[gtk+] Adwaita: Fix window shadow size

[Matthias Clasen <matthiasc src gnome org>]

commit dc836abbb43d0acfbeeca99cca94fb8d4410b6f9
Author: Matthias Clasen <mclasen redhat com>
Date:   Sat Nov 14 12:55:34 2015 -0500

    Adwaita: Fix window shadow size
    
    Ensure that the shadow extents don't change as we go to backdrop,
    to prevent windows from jumping.

 gtk/theme/Adwaita/_common.scss           |    4 ++++
 gtk/theme/Adwaita/gtk-contained-dark.css |    5 ++++-
 gtk/theme/Adwaita/gtk-contained.css      |    5 ++++-
 3 files changed, 12 insertions(+), 2 deletions(-)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index e4f27c3..519ca12 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -3262,7 +3262,11 @@ decoration {
   margin: 10px;
 
   &:backdrop {
+    /* the transparent shadow here is to enforce that the shadow extents don't
+     * change when we go to backdrop, to prevent jumping windows
+     */
     box-shadow: 0 2px 6px 2px transparentize(black, 0.8),
+                0 3px 9px 1px transparent,
                 0 0 0 1px $_wm_border_backdrop;
   }
   .tiled & {
diff --git a/gtk/theme/Adwaita/gtk-contained-dark.css b/gtk/theme/Adwaita/gtk-contained-dark.css
index 05f5b4e..b37f335 100644
--- a/gtk/theme/Adwaita/gtk-contained-dark.css
+++ b/gtk/theme/Adwaita/gtk-contained-dark.css
@@ -4409,7 +4409,10 @@ decoration {
   /* this is used for the resize cursor area */
   margin: 10px; }
   decoration:backdrop {
-    box-shadow: 0 2px 6px 2px rgba(0, 0, 0, 0.2), 0 0 0 1px rgba(28, 31, 31, 0.9); }
+    /* the transparent shadow here is to enforce that the shadow extents don't
+     * change when we go to backdrop, to prevent jumping windows
+     */
+    box-shadow: 0 2px 6px 2px rgba(0, 0, 0, 0.2), 0 3px 9px 1px transparent, 0 0 0 1px rgba(28, 31, 31, 
0.9); }
   .tiled decoration {
     border-radius: 0; }
   .popup decoration {
diff --git a/gtk/theme/Adwaita/gtk-contained.css b/gtk/theme/Adwaita/gtk-contained.css
index e640761..623508b 100644
--- a/gtk/theme/Adwaita/gtk-contained.css
+++ b/gtk/theme/Adwaita/gtk-contained.css
@@ -4581,7 +4581,10 @@ decoration {
   /* this is used for the resize cursor area */
   margin: 10px; }
   decoration:backdrop {
-    box-shadow: 0 2px 6px 2px rgba(0, 0, 0, 0.2), 0 0 0 1px rgba(0, 0, 0, 0.18); }
+    /* the transparent shadow here is to enforce that the shadow extents don't
+     * change when we go to backdrop, to prevent jumping windows
+     */
+    box-shadow: 0 2px 6px 2px rgba(0, 0, 0, 0.2), 0 3px 9px 1px transparent, 0 0 0 1px rgba(0, 0, 0, 0.18); }
   .tiled decoration {
     border-radius: 0; }
   .popup decoration {