[libdazzle] theming: avoid creating unnecessary css providers

[Christian Hergert <chergert src gnome org>]

commit ff7d869933e6564d9d6a3b71762550a72c5ad6d3
Author: Christian Hergert <chergert redhat com>
Date:   Mon Apr 16 16:03:48 2018 -0700

    theming: avoid creating unnecessary css providers
    
    If we get a resource directory without any children in the
    themes directory, we should ignore that and reduce our overhead
    in CSS tracking.
    
    In Builder, this reduces us from nearly 90 css providers to 10.

 src/theming/dzl-theme-manager.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)
---
diff --git a/src/theming/dzl-theme-manager.c b/src/theming/dzl-theme-manager.c
index cca4bdf..252cb6c 100644
--- a/src/theming/dzl-theme-manager.c
+++ b/src/theming/dzl-theme-manager.c
@@ -66,6 +66,19 @@ dzl_theme_manager_new (void)
   return g_object_new (DZL_TYPE_THEME_MANAGER, NULL);
 }
 
+static gboolean
+has_child_resources (const gchar *path)
+{
+  g_auto(GStrv) children = NULL;
+
+  if (g_str_has_prefix (path, "resource://"))
+    path += strlen ("resource://");
+
+  children = g_resources_enumerate_children (path, 0, NULL);
+
+  return children != NULL && children[0] != NULL;
+}
+
 /**
  * dzl_theme_manager_add_resources:
  * @self: a #DzlThemeManager
@@ -94,8 +107,8 @@ dzl_theme_manager_add_resources (DzlThemeManager *self,
   g_autoptr(GtkCssProvider) provider = NULL;
   g_autofree gchar *css_dir = NULL;
   g_autofree gchar *icons_dir = NULL;
-  GtkIconTheme *theme;
   const gchar *real_path = resource_path;
+  GtkIconTheme *theme;
 
   g_return_if_fail (DZL_IS_THEME_MANAGER (self));
   g_return_if_fail (resource_path != NULL);
@@ -112,11 +125,15 @@ dzl_theme_manager_add_resources (DzlThemeManager *self,
    */
   css_dir = g_build_path ("/", resource_path, "themes/", NULL);
   g_debug ("Including CSS overrides from %s", css_dir);
-  provider = dzl_css_provider_new (css_dir);
-  g_hash_table_insert (self->providers_by_path, g_strdup (resource_path), g_object_ref (provider));
-  gtk_style_context_add_provider_for_screen (gdk_screen_get_default (),
-                                             GTK_STYLE_PROVIDER (provider),
-                                             GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
+
+  if (has_child_resources (css_dir))
+    {
+      provider = dzl_css_provider_new (css_dir);
+      g_hash_table_insert (self->providers_by_path, g_strdup (resource_path), g_object_ref (provider));
+      gtk_style_context_add_provider_for_screen (gdk_screen_get_default (),
+                                                 GTK_STYLE_PROVIDER (provider),
+                                                 GTK_STYLE_PROVIDER_PRIORITY_APPLICATION);
+    }
 
   /*
    * Add the icons sub-directory so that Gtk can locate the themed