IconTheme: Move changed emission to an idle

By delaying the emission to an idle we avoid a lot of tricky
reentrancy issues. For instance, a normal gtk_icon_theme_choose_icon()
call could in very rare cases (when a user updated an icon theme) emit
a signal which could affect the icon currently being looked up.  This
kind of reentrancy is very hard to test against, especially when it is
so rare, so we're better of avoiding it.

There is no real value to get the change signal directly anyway. All
it can do is affect which icon is rendered the next frame, and we will
handle the queued emission before rendering. Not to mention that icon
theme change detection is polled anyway, so it is already delayed.

https://bugzilla.gnome.org/show_bug.cgi?id=694755

diff --git a/gtk/gtkicontheme.c b/gtk/gtkicontheme.c
index 4af25376e469d8f1bceb697d12c5dbfc7c4865dd..9a8e4b3d0c2c549d2cc1b3f001e9b3e45783ac44 100644 (file)
--- a/gtk/gtkicontheme.c
+++ b/gtk/gtkicontheme.c
@@ -203,7 +203,7 @@ struct _GtkIconThemePrivate
   glong last_stat_time;
   GList *dir_mtimes;
 
-  gulong reset_styles_idle;
+  gulong theme_changed_idle;
 };
 
 typedef struct {
@@ -795,7 +795,7 @@ free_dir_mtime (IconThemeDirMtime *dir_mtime)
 }
 
 static gboolean
-reset_styles_idle (gpointer user_data)
+theme_changed_idle (gpointer user_data)
 {
   GtkIconTheme *icon_theme;
   GtkIconThemePrivate *priv;
@@ -803,14 +803,27 @@ reset_styles_idle (gpointer user_data)
   icon_theme = GTK_ICON_THEME (user_data);
   priv = icon_theme->priv;
 
+  g_signal_emit (icon_theme, signal_changed, 0);
+
   if (priv->screen && priv->is_screen_singleton)
     gtk_style_context_reset_widgets (priv->screen);
 
-  priv->reset_styles_idle = 0;
+  priv->theme_changed_idle = 0;
 
   return FALSE;
 }
 
+static void
+queue_theme_changed (GtkIconTheme *icon_theme)
+{
+  GtkIconThemePrivate *priv = icon_theme->priv;
+
+  if (!priv->theme_changed_idle)
+    priv->theme_changed_idle =
+      gdk_threads_add_idle_full (GTK_PRIORITY_RESIZE - 2,
+                                 theme_changed_idle, icon_theme, NULL);
+}
+
 static void
 do_theme_change (GtkIconTheme *icon_theme)
 {
@@ -820,16 +833,13 @@ do_theme_change (GtkIconTheme *icon_theme)
 
   if (!priv->themes_valid)
     return;
-  
+
   GTK_NOTE (ICONTHEME, 
            g_print ("change to icon theme \"%s\"\n", priv->current_theme));
   blow_themes (icon_theme);
-  g_signal_emit (icon_theme, signal_changed, 0);
 
-  if (!priv->reset_styles_idle)
-    priv->reset_styles_idle = 
-      gdk_threads_add_idle_full (GTK_PRIORITY_RESIZE - 2, 
-                      reset_styles_idle, icon_theme, NULL);
+  queue_theme_changed (icon_theme);
+
 }
 
 static void
@@ -864,10 +874,10 @@ gtk_icon_theme_finalize (GObject *object)
   g_hash_table_destroy (priv->info_cache);
   g_assert (priv->info_cache_lru == NULL);
 
-  if (priv->reset_styles_idle)
+  if (priv->theme_changed_idle)
     {
-      g_source_remove (priv->reset_styles_idle);
-      priv->reset_styles_idle = 0;
+      g_source_remove (priv->theme_changed_idle);
+      priv->theme_changed_idle = 0;
     }
 
   unset_screen (icon_theme);
@@ -1410,9 +1420,7 @@ ensure_valid_themes (GtkIconTheme *icon_theme)
       load_themes (icon_theme);
 
       if (was_valid)
-       {
-         g_signal_emit (icon_theme, signal_changed, 0);
-       }
+        queue_theme_changed (icon_theme);
     }
 
   priv->loading_themes = FALSE;