Fix crash on exit

nyalldawson · nyalldawson · commit b6832916d784 · 2018-05-01T20:31:57.000+10:00
Because the map canvas is destroyed before the project instance,
and QgsProject emits the labelingEngineSettingsChange signal
during its destructor, the lambda slot was getting executed
with a dangling map canvas pointer.

Correctly set the receiver in the lambda connection instead
so that the connection gets destroyed along with the canvas.
diff --git a/src/app/qgisapp.cpp b/src/app/qgisapp.cpp
@@ -3253,7 +3253,7 @@ void QgisApp::setupConnections()
   } );
 
   connect( QgsProject::instance(), &QgsProject::labelingEngineSettingsChanged,
-           this, [ = ]
+           mMapCanvas, [ = ]
   {
     mMapCanvas->setLabelingEngineSettings( QgsProject::instance()->labelingEngineSettings() );
   } );

Original file line number	Diff line number	Diff line change
`@@ -3253,7 +3253,7 @@ void QgisApp::setupConnections()`
`3253`	`3253`	`} );`
`3254`	`3254`
`3255`	`3255`	`connect( QgsProject::instance(), &QgsProject::labelingEngineSettingsChanged,`
`3256`		`- this, [ = ]`
	`3256`	`+ mMapCanvas, [ = ]`
`3257`	`3257`	`{`
`3258`	`3258`	`mMapCanvas->setLabelingEngineSettings( QgsProject::instance()->labelingEngineSettings() );`
`3259`	`3259`	`} );`