[gtk+] Mention that gdk_window_create_similar_image_surface inherits the scale

[Debarshi Ray <debarshir src gnome org>]

commit 339f6e141a231e7d2d766bd93b6b2295c825afb5
Author: Debarshi Ray <debarshir gnome org>
Date:   Thu Dec 15 13:17:57 2016 +0100

    Mention that gdk_window_create_similar_image_surface inherits the scale
    
    https://bugzilla.gnome.org/show_bug.cgi?id=776132

 gdk/gdkwindow.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/gdk/gdkwindow.c b/gdk/gdkwindow.c
index 8c72268..6e77e4e 100644
--- a/gdk/gdkwindow.c
+++ b/gdk/gdkwindow.c
@@ -7743,6 +7743,10 @@ gdk_window_create_similar_surface (GdkWindow *     window,
  *                                              scale);
  * ]|
  *
+ * Note that unlike cairo_surface_create_similar_image(), the new
+ * surface's device scale is set to @scale, or to the scale factor of
+ * @window if @scale is 0.
+ *
  * Returns: a pointer to the newly allocated surface. The caller
  * owns the surface and should call cairo_surface_destroy() when done
  * with it.