Store the units-per-em inside the Backend

Instead of recomputing the number of units needed to fit in
an em each time clutter_units_em() is called, we can store this
value into the default Backend along with the resolution and
font name. The value should also be updated each time the
resolution and font are changed, to keep it up to date.

diff --git a/clutter/clutter-backend.c b/clutter/clutter-backend.c
index 2dd8a44..da8f77e 100644 (file)
--- a/clutter/clutter-backend.c
+++ b/clutter/clutter-backend.c
@@ -60,7 +60,8 @@ struct _ClutterBackendPrivate
   guint double_click_time;
   guint double_click_distance;
 
-  ClutterFixed resolution;
+  gdouble resolution;
+  gdouble units_per_em;
 
   cairo_font_options_t *font_options;
 
@@ -87,7 +88,9 @@ clutter_backend_dispose (GObject *gobject)
 
   if (clutter_context && clutter_context->events_queue)
     {
-      g_queue_foreach (clutter_context->events_queue, (GFunc) clutter_event_free, NULL);
+      g_queue_foreach (clutter_context->events_queue,
+                       (GFunc) clutter_event_free,
+                       NULL);
       g_queue_free (clutter_context->events_queue);
       clutter_context->events_queue = NULL;
     }
@@ -99,6 +102,57 @@ clutter_backend_dispose (GObject *gobject)
   G_OBJECT_CLASS (clutter_backend_parent_class)->dispose (gobject);
 }
 
+static inline void
+update_units_per_em (ClutterBackend *backend)
+{
+  ClutterBackendPrivate *priv = backend->priv;
+  const gchar *font_name;
+  gdouble dpi;
+
+  font_name = clutter_backend_get_font_name (backend);
+  dpi = clutter_backend_get_resolution (backend);
+
+  if (G_LIKELY (font_name != NULL && *font_name != '\0'))
+    {
+      PangoFontDescription *font_desc;
+      gdouble font_size = 0;
+
+      font_desc = pango_font_description_from_string (font_name);
+      if (G_LIKELY (font_desc != NULL))
+        {
+          gint pango_size;
+          gboolean is_absolute;
+
+          pango_size = pango_font_description_get_size (font_desc);
+          is_absolute =
+            pango_font_description_get_size_is_absolute (font_desc);
+          if (!is_absolute)
+            font_size = ((gdouble) font_size) / PANGO_SCALE;
+
+          pango_font_description_free (font_desc);
+        }
+
+      /* 10 points at 96 DPI is 12 pixels */
+      priv->units_per_em = 1.2 * font_size
+                         * dpi
+                         / 96.0;
+    }
+  else
+    priv->units_per_em = -1.0;
+}
+
+static void
+clutter_backend_real_resolution_changed (ClutterBackend *backend)
+{
+  update_units_per_em (backend);
+}
+
+static void
+clutter_backend_real_font_changed (ClutterBackend *backend)
+{
+  update_units_per_em (backend);
+}
+
 static void
 clutter_backend_class_init (ClutterBackendClass *klass)
 {
@@ -111,7 +165,7 @@ clutter_backend_class_init (ClutterBackendClass *klass)
   backend_signals[RESOLUTION_CHANGED] =
     g_signal_new (I_("resolution-changed"),
                   G_TYPE_FROM_CLASS (klass),
-                  G_SIGNAL_RUN_LAST,
+                  G_SIGNAL_RUN_FIRST,
                   G_STRUCT_OFFSET (ClutterBackendClass, resolution_changed),
                   NULL, NULL,
                   clutter_marshal_VOID__VOID,
@@ -120,11 +174,14 @@ clutter_backend_class_init (ClutterBackendClass *klass)
   backend_signals[FONT_CHANGED] =
     g_signal_new (I_("font-changed"),
                   G_TYPE_FROM_CLASS (klass),
-                  G_SIGNAL_RUN_LAST,
+                  G_SIGNAL_RUN_FIRST,
                   G_STRUCT_OFFSET (ClutterBackendClass, font_changed),
                   NULL, NULL,
                   clutter_marshal_VOID__VOID,
                   G_TYPE_NONE, 0);
+
+  klass->resolution_changed = clutter_backend_real_resolution_changed;
+  klass->font_changed = clutter_backend_real_font_changed;
 }
 
 static void
@@ -132,8 +189,10 @@ clutter_backend_init (ClutterBackend *backend)
 {
   ClutterBackendPrivate *priv;
 
