +503,8 @@ class CORE_EXPORT QgsProcessingParameterTypeExpression : public QgsProcessingPar
              << QgsProcessingOutputNumber::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 255, 131, 23 ); /* orange */ };
 };
 
 /**
@@ -580,6 +592,8 @@ class CORE_EXPORT QgsProcessingParameterTypeCrs : public QgsProcessingParameterT
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 255, 131, 23 ); /* orange */ };
 };
 
 /**
@@ -646,6 +660,8 @@ class CORE_EXPORT QgsProcessingParameterTypeRange : public QgsProcessingParamete
       return QStringList() << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -714,6 +730,8 @@ class CORE_EXPORT QgsProcessingParameterTypePoint : public QgsProcessingParamete
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 122, 0, 47 ); /* burgundy */ };
 };
 
 /**
@@ -782,6 +800,8 @@ class CORE_EXPORT QgsProcessingParameterTypeGeometry : public QgsProcessingParam
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 122, 0, 47 ); /* burgundy */ };
 };
 
 /**
@@ -851,6 +871,8 @@ class CORE_EXPORT QgsProcessingParameterTypeEnum : public QgsProcessingParameter
              << QgsProcessingOutputVariant::typeName()
              << QgsProcessingOutputNumber::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 152, 68, 201 ); /* purple */ };
 };
 
 /**
@@ -935,6 +957,8 @@ class CORE_EXPORT QgsProcessingParameterTypeExtent : public QgsProcessingParamet
              << QgsProcessingOutputMapLayer::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -998,6 +1022,8 @@ class CORE_EXPORT QgsProcessingParameterTypeMatrix : public QgsProcessingParamet
     {
       return QStringList();
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -1067,6 +1093,8 @@ class CORE_EXPORT QgsProcessingParameterTypeFile : public QgsProcessingParameter
              << QgsProcessingOutputVectorLayer::typeName()
              << QgsProcessingOutputMapLayer::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 80, 80, 80 ); /* dark gray */ };
 };
 
 /**
@@ -1224,6 +1252,8 @@ class CORE_EXPORT QgsProcessingParameterTypeVectorDestination : public QgsProces
     {
       return QStringList() << QObject::tr( "Path for new vector layer" );
     }
+
+    QColor modelColor() const override { return QColor( 122, 0, 47 ); /* burgundy */ };
 };
 
 /**
@@ -1300,6 +1330,8 @@ class CORE_EXPORT QgsProcessingParameterTypeFileDestination : public QgsProcessi
              << QgsProcessingOutputVectorLayer::typeName()
              << QgsProcessingOutputMapLayer::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 80, 80, 80 ); /* dark gray */ };
 };
 
 /**
@@ -1375,6 +1407,8 @@ class CORE_EXPORT QgsProcessingParameterTypeFolderDestination : public QgsProces
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 80, 80, 80 ); /* dark gray */ };
 };
 
 /**
@@ -1435,6 +1469,8 @@ class CORE_EXPORT QgsProcessingParameterTypeRasterDestination : public QgsProces
     {
       return QStringList() << QObject::tr( "Path for new raster layer" );
     }
+
+    QColor modelColor() const override { return QColor( 0, 180, 180 ); /* turquoise */ };
 };
 
 /**
@@ -1515,6 +1551,8 @@ class CORE_EXPORT QgsProcessingParameterTypeString : public QgsProcessingParamet
              << QgsProcessingOutputFolder::typeName()
              << QgsProcessingOutputString::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 255, 131, 23 ); /* orange */ };
 };
 
 /**
@@ -1652,6 +1690,8 @@ class CORE_EXPORT QgsProcessingParameterTypeMultipleLayers : public QgsProcessin
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 137, 150, 171 ); /* cold gray */ };
 };
 
 /**
@@ -1735,6 +1775,8 @@ class CORE_EXPORT QgsProcessingParameterTypeFeatureSource : public QgsProcessing
       else
         return QList<int>();
     }
+
+    QColor modelColor() const override { return QColor( 122, 0, 47 ); /* burgundy */  };
 };
 
 /**
@@ -1807,6 +1849,8 @@ class CORE_EXPORT QgsProcessingParameterTypeNumber : public QgsProcessingParamet
              << QgsProcessingOutputVariant::typeName()
              << QgsProcessingOutputString::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -1861,6 +1905,8 @@ class CORE_EXPORT QgsProcessingParameterTypeDistance : public QgsProcessingParam
              << QObject::tr( "field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field" )
              << QObject::tr( "expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression" );
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 
@@ -2027,6 +2073,8 @@ class CORE_EXPORT QgsProcessingParameterTypeDuration : public QgsProcessingParam
              << QObject::tr( "field:FIELD_NAME to use a data defined value taken from the FIELD_NAME field" )
              << QObject::tr( "expression:SOME EXPRESSION to use a data defined value calculated using a custom QGIS expression" );
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -2079,6 +2127,8 @@ class CORE_EXPORT QgsProcessingParameterTypeScale : public QgsProcessingParamete
     {
       return QStringList() << QObject::tr( "A numeric value representing the scale denominator" );
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -2205,6 +2255,8 @@ class CORE_EXPORT QgsProcessingParameterTypeFeatureSink : public QgsProcessingPa
     {
       return QStringList() << QObject::tr( "Path for new vector layer" );
     }
+
+    QColor modelColor() const override { return QColor( 122, 0, 47 ); /* burgundy */ };
 };
 
 /**
@@ -2404,6 +2456,8 @@ class CORE_EXPORT QgsProcessingParameterTypeColor : public QgsProcessingParamete
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 34, 157, 214 ); /* blue */ };
 };
 
