Add API to pass approximate layer rendering time estimatation to

map layer renderers These renderers can then use the layer rendering time for the previous map render job to refine their logic regarding when its appropriate to start compositing the layer render
qgis · Jan 27, 2021 · bb746c6 · bb746c6
1 parent ff36aa0
commit bb746c6
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Showing 6 changed files with 59 additions and 1 deletion.
diff --git a/python/core/auto_generated/qgsmaplayerrenderer.sip.in b/python/core/auto_generated/qgsmaplayerrenderer.sip.in
@@ -104,6 +104,7 @@ least partially) some data
 .. versionadded:: 3.18
 %End
 
+
   protected:
 
 

diff --git a/python/core/auto_generated/qgsmaprendererjob.sip.in b/python/core/auto_generated/qgsmaprendererjob.sip.in
@@ -145,6 +145,7 @@ Returns the total time it took to finish the job (in milliseconds).
 %End
 
 
+
     const QgsMapSettings &mapSettings() const;
 %Docstring
 Returns map settings with which this job was started.
@@ -191,6 +192,7 @@ emitted when asynchronous rendering is finished (or canceled).
 
 
 
+
 };
 
 

diff --git a/src/core/qgsmaplayerrenderer.h b/src/core/qgsmaplayerrenderer.h
@@ -118,6 +118,18 @@ class CORE_EXPORT QgsMapLayerRenderer
      */
     bool isReadyToCompose() const { return mReadyToCompose; }
 
+    /**
+     * Sets approximate render \a time (in ms) for the layer to render.
+     *
+     * This can be used to specifies a hint at the expected render times for the layer, so that
+     * the individual layer renderer subclasses can apply heuristics and determine appropriate update
+     * intervals during the render operation.
+     *
+     * \note Not available in Python bindings.
+     * \since QGIS 3.18
+     */
+    virtual void setLayerRenderingTimeHint( int time ) SIP_SKIP { Q_UNUSED( time ) }
+
   protected:
     QStringList mErrors;
     QString mLayerID;

diff --git a/src/core/qgsmaprendererjob.cpp b/src/core/qgsmaprendererjob.cpp
@@ -95,12 +95,17 @@ QHash<QgsMapLayer *, int> QgsMapRendererJob::perLayerRenderingTime() const
   QHash<QgsMapLayer *, int> result;
   for ( auto it = mPerLayerRenderingTime.constBegin(); it != mPerLayerRenderingTime.constEnd(); ++it )
   {
-    if ( auto &&lKey = it.key() )
+    if ( auto && lKey = it.key() )
       result.insert( lKey, it.value() );
   }
   return result;
 }
 
+void QgsMapRendererJob::setLayerRenderingTimeHints( const QHash<QString, int> &hints )
+{
+  mLayerRenderingTimeHints = hints;
+}
+
 const QgsMapSettings &QgsMapRendererJob::mapSettings() const
 {
   return mSettings;
@@ -399,6 +404,7 @@ LayerRenderJobs QgsMapRendererJob::prepareJobs( QPainter *painter, QgsLabelingEn
     job.img = nullptr;
     job.layer = ml;
     job.layerId = ml->id();
+    job.estimatedRenderingTime = mLayerRenderingTimeHints.value( ml->id(), 0 );
     job.renderingTime = -1;
 
     job.context = QgsRenderContext::fromMapSettings( mSettings );
@@ -438,6 +444,8 @@ LayerRenderJobs QgsMapRendererJob::prepareJobs( QPainter *painter, QgsLabelingEn
     QElapsedTimer layerTime;
     layerTime.start();
     job.renderer = ml->createMapRenderer( job.context );
+    if ( job.renderer )
+      job.renderer->setLayerRenderingTimeHint( job.estimatedRenderingTime );
 
     // If we are drawing with an alternative blending mode then we need to render to a separate image
     // before compositing this on the map. This effectively flattens the layer and prevents

diff --git a/src/core/qgsmaprendererjob.h b/src/core/qgsmaprendererjob.h
@@ -65,6 +65,18 @@ struct LayerRenderJob
   bool cached;
   QgsWeakMapLayerPointer layer;
   int renderingTime; //!< Time it took to render the layer in ms (it is -1 if not rendered or still rendering)
+
+  /**
+   * Estimated time for the layer to render, in ms.
+   *
+   * This can be used to specifies hints at the expected render times for the layer, so that
+   * the corresponding layer renderer can apply heuristics and determine appropriate update
+   * intervals during the render operation.
+   *
+   * \since QGIS 3.18
+   */
+  int estimatedRenderingTime = 0;
+
   QStringList errors; //!< Rendering errors
 
   /**
@@ -286,6 +298,20 @@ class CORE_EXPORT QgsMapRendererJob : public QObject
      */
     QHash< QgsMapLayer *, int > perLayerRenderingTime() const SIP_SKIP;
 
+    /**
+     * Sets approximate render times (in ms) for map layers.
+     *
+     * This can be used to specifies hints at the expected render times for layers, so that
+     * the individual layer renderers can apply heuristics and determine appropriate update
+     * intervals during the render operation.
+     *
+     * The keys for \a hints must be set to the corresponding layer IDs.
+     *
+     * \note Not available in Python bindings.
+     * \since QGIS 3.18
+     */
+    void setLayerRenderingTimeHints( const QHash< QString, int > &hints ) SIP_SKIP;
+
     /**
      * Returns map settings with which this job was started.
      * \returns A QgsMapSettings instance with render settings
@@ -326,6 +352,13 @@ class CORE_EXPORT QgsMapRendererJob : public QObject
     //! Render time (in ms) per layer, by layer ID
     QHash< QgsWeakMapLayerPointer, int > mPerLayerRenderingTime;
 
+    /**
+     * Approximate expected layer rendering time per layer, by layer ID
+     *
+     * \since QGIS 3.18
+     */
+    QHash< QString, int > mLayerRenderingTimeHints;
+
     /**
      * TRUE if layer rendering time should be recorded.
      */

diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
@@ -604,8 +604,10 @@ void QgsMapCanvas::refreshMap()
     mJob = new QgsMapRendererParallelJob( renderSettings );
   else
     mJob = new QgsMapRendererSequentialJob( renderSettings );
+
   connect( mJob, &QgsMapRendererJob::finished, this, &QgsMapCanvas::rendererJobFinished );
   mJob->setCache( mCache );
+  mJob->setLayerRenderingTimeHints( mLastLayerRenderTime );
 
   mJob->start();