Adding assertions for not-yet-implemented functionality for Metal.

Author: slembcke

cocos2d/CCClippingNode.m

@@ -34,6 +34,7 @@
 
 #import "CCNode_Private.h"
 #import "CCRenderDispatch.h"
+#import "CCConfiguration.h"
 
 static GLint _stencilBits = -1;
 
@@ -69,6 +70,8 @@ - (id)init
 
 - (id)initWithStencil:(CCNode *)stencil
 {
+    NSAssert([CCConfiguration sharedConfiguration].graphicsAPI == CCGraphicsAPIGL, @"CCClippingNode is not supported by the Metal renderer yet.");
+		
     if (self = [super init]) {
         self.stencil = stencil;
         self.alphaThreshold = 1;

cocos2d/CCRenderTexture.m

@@ -39,6 +39,7 @@
 #import "CCRenderer_Private.h"
 #import "CCRenderTexture_Private.h"
 #import "CCRenderDispatch.h"
+#import "CCMetalSupport_Private.h"
 
 #if __CC_PLATFORM_MAC
 #import <ApplicationServices/ApplicationServices.h>
@@ -385,6 +386,10 @@ -(void)draw:(CCRenderer *)renderer transform:(const GLKMatrix4 *)transform
 
 -(CGImageRef) newCGImage
 {
+	// TODO need to find out why getting pixels from a Metal texture doesn't seem to work.
+	// Workaround - use pixel buffers and a copy encoder?
+	NSAssert([CCConfiguration sharedConfiguration].graphicsAPI == CCGraphicsAPIGL, @"[CCRenderTexture -newCGImage] is only supported for GL.");
+	
 	NSAssert(_pixelFormat == CCTexturePixelFormat_RGBA8888,@"only RGBA8888 can be saved as image");
 
 	CGSize s = [self.texture contentSizeInPixels];
@@ -415,7 +420,7 @@ -(CGImageRef) newCGImage
     [self end];
 
 	// make data provider with data.
-	
+	// TODO find out why iref can't be used as the return value.
 	CGBitmapInfo bitmapInfo	= kCGImageAlphaPremultipliedLast | kCGBitmapByteOrderDefault;
 	CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, buffer, myDataLength, NULL);
 	CGColorSpaceRef colorSpaceRef = CGColorSpaceCreateDeviceRGB();

cocos2d/CCTexturePVR.m

@@ -506,6 +506,7 @@ - (BOOL)unpackPVRv3Data:(unsigned char*)dataPointer PVRLen:(NSUInteger)dataLengt
 
 - (BOOL)createGLTexture
 {
+	NSAssert([CCConfiguration sharedConfiguration].graphicsAPI == CCGraphicsAPIGL, @"PVR textures are not yet supported by Metal.");
 	__block BOOL retVal = NO;
 
 CCRenderDispatch(NO, ^{