[gtk+] gdkwindow: Use toplevel for getting root cords in move_to_rect()

[Matthias Clasen <matthiasc src gnome org>]

commit f6929cfef81171f1b59a3950e88e2ce5599d3286
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Aug 4 13:56:15 2016 +0800

    gdkwindow: Use toplevel for getting root cords in move_to_rect()
    
    The Wayland backend manages a set of fake root coordinate spaces, where
    each non-relative positioned toplevel (i.e. not popups, popovers,
    tooltips etc) make up the basis of separate fake root coordinate spaces.
    
    This means that the Wayland backend doesn't have the abilitiy get a
    proper root coordinate when querying on a non-toplevel GdkWindow. To
    avoid this issue, first find the toplevel, while translating the anchor
    rect coordinates so that they are in the toplevel window coordinate
    space. Then use this toplevel to translate the coordinates to root
    window coordinate space.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=769402

 gdk/gdkwindowimpl.c |   37 ++++++++++++++++++++++++++++++++++++-
 1 files changed, 36 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkwindowimpl.c b/gdk/gdkwindowimpl.c
index 11e49d5..c42c5aa 100644
--- a/gdk/gdkwindowimpl.c
+++ b/gdk/gdkwindowimpl.c
@@ -173,6 +173,29 @@ maybe_flip_position (gint      bounds_pos,
   return primary;
 }
 
+static GdkWindow *
+traverse_to_toplevel (GdkWindow *window,
+                      gint       x,
+                      gint       y,
+                      gint      *toplevel_x,
+                      gint      *toplevel_y)
+{
+  GdkWindow *parent;
+  gdouble xf = x;
+  gdouble yf = y;
+
+  while ((parent = gdk_window_get_effective_parent (window)) != NULL &&
+         (gdk_window_get_window_type (parent) != GDK_WINDOW_ROOT))
+    {
+      gdk_window_coords_to_parent (window, xf, yf, &xf, &yf);
+      window = parent;
+    }
+
+  *toplevel_x = (gint) xf;
+  *toplevel_y = (gint) yf;
+  return window;
+}
+
 static void
 gdk_window_impl_move_to_rect (GdkWindow          *window,
                               const GdkRectangle *rect,
@@ -182,6 +205,7 @@ gdk_window_impl_move_to_rect (GdkWindow          *window,
                               gint                rect_anchor_dx,
                               gint                rect_anchor_dy)
 {
+  GdkWindow *transient_for_toplevel;
   GdkDisplay *display;
   GdkMonitor *monitor;
   GdkRectangle bounds;
@@ -191,7 +215,18 @@ gdk_window_impl_move_to_rect (GdkWindow          *window,
   gboolean flipped_x;
   gboolean flipped_y;
 
-  gdk_window_get_root_coords (window->transient_for,
+  /*
+   * First translate the anchor rect to toplevel coordinates. This is needed
+   * because not all backends will be able to get root coordinates for
+   * non-toplevel windows.
+   */
+  transient_for_toplevel = traverse_to_toplevel (window->transient_for,
+                                                 root_rect.x,
+                                                 root_rect.y,
+                                                 &root_rect.x,
+                                                 &root_rect.y);
+
+  gdk_window_get_root_coords (transient_for_toplevel,
                               root_rect.x,
                               root_rect.y,
                               &root_rect.x,