[FEATURE] Allow setting paint effects on label background shapes

Can also be useful for improving text readability through
outer glows and blurs

Author: nyalldawson

python/core/qgstextrenderer.sip

@@ -538,6 +538,9 @@ class QgsTextBackgroundSettings
      */
     void readFromLayer( QgsVectorLayer* layer );
 
+    QgsPaintEffect* paintEffect() const;
+    void setPaintEffect( QgsPaintEffect* effect /Transfer/ );
+
     /** Writes settings to a layer's custom properties.
      * @param layer target vector layer
      * @see readFromLayer()

src/core/qgstextrenderer.cpp

@@ -629,6 +629,17 @@ void QgsTextBackgroundSettings::setJoinStyle( Qt::PenJoinStyle style )
   d->joinStyle = style;
 }
 
+QgsPaintEffect *QgsTextBackgroundSettings::paintEffect() const
+{
+  return d->paintEffect;
+}
+
+void QgsTextBackgroundSettings::setPaintEffect( QgsPaintEffect *effect )
+{
+  delete d->paintEffect;
+  d->paintEffect = effect;
+}
+
 void QgsTextBackgroundSettings::readFromLayer( QgsVectorLayer *layer )
 {
   d->enabled = layer->customProperty( QStringLiteral( "labeling/shapeDraw" ), QVariant( false ) ).toBool();
@@ -737,6 +748,16 @@ void QgsTextBackgroundSettings::readFromLayer( QgsVectorLayer *layer )
   }
   d->blendMode = QgsPainting::getCompositionMode(
                    static_cast< QgsPainting::BlendMode >( layer->customProperty( QStringLiteral( "labeling/shapeBlendMode" ), QVariant( QgsPainting::BlendNormal ) ).toUInt() ) );
+
+  if ( layer->customProperty( QStringLiteral( "labeling/shapeEffect" ) ).isValid() )
+  {
+    QDomDocument doc( QStringLiteral( "effect" ) );
+    doc.setContent( layer->customProperty( QStringLiteral( "labeling/shapeEffect" ) ).toString() );
+    QDomElement effectElem = doc.firstChildElement( QStringLiteral( "effect" ) ).firstChildElement( QStringLiteral( "effect" ) );
+    setPaintEffect( QgsApplication::paintEffectRegistry()->createEffect( effectElem ) );
+  }
+  else
+    setPaintEffect( nullptr );
 }
 
 void QgsTextBackgroundSettings::writeToLayer( QgsVectorLayer *layer ) const
@@ -767,6 +788,21 @@ void QgsTextBackgroundSettings::writeToLayer( QgsVectorLayer *layer ) const
   layer->setCustomProperty( QStringLiteral( "labeling/shapeJoinStyle" ), static_cast< unsigned int >( d->joinStyle ) );
   layer->setCustomProperty( QStringLiteral( "labeling/shapeOpacity" ), d->opacity );
   layer->setCustomProperty( QStringLiteral( "labeling/shapeBlendMode" ), QgsPainting::getBlendModeEnum( d->blendMode ) );
+
+  if ( d->paintEffect && !QgsPaintEffectRegistry::isDefaultStack( d->paintEffect ) )
+  {
+    QDomDocument doc( QStringLiteral( "effect" ) );
+    QDomElement effectElem = doc.createElement( QStringLiteral( "effect" ) );
+    d->paintEffect->saveProperties( doc, effectElem );
+    QString effectProps;
+    QTextStream stream( &effectProps );
+    effectElem.save( stream, -1 );
+    layer->setCustomProperty( QStringLiteral( "labeling/shapeEffect" ), effectProps );
+  }
+  else
+  {
+    layer->removeCustomProperty( QStringLiteral( "labeling/shapeEffect" ) );
+  }
 }
 
 void QgsTextBackgroundSettings::readXml( const QDomElement &elem )
@@ -879,6 +915,11 @@ void QgsTextBackgroundSettings::readXml( const QDomElement &elem )
   d->blendMode = QgsPainting::getCompositionMode(
                    static_cast< QgsPainting::BlendMode >( backgroundElem.attribute( QStringLiteral( "shapeBlendMode" ), QString::number( QgsPainting::BlendNormal ) ).toUInt() ) );
 
+  QDomElement effectElem = backgroundElem.firstChildElement( QStringLiteral( "effect" ) );
+  if ( !effectElem.isNull() )
+    setPaintEffect( QgsApplication::paintEffectRegistry()->createEffect( effectElem ) );
+  else
+    setPaintEffect( nullptr );
 }
 
 QDomElement QgsTextBackgroundSettings::writeXml( QDomDocument &doc ) const
@@ -910,6 +951,8 @@ QDomElement QgsTextBackgroundSettings::writeXml( QDomDocument &doc ) const
   backgroundElem.setAttribute( QStringLiteral( "shapeJoinStyle" ), static_cast< unsigned int >( d->joinStyle ) );
   backgroundElem.setAttribute( QStringLiteral( "shapeOpacity" ), d->opacity );
   backgroundElem.setAttribute( QStringLiteral( "shapeBlendMode" ), QgsPainting::getBlendModeEnum( d->blendMode ) );
+  if ( d->paintEffect && !QgsPaintEffectRegistry::isDefaultStack( d->paintEffect ) )
+    d->paintEffect->saveProperties( doc, backgroundElem );
   return backgroundElem;
 }
 
@@ -1952,7 +1995,14 @@ void QgsTextRenderer::drawBackground( QgsRenderContext &context, QgsTextRenderer
 {
   QgsTextBackgroundSettings background = format.background();
 
