Add QgsSymbolLayer::canCauseArtifactsBetweenAdjacentTiles()

Returns true if the symbol layer rendering can cause visible artifacts across a single feature when the feature is rendered as a series of adjacent map tiles each containing a portion of the feature's geometry. This depends on the symbol layer derived class itself - eg a simple solid color fill won't show any artifacts, but a shapeburst fill WILL.
qgis · Feb 12, 2021 · bdf5e4fe3b3c02da8060fca80c5f611b67539e23 · bdf5e4f
1 parent d5e2051
commit bdf5e4fe3b3c02da8060fca80c5f611b67539e23
diff --git a/python/core/auto_generated/symbology/qgsfillsymbollayer.sip.in b/python/core/auto_generated/symbology/qgsfillsymbollayer.sip.in
@@ -245,24 +245,20 @@ Caller takes ownership of the returned symbol layer.
 
     virtual QString layerType() const;
 
-
     virtual void startRender( QgsSymbolRenderContext &context );
 
-
     virtual void stopRender( QgsSymbolRenderContext &context );
 
-
     virtual void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context );
 
-
     virtual QVariantMap properties() const;
 
-
     virtual QgsGradientFillSymbolLayer *clone() const /Factory/;
 
-
     virtual double estimateMaxBleed( const QgsRenderContext &context ) const;
 
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+
 
     GradientType gradientType() const;
 %Docstring
@@ -450,24 +446,20 @@ Caller takes ownership of the returned symbol layer.
 
     virtual QString layerType() const;
 
-
     virtual void startRender( QgsSymbolRenderContext &context );
 
-
     virtual void stopRender( QgsSymbolRenderContext &context );
 
-
     virtual void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context );
 
-
     virtual QVariantMap properties() const;
 
-
     virtual QgsShapeburstFillSymbolLayer *clone() const /Factory/;
 
-
     virtual double estimateMaxBleed( const QgsRenderContext &context ) const;
 
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+
 
     void setBlurRadius( int blurRadius );
 %Docstring
@@ -2075,6 +2067,8 @@ Caller takes ownership of the returned symbol layer.
 
     virtual QgsRandomMarkerFillSymbolLayer *clone() const /Factory/;
 
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+
 
     virtual void setColor( const QColor &color );
 
@@ -2251,51 +2245,42 @@ Caller takes ownership of the returned symbol layer.
 
     virtual QString layerType() const;
 
-
     virtual void startRender( QgsSymbolRenderContext &context );
 
-
     virtual void stopRender( QgsSymbolRenderContext &context );
 
-
     virtual void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context );
 
-
     virtual QVariantMap properties() const;
 
-
     virtual QgsCentroidFillSymbolLayer *clone() const /Factory/;
 
-
     virtual void toSld( QDomDocument &doc, QDomElement &element, const QVariantMap &props ) const;
 
-
     virtual void setColor( const QColor &color );
 
     virtual QColor color() const;
 
-
     virtual QgsSymbol *subSymbol();
 
     virtual bool setSubSymbol( QgsSymbol *symbol /Transfer/ );
 
-
     virtual void setOutputUnit( QgsUnitTypes::RenderUnit unit );
 
     virtual QgsUnitTypes::RenderUnit outputUnit() const;
 
     virtual bool usesMapUnits() const;
 
-
     virtual void setMapUnitScale( const QgsMapUnitScale &scale );
 
     virtual QgsMapUnitScale mapUnitScale() const;
 
-
     virtual QSet<QString> usedAttributes( const QgsRenderContext &context ) const;
 
     virtual bool hasDataDefinedProperties() const;
 
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+
 
     void setPointOnSurface( bool pointOnSurface );
     bool pointOnSurface() const;

diff --git a/python/core/auto_generated/symbology/qgslinesymbollayer.sip.in b/python/core/auto_generated/symbology/qgslinesymbollayer.sip.in
@@ -660,6 +660,8 @@ calculating individual symbol angles.
 
     virtual QVariantMap properties() const;
 
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+
 
   protected:
 

diff --git a/python/core/auto_generated/symbology/qgssymbollayer.sip.in b/python/core/auto_generated/symbology/qgssymbollayer.sip.in
@@ -336,6 +336,16 @@ Sets layer's subsymbol. takes ownership of the passed symbol
     virtual bool isCompatibleWithSymbol( QgsSymbol *symbol ) const;
 %Docstring
 Returns if the layer can be used below the specified symbol
+%End
+
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+%Docstring
+Returns ``True`` if the symbol layer rendering can cause visible artifacts across a single feature
+when the feature is rendered as a series of adjacent map tiles each containing a portion of the feature's geometry.
+
+The default implementation returns ``False``.
+
+.. versionadded:: 3.18
 %End
 
     void setLocked( bool locked );

diff --git a/src/core/symbology/qgsarrowsymbollayer.cpp b/src/core/symbology/qgsarrowsymbollayer.cpp
@@ -830,3 +830,8 @@ QColor QgsArrowSymbolLayer::color() const
   return mSymbol.get() ? mSymbol->color() : mColor;
 }
 