 /**
@@ -2603,6 +2657,8 @@ class CORE_EXPORT QgsProcessingParameterTypeDateTime : public QgsProcessingParam
              << QgsProcessingOutputString::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 255, 131, 23 ); /* orange */ };
 };
 
 /**
@@ -2873,6 +2929,8 @@ class CORE_EXPORT QgsProcessingParameterTypePointCloudLayer : public QgsProcessi
              << QgsProcessingOutputFile::typeName()
              << QgsProcessingOutputFolder::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 137, 150, 171 ); /* cold gray */ };
 };
 
 /**
@@ -2943,6 +3001,8 @@ class CORE_EXPORT QgsProcessingParameterTypeAnnotationLayer : public QgsProcessi
              << QgsProcessingOutputMapLayer::typeName()
              << QgsProcessingOutputVariant::typeName();
     }
+
+    QColor modelColor() const override { return QColor( 137, 150, 171 ); /* cold gray */ };
 };
 
 /**
@@ -3003,6 +3063,8 @@ class CORE_EXPORT QgsProcessingParameterTypePointCloudDestination : public QgsPr
     {
       return QStringList() << QObject::tr( "Path for new point cloud layer" );
     }
+
+    QColor modelColor() const override { return QColor( 80, 80, 80 ); /* dark gray */ };
 };
 
 /**
@@ -3129,6 +3191,8 @@ class CORE_EXPORT QgsProcessingParameterTypeVectorTileDestination : public QgsPr
     {
       return QStringList() << QObject::tr( "Path for new vector tile layer" );
     }
+
+    QColor modelColor() const override { return QColor( 80, 80, 80 ); /* dark gray */ };
 };
 
 #endif // QGSPROCESSINGPARAMETERTYPEIMPL_H

src/gui/processing/models/qgsmodelarrowitem.cpp

@@ -20,6 +20,7 @@
 #include "qgsapplication.h"
 #include "qgsmodelgraphicsscene.h"
 #include "qgsmodelcomponentgraphicitem.h"
+#include "qgsmodelgraphicitem.h"
 #include <QPainter>
 #include <QApplication>
 #include <QPalette>
@@ -72,7 +73,7 @@ QgsModelArrowItem::QgsModelArrowItem( QgsModelComponentGraphicItem *startItem, M
 
 void QgsModelArrowItem::paint( QPainter *painter, const QStyleOptionGraphicsItem *, QWidget * )
 {
-  QColor color = mColor;
+  QColor color = mStartItem->linkColor( mStartEdge, mStartIndex );
 
   if ( mStartItem->state() == QgsModelComponentGraphicItem::Selected || mEndItem->state() == QgsModelComponentGraphicItem::Selected )
     color.setAlpha( 220 );
@@ -81,22 +82,23 @@ void QgsModelArrowItem::paint( QPainter *painter, const QStyleOptionGraphicsItem
   else
     color.setAlpha( 80 );
 
+  //
   QPen p = pen();
   p.setColor( color );
-  p.setWidth( 1 );
+  p.setWidth( 0 );
   painter->setPen( p );
+
   painter->setBrush( color );
   painter->setRenderHint( QPainter::Antialiasing );
 
-
   switch ( mStartMarker )
   {
-    case Marker::Circle:
-      painter->drawEllipse( mStartPoint, 3.0, 3.0 );
-      break;
     case Marker::ArrowHead:
       drawArrowHead( painter, mStartPoint, path().pointAtPercent( 0.0 ) - path().pointAtPercent( 0.05 ) );
       break;
+
+    // start marker are no longer drawn
+    case Marker::Circle:
     case Marker::NoMarker:
       break;
   }
@@ -113,7 +115,26 @@ void QgsModelArrowItem::paint( QPainter *painter, const QStyleOptionGraphicsItem
       break;
   }
 
+  painter->setBrush( color );
+  painter->setRenderHint( QPainter::Antialiasing );
   painter->setBrush( Qt::NoBrush );
+
+  // Set the painter back to regular stroke thickness
+  p = pen();
+  QColor endColor = mEndItem->linkColor( mEndEdge, mEndIndex );
+  color.setAlpha( 255 );
+
+  QLinearGradient gradient;
+  QPointF startPoint = path().pointAtPercent( 0.3 );
+  QPointF endPoint = path().pointAtPercent( 0.7 );
+  gradient.setStart( startPoint );
+  gradient.setFinalStop( endPoint );
+  gradient.setColorAt( 0, color );
+  gradient.setColorAt( 1, endColor );
+
+  p.setBrush( QBrush( gradient ) );
+  p.setWidth( 2 );
+  painter->setPen( p );
   painter->drawPath( path() );
 }
 

src/gui/processing/models/qgsmodelcomponentgraphicitem.cpp

@@ -29,6 +29,7 @@
 #include "qgsmodelviewmouseevent.h"
 #include "qgsmodelgroupboxdefinitionwidget.h"
 #include "qgsmessagelog.h"
+#include "qgsprocessingparameters.h"
 
 #include <QSvgRenderer>
 #include <QPicture>
@@ -496,40 +497,43 @@ QPixmap QgsModelComponentGraphicItem::iconPixmap() const
   return QPixmap();
 }
 
+
 void QgsModelComponentGraphicItem::updateButtonPositions()
 {
   mEditButton->setPosition( QPointF( itemSize().width() / 2.0 - mButtonSize.width() / 2.0 - BUTTON_MARGIN, itemSize().height() / 2.0 - mButtonSize.height() / 2.0 - BUTTON_MARGIN ) );
   mDeleteButton->setPosition( QPointF( itemSize().width() / 2.0 - mButtonSize.width() / 2.0 - BUTTON_MARGIN, mButtonSize.height() / 2.0 - itemSize().height() / 2.0 + BUTTON_MARGIN ) );
 
