[gtk+/gtk-3-4] quartz: fix coordinates for synthesized event

[Kristian Rietveld <kristian src gnome org>]

commit 49eb2f2b2c809c5c8518a1353b991bd297f8ba65
Author: Kristian Rietveld <kris lanedo com>
Date:   Sun Apr 22 17:11:38 2012 +0200

    quartz: fix coordinates for synthesized event
    
    Of course, we must pass coordinates in the NSWindow coordinate system
    when creating an NSEvent. This fixes drag icon positioning and makes
    the icon slide back to the correct position when the drag is
    canceled.

 gtk/gtkdnd-quartz.c |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkdnd-quartz.c b/gtk/gtkdnd-quartz.c
index 6b89b35..d9d8ca7 100644
--- a/gtk/gtkdnd-quartz.c
+++ b/gtk/gtkdnd-quartz.c
@@ -1090,7 +1090,7 @@ gtk_drag_begin_idle (gpointer arg)
 
   [nswindow dragImage:drag_image
                    at:point
-               offset:NSMakeSize(0, 0)
+               offset:NSZeroSize
                 event:info->nsevent
            pasteboard:pasteboard
                source:nswindow
@@ -1134,8 +1134,25 @@ gtk_drag_begin_internal (GtkWidget         *widget,
     {
       if (gdk_event_get_coords (event, &x, &y))
         {
+          /* We need to translate (x, y) to coordinates relative to the
+           * toplevel GdkWindow, which should be the GdkWindow backing
+           * nswindow. Then, we convert to the NSWindow coordinate system.
+           */
+          GdkWindow *window = event->any.window;
+          GdkWindow *toplevel = gdk_window_get_effective_toplevel (window);
+
+          while (window != toplevel)
+            {
+              double old_x = x;
+              double old_y = y;
+
+              gdk_window_coords_to_parent (window, old_x, old_y,
+                                           &x, &y);
+              window = gdk_window_get_effective_parent (window);
+            }
+
           point.x = x;
-          point.y = y;
+          point.y = gdk_window_get_height (window) - y;
         }
       time = (double)gdk_event_get_time (event);
     }