text: Check generated size of layouts in cache

By comparing the requested size against the computed sized for existing
Pango layouts we can avoid creating layouts where the requested size
matches that of a previously computed one.

In particular this optimisation means that when working with a fixed
positioning based layout (with no constraints on the size of the
ClutterText) the same PangoLayout can be used to calculate the preferred
width, height and also the layout used for the actual painting.

http://bugzilla.openedhand.com/show_bug.cgi?id=2078

Signed-off-by: Emmanuele Bassi <ebassi@linux.intel.com>

diff --git a/clutter/clutter-text.c b/clutter/clutter-text.c
index d06fd4c..3dce675 100644 (file)
--- a/clutter/clutter-text.c
+++ b/clutter/clutter-text.c
@@ -553,10 +553,59 @@ clutter_text_create_layout (ClutterText *text,
 
          return priv->cached_layouts[i].layout;
        }
-      else if (!found_free_cache &&
-               (priv->cached_layouts[i].age < oldest_cache->age))
+      else
         {
-         oldest_cache = priv->cached_layouts + i;
+          PangoRectangle logical_rect;
+          gint logical_height;
+          gfloat layout_height;
+          gint logical_width;
+          gfloat layout_width;
+
+          pango_layout_get_extents (priv->cached_layouts[i].layout, NULL, &logical_rect);
+
+          /* These calculations are taken from the _get_preferred_width and
+           * _get_preferred_height calls
+           */
+          logical_height = logical_rect.y + logical_rect.height;
+          layout_height = ceilf ((gfloat) logical_height / 1024.0f + 0.5);
+
+          logical_width = logical_rect.x + logical_rect.width;
+
+          layout_width = logical_width > 0
+            ? (logical_width / 1024.0f)
+            : 1;
+
+          if (allocation_height == -1 &&
+              allocation_width == layout_width)
+          {
+            /* We've been asked for our height for the width we gave as a result
+             * of a _get_preferred_width call
+             */
+            CLUTTER_NOTE (ACTOR, "ClutterText: %p: cache hit for size %.2fx%.2f " \
+                          "(matches width of extents)",
+                          text,
+                          allocation_width,
+                          allocation_height);
+
+            return priv->cached_layouts[i].layout;
+          }
+        else if (allocation_width == layout_width &&
+                 allocation_height == layout_height)
+          {
+            /* We've been asked for width and height we gave before */
+            CLUTTER_NOTE (ACTOR, "ClutterText: %p: cache hit for size %.2fx%.2f " \
+                          "(matches size of extents)",
+                          text,
+                          allocation_width,
+                          allocation_height);
+
+            return priv->cached_layouts[i].layout;
+          }
+        else if (!found_free_cache &&
+                 (priv->cached_layouts[i].age < oldest_cache->age))
+          {
+            oldest_cache = priv->cached_layouts + i;
+          }
         }
     }