-  if ( mExpandTopButton )
-  {
-    const QPointF pt = linkPoint( Qt::TopEdge, -1, true );
-    mExpandTopButton->setPosition( QPointF( 0, pt.y() ) );
-  }
   if ( mExpandBottomButton )
   {
     const QPointF pt = linkPoint( Qt::BottomEdge, -1, false );
     mExpandBottomButton->setPosition( QPointF( 0, pt.y() ) );
+
+    bool collapsed = mComponent->linksCollapsed( Qt::BottomEdge );
+    for ( QgsModelDesignerSocketGraphicItem *socket : std::as_const( mOutSockets ) )
+    {
+      const QPointF pt = linkPoint( Qt::BottomEdge, socket->index(), false );
+      socket->setPosition( pt );
+      socket->setVisible( !collapsed );
+    }
   }
 
 
-  bool collapsed = mComponent->linksCollapsed( Qt::TopEdge );
-  for ( QgsModelDesignerSocketGraphicItem *socket : std::as_const( mInSockets ) )
+  if ( mExpandTopButton )
   {
-    const QPointF pt = linkPoint( Qt::TopEdge, socket->index(), true );
-    socket->setPosition( pt );
-    socket->setVisible( !collapsed );
-  }
+    const QPointF pt = linkPoint( Qt::TopEdge, -1, true );
+    mExpandTopButton->setPosition( QPointF( 0, pt.y() ) );
 
-  collapsed = mComponent->linksCollapsed( Qt::BottomEdge );
-  for ( QgsModelDesignerSocketGraphicItem *socket : std::as_const( mOutSockets ) )
-  {
-    const QPointF pt = linkPoint( Qt::BottomEdge, socket->index(), false );
-    socket->setPosition( pt );
-    socket->setVisible( !collapsed );
+    bool collapsed = mComponent->linksCollapsed( Qt::TopEdge );
+    for ( QgsModelDesignerSocketGraphicItem *socket : std::as_const( mInSockets ) )
+    {
+      const QPointF pt = linkPoint( Qt::TopEdge, socket->index(), true );
+      socket->setPosition( pt );
+      socket->setVisible( !collapsed );
+    }
   }
 }
 
+
 QSizeF QgsModelComponentGraphicItem::itemSize() const
 {
   return !mTempSize.isValid() ? mComponent->size() : mTempSize;
@@ -563,15 +567,19 @@ void QgsModelComponentGraphicItem::fold( Qt::Edge edge, bool folded )
 
   // TODO - this is not so nice, consider moving this to model class
   if ( QgsProcessingModelChildAlgorithm *child = dynamic_cast<QgsProcessingModelChildAlgorithm *>( mComponent.get() ) )
+  {
     mModel->childAlgorithm( child->childId() ).setLinksCollapsed( edge, folded );
+  }
   else if ( QgsProcessingModelParameter *param = dynamic_cast<QgsProcessingModelParameter *>( mComponent.get() ) )
+  {
     mModel->parameterComponent( param->parameterName() ).setLinksCollapsed( edge, folded );
+  }
   else if ( QgsProcessingModelOutput *output = dynamic_cast<QgsProcessingModelOutput *>( mComponent.get() ) )
+  {
     mModel->childAlgorithm( output->childId() ).modelOutput( output->name() ).setLinksCollapsed( edge, folded );
-
+  }
 
   updateButtonPositions();
-
   prepareGeometryChange();
   emit updateArrowPaths();
   emit changed();
@@ -627,8 +635,8 @@ QPointF QgsModelComponentGraphicItem::linkPoint( Qt::Edge edge, int index, bool
         const QFontMetricsF fm( mFont );
         const double w = fm.boundingRect( text ).width();
         const double h = fm.height() * 1.2 * ( pointIndex + 1 ) + fm.height() / 2.0;
-        const double y = h + itemSize().height() / 2.0 + 5;
-        const double x = !mComponent->linksCollapsed( Qt::BottomEdge ) ? ( -itemSize().width() / 2 + 33 + w + 5 ) : 10;
+        const double y = h + itemSize().height() / 2.0 + 6.4;
+        const double x = !mComponent->linksCollapsed( Qt::BottomEdge ) ? ( -itemSize().width() / 2 + 33 + w + 10 ) : 10.4;
         return QPointF( incoming ? -itemSize().width() / 2 + offsetX : x, y );
       }
       break;
@@ -756,8 +764,8 @@ QgsModelParameterGraphicItem::QgsModelParameterGraphicItem( QgsProcessingModelPa
   svg.render( &painter );
   painter.end();
 
-  if ( const QgsProcessingParameterDefinition *paramDef = model->parameterDefinition( parameter->parameterName() ) )
-    setLabel( paramDef->description() );
+  if ( const QgsProcessingParameterDefinition *parameterDefinition = model->parameterDefinition( parameter->parameterName() ) )
+    setLabel( parameterDefinition->description() );
   else
     setLabel( QObject::tr( "Error (%1)" ).arg( parameter->parameterName() ) );
 }
@@ -838,17 +846,59 @@ QString QgsModelParameterGraphicItem::linkPointText( Qt::Edge, int index ) const
     return QString();
   }
 
-
   if ( const QgsProcessingModelParameter *parameter = dynamic_cast< const QgsProcessingModelParameter * >( component() ) )
   {
     QString text = this->model()->parameterDefinition( parameter->parameterName() )->type();
+
+    // Getting the default value to append to the box name
+    if ( const QgsProcessingParameterDefinition *paramDef = this->model()->parameterDefinition( parameter->parameterName() ) )
+    {
+      const QVariant paramValue = paramDef->defaultValue();
+
+      if ( paramValue.isValid() )
+      {
+        text += ": " + paramDef->userFriendlyString( paramValue );
+      }
+    }
     return truncatedTextForItem( text );
   }
 
