Improve the quality of text when the scale it is shown at screen is

smaller than the original, seems to work well down to about a scale
of 50%.
* clutter/pango/pangoclutter-fontmap.c:
(pango_clutter_font_map_default_substitute): turn off hinting.
* clutter/pango/pangoclutter-render.c: request linear filtering
instead of nearest neighbour when scaling down.
* tests/test-text.c: replaced test with a a test that renders a sample
grid with various pixel sizes and scales for visual inspection of
text rendering quality.

ChangeLog

@@ -1,3 +1,17 @@
+2007-10-11  Øyvind Kolås  <pippin@o-hand.com>
+
+	Improve the quality of text when the scale it is shown at screen is
+	smaller than the original, seems to work well down to about a scale
+	of 50%.
+
+	* clutter/pango/pangoclutter-fontmap.c:
+	(pango_clutter_font_map_default_substitute): turn off hinting.
+	* clutter/pango/pangoclutter-render.c: request linear filtering
+	instead of nearest neighbour when scaling down.
+	* tests/test-text.c: replaced test with a a test that renders a sample
+	grid with various pixel sizes and scales for visual inspection of
+	text rendering quality.
+
 2007-10-10  Emmanuele Bassi  <ebassi@openedhand.com>
 
 	* clutter/glx/clutter-backend-glx.c: Fix documentation of the

clutter/pango/pangoclutter-fontmap.c

@@ -196,6 +196,13 @@ pango_clutter_font_map_default_substitute (PangoFcFontMap *fcfontmap,
   if (FcPatternGet (pattern, FC_DPI, 0, &v) == FcResultNoMatch)
     FcPatternAddDouble (pattern, FC_DPI, fontmap->dpi_y);
 #endif
+
+   /* Turn off hinting, since we most of the time are not using the glyphs
+    * from our cache at their nativly rendered resolution
+    */
+   FcPatternDel (pattern, FC_HINTING);
+   FcPatternAddBool (pattern, FC_HINTING, FALSE);
+
   FcDefaultSubstitute (pattern);
 }
 

clutter/pango/pangoclutter-render.c

@@ -118,7 +118,11 @@ tc_get (tc_area *area, int width, int height)
 
 	  cogl_texture_bind (CGL_TEXTURE_2D, match->name);
 
-	  cogl_texture_set_filters (CGL_TEXTURE_2D, CGL_NEAREST, CGL_NEAREST);
+	  /* We might even want to use mipmapping instead of CGL_LINEAR here
+       * that should allow rerendering of glyphs to look nice even at scales
+       * far below 50%.
+       */
+	  cogl_texture_set_filters (CGL_TEXTURE_2D, CGL_LINEAR, CGL_NEAREST);
 
 	  cogl_texture_image_2d (CGL_TEXTURE_2D, 
 				 CGL_ALPHA,

tests/test-text.c

@@ -1,52 +1,73 @@
 #include <clutter/clutter.h>
 
-void
+#define STAGE_WIDTH  640
-frame_cb (ClutterTimeline *timeline, 
+#define STAGE_HEIGHT 480
-	  gint             frame_num, 
-	  gpointer         data)
-{
-  ClutterActor *label = (ClutterActor*)data;
-
-  clutter_actor_set_depth(label, -400 + (frame_num * 40));
-  clutter_actor_set_opacity (label, 255 - frame_num );
-}
 
+#define COLS 18
+#define ROWS 20
 
 int
 main (int argc, char *argv[])
 {
-  ClutterTimeline *timeline;
+  ClutterActor    *stage;
-  ClutterActor  *label;
-  ClutterActor  *stage;
   gchar           *text;
   gsize            size;
   ClutterColor     stage_color = { 0x00, 0x00, 0x00, 0xff };
-  ClutterColor     label_color = { 0x11, 0xdd, 0x11, 0xaa };
+  ClutterColor     label_color = { 0xff, 0xff, 0xff, 0xff };
 
   clutter_init (&argc, &argv);
 
   stage = clutter_stage_get_default ();
-
+  clutter_actor_set_size (stage, STAGE_WIDTH, STAGE_HEIGHT);
-  if (!g_file_get_contents ("test-text.c", &text, &size, NULL)) 
-    g_error("g_file_get_contents() of test-text.c failed");
-
-  clutter_actor_set_size (stage, 800, 600);
   clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
 
-  label = clutter_label_new_with_text ("Mono 8", text);
+  {
-  clutter_label_set_color (CLUTTER_LABEL (label), &label_color);
+    gint    font_size;
+    gdouble scale;
+    gint    row, col;
 
-  clutter_container_add_actor (CLUTTER_CONTAINER (stage), label);
+    for (row=0; row<ROWS; row++)
+      for (col=0; col<COLS; col++)
+        {
+          ClutterActor    *label;
+          gchar font_name[64];
+          gchar text[64];
+          gint    font_size = row+10;
+          gdouble scale = 0.17 + (1.5*col/COLS);
+
+          sprintf (font_name, "Sans %ipx", font_size);
+          sprintf (text, "OH");
+
+          if (row==0)
+            {
+              sprintf (font_name, "Sans 10px");
+              sprintf (text, "%1.2f", scale);
+              font_size = 10;
+              scale = 1.0;
+            }
+          if (col==0)
+            {
+              sprintf (font_name, "Sans 10px");
+              sprintf (text, "%ipx", font_size);
+              if (row==0)
+                sprintf (text, "");
+              font_size = 10;
+              scale = 1.0;
+            }
+
+          label = clutter_label_new_with_text (font_name, text);
+          clutter_label_set_color (CLUTTER_LABEL (label), &label_color);
+          clutter_actor_set_position (label, (1.0*STAGE_WIDTH/COLS)*col,
+                                             (1.0*STAGE_HEIGHT/ROWS)*row);
+          /*clutter_actor_set_clip (label, 0,0, (1.0*STAGE_WIDTH/COLS),
+                                              (1.0*STAGE_HEIGHT/ROWS));*/
+          clutter_actor_set_scale (label, scale, scale);
+          clutter_label_set_line_wrap (CLUTTER_LABEL (label), FALSE);
+          clutter_container_add_actor (CLUTTER_CONTAINER (stage), label);
+        }
+  }
   clutter_actor_show_all (stage);
 
-  timeline = clutter_timeline_new (400, 60); /* num frames, fps */
-  g_object_set(timeline, "loop", TRUE, NULL);   /* have it loop */
-
-  g_signal_connect(timeline, "new-frame",  G_CALLBACK (frame_cb), label);
-
-  /* and start it */
-  clutter_timeline_start (timeline);
-
   g_signal_connect (stage, "key-press-event",
 		    G_CALLBACK (clutter_main_quit), NULL);