[gtk+] x11: Return the exact pixel coverage in get_frame_extents

[Alexander Larsson <alexl src gnome org>]

commit 788478dff9466b6606d61aa977847b7d78077d0f
Author: Alexander Larsson <alexl redhat com>
Date:   Thu Nov 20 10:42:55 2014 +0100

    x11: Return the exact pixel coverage in get_frame_extents
    
    Rather than just rounding down the position *and* the size separately
    we correctly calculate a rectangle in scaled window coords that fully
    covers the real window size. This really only makes a difference
    when the window size/position isn't a multiple of the window scale.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=739750

 gdk/x11/gdkwindow-x11.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)
---
diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index c4b90af..525a798 100644
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -3262,10 +3262,14 @@ gdk_x11_window_get_frame_extents (GdkWindow    *window,
   if (vroots)
     XFree (vroots);
 
-  rect->x /= impl->window_scale;
-  rect->y /= impl->window_scale;
-  rect->width /= impl->window_scale;
-  rect->height /= impl->window_scale;
+  /* Here we extend the size to include the extra pixels if we round x/y down
+     as well as round the size up when we divide by scale so that the returned
+     size is guaranteed to cover the real pixels, but it may overshoot a bit
+     in case the window is not positioned/sized according to the scale */
+  rect->width = (rect->width + rect->x % impl->window_scale + impl->window_scale - 1) / impl->window_scale;
+  rect->height = (rect->height + rect->y % impl->window_scale + impl->window_scale - 1) / impl->window_scale;
+  rect->x = rect->x / impl->window_scale;
+  rect->y = rect->y / impl->window_scale;
   gdk_x11_display_error_trap_pop_ignored (display);
 }