QgisApp::closeProject(): cancel canvas jobs before closing the projec…

…t, to avoid rendering jobs to access deleted objects (fixes #44144)
qgis · Sep 24, 2021 · 0e45d51 · 0e45d51 · roya0045 · Jan 9, 2022
1 parent 4859506
commit 0e45d51
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Showing 4 changed files with 26 additions and 9 deletions.
diff --git a/python/gui/auto_generated/qgsmapcanvas.sip.in b/python/gui/auto_generated/qgsmapcanvas.sip.in
@@ -149,6 +149,7 @@ Make sure to remove any rendered images from cache (does nothing if cache is not
 .. versionadded:: 2.4
 %End
 
+
     void waitWhileRendering();
 %Docstring
 Blocks until the rendering job has finished.

diff --git a/src/app/qgisapp.cpp b/src/app/qgisapp.cpp
@@ -14000,6 +14000,7 @@ void QgisApp::closeProject()
   // clear out any stuff from project
   mMapCanvas->setLayers( QList<QgsMapLayer *>() );
   mMapCanvas->clearCache();
+  mMapCanvas->cancelJobs();
   mOverviewCanvas->setLayers( QList<QgsMapLayer *>() );
 
   // Avoid unnecessary layer changed handling for each layer removed - instead,

diff --git a/src/gui/qgsmapcanvas.cpp b/src/gui/qgsmapcanvas.cpp
@@ -254,12 +254,29 @@ QgsMapCanvas::~QgsMapCanvas()
   }
   mLastNonZoomMapTool = nullptr;
 
+  cancelJobs();
+
+  // delete canvas items prior to deleting the canvas
+  // because they might try to update canvas when it's
+  // already being destructed, ends with segfault
+  qDeleteAll( mScene->items() );
+
+  mScene->deleteLater();  // crashes in python tests on windows
+
+  delete mCache;
+}
+
+
+void QgsMapCanvas::cancelJobs()
+{
+
   // rendering job may still end up writing into canvas map item
   // so kill it before deleting canvas items
   if ( mJob )
   {
     whileBlocking( mJob )->cancel();
     delete mJob;
+    mJob = nullptr;
   }
 
   QList< QgsMapRendererQImageJob * >::const_iterator previewJob = mPreviewJobs.constBegin();
@@ -271,17 +288,9 @@ QgsMapCanvas::~QgsMapCanvas()
       delete *previewJob;
     }
   }
-
-  // delete canvas items prior to deleting the canvas
-  // because they might try to update canvas when it's
-  // already being destructed, ends with segfault
-  qDeleteAll( mScene->items() );
-
-  mScene->deleteLater();  // crashes in python tests on windows
-
-  delete mCache;
 }
 
+
 void QgsMapCanvas::setMagnificationFactor( double factor, const QgsPointXY *center )
 {
   // do not go higher or lower than min max magnification ratio

diff --git a/src/gui/qgsmapcanvas.h b/src/gui/qgsmapcanvas.h
@@ -200,6 +200,12 @@ class GUI_EXPORT QgsMapCanvas : public QGraphicsView, public QgsExpressionContex
      */
     void clearCache();
 
+    /**
+     * Cancel any rendering job, in a blocking way. Used for application closing.
+     * \note not available in Python bindings
+     */
+    void cancelJobs() SIP_SKIP;
+
     /**
      * Blocks until the rendering job has finished.
      *