[FEATURE] Interactive color assistant for data defined colors

python/core/qgsproperty.sip

@@ -58,6 +58,7 @@ class QgsPropertyDefinition
 
     StandardPropertyTemplate standardTemplate() const;
 
+    bool supportsAssistant() const;
 };
 
 class QgsProperty

src/core/qgsproperty.cpp

@@ -177,6 +177,11 @@ QgsPropertyDefinition::QgsPropertyDefinition( const QString& name, DataType data
     , mHelpText( helpText )
 {}
 
+bool QgsPropertyDefinition::supportsAssistant() const
+{
+  return mTypes == DataTypeNumeric || mStandardType == Size || mStandardType == StrokeWidth || mStandardType == ColorNoAlpha || mStandardType == ColorWithAlpha;
+}
+
 QString QgsPropertyDefinition::trString()
 {
   // just something to reduce translation redundancy

src/core/qgsproperty.h

@@ -150,6 +150,12 @@ class CORE_EXPORT QgsPropertyDefinition
      */
     StandardPropertyTemplate standardTemplate() const { return mStandardType; }
 
+    /**
+     * Returns true if the property is of a type which is compatible with property
+     * override assistants.
+     */
+    bool supportsAssistant() const;
+
   private:
 
     QString mName;

src/gui/qgspropertyassistantwidget.cpp

@@ -71,7 +71,16 @@ QgsPropertyAssistantWidget::QgsPropertyAssistantWidget( QWidget* parent ,
     case QgsPropertyDefinition::StrokeWidth:
     {
       mTransformerWidget = new QgsPropertySizeAssistantWidget( this, mDefinition, initialState );
+      break;
     }
+
+    case QgsPropertyDefinition::ColorNoAlpha:
+    case QgsPropertyDefinition::ColorWithAlpha:
+    {
+      mTransformerWidget = new QgsPropertyColorAssistantWidget( this, mDefinition, initialState );
+      break;
+    }
+
     default:
       break;
   }
@@ -370,3 +379,63 @@ QList<QgsSymbolLegendNode*> QgsPropertyAbstractTransformerWidget::generatePrevie
 {
   return QList< QgsSymbolLegendNode* >();
 }
+
+QgsPropertyColorAssistantWidget::QgsPropertyColorAssistantWidget( QWidget* parent, const QgsPropertyDefinition& definition, const QgsProperty& initialState )
+    : QgsPropertyAbstractTransformerWidget( parent, definition )
+{
+  setupUi( this );
+
+  layout()->setContentsMargins( 0, 0, 0, 0 );
+  layout()->setMargin( 0 );
+
+  bool supportsAlpha = definition.standardTemplate() == QgsPropertyDefinition::ColorWithAlpha;
+  mNullColorButton->setAllowAlpha( supportsAlpha );
+
+  if ( const QgsColorRampTransformer* colorTransform = dynamic_cast< const QgsColorRampTransformer* >( initialState.transformer() ) )
+  {
+    mNullColorButton->setColor( colorTransform->nullColor() );
+    mColorRampButton->setColorRamp( colorTransform->colorRamp() );
+  }
+
+  connect( mNullColorButton, &QgsColorButton::colorChanged, this, &QgsPropertyColorAssistantWidget::widgetChanged );
+  connect( mColorRampButton, &QgsColorRampButton::colorRampChanged, this, &QgsPropertyColorAssistantWidget::widgetChanged );
+}
+
+QgsColorRampTransformer* QgsPropertyColorAssistantWidget::createTransformer( double minValue, double maxValue ) const
+{
+  QgsColorRampTransformer* transformer = new QgsColorRampTransformer(
+    minValue,
+    maxValue,
+    mColorRampButton->colorRamp(),
+    mNullColorButton->color() );
+  return transformer;
+}
+
+QList<QgsSymbolLegendNode*> QgsPropertyColorAssistantWidget::generatePreviews( const QList<double>& breaks, QgsLayerTreeLayer* parent, const QgsSymbol* symbol, double minValue, double maxValue ) const
+{
+  QList< QgsSymbolLegendNode* > nodes;
+
+  const QgsMarkerSymbol* legendSymbol = dynamic_cast<const QgsMarkerSymbol*>( symbol );
+  std::unique_ptr< QgsMarkerSymbol > tempSymbol;
+
+  if ( !legendSymbol )
+  {
+    tempSymbol.reset( QgsMarkerSymbol::createSimple( QgsStringMap() ) );
+    legendSymbol = tempSymbol.get();
+  }
+  if ( !legendSymbol )
+    return nodes;
+
+  std::unique_ptr< QgsColorRampTransformer > t( createTransformer( minValue, maxValue ) );
+
+  for ( int i = 0; i < breaks.length(); i++ )
+  {
+    std::unique_ptr< QgsSymbolLegendNode > node;
+    std::unique_ptr< QgsMarkerSymbol > symbolClone( static_cast<QgsMarkerSymbol*>( legendSymbol->clone() ) );
+    symbolClone->setColor( t->color( breaks[i] ) );
+    node.reset( new QgsSymbolLegendNode( parent, QgsLegendSymbolItem( symbolClone.get(), QString::number( i ), QString() ) ) );
+    if ( node )
+      nodes << node.release();
+  }
+  return nodes;
+}

src/gui/qgspropertyassistantwidget.h

@@ -21,6 +21,7 @@
 #include "qgspanelwidget.h"
 #include "ui_qgspropertyassistantwidgetbase.h"
 #include "ui_qgspropertysizeassistantwidget.h"
+#include "ui_qgspropertycolorassistantwidget.h"
 #include "qgsproperty.h"
 #include "qgslayertreegroup.h"
 #include "qgssymbol.h"
@@ -71,6 +72,19 @@ class GUI_EXPORT QgsPropertySizeAssistantWidget : public QgsPropertyAbstractTran
     QList< QgsSymbolLegendNode* > generatePreviews( const QList<double>& breaks, QgsLayerTreeLayer* parent, const QgsSymbol* symbol, double minValue, double maxValue ) const override;
 };
 
