[processing][FEATURE] Add api for setting model component colors, and expose

the option to set manual colors for individual model comments

python/core/auto_generated/processing/models/qgsprocessingmodelcomponent.sip.in

@@ -69,6 +69,27 @@ Sets the ``size`` of the model component within the graphical modeler.
 
 .. seealso:: :py:func:`size`
 
+.. versionadded:: 3.14
+%End
+
+    QColor color() const;
+%Docstring
+Returns the color of the model component within the graphical modeler.
+
+An invalid color indicates that the default color for the component should be used.
+
+.. seealso:: :py:func:`setColor`
+
+.. versionadded:: 3.14
+%End
+
+    void setColor( const QColor &color );
+%Docstring
+Sets the ``color`` of the model component within the graphical modeler. An invalid ``color``
+indicates that the default color for the component should be used.
+
+.. seealso:: :py:func:`color`
+
 .. versionadded:: 3.14
 %End
 

python/core/core_auto.sip

@@ -428,6 +428,7 @@
 %Include auto_generated/processing/models/qgsprocessingmodelchildparametersource.sip
 %Include auto_generated/processing/models/qgsprocessingmodelcomment.sip
 %Include auto_generated/processing/models/qgsprocessingmodelcomponent.sip
+%Include auto_generated/processing/models/qgsprocessingmodelgroupbox.sip
 %Include auto_generated/processing/models/qgsprocessingmodeloutput.sip
 %Include auto_generated/processing/models/qgsprocessingmodelparameter.sip
 %Include auto_generated/processing/qgsprocessing.sip

python/gui/auto_generated/processing/qgsprocessingparameterdefinitionwidget.sip.in

@@ -157,6 +157,24 @@ Returns the comments for the parameter.
 
 .. seealso:: :py:func:`setComments`
 
+.. versionadded:: 3.14
+%End
+
+    void setCommentColor( const QColor &color );
+%Docstring
+Sets the color for the comments for the parameter.
+
+.. seealso:: :py:func:`commentColor`
+
+.. versionadded:: 3.14
+%End
+
+    QColor commentColor() const;
+%Docstring
+Returns the color for the comments for the parameter.
+
+.. seealso:: :py:func:`setCommentColor`
+
 .. versionadded:: 3.14
 %End
 

python/gui/auto_generated/qgscolorbutton.sip.in

@@ -210,11 +210,12 @@ Sets the string to use for the "no color" option in the button's drop-down menu.
    dialog
 %End
 
-    void setShowNull( bool showNull );
+    void setShowNull( bool showNull, const QString &nullString = QString() );
 %Docstring
 Sets whether a set to null (clear) option is shown in the button's drop-down menu.
 
 :param showNull: set to ``True`` to show a null option
+:param nullString: translated string to use for the null option. If not set, a default "Clear Color" string will be used.
 
 .. seealso:: :py:func:`showNull`
 

python/plugins/processing/modeler/ModelerGraphicItem.py

@@ -63,17 +63,20 @@ class ModelerInputGraphicItem(QgsModelParameterGraphicItem):
     def edit(self, edit_comment=False):
         existing_param = self.model().parameterDefinition(self.component().parameterName())
         comment = self.component().comment().description()
+        comment_color = self.component().comment().color()
         new_param = None
         if ModelerParameterDefinitionDialog.use_legacy_dialog(param=existing_param):
             # boo, old api
             dlg = ModelerParameterDefinitionDialog(self.model(),
                                                    param=existing_param)
             dlg.setComments(comment)
+            dlg.setCommentColor(comment_color)
             if edit_comment:
                 dlg.switchToCommentTab()
             if dlg.exec_():
                 new_param = dlg.param
                 comment = dlg.comments()
+                comment_color = dlg.commentColor()
         else:
             # yay, use new API!
             context = createContext()
@@ -84,12 +87,14 @@ class ModelerInputGraphicItem(QgsModelParameterGraphicItem):
                                                          definition=existing_param,
                                                          algorithm=self.model())
             dlg.setComments(comment)
+            dlg.setCommentColor(comment_color)
             if edit_comment:
                 dlg.switchToCommentTab()
 
             if dlg.exec_():
                 new_param = dlg.createParameter(existing_param.name())
                 comment = dlg.comments()
+                comment_color = dlg.commentColor()
 
         if new_param is not None:
             self.aboutToChange.emit(self.tr('Edit {}').format(new_param.description()))
@@ -97,6 +102,7 @@ class ModelerInputGraphicItem(QgsModelParameterGraphicItem):
             self.component().setParameterName(new_param.name())
             self.component().setDescription(new_param.name())
             self.component().comment().setDescription(comment)
+            self.component().comment().setColor(comment_color)
             self.model().addModelParameter(new_param, self.component())
             self.setLabel(new_param.description())
             self.requestModelRepaint.emit()
@@ -125,6 +131,7 @@ class ModelerChildAlgorithmGraphicItem(QgsModelChildAlgorithmGraphicItem):
         dlg = ModelerParametersDialog(elemAlg, self.model(), self.component().childId(),
                                       self.component().configuration())
         dlg.setComments(self.component().comment().description())
+        dlg.setCommentColor(self.component().comment().color())
         if edit_comment:
             dlg.switchToCommentTab()
         if dlg.exec_():
@@ -160,6 +167,7 @@ class ModelerOutputGraphicItem(QgsModelOutputGraphicItem):
         dlg = ModelerParameterDefinitionDialog(self.model(),
                                                param=self.model().parameterDefinition(param_name))
         dlg.setComments(self.component().comment().description())
+        dlg.setCommentColor(self.component().comment().color())
         if edit_comment:
             dlg.switchToCommentTab()
 
