[gtk+] Adwaita: notebook with hidden header style fix

[Lapo Calamandrei <lapo src gnome org>]

commit a0363e5f0a10703a98ae14971fe13f8aed138aba
Author: Lapo Calamandrei <calamandrei gmail com>
Date:   Wed Feb 3 15:23:17 2016 +0100

    Adwaita: notebook with hidden header style fix
    
    the stack styling is applied only when there is a header, hence
    when the stack node is not the notebook only child, should cure
    https://bugzilla.gnome.org/show_bug.cgi?id=760996

 gtk/theme/Adwaita/_common.scss           |    2 +-
 gtk/theme/Adwaita/gtk-contained-dark.css |    4 ++--
 gtk/theme/Adwaita/gtk-contained.css      |    4 ++--
 3 files changed, 5 insertions(+), 5 deletions(-)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 9d675ef..af20b46 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -1925,7 +1925,7 @@ notebook {
     }
   }
 
-  > stack {
+  > stack:not(:only-child) { // the :not(:only-child) is for "hidden" notebooks
     background-color: $base_color;
 
     &:backdrop { background-color: $backdrop_base_color; }
diff --git a/gtk/theme/Adwaita/gtk-contained-dark.css b/gtk/theme/Adwaita/gtk-contained-dark.css
index dfe955d..7f1611e 100644
--- a/gtk/theme/Adwaita/gtk-contained-dark.css
+++ b/gtk/theme/Adwaita/gtk-contained-dark.css
@@ -2368,9 +2368,9 @@ notebook > header {
       margin-bottom: 4px; }
       notebook > header.left tabs tab.reorderable-page, notebook > header.right tabs tab.reorderable-page {
         border-style: solid none; }
-notebook > stack {
+notebook > stack:not(:only-child) {
   background-color: #292929; }
-  notebook > stack:backdrop {
+  notebook > stack:not(:only-child):backdrop {
     background-color: #2c2c2c; }
 
 /**************
diff --git a/gtk/theme/Adwaita/gtk-contained.css b/gtk/theme/Adwaita/gtk-contained.css
index 3e61017..53678f9 100644
--- a/gtk/theme/Adwaita/gtk-contained.css
+++ b/gtk/theme/Adwaita/gtk-contained.css
@@ -2378,9 +2378,9 @@ notebook > header {
       margin-bottom: 4px; }
       notebook > header.left tabs tab.reorderable-page, notebook > header.right tabs tab.reorderable-page {
         border-style: solid none; }
-notebook > stack {
+notebook > stack:not(:only-child) {
   background-color: #ffffff; }
-  notebook > stack:backdrop {
+  notebook > stack:not(:only-child):backdrop {
     background-color: white; }
 
 /**************