[gnome-tweak-tool] Fix CSD window decorations

[John Stowers <jstowers src gnome org>]

commit 70441ce6c8b96e629e11dc20aab676c5b337f40e
Author: Yosef Or Boczko <yoseforb gmail com>
Date:   Thu Sep 19 22:42:21 2013 +0300

    Fix CSD window decorations
    
    https://bugzilla.gnome.org/show_bug.cgi?id=708407

 data/shell.css      |   10 ++++++++++
 gtweak/tweakview.py |    5 +++++
 2 files changed, 15 insertions(+), 0 deletions(-)
---
diff --git a/data/shell.css b/data/shell.css
index 07565d4..9796e00 100644
--- a/data/shell.css
+++ b/data/shell.css
@@ -22,6 +22,16 @@
     padding-top: 10px;
 }
 
+.tweak-titlebar-left:dir(ltr),
+.tweak-titlebar-right:dir(rtl) {
+    border-top-right-radius: 0;
+}
+
+.tweak-titlebar-right:dir(ltr),
+.tweak-titlebar-left:dir(rtl) {
+    border-top-left-radius: 0;
+}
+
 /* individual tweak theme changes */
 .tweak.title#title-theme {
     padding-top: 3px;
diff --git a/gtweak/tweakview.py b/gtweak/tweakview.py
index eb925ab..71d0996 100644
--- a/gtweak/tweakview.py
+++ b/gtweak/tweakview.py
@@ -64,6 +64,11 @@ class Window(Gtk.ApplicationWindow):
         right_header = Gtk.HeaderBar()
         right_header.props.show_close_button = True
 
+        left_header.get_style_context().add_class("titlebar")
+        left_header.get_style_context().add_class("tweak-titlebar-left")
+        right_header.get_style_context().add_class("titlebar")
+        right_header.get_style_context().add_class("tweak-titlebar-right")
+
         self.title = Gtk.Label("")
         self.title.get_style_context().add_class("title")
         right_header.set_custom_title(self.title)