[gnome-shell/wip/chergert/3-28-perf-fixes: 1/5] shell/app-system: Monitor for icon theme changes

[Christian Hergert <chergert src gnome org>]

commit 4cac5b4b284e8c948472226532ceca76e7091f0a
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Thu Aug 1 20:58:20 2019 -0300

    shell/app-system: Monitor for icon theme changes
    
    Whenever an app is installed, the usual routine is
    to run 'gtk-update-icon-cache' after installing all
    of the app's files.
    
    The side effect of that is that the .desktop file of
    the application is installed before the icon theme
    is updated. By the time GAppInfoMonitor emits the
    'changed' signal, the icon theme is not yet updated,
    leading to StIcon use the fallback icon.
    
    Under some circumstances (e.g. on very slow spinning
    disks) the app icon is never actually loaded, and we
    see the fallback icon forever.
    
    Monitor the icon theme for changes when an app is
    installed. Try as many as 6 times before giving up
    on detecting an icon theme update.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/661

 src/shell-app-system.c    | 56 +++++++++++++++++++++++++++++++++++++++++++++++
 src/st/st-texture-cache.c |  8 +++++++
 src/st/st-texture-cache.h |  2 ++
 3 files changed, 66 insertions(+)
---
diff --git a/src/shell-app-system.c b/src/shell-app-system.c
index 8edf757a90..90c59c9d20 100644
--- a/src/shell-app-system.c
+++ b/src/shell-app-system.c
@@ -14,6 +14,14 @@
 #include "shell-app-system-private.h"
 #include "shell-global.h"
 #include "shell-util.h"
+#include "st.h"
+
+/* Rescan for at most RESCAN_TIMEOUT_MS * MAX_RESCAN_RETRIES. That
+ * should be plenty of time for even a slow spinning drive to update
+ * the icon cache.
+ */
+#define RESCAN_TIMEOUT_MS 2500
+#define MAX_RESCAN_RETRIES 6
 
 /* Vendor prefixes are something that can be preprended to a .desktop
  * file name.  Undo this.
@@ -50,6 +58,9 @@ struct _ShellAppSystemPrivate {
   GHashTable *running_apps;
   GHashTable *id_to_app;
   GHashTable *startup_wm_class_to_id;
+
+  guint rescan_icons_timeout_id;
+  guint n_rescan_retries;
 };
 
 static void shell_app_system_finalize (GObject *object);
@@ -156,12 +167,54 @@ stale_app_remove_func (gpointer key,
   return app_is_stale (value);
 }
 
+static gboolean
+rescan_icon_theme_cb (gpointer user_data)
+{
+  ShellAppSystemPrivate *priv;
+  ShellAppSystem *self;
+  StTextureCache *texture_cache;
+  gboolean rescanned;
+
+  self = (ShellAppSystem *) user_data;
+  priv = self->priv;
+
+  texture_cache = st_texture_cache_get_default ();
+  rescanned = st_texture_cache_rescan_icon_theme (texture_cache);
+
+  priv->n_rescan_retries++;
+
+  if (rescanned || priv->n_rescan_retries >= MAX_RESCAN_RETRIES)
+    {
+      priv->n_rescan_retries = 0;
+      priv->rescan_icons_timeout_id = 0;
+      return G_SOURCE_REMOVE;
+    }
+
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+rescan_icon_theme (ShellAppSystem *self)
+{
+  ShellAppSystemPrivate *priv = self->priv;
+
+  priv->n_rescan_retries = 0;
+
+  if (priv->rescan_icons_timeout_id > 0)
+    return;
+
+  priv->rescan_icons_timeout_id = g_timeout_add (RESCAN_TIMEOUT_MS,
+                                                 rescan_icon_theme_cb,
+                                                 self);
+}
+
 static void
 installed_changed (GAppInfoMonitor *monitor,
                    gpointer         user_data)
 {
   ShellAppSystem *self = user_data;
 
+  rescan_icon_theme (self);
   scan_startup_wm_class_to_id (self);
 
   g_hash_table_foreach_remove (self->priv->id_to_app, stale_app_remove_func, NULL);
@@ -199,6 +252,9 @@ shell_app_system_finalize (GObject *object)
   g_hash_table_destroy (priv->id_to_app);
   g_hash_table_destroy (priv->startup_wm_class_to_id);
 
+  if (priv->rescan_icons_timeout_id)
+    g_source_remove (priv->rescan_icons_timeout_id);
+
   G_OBJECT_CLASS (shell_app_system_parent_class)->finalize (object);
 }
 
diff --git a/src/st/st-texture-cache.c b/src/st/st-texture-cache.c
index 6219071119..eee03937d8 100644
--- a/src/st/st-texture-cache.c
+++ b/src/st/st-texture-cache.c
@@ -1425,3 +1425,11 @@ st_texture_cache_get_default (void)
     instance = g_object_new (ST_TYPE_TEXTURE_CACHE, NULL);
   return instance;
 }
+
+gboolean
+st_texture_cache_rescan_icon_theme (StTextureCache *cache)
+{
+  StTextureCachePrivate *priv = cache->priv;
+
+  return gtk_icon_theme_rescan_if_needed (priv->icon_theme);
+}
diff --git a/src/st/st-texture-cache.h b/src/st/st-texture-cache.h
index 26f9c30ac1..606694c865 100644
--- a/src/st/st-texture-cache.h
+++ b/src/st/st-texture-cache.h
@@ -106,4 +106,6 @@ CoglTexture * st_texture_cache_load (StTextureCache       *cache,
                                      void                 *data,
                                      GError              **error);
 
+gboolean st_texture_cache_rescan_icon_theme (StTextureCache *cache);
+
 #endif /* __ST_TEXTURE_CACHE_H__ */