Private CCDirector.viewportRect property.

Former-commit-id: 782d106

Author: slembcke

cocos2d/CCDirector.m

@@ -444,6 +444,29 @@ -(CGSize)viewSizeInPixels
 	return _winSizeInPixels;
 }
 
+-(CGRect)viewportRect
+{
+	// TODO It's _possible_ that a user will use a non-axis aligned projection. Weird, but possible.
+	kmMat4 projection;
+	kmGLGetMatrix(KM_GL_PROJECTION, &projection);
+	
+	kmMat4 projectionInv;
+	kmMat4Inverse(&projectionInv, &projection);
+	
+	// Calculate z=0 using -> transform*[0, 0, 0, 1]/w
+	kmScalar zClip = projection.mat[14]/projection.mat[15];
+	
+	// Bottom left and top right coordinates of viewport in clip coords.
+	kmVec3 clipBL = {-1.0, -1.0, zClip};
+	kmVec3 clipTR = { 1.0,  1.0, zClip};
+	
+	kmVec3 glBL, glTR;
+	kmVec3TransformCoord(&glBL, &clipBL, &projectionInv);
+	kmVec3TransformCoord(&glTR, &clipTR, &projectionInv);
+	
+	return CGRectMake(glBL.x, glBL.y, glTR.x - glBL.x, glTR.y - glBL.y);
+}
+
 -(CGSize)designSize
 {
 	// Return the viewSize unless designSize has been set.

cocos2d/CCDirector_Private.h

@@ -46,6 +46,9 @@
  */
 @property (nonatomic,readwrite,strong) CCActionManager *actionManager;
 
+/// Rect of the visible screen area in GL coordinates.
+@property(nonatomic, readonly) CGRect viewportRect;
+
 /* Sets the glViewport*/
 -(void) setViewport;