+  QPainter *prevP = context.painter();
   QPainter *p = context.painter();
+  if ( background.paintEffect() && background.paintEffect()->enabled() )
+  {
+    background.paintEffect()->begin( context );
+    p = context.painter();
+  }
+
   //QgsDebugMsgLevel( QString( "Background label rotation: %1" ).arg( component.rotation() ), 4 );
 
   // shared calculations between shapes and SVG
@@ -2289,6 +2339,11 @@ void QgsTextRenderer::drawBackground( QgsRenderContext &context, QgsTextRenderer
     p->drawPicture( 0, 0, shapePict );
     p->restore();
   }
+  if ( background.paintEffect() && background.paintEffect()->enabled() )
+  {
+    background.paintEffect()->end( context );
+    context.setPainter( prevP );
+  }
 }
 
 void QgsTextRenderer::drawShadow( QgsRenderContext &context, const QgsTextRenderer::Component &component, const QgsTextFormat &format )

src/core/qgstextrenderer.h

@@ -577,6 +577,18 @@ class CORE_EXPORT QgsTextBackgroundSettings
      */
     void setJoinStyle( Qt::PenJoinStyle style );
 
+    /** Returns the current paint effect for the background shape.
+     * \returns paint effect
+     * \see setPaintEffect()
+     */
+    QgsPaintEffect *paintEffect() const;
+
+    /** Sets the current paint \a effect for the background shape.
+     * \param effect paint effect. Ownership is transferred to the background settings.
+     * \see paintEffect()
+     */
+    void setPaintEffect( QgsPaintEffect *effect );
+
     /** Reads settings from a layer's custom properties.
      * \param layer source vector layer
      * \see writeToLayer()

src/core/qgstextrenderer_p.h

@@ -111,6 +111,7 @@ class CORE_EXPORT QgsTextBackgroundSettingsPrivate : public QSharedData
       , strokeWidth( 0.0 )
       , strokeWidthUnits( QgsUnitTypes::RenderMillimeters )
       , joinStyle( Qt::BevelJoin )
+      , paintEffect( nullptr )
     {
     }
 
@@ -139,9 +140,15 @@ class CORE_EXPORT QgsTextBackgroundSettingsPrivate : public QSharedData
       , strokeWidthUnits( other.strokeWidthUnits )
       , strokeWidthMapUnitScale( other.strokeWidthMapUnitScale )
       , joinStyle( other.joinStyle )
+      , paintEffect( other.paintEffect ? other.paintEffect->clone() : nullptr )
     {
     }
 
+    ~QgsTextBackgroundSettingsPrivate()
+    {
+      delete paintEffect;
+    }
+
     bool enabled;
     QgsTextBackgroundSettings::ShapeType type;
     QString svgFile;
@@ -165,6 +172,7 @@ class CORE_EXPORT QgsTextBackgroundSettingsPrivate : public QSharedData
     QgsUnitTypes::RenderUnit strokeWidthUnits;
     QgsMapUnitScale strokeWidthMapUnitScale;
     Qt::PenJoinStyle joinStyle;
+    QgsPaintEffect *paintEffect;
 };
 
 

src/gui/qgstextformatwidget.cpp

@@ -264,6 +264,9 @@ void QgsTextFormatWidget::initWidget()
   mBufferEffect.reset( QgsPaintEffectRegistry::defaultStack() );
   connect( mBufferEffectWidget, &QgsEffectStackCompactWidget::changed, this, &QgsTextFormatWidget::updatePreview );
   mBufferEffectWidget->setPaintEffect( mBufferEffect.get() );
+  mBackgroundEffect.reset( QgsPaintEffectRegistry::defaultStack() );
+  connect( mBackgroundEffectWidget, &QgsEffectStackCompactWidget::changed, this, &QgsTextFormatWidget::updatePreview );
+  mBackgroundEffectWidget->setPaintEffect( mBackgroundEffect.get() );
 
   setDockMode( false );
 
@@ -695,6 +698,15 @@ void QgsTextFormatWidget::updateWidgetForFormat( const QgsTextFormat &format )
   mLoadSvgParams = false;
   on_mShapeTypeCmbBx_currentIndexChanged( background.type() ); // force update of shape background gui
 
+  if ( background.paintEffect() )
+    mBackgroundEffect.reset( background.paintEffect()->clone() );
+  else
+  {
+    mBackgroundEffect.reset( QgsPaintEffectRegistry::defaultStack() );
+    mBackgroundEffect->setEnabled( false );
+  }
+  mBackgroundEffectWidget->setPaintEffect( mBackgroundEffect.get() );
+
   // drop shadow
   mShadowDrawChkBx->setChecked( shadow.enabled() );
   mShadowUnderCmbBx->setCurrentIndex( shadow.shadowPlacement() );
@@ -780,6 +792,10 @@ QgsTextFormat QgsTextFormatWidget::format() const
   background.setJoinStyle( mShapePenStyleCmbBx->penJoinStyle() );
   background.setOpacity( 1.0 - mShapeTranspSpinBox->value() / 100.0 );
   background.setBlendMode( mShapeBlendCmbBx->blendMode() );
+  if ( mBackgroundEffect && !QgsPaintEffectRegistry::isDefaultStack( mBackgroundEffect.get() ) )
+    background.setPaintEffect( mBackgroundEffect->clone() );
+  else
+    background.setPaintEffect( nullptr );
   format.setBackground( background );
 
   // drop shadow

src/gui/qgstextformatwidget.h

@@ -137,6 +137,7 @@ class GUI_EXPORT QgsTextFormatWidget : public QWidget, protected Ui::QgsTextForm
     QgsMapCanvas *mMapCanvas = nullptr;
     QgsCharacterSelectorDialog *mCharDlg = nullptr;
     std::unique_ptr< QgsPaintEffect > mBufferEffect;
+    std::unique_ptr< QgsPaintEffect > mBackgroundEffect;
 
     QFontDatabase mFontDB;