[gnome-control-center] window: Split the window decorations between the header bars

[Felipe Borges <felipeborges src gnome org>]

commit 357e9443364765ccf9a297578e8d4f894a3dc504
Author: Felipe Borges <felipeborges gnome org>
Date:   Sun Sep 3 15:27:25 2017 +0200

    window: Split the window decorations between the header bars
    
    When application menus are not supported by the desktop environment
    or are disabled, Gtk+ makes the menu available with a fallback. For
    client-side decorations the fallback consists of adding a menu
    button at the begining of the titlebar. Since g-c-c has a split
    headerbar, we need to explicitly handle the decoration layout.
    
    This commit forces the "menu" to belong to the left headerbar, and
    leaves the other buttons to ble placed at the right headerbar.
    
    The "show-close-button" property has to be set in order to present
    any type of decoration buttons in the header bar.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=786692

 shell/cc-window.c |   34 ++++++++++++++++++++++++++++++++++
 shell/window.ui   |    1 +
 2 files changed, 35 insertions(+), 0 deletions(-)
---
diff --git a/shell/cc-window.c b/shell/cc-window.c
index 2eecbea..f051dad 100644
--- a/shell/cc-window.c
+++ b/shell/cc-window.c
@@ -721,8 +721,33 @@ window_key_press_event (GtkWidget   *win,
 }
 
 static void
+split_decorations (GtkSettings *settings,
+                   GParamSpec  *pspec,
+                   CcWindow    *self)
+{
+  g_autofree gchar *layout = NULL;
+  g_autofree gchar *layout_start = NULL;
+  g_autofree gchar *layout_end = NULL;
+  g_autofree gchar **buttons;
+
+  g_object_get (settings, "gtk-decoration-layout", &layout, NULL);
+
+  buttons = g_strsplit (layout, ":", -1);
+  layout_start = g_strconcat ("", buttons[0], ":", NULL);
+
+  if (g_strv_length (buttons) > 1)
+      layout_end = g_strconcat (":", buttons[1], NULL);
+  else
+      layout_end = g_strdup ("");
+
+  gtk_header_bar_set_decoration_layout (GTK_HEADER_BAR (self->header), layout_start);
+  gtk_header_bar_set_decoration_layout (GTK_HEADER_BAR (self->panel_headerbar), layout_end);
+}
+
+static void
 create_window (CcWindow *self)
 {
+  GtkSettings *settings;
   AtkObject *accessible;
 
   /* previous button */
@@ -765,6 +790,15 @@ create_window (CcWindow *self)
   gtk_widget_add_events (GTK_WIDGET (self), GDK_BUTTON_RELEASE_MASK);
   g_signal_connect (self, "button-release-event",
                     G_CALLBACK (window_button_release_event), self);
+
+  /* handle decorations for the split headers. */
+  settings = gtk_settings_get_default ();
+  g_signal_connect (settings,
+                    "notify::gtk-decoration-layout",
+                    G_CALLBACK (split_decorations),
+                    self);
+
+  split_decorations (settings, NULL, self);
 }
 
 static void
diff --git a/shell/window.ui b/shell/window.ui
index b3a73d7..3f48916 100644
--- a/shell/window.ui
+++ b/shell/window.ui
@@ -108,6 +108,7 @@
           <object class="GtkHeaderBar" id="header">
             <property name="visible">True</property>
             <property name="can_focus">False</property>
+            <property name="show-close-button">True</property>
             <property name="title" translatable="yes">Settings</property>
             <child>
               <object class="GtkButton" id="previous_button">