[gtk] icontheme: Add LRU cache back

[Timm Bäder <baedert src gnome org>]

commit 53132d023595ec8d4767207f5616d3989ef9a5ef
Author: Timm Bäder <mail baedert org>
Date:   Sun Sep 1 13:25:44 2019 +0200

    icontheme: Add LRU cache back
    
    Add a cache of icon infos that we keep around a little longer, to avoid
    loading icons from disk that only exist for a short amount of time (e.g.
    during one frame of a cell renderer snapshot).
    
    We make sure recently used items are kept alive by just adding them to
    the cache on lookup.

 gtk/gtkicontheme.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 7 deletions(-)
---
diff --git a/gtk/gtkicontheme.c b/gtk/gtkicontheme.c
index 643a12e5f4..e90240812c 100644
--- a/gtk/gtkicontheme.c
+++ b/gtk/gtkicontheme.c
@@ -130,6 +130,9 @@ typedef enum
 #define DEBUG_CACHE(args)
 #endif
 
+#define LRU_CACHE_SIZE 100
+#define MAX_LRU_TEXTURE_SIZE 128
+
 typedef struct _GtkIconInfoClass    GtkIconInfoClass;
 typedef struct _GtkIconThemeClass   GtkIconThemeClass;
 typedef struct _GtkIconThemePrivate GtkIconThemePrivate;
@@ -157,6 +160,9 @@ struct _GtkIconThemePrivate
 {
   GHashTable *info_cache;
 
+  GtkIconInfo *lru_cache[LRU_CACHE_SIZE];
+  int lru_cache_next;
+
   gchar *current_theme;
   gchar **search_path;
   gint search_path_len;
@@ -392,6 +398,34 @@ icon_info_key_equal (gconstpointer _a,
 
 G_DEFINE_TYPE_WITH_PRIVATE (GtkIconTheme, gtk_icon_theme, G_TYPE_OBJECT)
 
+static void
+add_to_lru_cache (GtkIconInfo *info)
+{
+  GtkIconTheme *theme = info->in_cache;
+  GtkIconThemePrivate *priv = gtk_icon_theme_get_instance_private (theme);
+
+  if (!theme)
+    return;
+
+  if (info->texture &&
+      info->texture->width <= MAX_LRU_TEXTURE_SIZE &&
+      info->texture->height <= MAX_LRU_TEXTURE_SIZE)
+    {
+      g_set_object (&priv->lru_cache[priv->lru_cache_next], info);
+      priv->lru_cache_next = (priv->lru_cache_next + 1) % LRU_CACHE_SIZE;
+    }
+}
+
+static void
+clear_lru_cache (GtkIconTheme *icon_theme)
+{
+  GtkIconThemePrivate *priv = gtk_icon_theme_get_instance_private (icon_theme);
+  int i;
+
+  for (i = 0; i < LRU_CACHE_SIZE; i ++)
+    g_clear_object (&priv->lru_cache[i]);
+}
+
 /**
  * gtk_icon_theme_new:
  * 
@@ -762,6 +796,7 @@ do_theme_change (GtkIconTheme *icon_theme)
   GtkIconThemePrivate *priv = icon_theme->priv;
 
   g_hash_table_remove_all (priv->info_cache);
+  clear_lru_cache (icon_theme);
 
   if (!priv->themes_valid)
     return;
@@ -794,13 +829,10 @@ blow_themes (GtkIconTheme *icon_theme)
 static void
 gtk_icon_theme_finalize (GObject *object)
 {
-  GtkIconTheme *icon_theme;
-  GtkIconThemePrivate *priv;
+  GtkIconTheme *icon_theme = GTK_ICON_THEME (object);
+  GtkIconThemePrivate *priv = gtk_icon_theme_get_instance_private (icon_theme);
   int i;
 
-  icon_theme = GTK_ICON_THEME (object);
-  priv = icon_theme->priv;
-
   g_hash_table_destroy (priv->info_cache);
 
   if (priv->theme_changed_idle)
@@ -817,8 +849,9 @@ gtk_icon_theme_finalize (GObject *object)
   g_list_free_full (priv->resource_paths, g_free);
 
   blow_themes (icon_theme);
+  clear_lru_cache (icon_theme);
 
-  G_OBJECT_CLASS (gtk_icon_theme_parent_class)->finalize (object);  
+  G_OBJECT_CLASS (gtk_icon_theme_parent_class)->finalize (object);
 }
 
 /**
@@ -1421,9 +1454,10 @@ ensure_valid_themes (GtkIconTheme *icon_theme)
         {
           g_hash_table_remove_all (priv->info_cache);
           blow_themes (icon_theme);
+          clear_lru_cache (icon_theme);
         }
     }
-  
+
   if (!priv->themes_valid)
     {
       load_themes (icon_theme);
@@ -1600,6 +1634,9 @@ real_choose_icon (GtkIconTheme       *icon_theme,
 
       icon_info = g_object_ref (icon_info);
 
+      /* Move item to front in LRU cache */
+      add_to_lru_cache (icon_info);
+
       return icon_info;
     }
 
@@ -3641,6 +3678,8 @@ icon_info_ensure_scale_and_texture (GtkIconInfo *icon_info)
     }
 
   g_assert (icon_info->texture != NULL);
+  add_to_lru_cache (icon_info);
+
   return TRUE;
 }