@@ -169,6 +177,7 @@ class ModelerOutputGraphicItem(QgsModelOutputGraphicItem):
             model_output.setDefaultValue(dlg.param.defaultValue())
             model_output.setMandatory(not (dlg.param.flags() & QgsProcessingParameterDefinition.FlagOptional))
             model_output.comment().setDescription(dlg.comments())
+            model_output.comment().setColor(dlg.commentColor())
             self.aboutToChange.emit(self.tr('Edit {}').format(model_output.description()))
             self.model().updateDestinationParameters()
             self.requestModelRepaint.emit()

python/plugins/processing/modeler/ModelerParameterDefinitionDialog.py

@@ -36,9 +36,12 @@ from qgis.PyQt.QtWidgets import (QDialog,
                                  QMessageBox,
                                  QTabWidget,
                                  QWidget,
-                                 QTextEdit)
+                                 QTextEdit,
+                                 QHBoxLayout)
+from qgis.PyQt.QtGui import QColor
 
-from qgis.gui import (QgsProcessingLayerOutputDestinationWidget)
+from qgis.gui import (QgsProcessingLayerOutputDestinationWidget,
+                      QgsColorButton)
 from qgis.core import (QgsApplication,
                        QgsSettings,
                        QgsProcessing,
@@ -210,8 +213,8 @@ class ModelerParameterDefinitionDialog(QDialog):
             if self.param is not None:
                 self.shapetypeCombo.setCurrentIndex(self.shapetypeCombo.findData(self.param.dataTypes()[0]))
             self.verticalLayout.addWidget(self.shapetypeCombo)
-        elif (self.paramType == parameters.PARAMETER_MULTIPLE
+        elif (self.paramType == parameters.PARAMETER_MULTIPLE or
-              or isinstance(self.param, QgsProcessingParameterMultipleLayers)):
+              isinstance(self.param, QgsProcessingParameterMultipleLayers)):
             self.verticalLayout.addWidget(QLabel(self.tr('Data type')))
             self.datatypeCombo = QComboBox()
             self.datatypeCombo.addItem(self.tr('Any Map Layer'), QgsProcessing.TypeMapLayer)
@@ -225,8 +228,8 @@ class ModelerParameterDefinitionDialog(QDialog):
             if self.param is not None:
                 self.datatypeCombo.setCurrentIndex(self.datatypeCombo.findData(self.param.layerType()))
             self.verticalLayout.addWidget(self.datatypeCombo)
-        elif (self.paramType == parameters.PARAMETER_MAP_LAYER or
+        elif (self.paramType == parameters.PARAMETER_MAP_LAYER
-              isinstance(self.param, QgsProcessingParameterMapLayer)):
+              or isinstance(self.param, QgsProcessingParameterMapLayer)):
             self.verticalLayout.addWidget(QLabel(self.tr('Data type')))
             self.datatypeCombo = QComboBox()
             self.datatypeCombo.addItem(self.tr('Any Map Layer'), QgsProcessing.TypeMapLayer)
@@ -239,11 +242,11 @@ class ModelerParameterDefinitionDialog(QDialog):
             if self.param is not None:
                 self.datatypeCombo.setCurrentIndex(self.datatypeCombo.findData(self.param.dataTypes()[0]))
             self.verticalLayout.addWidget(self.datatypeCombo)
-        elif (self.paramType in (parameters.PARAMETER_NUMBER, parameters.PARAMETER_DISTANCE, parameters.PARAMETER_SCALE)
+        elif (self.paramType in (parameters.PARAMETER_NUMBER, parameters.PARAMETER_DISTANCE, parameters.PARAMETER_SCALE) or
-              or isinstance(self.param, (QgsProcessingParameterNumber, QgsProcessingParameterDistance, QgsProcessingParameterScale))):
+              isinstance(self.param, (QgsProcessingParameterNumber, QgsProcessingParameterDistance, QgsProcessingParameterScale))):
 
