b=478816 check that gtk_drag_begin returns a non-NULL GdkDragContext r+sr=roc

widget/src/gtk2/nsDragService.cpp

@@ -176,40 +176,43 @@ nsDragService::InvokeDragSession(nsIDOMNode *aDOMNode,
     // length of this call
     mSourceDataItems = aArrayTransferables;
     // get the list of items we offer for drags
-    GtkTargetList *sourceList = 0;
+    GtkTargetList *sourceList = GetSourceList();
 
-    sourceList = GetSourceList();
+    if (!sourceList)
+        return NS_OK;
 
-    if (sourceList) {
-        // save our action type
-        GdkDragAction action = GDK_ACTION_DEFAULT;
+    // save our action type
+    GdkDragAction action = GDK_ACTION_DEFAULT;
 
-        if (aActionType & DRAGDROP_ACTION_COPY)
-            action = (GdkDragAction)(action | GDK_ACTION_COPY);
-        if (aActionType & DRAGDROP_ACTION_MOVE)
-            action = (GdkDragAction)(action | GDK_ACTION_MOVE);
-        if (aActionType & DRAGDROP_ACTION_LINK)
-            action = (GdkDragAction)(action | GDK_ACTION_LINK);
+    if (aActionType & DRAGDROP_ACTION_COPY)
+        action = (GdkDragAction)(action | GDK_ACTION_COPY);
+    if (aActionType & DRAGDROP_ACTION_MOVE)
+        action = (GdkDragAction)(action | GDK_ACTION_MOVE);
+    if (aActionType & DRAGDROP_ACTION_LINK)
+        action = (GdkDragAction)(action | GDK_ACTION_LINK);
 
-        // Create a fake event for the drag so we can pass the time
-        // (so to speak.)  If we don't do this the drag can end as a
-        // result of a button release that is actually _earlier_ than
-        // CurrentTime.  So we use the time on the last button press
-        // event, as that will always be older than the button release
-        // that ends any drag.
-        GdkEvent event;
-        memset(&event, 0, sizeof(GdkEvent));
-        event.type = GDK_BUTTON_PRESS;
-        event.button.window = mHiddenWidget->window;
-        event.button.time = nsWindow::mLastButtonPressTime;
+    // Create a fake event for the drag so we can pass the time
+    // (so to speak.)  If we don't do this the drag can end as a
+    // result of a button release that is actually _earlier_ than
+    // CurrentTime.  So we use the time on the last button press
+    // event, as that will always be older than the button release
+    // that ends any drag.
+    GdkEvent event;
+    memset(&event, 0, sizeof(GdkEvent));
+    event.type = GDK_BUTTON_PRESS;
+    event.button.window = mHiddenWidget->window;
+    event.button.time = nsWindow::mLastButtonPressTime;
 
-        // start our drag.
-        GdkDragContext *context = gtk_drag_begin(mHiddenWidget,
-                                                 sourceList,
-                                                 action,
-                                                 1,
-                                                 &event);
+    // start our drag.
+    GdkDragContext *context = gtk_drag_begin(mHiddenWidget,
+                                             sourceList,
+                                             action,
+                                             1,
+                                             &event);
 
+    if (!context) {
+        rv = NS_ERROR_FAILURE;
+    } else {
         PRBool needsFallbackIcon = PR_FALSE;
         nsIntRect dragRect;
         nsPresContext* pc;
@@ -239,11 +242,11 @@ nsDragService::InvokeDragSession(nsIDOMNode *aDOMNode,
 
         if (needsFallbackIcon)
           gtk_drag_set_icon_default(context);
-
-        gtk_target_list_unref(sourceList);
     }
 
-    return NS_OK;
+    gtk_target_list_unref(sourceList);
+
+    return rv;
 }
 
 PRBool