Include hicolor index.theme as a resource

index.theme file copied from upstream xdg/default-icon-theme
repository at tag 0.17:

https://gitlab.freedesktop.org/xdg/default-icon-theme/-/tree/0.17

Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/5303

gtk/gen-gtk-gresources-xml.py

@@ -70,6 +70,10 @@ for f in get_files('ui', '.ui'):
 
 xml += '\n'
 
+xml += '''
+    <file compressed="true">icons/hicolor.index.theme</file>
+'''
+
 for s in ['16x16', '32x32', '64x64', 'scalable']:
   for c in ['actions', 'categories', 'emblems', 'emotes', 'devices', 'mimetypes', 'places', 'status']:
     icons_dir = 'icons/{0}/{1}'.format(s,c)

gtk/gtkicontheme.c

@@ -1703,49 +1703,6 @@ gtk_icon_theme_get_theme_name (GtkIconTheme *self)
   return theme_name;
 }
 
-static const char builtin_hicolor_index[] =
-"[Icon Theme]\n"
-"Name=Hicolor\n"
-"Hidden=True\n"
-"Directories=16x16/actions,16x16/status,22x22/actions,24x24/actions,24x24/status,32x32/actions,32x32/status,48x48/status,64x64/actions,scalable/status,scalable/actions\n"
-"[16x16/actions]\n"
-"Size=16\n"
-"Type=Threshold\n"
-"[16x16/status]\n"
-"Size=16\n"
-"Type=Threshold\n"
-"[22x22/actions]\n"
-"Size=22\n"
-"Type=Threshold\n"
-"[24x24/actions]\n"
-"Size=24\n"
-"Type=Threshold\n"
-"[24x24/status]\n"
-"Size=24\n"
-"Type=Threshold\n"
-"[32x32/actions]\n"
-"Size=32\n"
-"Type=Threshold\n"
-"[32x32/status]\n"
-"Size=32\n"
-"Type=Threshold\n"
-"[48x48/status]\n"
-"Size=48\n"
-"Type=Threshold\n"
-"[64x64/actions]\n"
-"Size=64\n"
-"Type=Threshold\n"
-"[scalable/status]\n"
-"MinSize=1\n"
-"Size=128\n"
-"MaxSize=256\n"
-"Type=Scalable\n"
-"[scalable/actions]\n"
-"MinSize=1\n"
-"Size=128\n"
-"MaxSize=256\n"
-"Type=Scalable\n";
-
 static void
 insert_theme (GtkIconTheme *self,
               const char   *theme_name)
@@ -1812,9 +1769,20 @@ insert_theme (GtkIconTheme *self,
     {
       if (strcmp (theme_name, FALLBACK_ICON_THEME) == 0)
         {
+          const char *resource_path = "/org/gtk/libgtk/icons/hicolor.index.theme";
+          GBytes *index;
+
+          index = g_resources_lookup_data (resource_path,
+                                           G_RESOURCE_LOOKUP_FLAGS_NONE,
+                                           NULL);
+          if (!index)
+            g_error ("Cannot find resource %s", resource_path);
+
           theme_file = g_key_file_new ();
           g_key_file_set_list_separator (theme_file, ',');
-          g_key_file_load_from_data (theme_file, builtin_hicolor_index, -1, 0, NULL);
+          g_key_file_load_from_bytes (theme_file, index, G_KEY_FILE_NONE, NULL);
+
+          g_bytes_unref (index);
         }
       else
         return;