[gtk+] wayland: Improve guessing of popup placement for detached popup menus

[Jonas Ådahl <jadahl src gnome org>]

commit 85635457bc2204783a6a7b27435774aa5a93df35
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Jun 5 13:29:22 2015 +0800

    wayland: Improve guessing of popup placement for detached popup menus
    
    If a menu was not attached to any widget, we try to calculate its
    position given where the grabbed pointer is and what window has its
    focus. Previously we failed to do so if a "transfer window" was used
    for the grab, and this patch adds a code path that, if the menu window
    itself didn't have the grab, look for the transfer window and get the
    grab device from there.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=748951

 gdk/wayland/gdkwindow-wayland.c |   36 +++++++++++++++++++++++++++++++++---
 1 files changed, 33 insertions(+), 3 deletions(-)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index 590ff4d..fded03a 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -1184,12 +1184,42 @@ gdk_wayland_window_map (GdkWindow *window)
       /* Popup menus can appear without a transient parent, which means they
        * cannot be positioned properly on Wayland. This attempts to guess the
        * surface they should be positioned with by finding the surface beneath
-       * the device that created the grab for the popup window
+       * the device that created the grab for the popup window.
        */
       if (!impl->transient_for && impl->hint == GDK_WINDOW_TYPE_HINT_POPUP_MENU)
         {
-          transient_for = gdk_device_get_window_at_position (impl->grab_device, NULL, NULL);
-          transient_for = gdk_window_get_toplevel (transient_for);
+          GdkDevice *grab_device;
+
+          /* The popup menu window is not the grabbed window. This may mean
+           * that a "transfer window" (see gtkmenu.c) is used, and we need
+           * to find that window to get the grab device. If so is the case
+           * the "transfer window" can be retrieved via the
+           * "gdk-attached-grab-window" associated data field.
+           */
+          if (!impl->grab_device)
+            {
+              GdkWindow *attached_grab_window =
+                g_object_get_data (G_OBJECT (window),
+                                   "gdk-attached-grab-window");
+              if (attached_grab_window)
+                {
+                  GdkWindowImplWayland *attached_impl =
+                    GDK_WINDOW_IMPL_WAYLAND (attached_grab_window->impl);
+                  grab_device = attached_impl->grab_device;
+                  transient_for =
+                    gdk_device_get_window_at_position (grab_device,
+                                                       NULL, NULL);
+                }
+            }
+          else
+            {
+              grab_device = impl->grab_device;
+              transient_for =
+                gdk_device_get_window_at_position (grab_device, NULL, NULL);
+            }
+
+          if (transient_for)
+            transient_for = gdk_window_get_toplevel (transient_for);
 
           /* If the position was not explicitly set, start the popup at the
            * position of the device that holds the grab.