Make QgsCustomDropHandler a QObject, and only store weak pointers to …

…them

This means if a plugin registers a custom drop handler, but crashes
before it can deregister it, at least it won't leave the main
app in a crashy state.

python/gui/qgscustomdrophandler.sip

@@ -8,7 +8,7 @@
 
 
 
-class QgsCustomDropHandler
+class QgsCustomDropHandler : QObject
 {
 %Docstring
  Abstract base class that may be implemented to handle new types of data to be dropped in QGIS.

src/app/qgisapp.cpp

@@ -1334,10 +1334,11 @@ void QgisApp::dropEvent( QDropEvent *event )
   timer->setInterval( 50 );
 
   // first, allow custom handlers to directly operate on the mime data
-  const QList<QgsCustomDropHandler *> handlers = mCustomDropHandlers;
+  const QList<QPointer<QgsCustomDropHandler >> handlers = mCustomDropHandlers;
   for ( QgsCustomDropHandler *handler : handlers )
   {
-    handler->handleMimeData( event->mimeData() );
+    if ( handler )
+      handler->handleMimeData( event->mimeData() );
   }
 
   // get the file list
@@ -1415,10 +1416,10 @@ void QgisApp::dropEvent( QDropEvent *event )
       bool handled = false;
 
       // give custom drop handlers first priority at handling the file
-      const QList<QgsCustomDropHandler *> handlers = mCustomDropHandlers;
+      const QList<QPointer<QgsCustomDropHandler >>handlers = mCustomDropHandlers;
       for ( QgsCustomDropHandler *handler : handlers )
       {
-        if ( handler->handleFileDrop( file ) )
+        if ( handler && handler->handleFileDrop( file ) )
         {
           handled = true;
           break;
@@ -1490,7 +1491,7 @@ void QgisApp::handleDropUriList( const QgsMimeDataUtils::UriList &lst )
     {
       Q_FOREACH ( QgsCustomDropHandler *handler, mCustomDropHandlers )
       {
-        if ( handler->key() == u.providerKey )
+        if ( handler && handler->key() == u.providerKey )
         {
           handler->handleDrop( u );
           break;

src/app/qgisapp.h

@@ -2048,7 +2048,7 @@ class APP_EXPORT QgisApp : public QMainWindow, private Ui::MainWindow
     QList<QgsMapLayerConfigWidgetFactory *> mMapLayerPanelFactories;
     QList<QPointer<QgsOptionsWidgetFactory>> mOptionsWidgetFactories;
 
-    QList<QgsCustomDropHandler *> mCustomDropHandlers;
+    QList<QPointer<QgsCustomDropHandler>> mCustomDropHandlers;
 
     QDateTime mProjectLastModified;
 

src/gui/CMakeLists.txt

@@ -385,6 +385,7 @@ SET(QGIS_GUI_MOC_HDRS
   qgsconfigureshortcutsdialog.h
   qgscredentialdialog.h
   qgscurveeditorwidget.h
+  qgscustomdrophandler.h
   qgsdatumtransformdialog.h
   qgsdetaileditemdelegate.h
   qgsdetaileditemwidget.h
@@ -684,7 +685,6 @@ SET(QGIS_GUI_HDRS
   qgsattributeforminterface.h
   qgsattributeformlegacyinterface.h
   qgscursors.h
-  qgscustomdrophandler.h
   qgsdetaileditemdata.h
   qgsexpressionbuilderdialog.h
   qgsgeometryrubberband.h

src/gui/qgscustomdrophandler.h

@@ -30,8 +30,10 @@
  *
  * \since QGIS 3.0
  */
-class GUI_EXPORT QgsCustomDropHandler
+class GUI_EXPORT QgsCustomDropHandler : public QObject
 {
+    Q_OBJECT
+
   public:
     virtual ~QgsCustomDropHandler() = default;