From f019817f8f6452dec784d8217ef102231319d26c Mon Sep 17 00:00:00 2001
From: ReinUsesLisp <reinuseslisp@airmail.cc>
Date: Wed, 30 Oct 2019 00:23:09 -0300
Subject: 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).
---
 src/video_core/renderer_opengl/gl_shader_gen.cpp | 24 ++++--------------------
 1 file changed, 4 insertions(+), 20 deletions(-)

(limited to 'src/video_core/renderer_opengl/gl_shader_gen.cpp')

diff --git a/src/video_core/renderer_opengl/gl_shader_gen.cpp b/src/video_core/renderer_opengl/gl_shader_gen.cpp
index 0e22eede9..af17216bd 100644
--- a/src/video_core/renderer_opengl/gl_shader_gen.cpp
+++ b/src/video_core/renderer_opengl/gl_shader_gen.cpp
@@ -20,8 +20,7 @@ std::string GenerateVertexShader(const Device& device, const ShaderIR& ir, const
     std::string out = GetCommonDeclarations();
     out += R"(
 layout (std140, binding = EMULATION_UBO_BINDING) uniform vs_config {
-    vec4 viewport_flip;
-    uvec4 config_pack; // instance_id, flip_stage, y_direction, padding
+    float y_direction;
 };
 
 )";
@@ -35,23 +34,10 @@ layout (std140, binding = EMULATION_UBO_BINDING) uniform vs_config {
 void main() {
     execute_vertex();
 )";
-
     if (ir_b) {
         out += "    execute_vertex_b();";
     }
-
-    out += R"(
-
-    // Set Position Y direction
-    gl_Position.y *= utof(config_pack[2]);
-    // Check if the flip stage is VertexB
-    // Config pack's second value is flip_stage
-    if (config_pack[1] == 1) {
-        // Viewport can be flipped, which is unsupported by glViewport
-        gl_Position.xy *= viewport_flip.xy;
-    }
-}
-)";
+    out += "}\n";
     return out;
 }
 
@@ -59,8 +45,7 @@ std::string GenerateGeometryShader(const Device& device, const ShaderIR& ir) {
     std::string out = GetCommonDeclarations();
     out += R"(
 layout (std140, binding = EMULATION_UBO_BINDING) uniform gs_config {
-    vec4 viewport_flip;
-    uvec4 config_pack; // instance_id, flip_stage, y_direction, padding
+    float y_direction;
 };
 
 )";
@@ -87,8 +72,7 @@ layout (location = 6) out vec4 FragColor6;
 layout (location = 7) out vec4 FragColor7;
 
 layout (std140, binding = EMULATION_UBO_BINDING) uniform fs_config {
-    vec4 viewport_flip;
-    uvec4 config_pack; // instance_id, flip_stage, y_direction, padding
+    float y_direction;
 };
 
 )";
-- 
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