b=544211 propagate scroll events from GtkPlug to the embedder r=roc

dom/plugins/PluginModuleChild.cpp

@@ -199,6 +199,7 @@ PluginModuleChild::Init(const std::string& aPluginFilename,
 
 #if defined(MOZ_WIDGET_GTK2)
 typedef void (*GObjectDisposeFn)(GObject*);
+typedef gboolean (*GtkWidgetScrollEventFn)(GtkWidget*, GdkEventScroll*);
 typedef void (*GtkPlugEmbeddedFn)(GtkPlug*);
 
 static GObjectDisposeFn real_gtk_plug_dispose;
@@ -233,6 +234,92 @@ wrap_gtk_plug_dispose(GObject* object) {
     g_object_remove_toggle_ref(object, undo_bogus_unref, NULL);
 }
 
+static gboolean
+gtk_plug_scroll_event(GtkWidget *widget, GdkEventScroll *gdk_event)
+{
+    if (!GTK_WIDGET_TOPLEVEL(widget)) // in same process as its GtkSocket
+        return FALSE; // event not handled; propagate to GtkSocket
+
+    GdkWindow* socket_window = GTK_PLUG(widget)->socket_window;
+    if (!socket_window)
+        return FALSE;
+
+    // Propagate the event to the embedder.
+    GdkScreen* screen = gdk_drawable_get_screen(socket_window);
+    GdkWindow* plug_window = widget->window;
+    GdkWindow* event_window = gdk_event->window;
+    gint x = gdk_event->x;
+    gint y = gdk_event->y;
+    unsigned int button;
+    unsigned int button_mask = 0;
+    XEvent xevent;
+    Display* dpy = GDK_WINDOW_XDISPLAY(socket_window);
+
+    /* Translate the event coordinates to the plug window,
+     * which should be aligned with the socket window.
+     */
+    while (event_window != plug_window)
+    {
+        gint dx, dy;
+
+        gdk_window_get_position(event_window, &dx, &dy);
+        x += dx;
+        y += dy;
+
+        event_window = gdk_window_get_parent(event_window);
+        if (!event_window)
+            return FALSE;
+    }
+
+    switch (gdk_event->direction) {
+    case GDK_SCROLL_UP:
+        button = 4;
+        button_mask = Button4Mask;
+        break;
+    case GDK_SCROLL_DOWN:
+        button = 5;
+        button_mask = Button5Mask;
+        break;
+    case GDK_SCROLL_LEFT:
+        button = 6;
+        break;
+    case GDK_SCROLL_RIGHT:
+        button = 7;
+        break;
+    default:
+        return FALSE; // unknown GdkScrollDirection
+    }
+
+    memset(&xevent, 0, sizeof(xevent));
+    xevent.xbutton.type = ButtonPress;
+    xevent.xbutton.window = GDK_WINDOW_XWINDOW(socket_window);
+    xevent.xbutton.root = GDK_WINDOW_XWINDOW(gdk_screen_get_root_window(screen));
+    xevent.xbutton.subwindow = GDK_WINDOW_XWINDOW(plug_window);
+    xevent.xbutton.time = gdk_event->time;
+    xevent.xbutton.x = x;
+    xevent.xbutton.y = y;
+    xevent.xbutton.x_root = gdk_event->x_root;
+    xevent.xbutton.y_root = gdk_event->y_root;
+    xevent.xbutton.state = gdk_event->state;
+    xevent.xbutton.button = button;
+    xevent.xbutton.same_screen = True;
+
+    gdk_error_trap_push();
+
+    XSendEvent(dpy, xevent.xbutton.window,
+               True, ButtonPressMask, &xevent);
+
+    xevent.xbutton.type = ButtonRelease;
+    xevent.xbutton.state |= button_mask;
+    XSendEvent(dpy, xevent.xbutton.window,
+               True, ButtonReleaseMask, &xevent);
+
+    gdk_display_sync(gdk_screen_get_display(screen));
+    gdk_error_trap_pop();
+
+    return TRUE; // event handled
+}
+
 static void
 wrap_gtk_plug_embedded(GtkPlug* plug) {
     GdkWindow* socket_window = plug->socket_window;
@@ -350,6 +437,18 @@ PluginModuleChild::InitGraphics()
     real_gtk_plug_dispose = *dispose;
     *dispose = wrap_gtk_plug_dispose;
 
+    // If we ever stop setting GDK_NATIVE_WINDOWS, we'll also need to
+    // gtk_widget_add_events GDK_SCROLL_MASK or GDK client-side windows will
+    // not tell us about the scroll events that it intercepts.  With native
+    // windows, this is called when GDK intercepts the events; if GDK doesn't
+    // intercept the events, then the X server will instead send them directly
+    // to an ancestor (embedder) window.
+    GtkWidgetScrollEventFn* scroll_event =
+        &GTK_WIDGET_CLASS(gtk_plug_class)->scroll_event;
+    if (!*scroll_event) {
+        *scroll_event = gtk_plug_scroll_event;
+    }
+
     GtkPlugEmbeddedFn* embedded = &GTK_PLUG_CLASS(gtk_plug_class)->embedded;
     real_gtk_plug_embedded = *embedded;
     *embedded = wrap_gtk_plug_embedded;