[gnome-games] ui: Cache scaled cover in GameThumbnail

[Adrien Plazas <aplazas src gnome org>]

commit 927b2dedbadc61348d87432652f204289e49f706
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Tue Jul 12 21:47:12 2016 +0200

    ui: Cache scaled cover in GameThumbnail
    
    This avoid rescaling the cover again and again and hence speeds up
    drawing it.
    
    Fixes #301

 src/ui/game-thumbnail.vala |   36 ++++++++++++++++++++++++++----------
 1 files changed, 26 insertions(+), 10 deletions(-)
---
diff --git a/src/ui/game-thumbnail.vala b/src/ui/game-thumbnail.vala
index b40a79f..12fa05d 100644
--- a/src/ui/game-thumbnail.vala
+++ b/src/ui/game-thumbnail.vala
@@ -48,6 +48,10 @@ private class Games.GameThumbnail: Gtk.DrawingArea {
                default = null;
        }
 
+       private Gdk.Pixbuf? cover_cache;
+       private int previous_cover_width;
+       private int previous_cover_height;
+
        public struct DrawingContext {
                Cairo.Context cr;
                Gdk.Window? window;
@@ -109,11 +113,7 @@ private class Games.GameThumbnail: Gtk.DrawingArea {
        }
 
        public bool draw_cover (DrawingContext context) {
-               var g_icon = cover.get_cover ();
-               if (g_icon == null)
-                       return false;
-
-               var pixbuf = get_scaled_cover (context, g_icon);
+               var pixbuf = get_scaled_cover (context);
                if (pixbuf == null)
                        return false;
 
@@ -180,25 +180,41 @@ private class Games.GameThumbnail: Gtk.DrawingArea {
                }
        }
 
-       private Gdk.Pixbuf? get_scaled_cover (DrawingContext context, GLib.Icon? icon) {
-               if (icon == null)
+       private Gdk.Pixbuf? get_scaled_cover (DrawingContext context) {
+               if (previous_cover_width != context.width) {
+                       previous_cover_width = context.width;
+                       cover_cache = null;
+               }
+
+               if (previous_cover_height != context.height) {
+                       previous_cover_height = context.height;
+                       cover_cache = null;
+               }
+
+               if (cover_cache != null)
+                       return cover_cache;
+
+               var g_icon = cover.get_cover ();
+               if (g_icon == null)
                        return null;
 
                var theme = Gtk.IconTheme.get_default ();
                var lookup_flags = Gtk.IconLookupFlags.FORCE_SIZE | Gtk.IconLookupFlags.FORCE_REGULAR;
                var size = int.min (context.width, context.height) - COVER_MARGIN * 2;
-               var icon_info = theme.lookup_by_gicon (icon, (int) size, lookup_flags);
+               var icon_info = theme.lookup_by_gicon (g_icon, (int) size, lookup_flags);
 
                try {
-                       return icon_info.load_icon ();
+                       cover_cache = icon_info.load_icon ();
                }
                catch (Error e) {
                        warning (@"Couldn't load the icon: $(e.message)\n");
-                       return null;
                }
+
+               return cover_cache;
        }
 
        private void invalidate_cover () {
+               cover_cache = null;
                queue_draw ();
        }