-            if (self.paramType == parameters.PARAMETER_DISTANCE
+            if (self.paramType == parameters.PARAMETER_DISTANCE or
-                    or isinstance(self.param, QgsProcessingParameterDistance)):
+                    isinstance(self.param, QgsProcessingParameterDistance)):
                 self.verticalLayout.addWidget(QLabel(self.tr('Linked input')))
                 self.parentCombo = QComboBox()
                 self.parentCombo.addItem('', '')
@@ -334,15 +337,26 @@ class ModelerParameterDefinitionDialog(QDialog):
         self.commentLayout = QVBoxLayout()
         self.commentEdit = QTextEdit()
         self.commentEdit.setAcceptRichText(False)
-        self.commentLayout.addWidget(self.commentEdit)
+        self.commentLayout.addWidget(self.commentEdit, 1)
+
+        hl = QHBoxLayout()
+        hl.setContentsMargins(0, 0, 0, 0)
+        hl.addWidget(QLabel(self.tr('Color')))
+        self.comment_color_button = QgsColorButton()
+        self.comment_color_button.setAllowOpacity(True)
+        self.comment_color_button.setWindowTitle(self.tr('Comment Color'))
+        self.comment_color_button.setShowNull(True, self.tr('Default'))
+        hl.addWidget(self.comment_color_button)
+        self.commentLayout.addLayout(hl)
+
         w2 = QWidget()
         w2.setLayout(self.commentLayout)
         self.tab.addTab(w2, self.tr('Comments'))
 
         self.buttonBox = QDialogButtonBox(self)
         self.buttonBox.setOrientation(Qt.Horizontal)
-        self.buttonBox.setStandardButtons(QDialogButtonBox.Cancel
+        self.buttonBox.setStandardButtons(QDialogButtonBox.Cancel |
-                                          | QDialogButtonBox.Ok)
+                                          QDialogButtonBox.Ok)
         self.buttonBox.setObjectName('buttonBox')
         self.buttonBox.accepted.connect(self.accept)
         self.buttonBox.rejected.connect(self.reject)
@@ -357,6 +371,15 @@ class ModelerParameterDefinitionDialog(QDialog):
     def comments(self):
         return self.commentEdit.toPlainText()
 
+    def setCommentColor(self, color):
+        if color.isValid():
+            self.comment_color_button.setColor(color)
+        else:
+            self.comment_color_button.setToNull()
+
+    def commentColor(self):
+        return self.comment_color_button.color() if not self.comment_color_button.isNull() else QColor()
+
     def accept(self):
         description = self.nameTextBox.text()
         if description.strip() == '':
@@ -374,8 +397,8 @@ class ModelerParameterDefinitionDialog(QDialog):
                 i += 1
         else:
             name = self.param.name()
-        if (self.paramType == parameters.PARAMETER_TABLE_FIELD
+        if (self.paramType == parameters.PARAMETER_TABLE_FIELD or
-                or isinstance(self.param, QgsProcessingParameterField)):
+                isinstance(self.param, QgsProcessingParameterField)):
             if self.parentCombo.currentIndex() < 0:
                 QMessageBox.warning(self, self.tr('Unable to define parameter'),
                                     self.tr('Wrong or missing parameter values'))
@@ -388,39 +411,39 @@ class ModelerParameterDefinitionDialog(QDialog):
             self.param = QgsProcessingParameterField(name, description, defaultValue=default,
                                                      parentLayerParameterName=parent, type=datatype,
                                                      allowMultiple=self.multipleCheck.isChecked())
-        elif (self.paramType == parameters.PARAMETER_BAND
+        elif (self.paramType == parameters.PARAMETER_BAND or
-              or isinstance(self.param, QgsProcessingParameterBand)):
+              isinstance(self.param, QgsProcessingParameterBand)):
             if self.parentCombo.currentIndex() < 0:
                 QMessageBox.warning(self, self.tr('Unable to define parameter'),
                                     self.tr('Wrong or missing parameter values'))
                 return
             parent = self.parentCombo.currentData()
             self.param = QgsProcessingParameterBand(name, description, None, parent)
-        elif (self.paramType == parameters.PARAMETER_MAP_LAYER
+        elif (self.paramType == parameters.PARAMETER_MAP_LAYER or
-              or isinstance(self.param, QgsProcessingParameterMapLayer)):
+              isinstance(self.param, QgsProcessingParameterMapLayer)):
             self.param = QgsProcessingParameterMapLayer(
                 name, description, types=[self.datatypeCombo.currentData()])
-        elif (self.paramType == parameters.PARAMETER_RASTER
+        elif (self.paramType == parameters.PARAMETER_RASTER or
-              or isinstance(self.param, QgsProcessingParameterRasterLayer)):
+              isinstance(self.param, QgsProcessingParameterRasterLayer)):
             self.param = QgsProcessingParameterRasterLayer(
                 name, description)
-        elif (self.paramType == parameters.PARAMETER_TABLE
+        elif (self.paramType == parameters.PARAMETER_TABLE or
-              or isinstance(self.param, QgsProcessingParameterVectorLayer)):
+              isinstance(self.param, QgsProcessingParameterVectorLayer)):
             self.param = QgsProcessingParameterVectorLayer(
                 name, description,
                 [self.shapetypeCombo.currentData()])
-        elif (self.paramType == parameters.PARAMETER_VECTOR
+        elif (self.paramType == parameters.PARAMETER_VECTOR or
-              or isinstance(self.param, QgsProcessingParameterFeatureSource)):
+              isinstance(self.param, QgsProcessingParameterFeatureSource)):
             self.param = QgsProcessingParameterFeatureSource(
                 name, description,
                 [self.shapetypeCombo.currentData()])
-        elif (self.paramType == parameters.PARAMETER_MULTIPLE
+        elif (self.paramType == parameters.PARAMETER_MULTIPLE or
-              or isinstance(self.param, QgsProcessingParameterMultipleLayers)):
+              isinstance(self.param, QgsProcessingParameterMultipleLayers)):
             self.param = QgsProcessingParameterMultipleLayers(
                 name, description,
                 self.datatypeCombo.currentData())
-        elif (self.paramType == parameters.PARAMETER_DISTANCE
+        elif (self.paramType == parameters.PARAMETER_DISTANCE or
-              or isinstance(self.param, QgsProcessingParameterDistance)):
+              isinstance(self.param, QgsProcessingParameterDistance)):
             self.param = QgsProcessingParameterDistance(name, description,
                                                         self.defaultTextBox.text())
             try:
@@ -442,12 +465,12 @@ class ModelerParameterDefinitionDialog(QDialog):
             parent = self.parentCombo.currentData()
             if parent:
                 self.param.setParentParameterName(parent)
-        elif (self.paramType == parameters.PARAMETER_SCALE
+        elif (self.paramType == parameters.PARAMETER_SCALE or
-              or isinstance(self.param, QgsProcessingParameterScale)):
+              isinstance(self.param, QgsProcessingParameterScale)):
             self.param = QgsProcessingParameterScale(name, description,
                                                      self.defaultTextBox.text())
-        elif (self.paramType == parameters.PARAMETER_NUMBER
+        elif (self.paramType == parameters.PARAMETER_NUMBER or
-              or isinstance(self.param, QgsProcessingParameterNumber)):
+              isinstance(self.param, QgsProcessingParameterNumber)):
 
