Implement responsive map refresh when canvas z range changes

python/core/auto_generated/qgsmaplayerelevationproperties.sip.in

@@ -37,6 +37,11 @@ how an individual QgsMapLayer behaves with relation to z values or elevations.
     QgsMapLayerElevationProperties( QObject *parent /TransferThis/ );
 %Docstring
 Constructor for QgsMapLayerElevationProperties, with the specified ``parent`` object.
+%End
+
+    virtual bool hasElevation() const;
+%Docstring
+Returns ``True`` if the layer has an elevation or z component.
 %End
 
     virtual QDomElement writeXml( QDomElement &element, QDomDocument &doc, const QgsReadWriteContext &context ) = 0;

python/gui/auto_generated/qgsmapcanvas.sip.in

@@ -979,6 +979,8 @@ Returns the range of z-values which will be visible in the map.
 
 .. seealso:: :py:func:`setZRange`
 
+.. seealso:: :py:func:`zRangeChanged`
+
 .. versionadded:: 3.18
 %End
 
@@ -988,6 +990,8 @@ Sets the ``range`` of z-values which will be visible in the map.
 
 .. seealso:: :py:func:`zRange`
 
+.. seealso:: :py:func:`zRangeChanged`
+
 .. versionadded:: 3.18
 %End
 
@@ -1171,6 +1175,16 @@ Emitted when the map canvas temporal range changes.
 .. versionadded:: 3.14
 %End
 
+    void zRangeChanged();
+%Docstring
+Emitted when the map canvas z (elevation) range changes.
+
+.. seealso:: :py:func:`zRange`
+
+.. seealso:: :py:func:`setZRange`
+
+.. versionadded:: 3.18
+%End
 
     void contextMenuAboutToShow( QMenu *menu, QgsMapMouseEvent *event );
 %Docstring
@@ -1180,7 +1194,6 @@ Can be used to extend the context menu.
 .. versionadded:: 3.16
 %End
 
-
   protected:
 
     virtual bool event( QEvent *e );

src/core/qgsmaplayerelevationproperties.cpp

@@ -22,6 +22,11 @@ QgsMapLayerElevationProperties::QgsMapLayerElevationProperties( QObject *parent
 {
 }
 
+bool QgsMapLayerElevationProperties::hasElevation() const
+{
+  return false;
+}
+
 bool QgsMapLayerElevationProperties::isVisibleInZRange( const QgsDoubleRange & ) const
 {
   return true;

src/core/qgsmaplayerelevationproperties.h

@@ -58,6 +58,11 @@ class CORE_EXPORT QgsMapLayerElevationProperties : public QObject
      */
     QgsMapLayerElevationProperties( QObject *parent SIP_TRANSFERTHIS );
 
+    /**
+     * Returns TRUE if the layer has an elevation or z component.
+     */
+    virtual bool hasElevation() const;
+
     /**
      * Writes the properties to a DOM \a element, to be used later with readXml().
      *

src/gui/qgsmapcanvas.cpp

@@ -84,6 +84,7 @@ email                : sherman at mrcc.com
 #include "qgsruntimeprofiler.h"
 #include "qgsprojectionselectiondialog.h"
 #include "qgsannotationlayer.h"
+#include "qgsmaplayerelevationproperties.h"
 
 /**
  * \ingroup gui
@@ -731,6 +732,7 @@ void QgsMapCanvas::rendererJobFinished()
   {
     mRefreshAfterJob = false;
     clearTemporalCache();
+    clearElevationCache();
     refresh();
   }
 }
@@ -806,6 +808,24 @@ void QgsMapCanvas::clearTemporalCache()
   }
 }
 
+void QgsMapCanvas::clearElevationCache()
+{
+  if ( mCache )
+  {
+    const QList<QgsMapLayer *> layerList = mapSettings().layers();
+    for ( QgsMapLayer *layer : layerList )
+    {
+      if ( layer->elevationProperties() && layer->elevationProperties()->hasElevation() )
+      {
+        if ( layer->elevationProperties()->flags() & QgsMapLayerElevationProperties::FlagDontInvalidateCachedRendersWhenRangeChanges )
+          continue;
+
+        mCache->invalidateCacheForLayer( layer );
+      }
+    }
+  }
+}
+
 void QgsMapCanvas::showContextMenu( QgsMapMouseEvent *event )
 {
   const QgsPointXY mapPoint = event->originalMapPoint();
@@ -1333,7 +1353,19 @@ QgsDoubleRange QgsMapCanvas::zRange() const
 
 void QgsMapCanvas::setZRange( const QgsDoubleRange &range )
 {
+  if ( zRange() == range )
+    return;
+
   mSettings.setZRange( range );
+
+  emit zRangeChanged();
+
+  // we need to discard any previously cached images which are elevation aware, so that these will be updated when
+  // the canvas is redrawn
+  if ( !mJob )
+    clearElevationCache();
+
+  autoRefreshTriggered();
 }
 
 void QgsMapCanvas::zoomToFeatureExtent( QgsRectangle &rect )

src/gui/qgsmapcanvas.h

@@ -883,6 +883,8 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
      * Returns the range of z-values which will be visible in the map.
      *
      * \see setZRange()
+     * \see zRangeChanged()
+     *
      * \since QGIS 3.18
      */
     QgsDoubleRange zRange() const;
@@ -891,6 +893,8 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
      * Sets the \a range of z-values which will be visible in the map.
      *
      * \see zRange()
+     * \see zRangeChanged()
+     *
      * \since QGIS 3.18
      */
     void setZRange( const QgsDoubleRange &range );
@@ -1060,6 +1064,15 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
      */
     void temporalRangeChanged();
 
+    /**
+     * Emitted when the map canvas z (elevation) range changes.
+     *
+     * \see zRange()
+     * \see setZRange()
+     *
+     * \since QGIS 3.18
+     */
+    void zRangeChanged();
 
     /**
      * Emitted before the map canvas context menu will be shown.
@@ -1069,7 +1082,6 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
      */
     void contextMenuAboutToShow( QMenu *menu, QgsMapMouseEvent *event );
 
-
   protected:
 
     bool event( QEvent *e ) override;
@@ -1329,6 +1341,11 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView
      */
     void clearTemporalCache();
 
+    /**
+     * Removes any rendered images of elevation aware layers from cache
+     */
+    void clearElevationCache();
+
     void showContextMenu( QgsMapMouseEvent *event );
 
     friend class TestQgsMapCanvas;