+  return QString();
+}
+
+
+QString QgsModelParameterGraphicItem::linkedParameterDataType( Qt::Edge /* unused in this implementation because parameters only have a bottom edge */, int index ) const
+{
+  if ( index < 0 )
+  {
+    return QString();
+  }
+
+  if ( const QgsProcessingModelParameter *parameter = dynamic_cast< const QgsProcessingModelParameter * >( component() ) )
+  {
+    return this->model()->parameterDefinition( parameter->parameterName() )->type();
+  }
 
   return QString();
 }
 
+
+QColor QgsModelParameterGraphicItem::linkColor( Qt::Edge /* unused in this implementation because parameters only have a bottom edge */, int index ) const
+{
+  if ( index < 0 )
+  {
+    return fallbackColor();
+  }
+
+  if ( const QgsProcessingModelParameter *parameter = dynamic_cast< const QgsProcessingModelParameter * >( component() ) )
+  {
+    return this->model()->parameterDefinition( parameter->parameterName() )->modelColor();
+  }
+
+  return fallbackColor();
+}
+
+
 void QgsModelParameterGraphicItem::updateStoredComponentPosition( const QPointF &pos, const QSizeF &size )
 {
   if ( QgsProcessingModelParameter *param = dynamic_cast<QgsProcessingModelParameter *>( component() ) )
@@ -1087,6 +1137,88 @@ int QgsModelChildAlgorithmGraphicItem::linkPointCount( Qt::Edge edge ) const
   return 0;
 }
 
+
+QString QgsModelComponentGraphicItem::linkedParameterDataType( Qt::Edge edge, int index ) const
+{
+  if ( const QgsProcessingModelChildAlgorithm *child = dynamic_cast<const QgsProcessingModelChildAlgorithm *>( component() ) )
+  {
+    if ( !child->algorithm() )
+    {
+      return QString();
+    }
+
+    switch ( edge )
+    {
+      case Qt::BottomEdge:
+      {
+        if ( index <= child->algorithm()->outputDefinitions().size() - 1 )
+        {
+          return child->algorithm()->outputDefinitions().at( index )->type();
+        }
+        return QString();
+      }
+      case Qt::TopEdge:
+      {
+        QgsProcessingParameterDefinitions params = child->algorithm()->parameterDefinitions();
+
+        if ( index <= params.size() - 1 )
+        {
+          return params.at( index )->type();
+        }
+
+        return QString();
+      }
+
+      case Qt::LeftEdge:
+      case Qt::RightEdge:
+        break;
+    }
+  }
+
+  return QString();
+}
+
+QColor QgsModelComponentGraphicItem::linkColor( Qt::Edge edge, int index ) const
+{
+  if ( const QgsProcessingModelChildAlgorithm *child = dynamic_cast<const QgsProcessingModelChildAlgorithm *>( component() ) )
+  {
+    if ( !child->algorithm() )
+    {
+      return fallbackColor();
+    }
+
+    switch ( edge )
+    {
+      case Qt::BottomEdge:
+      {
+        if ( index <= child->algorithm()->outputDefinitions().size() - 1 )
+        {
+          return child->algorithm()->outputDefinitions().at( index )->modelColor();
+        }
+        return fallbackColor();
+      }
+      case Qt::TopEdge:
+      {
+        QgsProcessingParameterDefinitions params = child->algorithm()->parameterDefinitions();
+
+        if ( index <= params.size() - 1 )
+        {
+          return params.at( index )->modelColor();
+        }
+
+        return fallbackColor();
+      }
+
+      case Qt::LeftEdge:
+      case Qt::RightEdge:
+        break;
+    }
+  }
+
+  return fallbackColor();
+}
+
+
 QString QgsModelChildAlgorithmGraphicItem::linkPointText( Qt::Edge edge, int index ) const
 {
   if ( index < 0 )
@@ -1099,6 +1231,7 @@ QString QgsModelChildAlgorithmGraphicItem::linkPointText( Qt::Edge edge, int ind
 
     const QVariantMap inputs = mResults.inputs();
     const QVariantMap outputs = mResults.outputs();
+
     switch ( edge )
     {
       case Qt::BottomEdge:
@@ -1115,10 +1248,6 @@ QString QgsModelChildAlgorithmGraphicItem::linkPointText( Qt::Edge edge, int ind
 
         const QgsProcessingOutputDefinition *output = child->algorithm()->outputDefinitions().at( index );
         QString title = output->description();
-        if ( outputs.contains( output->name() ) )
-        {
-          title += QStringLiteral( ": %1" ).arg( outputs.value( output->name() ).toString() );
-        }
         return truncatedTextForItem( title );
       }
 
@@ -1140,9 +1269,51 @@ QString QgsModelChildAlgorithmGraphicItem::linkPointText( Qt::Edge edge, int ind
           return QString();
         }
 