             type = self.type_combo.currentData()
             self.param = QgsProcessingParameterNumber(name, description, type,

python/plugins/processing/modeler/ModelerParametersDialog.py

@@ -27,6 +27,7 @@ from qgis.PyQt.QtCore import Qt
 from qgis.PyQt.QtWidgets import (QDialog, QDialogButtonBox, QLabel, QLineEdit,
                                  QFrame, QPushButton, QSizePolicy, QVBoxLayout,
                                  QHBoxLayout, QWidget, QTabWidget, QTextEdit)
+from qgis.PyQt.QtGui import QColor
 
 from qgis.core import (Qgis,
                        QgsProject,
@@ -50,7 +51,8 @@ from qgis.gui import (QgsGui,
                       QgsProcessingModelerParameterWidget,
                       QgsProcessingParameterWidgetContext,
                       QgsPanelWidget,
-                      QgsPanelWidgetStack)
+                      QgsPanelWidgetStack,
+                      QgsColorButton)
 from qgis.utils import iface
 
 from processing.gui.wrappers import WidgetWrapperFactory
@@ -101,6 +103,12 @@ class ModelerParametersDialog(QDialog):
     def comments(self):
         return self.widget.comments()
 
+    def setCommentColor(self, color):
+        self.widget.setCommentColor(color)
+
+    def commentColor(self):
+        return self.widget.commentColor()
+
     def switchToCommentTab(self):
         self.widget.switchToCommentTab()
 
@@ -534,7 +542,18 @@ class ModelerParametersWidget(QWidget):
         self.commentLayout = QVBoxLayout()
         self.commentEdit = QTextEdit()
         self.commentEdit.setAcceptRichText(False)
-        self.commentLayout.addWidget(self.commentEdit)
+        self.commentLayout.addWidget(self.commentEdit, 1)
+
+        hl = QHBoxLayout()
+        hl.setContentsMargins(0, 0, 0, 0)
+        hl.addWidget(QLabel(self.tr('Color')))
+        self.comment_color_button = QgsColorButton()
+        self.comment_color_button.setAllowOpacity(True)
+        self.comment_color_button.setWindowTitle(self.tr('Comment Color'))
+        self.comment_color_button.setShowNull(True, self.tr('Default'))
+        hl.addWidget(self.comment_color_button)
+        self.commentLayout.addLayout(hl)
+
         w2 = QWidget()
         w2.setLayout(self.commentLayout)
         self.tab.addTab(w2, self.tr('Comments'))
@@ -547,6 +566,15 @@ class ModelerParametersWidget(QWidget):
     def comments(self):
         return self.commentEdit.toPlainText()
 
+    def setCommentColor(self, color):
+        if color.isValid():
+            self.comment_color_button.setColor(color)
+        else:
+            self.comment_color_button.setToNull()
+
+    def commentColor(self):
+        return self.comment_color_button.color() if not self.comment_color_button.isNull() else QColor()
+
     def getAvailableDependencies(self):
         return self.widget.getAvailableDependencies()
 
@@ -566,4 +594,5 @@ class ModelerParametersWidget(QWidget):
         alg = self.widget.createAlgorithm()
         if alg:
             alg.comment().setDescription(self.comments())
+            alg.comment().setColor(self.commentColor())
         return alg

src/core/CMakeLists.txt

@@ -155,6 +155,7 @@ SET(QGIS_CORE_SRCS
   processing/models/qgsprocessingmodelchildparametersource.cpp
   processing/models/qgsprocessingmodelcomment.cpp
   processing/models/qgsprocessingmodelcomponent.cpp
+  processing/models/qgsprocessingmodelgroupbox.cpp
   processing/models/qgsprocessingmodelparameter.cpp
   processing/models/qgsprocessingmodeloutput.cpp
 
