CCEffectRenderer - Don't use the node's default shader for render target copy operations

When direct rendering is disabled or when stacking and not stitching, don't use the affected
node's default shader (probably color*texture) to do compositing operations. Instead we just
want texture to be unmultiplied by node color.

Create a texture only shader to do these texture-only compositing passes.

Author: Thayer J Andrews

cocos2d/CCEffectRenderer.m

@@ -123,11 +123,24 @@ @interface CCEffectRenderer ()
 @property (nonatomic, assign) GLKVector4 oldViewport;
 @property (nonatomic, assign) GLint oldFBO;
 
++(CCShader *)sharedCopyShader;
+
 @end
 
 
 @implementation CCEffectRenderer
 
++ (CCShader *)sharedCopyShader
+{
+	static dispatch_once_t once;
+	static CCShader *copyShader = nil;
+	dispatch_once(&once, ^{
+        copyShader = [[CCShader alloc] initWithFragmentShaderSource:@"void main(){gl_FragColor = texture2D(cc_MainTexture, cc_FragTexCoord1);}"];
+        copyShader.debugName = @"CCEffectRendererTextureCopyShader";
+	});
+	return copyShader;
+}
+
 -(id)init
 {
     if((self = [super init]))
@@ -214,6 +227,7 @@ -(void)drawSprite:(CCSprite *)sprite withEffect:(CCEffect *)effect uniforms:(NSM
         [renderer pushGroup];
 
         CCTexture *backup = sprite.texture;
+        sprite.shader = [CCEffectRenderer sharedCopyShader];
         sprite.texture = previousPassRT.texture;
         [sprite enqueueTriangles:renderer transform:transform];
         sprite.texture = backup;