effects: Fix stacking of offscreen-based effects

Stacking multiple effects sub-classing ClutterOffscreenEffect requires
a small fix in the code that computes the screen coordinates of the
actor to position the FBO correctly with regards to the stage.

diff --git a/clutter/clutter-offscreen-effect.c b/clutter/clutter-offscreen-effect.c
index b55d8b2..e3ce817 100644 (file)
--- a/clutter/clutter-offscreen-effect.c
+++ b/clutter/clutter-offscreen-effect.c
@@ -204,6 +204,7 @@ get_screen_offsets (ClutterActor *actor,
 {
   ClutterVertex verts[4];
   gfloat x_min = G_MAXFLOAT, y_min = G_MAXFLOAT;
+  gfloat v[4] = { 0, };
   gint i;
 
   /* Get the actors allocation transformed into screen coordinates.
@@ -231,6 +232,17 @@ get_screen_offsets (ClutterActor *actor,
   *y_offset = ROUND (y_min);
 
 #undef ROUND
+
+  /* since we're setting up a viewport with a negative offset to paint
+   * in an FBO with the same modelview and projection matrices as the
+   * stage, we need to offset the computed absolute allocation vertices
+   * with the current viewport's X and Y offsets. this works even with
+   * the default case where the viewport is set up by Clutter to be
+   * (0, 0, stage_width, stage_height)
+   */
+  cogl_get_viewport (v);
+  *x_offset -= v[0];
+  *y_offset -= v[1];
 }
 
 static gboolean

diff --git a/tests/interactive/test-rotate.c b/tests/interactive/test-rotate.c
index f801869..4f10dda 100644 (file)
--- a/tests/interactive/test-rotate.c
+++ b/tests/interactive/test-rotate.c
@@ -40,6 +40,7 @@ test_rotate_main (int argc, char *argv[])
   clutter_actor_set_position (hand, 240, 140);
   clutter_actor_show (hand);
   clutter_actor_add_effect_with_name (hand, "desaturate", clutter_desaturate_effect_new (0.75));
+  clutter_actor_add_effect_with_name (hand, "blur", clutter_blur_effect_new ());
   clutter_actor_animate_with_timeline (hand, CLUTTER_LINEAR, timeline,
                                        "@effects.desaturate.factor", 1.0,
                                        NULL);