@@ -1197,6 +1198,7 @@ SET(QGIS_CORE_HDRS
   processing/models/qgsprocessingmodelchildparametersource.h
   processing/models/qgsprocessingmodelcomment.h
   processing/models/qgsprocessingmodelcomponent.h
+  processing/models/qgsprocessingmodelgroupbox.h
   processing/models/qgsprocessingmodeloutput.h
   processing/models/qgsprocessingmodelparameter.h
   processing/qgsprocessing.h

src/core/processing/models/qgsprocessingmodelchildalgorithm.cpp

@@ -68,7 +68,10 @@ void QgsProcessingModelChildAlgorithm::copyNonDefinitionPropertiesFromModel( Qgs
   for ( auto it = mModelOutputs.begin(); it != mModelOutputs.end(); ++it )
   {
     if ( !existingChild.modelOutputs().value( it.key() ).position().isNull() )
+    {
       it.value().setPosition( existingChild.modelOutputs().value( it.key() ).position() );
+      it.value().setSize( existingChild.modelOutputs().value( it.key() ).size() );
+    }
     else
       it.value().setPosition( position() + QPointF( size().width(), ( i + 1.5 ) * size().height() ) );
 
@@ -79,6 +82,7 @@ void QgsProcessingModelChildAlgorithm::copyNonDefinitionPropertiesFromModel( Qgs
         comment->setDescription( existingComment->description() );
         comment->setSize( existingComment->size() );
         comment->setPosition( existingComment->position() );
+        comment->setColor( existingComment->color() );
       }
     }
     i++;

src/core/processing/models/qgsprocessingmodelcomponent.cpp

@@ -17,6 +17,7 @@
 
 #include "qgsprocessingmodelcomponent.h"
 #include "qgsprocessingmodelcomment.h"
+#include "qgssymbollayerutils.h"
 
 ///@cond NOT_STABLE
 
@@ -54,6 +55,16 @@ void QgsProcessingModelComponent::setSize( QSizeF size )
   mSize = size;
 }
 
+QColor QgsProcessingModelComponent::color() const
+{
+  return mColor;
+}
+
+void QgsProcessingModelComponent::setColor( const QColor &color )
+{
+  mColor = color;
+}
+
 bool QgsProcessingModelComponent::linksCollapsed( Qt::Edge edge ) const
 {
   switch ( edge )
@@ -103,6 +114,7 @@ void QgsProcessingModelComponent::saveCommonProperties( QVariantMap &map ) const
   map.insert( QStringLiteral( "component_height" ), mSize.height() );
   map.insert( QStringLiteral( "parameters_collapsed" ), mTopEdgeLinksCollapsed );
   map.insert( QStringLiteral( "outputs_collapsed" ), mBottomEdgeLinksCollapsed );
+  map.insert( QStringLiteral( "color" ), mColor.isValid() ? QgsSymbolLayerUtils::encodeColor( mColor ) : QString() );
   if ( comment() )
     map.insert( QStringLiteral( "comment" ), comment()->toVariant() );
 }
@@ -116,6 +128,7 @@ void QgsProcessingModelComponent::restoreCommonProperties( const QVariantMap &ma
   mDescription = map.value( QStringLiteral( "component_description" ) ).toString();
   mSize.setWidth( map.value( QStringLiteral( "component_width" ), QString::number( DEFAULT_COMPONENT_WIDTH ) ).toDouble() );
   mSize.setHeight( map.value( QStringLiteral( "component_height" ), QString::number( DEFAULT_COMPONENT_HEIGHT ) ).toDouble() );
+  mColor = map.value( QStringLiteral( "color" ) ).toString().isEmpty() ? QColor() : QgsSymbolLayerUtils::decodeColor( map.value( QStringLiteral( "color" ) ).toString() );
   mTopEdgeLinksCollapsed = map.value( QStringLiteral( "parameters_collapsed" ) ).toBool();
   mBottomEdgeLinksCollapsed = map.value( QStringLiteral( "outputs_collapsed" ) ).toBool();
   if ( comment() )

src/core/processing/models/qgsprocessingmodelcomponent.h

@@ -22,6 +22,7 @@
 #include "qgis.h"
 #include <QPointF>
 #include <QSizeF>
+#include <QColor>
 
 class QgsProcessingModelComment;
 
@@ -76,6 +77,25 @@ class CORE_EXPORT QgsProcessingModelComponent
      */
     void setSize( QSizeF size );
 
+    /**
+     * Returns the color of the model component within the graphical modeler.
+     *
+     * An invalid color indicates that the default color for the component should be used.
+     *
+     * \see setColor()
+     * \since QGIS 3.14
+     */
+    QColor color() const;
+
+    /**
+     * Sets the \a color of the model component within the graphical modeler. An invalid \a color
+     * indicates that the default color for the component should be used.
+     *
+     * \see color()
+     * \since QGIS 3.14
+     */
+    void setColor( const QColor &color );
+
     /**
      * Returns TRUE if the link points for the specified \a edge should be shown collapsed or not.
      * \see setLinksCollapsed()
@@ -158,6 +178,7 @@ class CORE_EXPORT QgsProcessingModelComponent
     QString mDescription;
 