+class GUI_EXPORT QgsPropertyColorAssistantWidget : public QgsPropertyAbstractTransformerWidget, private Ui::PropertyColorAssistant
+{
+    Q_OBJECT
+
+  public:
+
+    QgsPropertyColorAssistantWidget( QWidget* parent = nullptr, const QgsPropertyDefinition& definition = QgsPropertyDefinition(), const QgsProperty& initialState = QgsProperty() );
+
+    virtual QgsColorRampTransformer* createTransformer( double minValue, double maxValue ) const override;
+
+    QList< QgsSymbolLegendNode* > generatePreviews( const QList<double>& breaks, QgsLayerTreeLayer* parent, const QgsSymbol* symbol, double minValue, double maxValue ) const override;
+};
+
 ///@endcond PRIVATE
 
 class GUI_EXPORT QgsPropertyAssistantWidget : public QgsPanelWidget, private Ui::PropertyAssistantBase

src/gui/qgspropertyoverridebutton.cpp

@@ -404,7 +404,7 @@ void QgsPropertyOverrideButton::aboutToShowMenu()
     mDefineMenu->addAction( mActionPasteExpr );
   }
 
-  if ( !mDefinition.name().isEmpty() )
+  if ( !mDefinition.name().isEmpty() && mDefinition.supportsAssistant() )
   {
     mDefineMenu->addSeparator();
     mActionAssistant->setCheckable( mProperty.transformer() );
@@ -599,7 +599,7 @@ void QgsPropertyOverrideButton::updateGui()
   {
     icon = mProperty.isActive() ? QgsApplication::getThemeIcon( QStringLiteral( "/mIconDataDefineOn.svg" ) ) : QgsApplication::getThemeIcon( QStringLiteral( "/mIconDataDefine.svg" ) );
 
-    if ( !mFieldNameList.contains( mFieldName ) )
+    if ( !mFieldNameList.contains( mFieldName ) && !mProperty.transformer() )
     {
       icon = QgsApplication::getThemeIcon( QStringLiteral( "/mIconDataDefineError.svg" ) );
       deftip = tr( "'%1' field missing" ).arg( mFieldName );

src/ui/qgspropertycolorassistantwidget.ui

@@ -0,0 +1,110 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>PropertyColorAssistant</class>
+ <widget class="QWidget" name="PropertyColorAssistant">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>267</width>
+    <height>163</height>
+   </rect>
+  </property>
+  <layout class="QGridLayout" name="gridLayout_2" columnstretch="0,0">
+   <item row="3" column="0">
+    <widget class="QLabel" name="label_8">
+     <property name="text">
+      <string>Color when NULL</string>
+     </property>
+    </widget>
+   </item>
+   <item row="3" column="1">
+    <widget class="QgsColorButton" name="mNullColorButton">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="minimumSize">
+      <size>
+       <width>120</width>
+       <height>0</height>
+      </size>
+     </property>
+     <property name="maximumSize">
+      <size>
+       <width>16777215</width>
+       <height>16777215</height>
+      </size>
+     </property>
+     <property name="text">
+      <string/>
+     </property>
+    </widget>
+   </item>
+   <item row="4" column="0">
+    <spacer name="verticalSpacer">
+     <property name="orientation">
+      <enum>Qt::Vertical</enum>
+     </property>
+     <property name="sizeHint" stdset="0">
+      <size>
+       <width>20</width>
+       <height>40</height>
+      </size>
+     </property>
+    </spacer>
+   </item>
+   <item row="2" column="0" colspan="2">
+    <widget class="QgsColorRampButton" name="mColorRampButton">
+     <property name="sizePolicy">
+      <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+       <horstretch>0</horstretch>
+       <verstretch>0</verstretch>
+      </sizepolicy>
+     </property>
+     <property name="minimumSize">
+      <size>
+       <width>120</width>
+       <height>0</height>
+      </size>
+     </property>
+     <property name="maximumSize">
+      <size>
+       <width>16777215</width>
+       <height>16777215</height>
+      </size>
+     </property>
+    </widget>
+   </item>
+   <item row="1" column="0" colspan="2">
+    <widget class="QLabel" name="label">
+     <property name="text">
+      <string>Color ramp</string>
+     </property>
+    </widget>
+   </item>
+  </layout>
+ </widget>
+ <customwidgets>
+  <customwidget>
+   <class>QgsColorRampButton</class>
+   <extends>QToolButton</extends>
+   <header>qgscolorrampbutton.h</header>
+   <container>1</container>
+  </customwidget>
+  <customwidget>
+   <class>QgsColorButton</class>
+   <extends>QToolButton</extends>
+   <header>qgscolorbutton.h</header>
+   <container>1</container>
+  </customwidget>
+ </customwidgets>
+ <tabstops>
+  <tabstop>mColorRampButton</tabstop>
+  <tabstop>mNullColorButton</tabstop>
+ </tabstops>
+ <resources/>
+ <connections/>
+</ui>