Merge pull request #4204 from nyalldawson/cancel_without_blocking

Don't block when canceling canvas render jobs

Author: nyalldawson

python/core/qgsmaprenderercustompainterjob.sip

@@ -19,6 +19,7 @@ class QgsMapRendererCustomPainterJob : QgsMapRendererJob
 
     virtual void start();
     virtual void cancel();
+    virtual void cancelWithoutBlocking();
     virtual void waitForFinished();
     virtual bool isActive() const;
     virtual bool usedCachedLabels() const;

python/core/qgsmaprendererjob.sip

@@ -18,6 +18,8 @@ class QgsMapRendererJob : QObject
     //! Does nothing if the rendering is not active.
     virtual void cancel() = 0;
 
+    virtual void cancelWithoutBlocking() = 0;
+
     //! Block until the job has finished.
     virtual void waitForFinished() = 0;
 

python/core/qgsmaprendererparalleljob.sip

@@ -18,6 +18,7 @@ class QgsMapRendererParallelJob : QgsMapRendererQImageJob
 
     virtual void start();
     virtual void cancel();
+    virtual void cancelWithoutBlocking();
     virtual void waitForFinished();
     virtual bool isActive() const;
     virtual bool usedCachedLabels() const;

python/core/qgsmaprenderersequentialjob.sip

@@ -19,6 +19,7 @@ class QgsMapRendererSequentialJob : QgsMapRendererQImageJob
 
     virtual void start();
     virtual void cancel();
+    virtual void cancelWithoutBlocking();
     virtual void waitForFinished();
     virtual bool isActive() const;
     virtual bool usedCachedLabels() const;

src/core/qgsmaprenderercustompainterjob.cpp

@@ -109,14 +109,7 @@ void QgsMapRendererCustomPainterJob::cancel()
 
   QgsDebugMsg( "QPAINTER canceling" );
   disconnect( &mFutureWatcher, &QFutureWatcher<void>::finished, this, &QgsMapRendererCustomPainterJob::futureFinished );
-
-  mLabelJob.context.setRenderingStopped( true );
-  for ( LayerRenderJobs::iterator it = mLayerJobs.begin(); it != mLayerJobs.end(); ++it )
-  {
-    it->context.setRenderingStopped( true );
-    if ( it->renderer && it->renderer->feedback() )
-      it->renderer->feedback()->cancel();
-  }
+  cancelWithoutBlocking();
 
   QTime t;
   t.start();
@@ -130,6 +123,23 @@ void QgsMapRendererCustomPainterJob::cancel()
   QgsDebugMsg( "QPAINTER canceled" );
 }
 
+void QgsMapRendererCustomPainterJob::cancelWithoutBlocking()
+{
+  if ( !isActive() )
+  {
+    QgsDebugMsg( "QPAINTER not running!" );
+    return;
+  }
+
+  mLabelJob.context.setRenderingStopped( true );
+  for ( LayerRenderJobs::iterator it = mLayerJobs.begin(); it != mLayerJobs.end(); ++it )
+  {
+    it->context.setRenderingStopped( true );
+    if ( it->renderer && it->renderer->feedback() )
+      it->renderer->feedback()->cancel();
+  }
+}
+
 void QgsMapRendererCustomPainterJob::waitForFinished()
 {
   if ( !isActive() )

src/core/qgsmaprenderercustompainterjob.h

@@ -39,6 +39,7 @@ class CORE_EXPORT QgsMapRendererCustomPainterJob : public QgsMapRendererJob
 
     virtual void start() override;
     virtual void cancel() override;
+    virtual void cancelWithoutBlocking() override;
     virtual void waitForFinished() override;
     virtual bool isActive() const override;
     virtual bool usedCachedLabels() const override;

src/core/qgsmaprendererjob.h

@@ -121,6 +121,13 @@ class CORE_EXPORT QgsMapRendererJob : public QObject
     //! Does nothing if the rendering is not active.
     virtual void cancel() = 0;
 
+    /**
+     * Triggers cancelation of the rendering job without blocking. The render job will continue
+     * to operate until it is able to cancel, at which stage the finished() signal will be emitted.
+     * Does nothing if the rendering is not active.
+     */
+    virtual void cancelWithoutBlocking() = 0;
+
     //! Block until the job has finished.
     virtual void waitForFinished() = 0;
 
@@ -296,6 +303,7 @@ class CORE_EXPORT QgsMapRendererQImageJob : public QgsMapRendererJob
 
     //! Get a preview/resulting image
     virtual QImage renderedImage() = 0;
+
 };
 
 

src/core/qgsmaprendererparalleljob.cpp

@@ -108,6 +108,28 @@ void QgsMapRendererParallelJob::cancel()
   Q_ASSERT( mStatus == Idle );
 }
 
+void QgsMapRendererParallelJob::cancelWithoutBlocking()
+{
+  if ( !isActive() )
+    return;
+
+  QgsDebugMsg( QString( "PARALLEL cancel at status %1" ).arg( mStatus ) );
+
+  mLabelJob.context.setRenderingStopped( true );
+  for ( LayerRenderJobs::iterator it = mLayerJobs.begin(); it != mLayerJobs.end(); ++it )
+  {
+    it->context.setRenderingStopped( true );
+    if ( it->renderer && it->renderer->feedback() )
+      it->renderer->feedback()->cancel();
+  }
+
+  if ( mStatus == RenderingLayers )
+  {
+    disconnect( &mFutureWatcher, &QFutureWatcher<void>::finished, this, &QgsMapRendererParallelJob::renderLayersFinished );
+    connect( &mFutureWatcher, &QFutureWatcher<void>::finished, this, &QgsMapRendererParallelJob::renderingFinished );
+  }
+}
+
 void QgsMapRendererParallelJob::waitForFinished()
 {
   if ( !isActive() )

src/core/qgsmaprendererparalleljob.h

@@ -36,6 +36,7 @@ class CORE_EXPORT QgsMapRendererParallelJob : public QgsMapRendererQImageJob
 
     virtual void start() override;
     virtual void cancel() override;
+    virtual void cancelWithoutBlocking() override;
     virtual void waitForFinished() override;
     virtual bool isActive() const override;
 

src/core/qgsmaprenderersequentialjob.cpp

@@ -83,6 +83,15 @@ void QgsMapRendererSequentialJob::cancel()
   Q_ASSERT( !mInternalJob && !mPainter );
 }
 
+void QgsMapRendererSequentialJob::cancelWithoutBlocking()
+{
+  if ( !isActive() )
+    return;
+
+  QgsDebugMsg( "sequential - cancel internal" );
+  mInternalJob->cancelWithoutBlocking();
+}
+
 void QgsMapRendererSequentialJob::waitForFinished()
 {
   if ( !isActive() )