Bug 1166741 - Workaround for GTK3 bug where file choosers' delegate refcount is not incremented. r=karlt

widget/gtk/mozgtk/mozgtk.c

@@ -209,6 +209,7 @@ STUB(gtk_file_chooser_set_local_only)
 STUB(gtk_file_chooser_set_preview_widget)
 STUB(gtk_file_chooser_set_preview_widget_active)
 STUB(gtk_file_chooser_set_select_multiple)
+STUB(gtk_file_chooser_widget_get_type)
 STUB(gtk_file_filter_add_pattern)
 STUB(gtk_file_filter_new)
 STUB(gtk_file_filter_set_name)

widget/gtk/nsFilePicker.cpp

@@ -165,7 +165,8 @@ NS_IMPL_ISUPPORTS(nsFilePicker, nsIFilePicker)
 nsFilePicker::nsFilePicker()
   : mSelectedType(0),
     mRunning(false),
-    mAllowURLs(false)
+    mAllowURLs(false),
+    mFileChooserDelegate(nullptr)
 {
 }
 
@@ -431,6 +432,27 @@ nsFilePicker::Open(nsIFilePickerShownCallback *aCallback)
     } else {
       nsAutoCString directory;
       defaultPath->GetNativePath(directory);
+
+#if (MOZ_WIDGET_GTK == 3)
+      // Workaround for problematic refcounting in GTK3 before 3.16.
+      // We need to keep a reference to the dialog's internal delegate.
+      // Otherwise, if our dialog gets destroyed, we'll lose the dialog's
+      // delegate by the time this gets processed in the event loop.
+      // See: https://bugzilla.mozilla.org/show_bug.cgi?id=1166741
+      GtkDialog *dialog = GTK_DIALOG(file_chooser);
+      GtkContainer *area = GTK_CONTAINER(gtk_dialog_get_content_area(dialog));
+      gtk_container_forall(area, [](GtkWidget *widget,
+                                    gpointer data) {
+          if (GTK_IS_FILE_CHOOSER_WIDGET(widget)) {
+            auto result = static_cast<GtkFileChooserWidget**>(data);
+            *result = GTK_FILE_CHOOSER_WIDGET(widget);
+          }
+      }, &mFileChooserDelegate);
+
+      if (mFileChooserDelegate)
+        g_object_ref(mFileChooserDelegate);
+#endif
+
       gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(file_chooser),
                                           directory.get());
     }
@@ -548,6 +570,21 @@ nsFilePicker::Done(GtkWidget* file_chooser, gint response)
   // been released.
   gtk_widget_destroy(file_chooser);
 
+#if (MOZ_WIDGET_GTK == 3)
+      if (mFileChooserDelegate) {
+        // Properly deref our acquired reference. We call this after
+        // gtk_widget_destroy() to try and ensure that pending file info
+        // queries caused by updating the current folder have been cancelled.
+        // However, we do not know for certain when the callback will run after
+        // cancelled.
+        g_idle_add([](gpointer data) -> gboolean {
+            g_object_unref(data);
+            return G_SOURCE_REMOVE;
+        }, mFileChooserDelegate);
+        mFileChooserDelegate = nullptr;
+      }
+#endif
+
   if (mCallback) {
     mCallback->Done(result);
     mCallback = nullptr;

widget/gtk/nsFilePicker.h

@@ -73,6 +73,8 @@ protected:
 
 private:
   static nsIFile *mPrevDisplayDirectory;
+
+  GtkFileChooserWidget *mFileChooserDelegate;
 };
 
 #endif