From 087cb8b5e03714b6821bd8ffbd6fb54b07a7905e Mon Sep 17 00:00:00 2001
From: raven02 <jacky.kktsui@yahoo.com.hk>
Date: Sat, 27 Jul 2013 06:24:59 +0800
Subject: [PATCH] Clamp vpX0/vpY0 to zero when negative value retured

---
 GPU/GLES/StateMapping.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/GPU/GLES/StateMapping.cpp b/GPU/GLES/StateMapping.cpp
index 6b7a53cc93..501c31bd33 100644
--- a/GPU/GLES/StateMapping.cpp
+++ b/GPU/GLES/StateMapping.cpp
@@ -364,6 +364,11 @@ void TransformDrawEngine::ApplyDrawState(int prim) {
 
 		// Flip vpY0 to match the OpenGL coordinate system.
 		vpY0 = renderHeight - (vpY0 + vpHeight);
+		
+		// Clamp vpX0/vpY0 to zero when negative value retured.
+		vpY0 = vpY0 < 0 ? 0 : vpY0;
+		vpX0 = vpX0 < 0 ? 0 : vpX0;
+		
 		glstate.viewport.set(vpX0 + renderX, vpY0 + renderY, vpWidth, vpHeight);
 		// Sadly, as glViewport takes integers, we will not be able to support sub pixel offsets this way. But meh.
 		// shaderManager_->DirtyUniform(DIRTY_PROJMATRIX);