-        QString title = params.at( index )->description();
-        if ( !inputs.value( params.at( index )->name() ).toString().isEmpty() )
-          title += QStringLiteral( ": %1" ).arg( inputs.value( params.at( index )->name() ).toString() );
+        const QgsProcessingParameterDefinition *param = params.at( index );
+        QString name = param->name();
+        QString title = param->description();
+        QgsProcessingModelChildParameterSources paramSources = child->parameterSources().value( name );
+        QString parameterValueAsString;
+
+        if ( paramSources.empty() )
+        {
+          QgsProcessingModelChildParameterSource firstParameterSource = paramSources[0];
+
+          switch ( firstParameterSource.source() )
+          {
+            case Qgis::ProcessingModelChildParameterSource::ChildOutput:
+              parameterValueAsString = QStringLiteral( ": %1" ).arg(
+                firstParameterSource.friendlyIdentifier( const_cast<QgsProcessingModelAlgorithm *>( model() ) )
+              );
+              break;
+
+            case Qgis::ProcessingModelChildParameterSource::Expression:
+              parameterValueAsString = QStringLiteral( ": %1" ).arg( firstParameterSource.expression() );
+              break;
+
+            case Qgis::ProcessingModelChildParameterSource::ExpressionText:
+              parameterValueAsString = QStringLiteral( ": %1" ).arg( firstParameterSource.expressionText() );
+              break;
+
+            case Qgis::ProcessingModelChildParameterSource::ModelOutput:
+              parameterValueAsString = QStringLiteral( ": <%1>" ).arg( firstParameterSource.friendlyIdentifier( const_cast<QgsProcessingModelAlgorithm *>( model() ) ) );
+              break;
+
+            case Qgis::ProcessingModelChildParameterSource::ModelParameter:
+            {
+              const QString friendlyName = firstParameterSource.friendlyIdentifier( const_cast<QgsProcessingModelAlgorithm *>( model() ) );
+              parameterValueAsString = friendlyName.isEmpty() ? QStringLiteral( ":" ) : QStringLiteral( ": <%1>" ).arg( friendlyName );
+              break;
+            }
+
+            case Qgis::ProcessingModelChildParameterSource::StaticValue:
+            default:
+              const QVariant paramValue = paramSources[0].staticValue();
+              parameterValueAsString = QStringLiteral( ": %1" ).arg( param->userFriendlyString( paramValue ) );
+          }
+          title += parameterValueAsString;
+        }
+
         return truncatedTextForItem( title );
       }
 

src/gui/processing/models/qgsmodelcomponentgraphicitem.h

@@ -137,8 +137,22 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
      */
     void setItemRect( QRectF rect );
 
+    /**
+     * Returns the data type of the linked parameter at the specified \a index on the specified \a edge.
+     * 
+     * \since QGIS 4.0
+     */
+    virtual QString linkedParameterDataType( Qt::Edge edge, int index ) const;
+
 #ifndef SIP_RUN
 
+    /**
+     * Returns the color of the link at the specified \a index on the specified \a edge.
+     * 
+     * \since QGIS 4.0
+     */
+    virtual QColor linkColor( Qt::Edge edge, int index ) const;
+
     /**
      * Shows a preview of setting a new \a rect for the item.
      */
@@ -237,7 +251,7 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
 
     /**
      * Returns the output socket graphics items at the specified \a index.
-     * 
+     *
      * May return NULLPTR if no corresponding output socket exists.
      * \since QGIS 3.44
      */
@@ -363,6 +377,13 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
      */
     void updateButtonPositions();
 
+    /**
+     * Returns the fallback color if the parameter or output does not have a specific color.
+     * 
+     * \since QGIS 4.0
+     */
+    QColor fallbackColor() const { return mFallbackColor; };
+
   private:
     QSizeF itemSize() const;
 
@@ -400,6 +421,7 @@ class GUI_EXPORT QgsModelComponentGraphicItem : public QGraphicsObject
 
     bool mIsHovering = false;
     QSizeF mTempSize;
+    QColor mFallbackColor = QColor( 128, 128, 128 ); /* mid gray */
 };
 Q_DECLARE_OPERATORS_FOR_FLAGS( QgsModelComponentGraphicItem::Flags )
 
@@ -427,6 +449,10 @@ class GUI_EXPORT QgsModelParameterGraphicItem : public QgsModelComponentGraphicI
     void contextMenuEvent( QGraphicsSceneContextMenuEvent *event ) override;
     bool canDeleteComponent() override;
 
+    QString linkedParameterDataType( Qt::Edge, int index ) const override;
+
+    QColor linkColor( Qt::Edge edge, int index ) const override;
+
   protected:
     QColor fillColor( State state ) const override;
     QColor strokeColor( State state ) const override;

src/gui/processing/models/qgsmodelgraphicitem.cpp

@@ -21,6 +21,11 @@
 #include "qgsmodelgraphicsview.h"
 #include "qgsmodelviewtool.h"
 #include "qgsmodelviewmouseevent.h"
+#include "qgsprocessingmodelcomponent.h"
+#include "qgsprocessingoutputs.h"
+#include "qgsprocessingparameters.h"
+#include "qgsprocessingmodelchildalgorithm.h"
+#include "qgsprocessingalgorithm.h"
 #include <QGraphicsSceneMouseEvent>
 #include <QPainter>
 #include <QSvgRenderer>
@@ -180,13 +185,35 @@ QgsModelDesignerSocketGraphicItem::QgsModelDesignerSocketGraphicItem( QgsModelCo
 
 void QgsModelDesignerSocketGraphicItem::paint( QPainter *painter, const QStyleOptionGraphicsItem *, QWidget * )
 {
-  painter->setPen( QPen() );
-  painter->setBrush( QBrush( QColor( 0, 0, 0, mHoverState ? 200 : 33 ), Qt::SolidPattern ) );
+  QColor outlineColor = socketColor();
+  QColor fillColor = QColor( outlineColor );
+
+  if ( isInput() )
+  {
+    fillColor.setAlpha( isDefaultParameterValue() ? 30 : 255 );
+  }
+  else
+  {
+    // outputs are always filled sockets
+    fillColor.setAlpha( 255 );
+  }
+
+  // Outline style
+  painter->setPen( QPen( outlineColor, mHoverState ? mSocketOutlineWidth * 2 : mSocketOutlineWidth ) );
+
+  // Fill style
+  painter->setBrush( QBrush( fillColor, Qt::SolidPattern ) );
 
   painter->setRenderHint( QPainter::Antialiasing );
 
