docs: Document the DeformEffect wrap-mode change

The change from CoglVertexBuffer to CoglPrimitive led to a change of the
default wrap-mode for the pipeline. Since using REPEAT can introduce
artifacts when sampling outside the [ 0, 1 ] texture coordinates range,
and since the default wrap mode was not documented anyway, we want to
keep the change from REPEAT to CLAMP, but it's worth adding an entry in
the release notes.

diff --git a/README.in b/README.in
index 433de68..9ab556a 100644 (file)
--- a/README.in
+++ b/README.in
@@ -289,6 +289,16 @@ features).
 Release Notes for Clutter 1.10
 -------------------------------------------------------------------------------
 
+• ClutterDeformEffect switched from using CoglVertexBuffer to using the
+  CoglPrimitive API internally, to improve performance and use non-deprecated
+  Cogl API. CoglPrimitive converts COGL_WRAP_MODE_AUTOMATIC to
+  COGL_WRAP_MODE_CLAMP_TO_EDGE, unlike CoglVertexBuffer which converts it to
+  COGL_WRAP_MODE_REPEAT. This prevents artifacts when sampling texture
+  coordinates outside the [ 0, 1 ] range. This change may cause the back
+  texture to not be painted if its coordinates go outside the allowed range,
+  for instance when using a custom transformation matrix on the back material
+  used by the ClutterDeformEffect.
+
 • The "default stage" has been deprecated; since the 1.0 release, the default
   stage creation was deferred to the call to clutter_stage_get_default(), and
   the preferred way for getting a ClutterStage was calling clutter_stage_new()