[metacity] constraints: account for decorations when positioning modal dialogs

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 10fc45724bded4bd21a2af38b72ca39145180c54
Author: Giovanni Campagna <gcampagn redhat com>
Date:   Mon Sep 2 11:22:11 2013 +0200

    constraints: account for decorations when positioning modal dialogs
    
    What we want to achieve is that the dialog is visually centered
    on the parent, including the decorations for both, and making sure
    that CSD/frame_extents are respected.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707194

 src/core/constraints.c |   24 +++++++++++++++++-------
 1 files changed, 17 insertions(+), 7 deletions(-)
---
diff --git a/src/core/constraints.c b/src/core/constraints.c
index db4e8d6..dda3350 100644
--- a/src/core/constraints.c
+++ b/src/core/constraints.c
@@ -822,18 +822,28 @@ constrain_modal_dialog (MetaWindow         *window,
 {
   int x, y;
   MetaWindow *parent = meta_window_get_transient_for (window);
+  MetaRectangle child_rect, parent_rect;
   gboolean constraint_already_satisfied;
 
   if (!meta_window_is_attached_dialog (window))
     return TRUE;
 
-  x = parent->rect.x + (parent->rect.width / 2 - info->current.width / 2);
-  y = parent->rect.y + (parent->rect.height / 2 - info->current.height / 2);
-  if (parent->frame)
-    {
-      x += parent->frame->rect.x;
-      y += parent->frame->rect.y;
-   }
+  /* We want to center the dialog on the parent, including the decorations
+     for both of them. info->current is in client X window coordinates, so we need
+     to convert them to frame coordinates, apply the centering and then
+     convert back to client.
+  */
+
+  child_rect = info->current;
+  extend_by_frame (window, &child_rect, info->borders);
+
+  meta_window_get_outer_rect (parent, &parent_rect);
+
+  child_rect.x = parent_rect.x + (parent_rect.width / 2 - child_rect.width / 2);
+  child_rect.y = parent_rect.y + (parent_rect.height / 2 - child_rect.height / 2);
+  unextend_by_frame (window, &child_rect, info->borders);
+  x = child_rect.x;
+  y = child_rect.y;
 
   constraint_already_satisfied = (x == info->current.x) && (y == info->current.y);