-  constexpr float DISPLAY_SIZE = 3.2;
-  painter->drawEllipse( position(), DISPLAY_SIZE, DISPLAY_SIZE );
+  // Radius of the socket circle
+  constexpr float DISPLAY_SIZE = 4;
+
+  // Offset of the socket to separate from the label
+  constexpr float ELLIPSE_OFFSET = 0.4;
+  QPointF ellipsePosition = QPointF( position().x() + ELLIPSE_OFFSET, position().y() + ELLIPSE_OFFSET );
+  painter->drawEllipse( ellipsePosition, DISPLAY_SIZE, DISPLAY_SIZE );
+
   /* Uncomment to display bounding box */
 #if 0
   painter->save();
@@ -197,4 +224,70 @@ void QgsModelDesignerSocketGraphicItem::paint( QPainter *painter, const QStyleOp
 #endif
 }
 
+
+QColor QgsModelDesignerSocketGraphicItem::socketColor() const
+{
+  return mComponentItem->linkColor( mEdge, mIndex );
+}
+
+
+bool QgsModelDesignerSocketGraphicItem::isDefaultParameterValue() const
+{
+  if ( !mComponent )
+  {
+    return false;
+  }
+
+  const QgsProcessingModelChildAlgorithm *child = dynamic_cast<const QgsProcessingModelChildAlgorithm *>( mComponent );
+
+  if ( !child )
+  {
+    return false;
+  }
+
+  bool isDefaultValue = true;
+
+  // We can only know if the socket should be filled if the algorithm is non null
+  if ( child->algorithm() )
+  {
+    switch ( mEdge )
+    {
+      // Input params
+      case Qt::TopEdge:
+      {
+        const QgsProcessingParameterDefinitions params = child->algorithm()->parameterDefinitions();
+        const QgsProcessingParameterDefinition *param = params.value( mIndex );
+        if ( !param )
+          break;
+
+        const QString name = param->name();
+
+        QgsProcessingModelChildParameterSources paramSources = child->parameterSources().value( name );
+        if ( paramSources.empty() )
+        {
+          break;
+        }
+
+        // The default value can only happen in the case of the parameter uses a static value
+        if ( paramSources[0].source() != Qgis::ProcessingModelChildParameterSource::StaticValue )
+        {
+          isDefaultValue = false;
+          break;
+        }
+
+        isDefaultValue = paramSources[0].staticValue() == param->defaultValue();
+        break;
+      }
+
+      // Outputs
+      case Qt::BottomEdge:
+      case Qt::LeftEdge:
+      case Qt::RightEdge:
+        break;
+    }
+  }
+
+  return isDefaultValue;
+}
+
 ///@endcond

src/gui/processing/models/qgsmodelgraphicitem.h

@@ -171,7 +171,7 @@ class GUI_EXPORT QgsModelDesignerSocketGraphicItem : public QgsModelDesignerFlat
     void paint( QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget = nullptr ) override;
 
     /**
-     * Returns the index of this socket in either QgsModelDesignerSocketGraphicItem::mInSockets 
+     * Returns the index of this socket in either QgsModelDesignerSocketGraphicItem::mInSockets
      * or QgsModelDesignerSocketGraphicItem::mOutSockets array
      */
     int index() const { return mIndex; };
@@ -201,11 +201,27 @@ class GUI_EXPORT QgsModelDesignerSocketGraphicItem : public QgsModelDesignerFlat
      */
     QgsModelComponentGraphicItem *componentItem() { return mComponentItem; };
 
+    /*
+     * Returns the color of the socket based on the type of data the param corresponds to.
+     * \since QGIS 4.0
+     */
+    QColor socketColor() const;
+
+    /*
+     * Returns TRUE if the parameter is set to the default parameter value.
+     * \since QGIS 4.0
+     */
+    bool isDefaultParameterValue() const;
+  signals:
+
+
   private:
     QgsModelComponentGraphicItem *mComponentItem = nullptr;
     QgsProcessingModelComponent *mComponent = nullptr;
     int mIndex = -1;
     Qt::Edge mEdge = Qt::Edge::TopEdge;
+    QColor mSocketColor = QColor( 200, 200, 200 );
+    float mSocketOutlineWidth = 1.5;
 };
 
 ///@endcond

src/gui/processing/models/qgsmodelviewtoollink.cpp

@@ -122,7 +122,7 @@ void QgsModelViewToolLink::modelReleaseEvent( QgsModelViewMouseEvent *event )
    * whether the user dragged :
    *    - From an input socket to an output socket
    *    - From an output socket to an input socket
-   * 
+   *
    * In the code, we always come back to the first case
    */
   if ( !mToSocket->isInput() )

tests/src/analysis/testqgsprocessing.cpp

@@ -2996,6 +2996,9 @@ void TestQgsProcessing::parameterBoolean()
   QCOMPARE( def->valueAsPythonString( QVariant(), context ), QStringLiteral( "None" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( true ) ), QString( "true" ) );
+  QCOMPARE( def->userFriendlyString( QVariant( false ) ), QString( "false" ) );
+
   QString pythonCode = def->asPythonString();
   QCOMPARE( pythonCode, QStringLiteral( "QgsProcessingParameterBoolean('non_optional_default_false', '', defaultValue=None)" ) );
 
@@ -3211,6 +3214,8 @@ void TestQgsProcessing::parameterCrs()
   QVERIFY( def->checkValueIsAcceptable( QgsProcessingFeatureSourceDefinition( QgsProperty::fromValue( QVariant::fromValue( r1 ) ) ) ) );
   QVERIFY( def->checkValueIsAcceptable( QgsProcessingOutputLayerDefinition( r1->id() ) ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( "EPSG:3857" ) ), QgsCoordinateReferenceSystem( QStringLiteral( "EPSG:3857" ) ).userFriendlyIdentifier( Qgis::CrsIdentifierType::ShortString ) );
+
   // using map layer
   QVariantMap params;
   params.insert( "non_optional", v1->id() );
@@ -3870,6 +3875,10 @@ void TestQgsProcessing::parameterExtent()
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "c:\\test\\new data\\test.dat" ), context ), QVariant( QStringLiteral( "c:\\test\\new data\\test.dat" ) ) );
   QCOMPARE( def->valueAsJsonObject( QgsGeometry::fromWkt( QStringLiteral( "LineString( 10 10, 20 20)" ) ), context ), QVariant( QStringLiteral( "LineString (10 10, 20 20)" ) ) );
 