+bool QgsArrowSymbolLayer::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  return true;
+}
+
diff --git a/src/core/symbology/qgsarrowsymbollayer.h b/src/core/symbology/qgsarrowsymbollayer.h
@@ -145,6 +145,7 @@ class CORE_EXPORT QgsArrowSymbolLayer : public QgsLineSymbolLayer
     void renderPolyline( const QPolygonF &points, QgsSymbolRenderContext &context ) override;
     void setColor( const QColor &c ) override;
     QColor color() const override;
+    bool canCauseArtifactsBetweenAdjacentTiles() const override;
 
   private:
 #ifdef SIP_RUN

diff --git a/src/core/symbology/qgsfillsymbollayer.cpp b/src/core/symbology/qgsfillsymbollayer.cpp
@@ -988,6 +988,11 @@ double QgsGradientFillSymbolLayer::estimateMaxBleed( const QgsRenderContext &con
   return offsetBleed;
 }
 
+bool QgsGradientFillSymbolLayer::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  return true;
+}
+
 void QgsGradientFillSymbolLayer::setOutputUnit( QgsUnitTypes::RenderUnit unit )
 {
   mOffsetUnit = unit;
@@ -1618,6 +1623,11 @@ double QgsShapeburstFillSymbolLayer::estimateMaxBleed( const QgsRenderContext &c
   return offsetBleed;
 }
 
+bool QgsShapeburstFillSymbolLayer::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  return true;
+}
+
 void QgsShapeburstFillSymbolLayer::setOutputUnit( QgsUnitTypes::RenderUnit unit )
 {
   mDistanceUnit = unit;
@@ -4049,6 +4059,11 @@ bool QgsCentroidFillSymbolLayer::hasDataDefinedProperties() const
   return false;
 }
 
+bool QgsCentroidFillSymbolLayer::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  return true;
+}
+
 void QgsCentroidFillSymbolLayer::setOutputUnit( QgsUnitTypes::RenderUnit unit )
 {
   if ( mMarker )
@@ -4616,6 +4631,11 @@ QgsRandomMarkerFillSymbolLayer *QgsRandomMarkerFillSymbolLayer::clone() const
   return res.release();
 }
 
+bool QgsRandomMarkerFillSymbolLayer::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  return true;
+}
+
 QgsSymbol *QgsRandomMarkerFillSymbolLayer::subSymbol()
 {
   return mMarker.get();

diff --git a/src/core/symbology/qgsfillsymbollayer.h b/src/core/symbology/qgsfillsymbollayer.h
@@ -254,18 +254,13 @@ class CORE_EXPORT QgsGradientFillSymbolLayer : public QgsFillSymbolLayer
     // implemented from base classes
 
     QString layerType() const override;
-
     void startRender( QgsSymbolRenderContext &context ) override;
-
     void stopRender( QgsSymbolRenderContext &context ) override;
-
     void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context ) override;
-
     QVariantMap properties() const override;
-
     QgsGradientFillSymbolLayer *clone() const override SIP_FACTORY;
-
     double estimateMaxBleed( const QgsRenderContext &context ) const override;
+    bool canCauseArtifactsBetweenAdjacentTiles() const override;
 
     //! Type of gradient, e.g., linear or radial
     GradientType gradientType() const { return mGradientType; }
@@ -454,18 +449,13 @@ class CORE_EXPORT QgsShapeburstFillSymbolLayer : public QgsFillSymbolLayer
     // implemented from base classes
 
     QString layerType() const override;
-
     void startRender( QgsSymbolRenderContext &context ) override;
-
     void stopRender( QgsSymbolRenderContext &context ) override;
-
     void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context ) override;
-
     QVariantMap properties() const override;
-
     QgsShapeburstFillSymbolLayer *clone() const override SIP_FACTORY;
-
     double estimateMaxBleed( const QgsRenderContext &context ) const override;
+    bool canCauseArtifactsBetweenAdjacentTiles() const override;
 
     /**
      * Sets the blur radius, which controls the amount of blurring applied to the fill.
@@ -1860,6 +1850,7 @@ class CORE_EXPORT QgsRandomMarkerFillSymbolLayer : public QgsFillSymbolLayer
     void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context ) override;
     QVariantMap properties() const override;
     QgsRandomMarkerFillSymbolLayer *clone() const override SIP_FACTORY;
+    bool canCauseArtifactsBetweenAdjacentTiles() const override;
 
     void setColor( const QColor &color ) override;
     QColor color() const override;
@@ -2037,34 +2028,24 @@ class CORE_EXPORT QgsCentroidFillSymbolLayer : public QgsFillSymbolLayer
     // implemented from base classes
 