     QSizeF mSize = QSizeF( DEFAULT_COMPONENT_WIDTH, DEFAULT_COMPONENT_HEIGHT );
+    QColor mColor;
 
     bool mTopEdgeLinksCollapsed = true;
     bool mBottomEdgeLinksCollapsed = true;

src/core/processing/models/qgsprocessingmodelgroupbox.cpp

@@ -0,0 +1,47 @@
+/***************************************************************************
+                         qgsprocessingmodelgroupbox.cpp
+                         --------------------------
+    begin                : March 2020
+    copyright            : (C) 2020 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#include "qgsprocessingmodelgroupbox.h"
+
+///@cond NOT_STABLE
+
+QgsProcessingModelGroupBox::QgsProcessingModelGroupBox( const QString &description )
+  : QgsProcessingModelComponent( description )
+{
+  setSize( QSizeF( 100, 60 ) );
+}
+
+QgsProcessingModelGroupBox *QgsProcessingModelGroupBox::clone() const
+{
+  return new QgsProcessingModelGroupBox( *this );
+}
+
+QVariant QgsProcessingModelGroupBox::toVariant() const
+{
+  QVariantMap map;
+  saveCommonProperties( map );
+  return map;
+}
+
+bool QgsProcessingModelGroupBox::loadVariant( const QVariantMap &map )
+{
+  restoreCommonProperties( map );
+  return true;
+}
+
+
+///@endcond

src/core/processing/models/qgsprocessingmodelgroupbox.h

@@ -0,0 +1,59 @@
+/***************************************************************************
+                         qgsprocessingmodelgroupbox.h
+                         --------------------------
+    begin                : March 2020
+    copyright            : (C) 2020 by Nyall Dawson
+    email                : nyall dot dawson at gmail dot com
+ ***************************************************************************/
+
+/***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSPROCESSINGMODELGROUPBOX_H
+#define QGSPROCESSINGMODELGROUPBOX_H
+
+#include "qgis_core.h"
+#include "qgis.h"
+#include "qgsprocessingmodelcomponent.h"
+#include "qgsprocessingparameters.h"
+
+///@cond NOT_STABLE
+
+/**
+ * Represents a group box in a model.
+ * \ingroup core
+ * \since QGIS 3.14
+ */
+class CORE_EXPORT QgsProcessingModelGroupBox : public QgsProcessingModelComponent
+{
+  public:
+
+    /**
+     * Constructor for QgsProcessingModelGroupBox with the specified \a description.
+     */
+    QgsProcessingModelGroupBox( const QString &description = QString() );
+
+    QgsProcessingModelGroupBox *clone() const override SIP_FACTORY;
+
+    /**
+     * Saves this group box to a QVariant.
+     * \see loadVariant()
+     */
+    QVariant toVariant() const;
+
+    /**
+     * Loads this group box from a QVariantMap.
+     * \see toVariant()
+     */
+    bool loadVariant( const QVariantMap &map );
+};
+
+///@endcond
+
+#endif // QGSPROCESSINGMODELGROUPBOX_H

src/gui/processing/models/qgsmodelcomponentgraphicitem.cpp

@@ -318,8 +318,33 @@ bool QgsModelComponentGraphicItem::contains( const QPointF &point ) const
 void QgsModelComponentGraphicItem::paint( QPainter *painter, const QStyleOptionGraphicsItem *, QWidget * )
 {
   const QRectF rect = itemRect();
-  QColor color = fillColor( state() );
+  QColor color;
-  QColor stroke = strokeColor( state() );
+  QColor stroke;
+  QColor foreColor;
+  if ( mComponent->color().isValid() )
+  {
+    color = mComponent->color();
+    switch ( state() )
+    {
+      case Selected:
+        color = color.darker( 110 );
+        break;
+      case Hover:
+        color = color.darker( 105 );
+        break;
+
+      case Normal:
+        break;
+    }
+    stroke = color.darker( 110 );
+    foreColor = color.lightness() > 150 ? QColor( 0, 0, 0 ) : QColor( 255, 255, 255 );
+  }
+  else
+  {
+    color = fillColor( state() );
+    stroke = strokeColor( state() );
+    foreColor = textColor( state() );
+  }
 
   QPen strokePen = QPen( stroke, 0 ) ; // 0 width "cosmetic" pen
   strokePen.setStyle( strokeStyle( state() ) );
@@ -327,7 +352,7 @@ void QgsModelComponentGraphicItem::paint( QPainter *painter, const QStyleOptionG
   painter->setBrush( QBrush( color, Qt::SolidPattern ) );
   painter->drawRect( rect );
   painter->setFont( font() );
-  painter->setPen( QPen( textColor( state() ) ) );
+  painter->setPen( QPen( foreColor ) );
 