+  QCOMPARE( def->userFriendlyString( QgsReferencedRectangle( QgsRectangle( 11, 12, 13, 14 ), QgsCoordinateReferenceSystem( "epsg:4326" ) ) ), QStringLiteral( "[EPSG:4326] Polygon" ) );
+  QCOMPARE( def->userFriendlyString( QgsRectangle( 11, 12, 13, 14 ) ), QStringLiteral( "Polygon" ) );
+  QCOMPARE( def->userFriendlyString( QVariant( "1,2,3,4" ) ), QStringLiteral( "1,2,3,4" ) );
+
   bool ok = false;
   QCOMPARE( def->valueAsString( QVariant(), context, ok ), QString() );
   QVERIFY( ok );
@@ -4111,6 +4120,12 @@ void TestQgsProcessing::parameterPoint()
   QCOMPARE( def->valueAsJsonObject( QgsReferencedPointXY( QgsPointXY( 11, 12 ), QgsCoordinateReferenceSystem( "epsg:4326" ) ), context ), QVariant( QStringLiteral( "11,12 [EPSG:4326]" ) ) );
   QCOMPARE( def->valueAsJsonObject( QgsGeometry::fromWkt( QStringLiteral( "LineString( 10 10, 20 20)" ) ), context ), QVariant( QStringLiteral( "LineString (10 10, 20 20)" ) ) );
 
+  QCOMPARE( def->userFriendlyString( QgsReferencedPointXY( QgsPointXY( 11, 12 ), QgsCoordinateReferenceSystem( "epsg:4326" ) ) ), QStringLiteral( "[EPSG:4326] 11, 12" ) );
+  QCOMPARE( def->userFriendlyString( QgsPointXY( 11, 12 ) ), QStringLiteral( "11, 12" ) );
+
+  QCOMPARE( def->userFriendlyString( QgsReferencedPointXY( QgsPointXY( 11.1, 12.2 ), QgsCoordinateReferenceSystem( "epsg:4326" ) ) ), QStringLiteral( "[EPSG:4326] 11.1, 12.2" ) );
+  QCOMPARE( def->userFriendlyString( QgsPointXY( 11.1, 12.2 ) ), QStringLiteral( "11.1, 12.2" ) );
+
   bool ok = false;
   QCOMPARE( def->valueAsString( QVariant(), context, ok ), QString() );
   QVERIFY( ok );
@@ -4326,6 +4341,10 @@ void TestQgsProcessing::parameterGeometry()
   // With Srid as string
   QCOMPARE( def->valueAsPythonString( QgsReferencedGeometry( QgsGeometry::fromWkt( QStringLiteral( "LineString( 10 10, 20 20)" ) ), QgsCoordinateReferenceSystem( "EPSG:4326" ) ), context ), QStringLiteral( "'CRS=EPSG:4326;LineString (10 10, 20 20)'" ) );
 
+  QCOMPARE( def->userFriendlyString( QgsGeometry::fromWkt( QStringLiteral( "Polygon ((11.1 12.2, 13.3 12.2, 13.3 14.4, 11.1 14.4, 11.1 12.2))" ) ) ), QStringLiteral( "Polygon" ) );
+  QCOMPARE( def->userFriendlyString( QgsReferencedGeometry( QgsGeometry::fromWkt( QStringLiteral( "LineString( 10 10, 20 20)" ) ), QgsCoordinateReferenceSystem( "EPSG:4326" ) ) ), QStringLiteral( "[EPSG:4326] Line" ) );
+  QCOMPARE( def->userFriendlyString( QStringLiteral( "Polygon ((11.1 12.2, 13.3 12.2, 13.3 14.4, 11.1 14.4, 11.1 12.2))" ) ), QStringLiteral( "Polygon" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( "LineString( 10 10, 20 20)", context ), QVariant( QStringLiteral( "LineString( 10 10, 20 20)" ) ) );
   QCOMPARE( def->valueAsJsonObject( QgsGeometry::fromWkt( QStringLiteral( "LineString( 10 10, 20 20)" ) ), context ), QVariant( QStringLiteral( "LineString (10 10, 20 20)" ) ) );
@@ -4505,6 +4524,8 @@ void TestQgsProcessing::parameterFile()
   QCOMPARE( def->valueAsJsonObject( "uri='complex' username=\"complex\"", context ), QVariant( QStringLiteral( "uri='complex' username=\"complex\"" ) ) );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "c:\\test\\new data\\test.dat" ), context ), QVariant( QStringLiteral( "c:\\test\\new data\\test.dat" ) ) );
 
+  QCOMPARE( def->userFriendlyString( "bricks.bmp" ), QStringLiteral( "bricks.bmp" ) );
+
   const QString testDataDir = QStringLiteral( TEST_DATA_DIR ) + '/'; //defined in CmakeLists.txt
   // ensure valueAsJsonObject doesn't try to load a file path as a layer
   QCOMPARE( context.temporaryLayerStore()->count(), 0 );
@@ -5256,6 +5277,8 @@ void TestQgsProcessing::parameterDistance()
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "1.1" ), context ), QStringLiteral( "1.1" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( 5 ) ), QStringLiteral( "5 ft" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( 5 ) );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "1.1" ), context ), QVariant( QStringLiteral( "1.1" ) ) );
@@ -5371,6 +5394,7 @@ void TestQgsProcessing::parameterArea()
   QCOMPARE( def->valueAsPythonString( 5, context ), QStringLiteral( "5" ) );
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "1.1" ), context ), QStringLiteral( "1.1" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
+  QCOMPARE( def->userFriendlyString( QVariant( 5 ) ), QStringLiteral( "5 square feet" ) );
 
