gl_shader_decompiler: Correct gl_FragCoord.x/y when render target is rescaled

src/video_core/renderer_opengl/gl_rasterizer.cpp

@@ -651,7 +651,7 @@ void RasterizerOpenGL::DrawPrelude() {
     SyncViewport(state, res_scaling);
     SyncScissorTest(state, res_scaling);
 
-    shader_program_manager->SetConstants(gpu);
+    shader_program_manager->SetConstants(gpu, res_scaling);
     shader_program_manager->ApplyTo(state);
     state.Apply();
 

src/video_core/renderer_opengl/gl_shader_decompiler.cpp

@@ -943,12 +943,20 @@ private:
         case Attribute::Index::Position:
             switch (stage) {
             case ProgramType::Geometry:
-                return {fmt::format("gl_in[{}].gl_Position{}", Visit(buffer).AsUint(),
-                                    GetSwizzle(element)),
-                        Type::Float};
-            case ProgramType::Fragment:
-                return {element == 3 ? "1.0f" : ("gl_FragCoord"s + GetSwizzle(element)),
-                        Type::Float};
+                return fmt::format("gl_in[{}].gl_Position{}", Visit(buffer).AsUint(),
+                                   GetSwizzle(element));
+            case ProgramType::Fragment: {
+                switch (element) {
+                case 0:
+                    return "(gl_FragCoord.x / utof(config_pack[3]))";
+                case 1:
+                    return "(gl_FragCoord.y / utof(config_pack[3]))";
+                case 2:
+                    return "gl_FragCoord.z";
+                case 3:
+                    return "1.0f";
+                }
+            }
             default:
                 UNREACHABLE();
             }

src/video_core/renderer_opengl/gl_shader_manager.cpp

@@ -4,6 +4,7 @@
 
 #include <array>
 #include "common/common_types.h"
+#include "core/settings.h"
 #include "video_core/engines/maxwell_3d.h"
 #include "video_core/renderer_opengl/gl_shader_manager.h"
 
@@ -37,7 +38,7 @@ ProgramManager::ProgramManager() {
 
 ProgramManager::~ProgramManager() = default;
 
-void ProgramManager::SetConstants(Tegra::Engines::Maxwell3D& maxwell_3d) {
+void ProgramManager::SetConstants(Tegra::Engines::Maxwell3D& maxwell_3d, bool rescaling) {
     const auto& regs = maxwell_3d.regs;
     const auto& state = maxwell_3d.state;
 
@@ -61,6 +62,8 @@ void ProgramManager::SetConstants(Tegra::Engines::Maxwell3D& maxwell_3d) {
     // Y_NEGATE controls what value S2R returns for the Y_DIRECTION system value.
     const GLfloat y_direction = regs.screen_y_control.y_negate == 0 ? 1.0f : -1.0f;
 
+    const GLfloat rescale_factor = rescaling ? Settings::values.resolution_factor : 1.0f;
+
     for (const auto stage :
          std::array{current_state.vertex, current_state.geometry, current_state.fragment}) {
         if (!stage) {
@@ -70,6 +73,7 @@ void ProgramManager::SetConstants(Tegra::Engines::Maxwell3D& maxwell_3d) {
         stage->SetFlipStage(flip_stage);
         stage->SetYDirection(y_direction);
         stage->SetViewportScale(flip_x, flip_y);
+        stage->SetRescalingFactor(rescale_factor);
         stage->UpdateConstants();
     }
 }

src/video_core/renderer_opengl/gl_shader_manager.h

@@ -40,6 +40,10 @@ public:
         state.y_direction = y_direction;
     }
 
+    void SetRescalingFactor(GLfloat rescaling_factor) {
+        state.rescaling_factor = rescaling_factor;
+    }
+
     void SetViewportScale(GLfloat x, GLfloat y) {
         state.viewport_scale = {x, y};
     }
@@ -52,6 +56,7 @@ private:
                 GLuint instance_id;
                 GLuint flip_stage;
                 GLfloat y_direction;
+                GLfloat rescaling_factor;
             };
         };
 
@@ -67,7 +72,7 @@ public:
     explicit ProgramManager();
     ~ProgramManager();
 
-    void SetConstants(Tegra::Engines::Maxwell3D& maxwell_3d);
+    void SetConstants(Tegra::Engines::Maxwell3D& maxwell_3d, bool rescaling);
 
     void ApplyTo(OpenGLState& state);