[gnome-terminal] app: Automatically determine if headerbars should be used

[Christian Persch <chpe src gnome org>]

commit 62c807a7433ae031085d69b9ead614e9ad14c5da
Author: Christian Persch <chpe src gnome org>
Date:   Tue Feb 26 22:07:08 2019 +0100

    app: Automatically determine if headerbars should be used
    
    If the XDG_CURRENT_DESKTOP env var contains either GNOME or GNOME-Classic,
    use headerbars, unless the user has explicitly set the pref.
    
    NOTE! This makes it unnecessary for distributions to override the default
    value of the headerbar pref.

 src/org.gnome.Terminal.gschema.xml |  4 +--
 src/terminal-app.c                 | 56 ++++++++++++++++++++++++++++++++++----
 2 files changed, 52 insertions(+), 8 deletions(-)
---
diff --git a/src/org.gnome.Terminal.gschema.xml b/src/org.gnome.Terminal.gschema.xml
index b9ba2390..e4e0c003 100644
--- a/src/org.gnome.Terminal.gschema.xml
+++ b/src/org.gnome.Terminal.gschema.xml
@@ -744,8 +744,8 @@
          when gnome-terminal-server is restarted.
     -->
 
-    <key name="headerbar" type="b">
-      <default>false</default>
+    <key name="headerbar" type="mb">
+      <default>nothing</default>
     </key>
 
     <key name="unified-menu" type="b">
diff --git a/src/terminal-app.c b/src/terminal-app.c
index db1c4c36..832c3325 100644
--- a/src/terminal-app.c
+++ b/src/terminal-app.c
@@ -212,6 +212,55 @@ terminal_app_init_debug (void)
 
 /* Helper functions */
 
+static gboolean
+strv_contains_gnome (char **strv)
+{
+  if (strv == NULL)
+    return FALSE;
+
+  for (int i = 0; strv[i] != NULL; i++) {
+    if (g_ascii_strcasecmp (strv[i], "gnome") == 0 ||
+        g_ascii_strcasecmp (strv[i], "gnome-classic") == 0)
+      return TRUE;
+  }
+
+  return FALSE;
+}
+
+/*
+ * terminal_app_should_use_headerbar:
+ *
+ * Determines if the app should use headerbars. This is determined
+ * * If GNOME_TERMINAL_HEADERBAR env var is set, the app uses headerbars iff
+ *   the value is 1
+ * * Otherwise, if the pref is set, the pref value is used
+ * * Otherwise, if XDG_CURRENT_DESKTOP contains GNOME or GNOME-Classic,
+ *   headerbar is used
+ * * Otherwise, headerbar is not used.
+ */
+static gboolean
+terminal_app_should_use_headerbar (TerminalApp *app)
+{
+  const char *env = g_getenv("GNOME_TERMINAL_HEADERBAR");
+  if (env != NULL)
+    return g_strcmp0 (env, "1") == 0;
+
+  gboolean set, use;
+  g_settings_get (app->global_settings, TERMINAL_SETTING_HEADERBAR_KEY, "mb", &set, &use);
+  if (set)
+    return use;
+
+  const char *desktop = g_getenv ("XDG_CURRENT_DESKTOP");
+  if (desktop == NULL)
+    return FALSE;
+
+  char **desktops = g_strsplit (desktop, G_SEARCHPATH_SEPARATOR_S, -1);
+  use = strv_contains_gnome (desktops);
+  g_strfreev (desktops);
+
+  return use;
+}
+
 static gboolean
 load_css_from_resource (GApplication *application,
                         GtkCssProvider *provider,
@@ -788,12 +837,7 @@ terminal_app_init (TerminalApp *app)
    * to override, so we cache them on startup and don't react to changes.
    */
   app->unified_menu = g_settings_get_boolean (app->global_settings, TERMINAL_SETTING_UNIFIED_MENU_KEY);
-
-  const char *env = g_getenv("GNOME_TERMINAL_HEADERBAR");
-  if (env != NULL)
-    app->use_headerbar = g_strcmp0 (env, "1") == 0;
-  else
-    app->use_headerbar = g_settings_get_boolean (app->global_settings, TERMINAL_SETTING_HEADERBAR_KEY);
+  app->use_headerbar = terminal_app_should_use_headerbar (app);
 
 #if GTK_CHECK_VERSION (3, 19, 0)
   GtkSettings *gtk_settings = gtk_settings_get_default ();