gl_rasterizer: Emulate viewport flipping with ARB_clip_control

Emulates negative y viewports with ARB_clip_control. This allows us to
more easily emulated pipelines with tessellation and/or geometry shader
stages. It also avoids corrupting games with transform feedbacks and
negative viewports (gl_Position.y was being modified).

1 files changed, 5 insertions, 0 deletions

diff --git a/src/video_core/renderer_opengl/gl_state.h b/src/video_core/renderer_opengl/gl_state.h
index cca25206b..eaff22bda 100644
--- a/src/video_core/renderer_opengl/gl_state.h
+++ b/src/video_core/renderer_opengl/gl_state.h
@@ -146,6 +146,10 @@ public:
 
     std::array<bool, 8> clip_distance = {}; // GL_CLIP_DISTANCE
 
+    struct {
+        GLenum origin = GL_LOWER_LEFT;
+    } clip_control;
+
     OpenGLState();
 
     /// Get the currently active OpenGL state
@@ -182,6 +186,7 @@ public:
     void ApplyDepthClamp();
     void ApplyPolygonOffset();
     void ApplyAlphaTest();
+    void ApplyClipControl();
 
     /// Resets any references to the given resource
     OpenGLState& UnbindTexture(GLuint handle);