From bceca34ef9948ed1d0f3c1ee6793d8c97b291ac1 Mon Sep 17 00:00:00 2001
From: Emmanuele Bassi <ebassi@gnome.org>
Date: Thu, 10 Oct 2013 13:37:11 +0100
Subject: [PATCH] paint-nodes: Clarify color handling for TextureNode

The TextureNode premultiplies the blend color passed to the node
constructor, so we need to document the fact properly to avoid
causing premultiplication twice.

We can also allow passing NULL for a color, and use a fully opaque
white, to make the code slightly more friendly.
---
 clutter/clutter-paint-nodes.c | 24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/clutter/clutter-paint-nodes.c b/clutter/clutter-paint-nodes.c
index 2b95d413d..d1b574d23 100644
--- a/clutter/clutter-paint-nodes.c
+++ b/clutter/clutter-paint-nodes.c
@@ -652,7 +652,7 @@ clutter_scaling_filter_to_cogl_pipeline_filter (ClutterScalingFilter filter)
 /**
  * clutter_texture_node_new:
  * @texture: a #CoglTexture
- * @color: a #ClutterColor
+ * @color: (allow-none): a #ClutterColor used for blending, or %NULL
  * @min_filter: the minification filter for the texture
  * @mag_filter: the magnification filter for the texture
  *
@@ -661,6 +661,10 @@ clutter_scaling_filter_to_cogl_pipeline_filter (ClutterScalingFilter filter)
  * This function will take a reference on @texture, so it is safe to
  * call cogl_object_unref() on @texture when it returns.
  *
+ * The @color must not be pre-multiplied with its #ClutterColor.alpha
+ * channel value; if @color is %NULL, a fully opaque white color will
+ * be used for blending.
+ *
  * Return value: (transfer full): the newly created #ClutterPaintNode.
  *   Use clutter_paint_node_unref() when done
  *
@@ -686,12 +690,18 @@ clutter_texture_node_new (CoglTexture          *texture,
   mag_f = clutter_scaling_filter_to_cogl_pipeline_filter (mag_filter);
   cogl_pipeline_set_layer_filters (tnode->pipeline, 0, min_f, mag_f);
 
-  cogl_color_init_from_4ub (&cogl_color,
-                            color->red,
-                            color->green,
-                            color->blue,
-                            color->alpha);
-  cogl_color_premultiply (&cogl_color);
+  if (color != NULL)
+    {
+      cogl_color_init_from_4ub (&cogl_color,
+                                color->red,
+                                color->green,
+                                color->blue,
+                                color->alpha);
+      cogl_color_premultiply (&cogl_color);
+    }
+  else
+    cogl_color_init_from_4ub (&cogl_color, 255, 255, 255, 255);
+
   cogl_pipeline_set_color (tnode->pipeline, &cogl_color);
 
   return (ClutterPaintNode *) tnode;