Post-draw GL read-backs now work from antialiased framebuffer (fix openframeworks#822; replaces commit 29e8034).

We're now setting display-mapped 'resolve' buffer (defaultFramebuffer) as current framebuffer after a draw, rather than the fsaa buffer. The fsaa buffer is set as current again before next draw.

Author: mcforman

addons/ofxiPhone/src/gl/ES1Renderer.m

@@ -48,6 +48,11 @@ -(EAGLContext*) context {
 
 - (void)startRender {
     [EAGLContext setCurrentContext:context];
+
+	if(fsaaEnabled) {
+		// Set up so that we draw into the multisampled buffer.
+		glBindFramebufferOES(GL_FRAMEBUFFER_OES, fsaaFrameBuffer);
+	}
 }
 
 - (void)finishRender {
@@ -70,8 +75,11 @@ - (void)finishRender {
     [context presentRenderbuffer:GL_RENDERBUFFER_OES];
 
 	if(fsaaEnabled) {
-		glBindFramebufferOES(GL_FRAMEBUFFER_OES, fsaaFrameBuffer);
-    }
+		// Set current fb to the 'resolve' buffer (mapped to the display). This means GL state is such that we can
+		//  read back (screen-grabs, texture-grabs, etc.) from within event handling methods.
+		//  Caveat: Can't execute direct GL draws from event handling methods...but don't think we should be anyway.
+		glBindFramebufferOES(GL_FRAMEBUFFER_OES, defaultFramebuffer);
+	}
 }
 
 - (BOOL)resizeFromLayer:(CAEAGLLayer *)layer {