-  priv = backend->priv = CLUTTER_BACKEND_GET_PRIVATE(backend);
+  priv = backend->priv = CLUTTER_BACKEND_GET_PRIVATE (backend);
+
   priv->resolution = -1.0;
+  priv->units_per_em = -1.0;
 }
 
 void
@@ -289,15 +348,30 @@ _clutter_backend_init_events (ClutterBackend *backend)
     klass->init_events (backend);
 }
 
+ClutterUnit
+_clutter_backend_get_units_per_em (ClutterBackend *backend)
+{
+  ClutterBackendPrivate *priv;
+
+  g_return_val_if_fail (CLUTTER_IS_BACKEND (backend), 0);
+
+  priv = backend->priv;
+
+  if (G_UNLIKELY (priv->units_per_em < 0))
+    update_units_per_em (backend);
+
+  return priv->units_per_em;
+}
 
 /**
  * clutter_get_default_backend:
  *
- * FIXME
+ * Retrieves the default #ClutterBackend used by Clutter. The
+ * #ClutterBackend holds backend-specific configuration options.
  *
  * Return value: the default backend. You should not ref or
- * unref the returned object. Applications should not rarely need
- * to use this.
+ *   unref the returned object. Applications should rarely need
+ *   to use this.
  *
  * Since: 0.4
  */
@@ -406,19 +480,16 @@ void
 clutter_backend_set_resolution (ClutterBackend *backend,
                                 gdouble         dpi)
 {
-  ClutterFixed fixed_dpi;
   ClutterBackendPrivate *priv;
 
   g_return_if_fail (CLUTTER_IS_BACKEND (backend));
 
+  priv = backend->priv;
+
   if (dpi < 0)
     dpi = -1.0;
 
-  priv = backend->priv;
-
-  fixed_dpi = CLUTTER_FLOAT_TO_FIXED (dpi);
-  if (priv->resolution != fixed_dpi)
-    priv->resolution = fixed_dpi;
+  priv->resolution = dpi;
 
   if (CLUTTER_CONTEXT ()->font_map)
     cogl_pango_font_map_set_resolution (CLUTTER_CONTEXT ()->font_map, dpi);
@@ -443,7 +514,7 @@ clutter_backend_get_resolution (ClutterBackend *backend)
 {
   g_return_val_if_fail (CLUTTER_IS_BACKEND (backend), -1.0);
 
-  return CLUTTER_FIXED_TO_FLOAT (backend->priv->resolution);
+  return backend->priv->resolution;
 }
 
 /**

diff --git a/clutter/clutter-private.h b/clutter/clutter-private.h
index c65bfb0..d6f7d11 100644 (file)
--- a/clutter/clutter-private.h
+++ b/clutter/clutter-private.h
@@ -194,6 +194,8 @@ void          _clutter_backend_init_events    (ClutterBackend  *backend);
 
 ClutterFeatureFlags _clutter_backend_get_features (ClutterBackend *backend);
 
+ClutterUnit   _clutter_backend_get_units_per_em   (ClutterBackend *backend);
+
 void          _clutter_feature_init (void);
 
 /* Picking code */

diff --git a/clutter/clutter-units.c b/clutter/clutter-units.c
index 88b2e7f..4b9d44e 100644 (file)
--- a/clutter/clutter-units.c
+++ b/clutter/clutter-units.c
@@ -168,39 +168,10 @@ ClutterUnit
 clutter_units_em (gdouble em)
 {
   ClutterBackend *backend;
-  const gchar *font_name;
-  gdouble dpi;
-  ClutterUnit retval = 0;
 
   backend = clutter_get_default_backend ();
 
-  dpi = clutter_backend_get_resolution (backend);
-  font_name = clutter_backend_get_font_name (backend);
-  if (G_LIKELY ((font_name && *font_name != '\0')))
-    {
-      PangoFontDescription *font_desc;
-      gdouble font_size = 0;
-
-      font_desc = pango_font_description_from_string (font_name);
-      if (G_LIKELY (font_desc != NULL))
-        {
-          gint pango_size;
-          gboolean is_absolute;
-
-          pango_size = pango_font_description_get_size (font_desc);
-          is_absolute =
-            pango_font_description_get_size_is_absolute (font_desc);
-          if (!is_absolute)
-            font_size = ((gdouble) font_size) / PANGO_SCALE;
-
-          pango_font_description_free (font_desc);
-        }
-
-      /* 10 points at 96 DPI is 12 pixels */
-      retval = 1.2 * font_size * dpi / 96.0;
-    }
-
-  return retval;
+  return em * _clutter_backend_get_units_per_em (backend);
 }
 
 static GTypeInfo _info = {