   QString text;
 

src/gui/processing/qgsprocessingparameterdefinitionwidget.cpp

@@ -22,6 +22,7 @@
 #include "qgsapplication.h"
 #include "qgsprocessingregistry.h"
 #include "qgsprocessingparametertype.h"
+#include "qgscolorbutton.h"
 #include <QVBoxLayout>
 #include <QLabel>
 #include <QLineEdit>
@@ -145,7 +146,18 @@ QgsProcessingParameterDefinitionDialog::QgsProcessingParameterDefinitionDialog(
   QVBoxLayout *commentLayout = new QVBoxLayout();
   mCommentEdit = new QTextEdit();
   mCommentEdit->setAcceptRichText( false );
-  commentLayout->addWidget( mCommentEdit );
+  commentLayout->addWidget( mCommentEdit, 1 );
+
+  QHBoxLayout *hl = new QHBoxLayout();
+  hl->setContentsMargins( 0, 0, 0, 0 );
+  hl->addWidget( new QLabel( tr( "Color" ) ) );
+  mCommentColorButton = new QgsColorButton();
+  mCommentColorButton->setAllowOpacity( true );
+  mCommentColorButton->setWindowTitle( tr( "Comment Color" ) );
+  mCommentColorButton->setShowNull( true, tr( "Default" ) );
+  hl->addWidget( mCommentColorButton );
+  commentLayout->addLayout( hl );
+
   QWidget *w2 = new QWidget();
   w2->setLayout( commentLayout );
   mTabWidget->addTab( w2, tr( "Comments" ) );
@@ -178,6 +190,19 @@ QString QgsProcessingParameterDefinitionDialog::comments() const
   return mCommentEdit->toPlainText();
 }
 
+void QgsProcessingParameterDefinitionDialog::setCommentColor( const QColor &color )
+{
+  if ( color.isValid() )
+    mCommentColorButton->setColor( color );
+  else
+    mCommentColorButton->setToNull();
+}
+
+QColor QgsProcessingParameterDefinitionDialog::commentColor() const
+{
+  return !mCommentColorButton->isNull() ? mCommentColorButton->color() : QColor();
+}
+
 void QgsProcessingParameterDefinitionDialog::switchToCommentTab()
 {
   mTabWidget->setCurrentIndex( 1 );

src/gui/processing/qgsprocessingparameterdefinitionwidget.h

@@ -31,6 +31,7 @@ class QLineEdit;
 class QCheckBox;
 class QTabWidget;
 class QTextEdit;
+class QgsColorButton;
 
 /**
  * Abstract base class for widgets which allow users to specify the properties of a
@@ -183,6 +184,20 @@ class GUI_EXPORT QgsProcessingParameterDefinitionDialog: public QDialog
      */
     QString comments() const;
 
+    /**
+     * Sets the color for the comments for the parameter.
+     * \see commentColor()
+     * \since QGIS 3.14
+     */
+    void setCommentColor( const QColor &color );
+
+    /**
+     * Returns the color for the comments for the parameter.
+     * \see setCommentColor()
+     * \since QGIS 3.14
+     */
+    QColor commentColor() const;
+
     /**
      * Switches the dialog to the comments tab.
      */
@@ -195,6 +210,7 @@ class GUI_EXPORT QgsProcessingParameterDefinitionDialog: public QDialog
 
     QTabWidget *mTabWidget = nullptr;
     QTextEdit *mCommentEdit = nullptr;
+    QgsColorButton *mCommentColorButton = nullptr;
     QgsProcessingParameterDefinitionWidget *mWidget = nullptr;
 
 };

src/gui/qgscolorbutton.cpp

@@ -508,7 +508,7 @@ void QgsColorButton::prepareMenu()
   {
     if ( mShowNull )
     {
-      QAction *nullAction = new QAction( tr( "Clear Color" ), this );
+      QAction *nullAction = new QAction( mNullColorString.isEmpty() ? tr( "Clear Color" ) : mNullColorString, this );
       nullAction->setIcon( createMenuIcon( Qt::transparent, false ) );
       mMenu->addAction( nullAction );
       connect( nullAction, &QAction::triggered, this, &QgsColorButton::setToNull );
@@ -825,9 +825,10 @@ void QgsColorButton::setDefaultColor( const QColor &color )
   mDefaultColor = color;
 }
 
-void QgsColorButton::setShowNull( bool showNull )
+void QgsColorButton::setShowNull( bool showNull, const QString &nullString )
 {
   mShowNull = showNull;
+  mNullColorString = nullString;
 }
 
 bool QgsColorButton::showNull() const

src/gui/qgscolorbutton.h

@@ -202,11 +202,12 @@ class GUI_EXPORT QgsColorButton : public QToolButton
     /**
      * Sets whether a set to null (clear) option is shown in the button's drop-down menu.
      * \param showNull set to TRUE to show a null option
+     * \param nullString translated string to use for the null option. If not set, a default "Clear Color" string will be used.
      * \see showNull()
      * \see isNull()
      * \since QGIS 2.16
      */
-    void setShowNull( bool showNull );
+    void setShowNull( bool showNull, const QString &nullString = QString() );
 
     /**
      * Returns whether the set to null (clear) option is shown in the button's drop-down menu.
@@ -481,6 +482,7 @@ class GUI_EXPORT QgsColorButton : public QToolButton
     bool mShowNoColorOption = false;
     QString mNoColorString;
     bool mShowNull = false;
+    QString mNullColorString;
 