     QString layerType() const override;
-
     void startRender( QgsSymbolRenderContext &context ) override;
-
     void stopRender( QgsSymbolRenderContext &context ) override;
-
     void renderPolygon( const QPolygonF &points, const QVector<QPolygonF> *rings, QgsSymbolRenderContext &context ) override;
-
     QVariantMap properties() const override;
-
     QgsCentroidFillSymbolLayer *clone() const override SIP_FACTORY;
-
     void toSld( QDomDocument &doc, QDomElement &element, const QVariantMap &props ) const override;
-
     void setColor( const QColor &color ) override;
     QColor color() const override;
-
     QgsSymbol *subSymbol() override;
     bool setSubSymbol( QgsSymbol *symbol SIP_TRANSFER ) override;
-
     void setOutputUnit( QgsUnitTypes::RenderUnit unit ) override;
     QgsUnitTypes::RenderUnit outputUnit() const override;
     bool usesMapUnits() const override;
-
     void setMapUnitScale( const QgsMapUnitScale &scale ) override;
     QgsMapUnitScale mapUnitScale() const override;
-
     QSet<QString> usedAttributes( const QgsRenderContext &context ) const override;
     bool hasDataDefinedProperties() const override;
+    bool canCauseArtifactsBetweenAdjacentTiles() const override;
 
     void setPointOnSurface( bool pointOnSurface ) { mPointOnSurface = pointOnSurface; }
     bool pointOnSurface() const { return mPointOnSurface; }

diff --git a/src/core/symbology/qgslinesymbollayer.cpp b/src/core/symbology/qgslinesymbollayer.cpp
@@ -1351,6 +1351,24 @@ QVariantMap QgsTemplatedLineSymbolLayerBase::properties() const
   return map;
 }
 
+bool QgsTemplatedLineSymbolLayerBase::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  switch ( mPlacement )
+  {
+    case QgsTemplatedLineSymbolLayerBase::Interval:
+    case QgsTemplatedLineSymbolLayerBase::CentralPoint:
+    case QgsTemplatedLineSymbolLayerBase::SegmentCenter:
+      return true;
+
+    case QgsTemplatedLineSymbolLayerBase::Vertex:
+    case QgsTemplatedLineSymbolLayerBase::CurvePoint:
+    case QgsTemplatedLineSymbolLayerBase::LastVertex:
+    case QgsTemplatedLineSymbolLayerBase::FirstVertex:
+      return false;
+  }
+  return false;
+}
+
 void QgsTemplatedLineSymbolLayerBase::copyTemplateSymbolProperties( QgsTemplatedLineSymbolLayerBase *destLayer ) const
 {
   destLayer->setSubSymbol( const_cast< QgsTemplatedLineSymbolLayerBase * >( this )->subSymbol()->clone() );

diff --git a/src/core/symbology/qgslinesymbollayer.h b/src/core/symbology/qgslinesymbollayer.h
@@ -599,6 +599,7 @@ class CORE_EXPORT QgsTemplatedLineSymbolLayerBase : public QgsLineSymbolLayer
     void setMapUnitScale( const QgsMapUnitScale &scale ) FINAL;
     QgsMapUnitScale mapUnitScale() const FINAL;
     QVariantMap properties() const override;
+    bool canCauseArtifactsBetweenAdjacentTiles() const override;
 
   protected:
 

diff --git a/src/core/symbology/qgssymbollayer.cpp b/src/core/symbology/qgssymbollayer.cpp
@@ -234,6 +234,11 @@ bool QgsSymbolLayer::isCompatibleWithSymbol( QgsSymbol *symbol ) const
   return symbol->type() == mType;
 }
 
+bool QgsSymbolLayer::canCauseArtifactsBetweenAdjacentTiles() const
+{
+  return false;
+}
+
 bool QgsSymbolLayer::usesMapUnits() const
 {
   return false;

diff --git a/src/core/symbology/qgssymbollayer.h b/src/core/symbology/qgssymbollayer.h
@@ -361,6 +361,16 @@ class CORE_EXPORT QgsSymbolLayer
     //! Returns if the layer can be used below the specified symbol
     virtual bool isCompatibleWithSymbol( QgsSymbol *symbol ) const;
 
+    /**
+     * Returns TRUE if the symbol layer rendering can cause visible artifacts across a single feature
+     * when the feature is rendered as a series of adjacent map tiles each containing a portion of the feature's geometry.
+     *
+     * The default implementation returns FALSE.
+     *
+     * \since QGIS 3.18
+     */
+    virtual bool canCauseArtifactsBetweenAdjacentTiles() const;
+
     void setLocked( bool locked ) { mLocked = locked; }
     bool isLocked() const { return mLocked; }