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( 5 ) );
@@ -5487,6 +5511,7 @@ void TestQgsProcessing::parameterVolume()
   QCOMPARE( def->valueAsPythonString( 5, context ), QStringLiteral( "5" ) );
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "1.1" ), context ), QStringLiteral( "1.1" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
+  QCOMPARE( def->userFriendlyString( QVariant( 5 ) ), QStringLiteral( "5 cubic feet" ) );
 
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( 5 ) );
@@ -5600,6 +5625,8 @@ void TestQgsProcessing::parameterDuration()
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "1.1" ), context ), QStringLiteral( "1.1" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( 5 ) ), QStringLiteral( "5 d" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( 5 ) );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "1.1" ), context ), QVariant( QStringLiteral( "1.1" ) ) );
@@ -5703,6 +5730,8 @@ void TestQgsProcessing::parameterScale()
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "1.1" ), context ), QStringLiteral( "1.1" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( 5 ) ), QStringLiteral( "5" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( "5" ) );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "1.1" ), context ), QVariant( QStringLiteral( "1.1" ) ) );
@@ -5822,6 +5851,8 @@ void TestQgsProcessing::parameterNumber()
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "1.1" ), context ), QStringLiteral( "1.1" ) );
   QCOMPARE( def->valueAsPythonString( QVariant::fromValue( QgsProperty::fromExpression( "\"a\"=1" ) ), context ), QStringLiteral( "QgsProperty.fromExpression('\"a\"=1')" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( 5 ) ), QStringLiteral( "5" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( "5" ) );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "1.1" ), context ), QVariant( QStringLiteral( "1.1" ) ) );
@@ -6443,6 +6474,10 @@ void TestQgsProcessing::parameterEnum()
   QCOMPARE( def->valueAsPythonComment( QVariantList() << 1 << 2, context ), QStringLiteral( "B,C" ) );
   QCOMPARE( def->valueAsPythonComment( QStringLiteral( "1,2" ), context ), QStringLiteral( "B,C" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( 0 ) ), QString( "A" ) );
+  QCOMPARE( def->userFriendlyString( QVariant( 1 ) ), QString( "B" ) );
+  QCOMPARE( def->userFriendlyString( QVariant( 2 ) ), QString( "C" ) );
+
   pythonCode = def->asPythonString();
   QCOMPARE( pythonCode, QStringLiteral( "QgsProcessingParameterEnum('non_optional', '', options=['A','B','C'], allowMultiple=True, usesStaticStrings=False, defaultValue=5)" ) );
 
@@ -6694,6 +6729,8 @@ void TestQgsProcessing::parameterString()
   QCOMPARE( def->valueAsPythonString( "uri='complex' username=\"complex\"", context ), QStringLiteral( "'uri=\\'complex\\' username=\"complex\"'" ) );
   QCOMPARE( def->valueAsPythonString( QStringLiteral( "c:\\test\\new data\\test.dat" ), context ), QStringLiteral( "'c:\\\\test\\\\new data\\\\test.dat'" ) );
 
+  QCOMPARE( def->userFriendlyString( QVariant( "Hello" ) ), QStringLiteral( "Hello" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( 5, context ), QVariant( 5 ) );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "abc" ), context ), QVariant( QStringLiteral( "abc" ) ) );
@@ -9711,6 +9748,8 @@ void TestQgsProcessing::parameterColor()
   QCOMPARE( def->valueAsPythonString( QColor( 255, 0, 0 ), context ), QStringLiteral( "QColor(255, 0, 0)" ) );
   QCOMPARE( def->valueAsPythonString( QColor( 255, 0, 0, 100 ), context ), QStringLiteral( "QColor(255, 0, 0, 100)" ) );
 
+  QCOMPARE( def->userFriendlyString( QColor( 255, 0, 0 ) ), QStringLiteral( "#ff0000" ) );
+
   QCOMPARE( def->valueAsJsonObject( QVariant(), context ), QVariant() );
   QCOMPARE( def->valueAsJsonObject( QStringLiteral( "#ff0000" ), context ), QVariant( QStringLiteral( "#ff0000" ) ) );
   QCOMPARE( def->valueAsJsonObject( QColor(), context ), QVariant( QString() ) );
@@ -11174,6 +11213,10 @@ void TestQgsProcessing::parameterDateTime()
   QCOMPARE( def->valueAsString( QDate( 2014, 12, 31 ), context, ok ), QStringLiteral( "2014-12-31" ) );
   QVERIFY( ok );
 
+  QCOMPARE( def->userFriendlyString( QDate( 2014, 12, 31 ) ), QStringLiteral( "2014-12-31" ) );
+  QCOMPARE( def->userFriendlyString( QTime( 12, 11, 10 ) ), QStringLiteral( "12:11:10" ) );
+  QCOMPARE( def->userFriendlyString( QDateTime( QDate( 2014, 12, 31 ), QTime( 12, 11, 10 ) ) ), QStringLiteral( "2014-12-31T12:11:10" ) );
+
   pythonCode = def->asPythonString();
   QCOMPARE( pythonCode, QStringLiteral( "QgsProcessingParameterDateTime('non_optional', '', type=QgsProcessingParameterDateTime.Date, minValue=QDateTime(QDate(2015, 1, 1), QTime(0, 0, 0)), maxValue=QDateTime(QDate(2015, 12, 31), QTime(0, 0, 0)), defaultValue=QDate(2010, 4, 3))" ) );