     QPoint mDragStartPosition;
     bool mPickingColor = false;

tests/src/analysis/testqgsprocessing.cpp

@@ -8266,16 +8266,20 @@ void TestQgsProcessing::modelerAlgorithm()
   QCOMPARE( comment.position(), QPointF( 11, 14 ) );
   comment.setDescription( QStringLiteral( "a comment" ) );
   QCOMPARE( comment.description(), QStringLiteral( "a comment" ) );
+  comment.setColor( QColor( 123, 45, 67 ) );
+  QCOMPARE( comment.color(), QColor( 123, 45, 67 ) );
   std::unique_ptr< QgsProcessingModelComment > commentClone( comment.clone() );
   QCOMPARE( commentClone->toVariant(), comment.toVariant() );
   QCOMPARE( commentClone->size(), QSizeF( 9, 8 ) );
   QCOMPARE( commentClone->position(), QPointF( 11, 14 ) );
   QCOMPARE( commentClone->description(), QStringLiteral( "a comment" ) );
+  QCOMPARE( commentClone->color(), QColor( 123, 45, 67 ) );
   QgsProcessingModelComment comment2;
   comment2.loadVariant( comment.toVariant().toMap() );
   QCOMPARE( comment2.size(), QSizeF( 9, 8 ) );
   QCOMPARE( comment2.position(), QPointF( 11, 14 ) );
   QCOMPARE( comment2.description(), QStringLiteral( "a comment" ) );
+  QCOMPARE( comment2.color(), QColor( 123, 45, 67 ) );
 
   QMap< QString, QString > friendlyOutputNames;
   QgsProcessingModelChildAlgorithm child( QStringLiteral( "some_id" ) );
@@ -8463,6 +8467,21 @@ void TestQgsProcessing::modelerAlgorithm()
   a2.setDescription( QStringLiteral( "alg2" ) );
   a2.setPosition( QPointF( 112, 131 ) );
   a2.setSize( QSizeF( 44, 55 ) );
+  a2.comment()->setSize( QSizeF( 111, 222 ) );
+  a2.comment()->setPosition( QPointF( 113, 114 ) );
+  a2.comment()->setDescription( QStringLiteral( "c" ) );
+  a2.comment()->setColor( QColor( 255, 254, 253 ) );
+  QgsProcessingModelOutput oo;
+  oo.setPosition( QPointF( 312, 331 ) );
+  oo.setSize( QSizeF( 344, 355 ) );
+  oo.comment()->setSize( QSizeF( 311, 322 ) );
+  oo.comment()->setPosition( QPointF( 313, 314 ) );
+  oo.comment()->setDescription( QStringLiteral( "c3" ) );
+  oo.comment()->setColor( QColor( 155, 14, 353 ) );
+  QMap< QString, QgsProcessingModelOutput > a2Outs;
+  a2Outs.insert( QStringLiteral( "out1" ), oo );
+  a2.setModelOutputs( a2Outs );
+
   algs.insert( QStringLiteral( "a" ), a1 );
   algs.insert( QStringLiteral( "b" ), a2 );
   alg.setChildAlgorithms( algs );
@@ -8473,10 +8492,28 @@ void TestQgsProcessing::modelerAlgorithm()
   QgsProcessingModelChildAlgorithm a2other;
   a2other.setChildId( QStringLiteral( "b" ) );
   a2other.setDescription( QStringLiteral( "alg2 other" ) );
+  QgsProcessingModelOutput oo2;
+  QMap< QString, QgsProcessingModelOutput > a2Outs2;
+  a2Outs2.insert( QStringLiteral( "out1" ), oo2 );
+  a2other.setModelOutputs( a2Outs2 );
+
   a2other.copyNonDefinitionPropertiesFromModel( &alg );
   QCOMPARE( a2other.description(), QStringLiteral( "alg2 other" ) );
   QCOMPARE( a2other.position(), QPointF( 112, 131 ) );
   QCOMPARE( a2other.size(), QSizeF( 44, 55 ) );
+  QCOMPARE( a2other.comment()->size(), QSizeF( 111, 222 ) );
+  QCOMPARE( a2other.comment()->position(), QPointF( 113, 114 ) );
+  // should not be copied
+  QCOMPARE( a2other.comment()->description(), QString() );
+  QVERIFY( !a2other.comment()->color().isValid() );
+
+  QCOMPARE( a2other.modelOutput( QStringLiteral( "out1" ) ).position(), QPointF( 312, 331 ) );
+  QCOMPARE( a2other.modelOutput( QStringLiteral( "out1" ) ).size(), QSizeF( 344, 355 ) );
+  QCOMPARE( a2other.modelOutput( QStringLiteral( "out1" ) ).comment()->size(), QSizeF( 311, 322 ) );
+  QCOMPARE( a2other.modelOutput( QStringLiteral( "out1" ) ).comment()->position(), QPointF( 313, 314 ) );
+  // should be copied for outputs
+  QCOMPARE( a2other.modelOutput( QStringLiteral( "out1" ) ).comment()->description(), QStringLiteral( "c3" ) );
+  QCOMPARE( a2other.modelOutput( QStringLiteral( "out1" ) ).comment()->color(), QColor( 155, 14, 353 ) );
 
   QgsProcessingModelChildAlgorithm a3;
   a3.setChildId( QStringLiteral( "c" ) );