From f95b7c58779f01d9077996da67953d8d9acd058c Mon Sep 17 00:00:00 2001
From: gdkchan <gab.dark.100@gmail.com>
Date: Sat, 29 Jul 2023 18:47:03 -0300
Subject: Fix incorrect fragment origin when YNegate is enabled (#4673)

* Fix incorrect fragment origin when YNegate is enabled

* Shader cache version bump

* Do not update support buffer if shader does not read gl_FragCoord

* Pass unscaled viewport size to the support buffer
---
 .../Engine/Threed/SpecializationStateUpdater.cs    | 14 +++++++
 .../Engine/Threed/StateUpdater.cs                  | 47 ++++++++++++++++++++--
 2 files changed, 58 insertions(+), 3 deletions(-)

(limited to 'src/Ryujinx.Graphics.Gpu/Engine')

diff --git a/src/Ryujinx.Graphics.Gpu/Engine/Threed/SpecializationStateUpdater.cs b/src/Ryujinx.Graphics.Gpu/Engine/Threed/SpecializationStateUpdater.cs
index cbf1573c..b2935a5b 100644
--- a/src/Ryujinx.Graphics.Gpu/Engine/Threed/SpecializationStateUpdater.cs
+++ b/src/Ryujinx.Graphics.Gpu/Engine/Threed/SpecializationStateUpdater.cs
@@ -342,5 +342,19 @@ namespace Ryujinx.Graphics.Gpu.Engine.Threed
                 Signal();
             }
         }
+
+        /// <summary>
+        /// Sets the Y negate enabled state.
+        /// </summary>
+        /// <param name="enabled">True if Y negate of the fragment coordinates is enabled</param>
+        public void SetYNegateEnabled(bool enabled)
+        {
+            if (enabled != _graphics.YNegateEnabled)
+            {
+                _graphics.YNegateEnabled = enabled;
+
+                Signal();
+            }
+        }
     }
 }
diff --git a/src/Ryujinx.Graphics.Gpu/Engine/Threed/StateUpdater.cs b/src/Ryujinx.Graphics.Gpu/Engine/Threed/StateUpdater.cs
index b4f56245..c0c2d5b3 100644
--- a/src/Ryujinx.Graphics.Gpu/Engine/Threed/StateUpdater.cs
+++ b/src/Ryujinx.Graphics.Gpu/Engine/Threed/StateUpdater.cs
@@ -37,6 +37,7 @@ namespace Ryujinx.Graphics.Gpu.Engine.Threed
 
         private ProgramPipelineState _pipeline;
 
+        private bool _fsReadsFragCoord;
         private bool _vsUsesDrawParameters;
         private bool _vtgWritesRtLayer;
         private byte _vsClipDistancesWritten;
@@ -692,12 +693,11 @@ namespace Ryujinx.Graphics.Gpu.Engine.Threed
             var face = _state.State.FaceState;
 
             bool disableTransform = _state.State.ViewportTransformEnable == 0;
+            bool yNegate = yControl.HasFlag(YControl.NegateY);
 
             UpdateFrontFace(yControl, face.FrontFace);
             UpdateDepthMode();
 
-            bool flipY = yControl.HasFlag(YControl.NegateY);
-
             Span<Viewport> viewports = stackalloc Viewport[Constants.TotalViewports];
 
             for (int index = 0; index < Constants.TotalViewports; index++)
@@ -719,7 +719,7 @@ namespace Ryujinx.Graphics.Gpu.Engine.Threed
                 float scaleX = MathF.Abs(transform.ScaleX);
                 float scaleY = transform.ScaleY;
 
-                if (flipY)
+                if (yNegate)
                 {
                     scaleY = -scaleY;
                 }
@@ -771,8 +771,17 @@ namespace Ryujinx.Graphics.Gpu.Engine.Threed
                 _channel.TextureManager.RenderTargetScale,
                 disableTransform);
 
+            // Viewport size is only used on the shader when YNegate is enabled,
+            // and if the fragment shader accesses gl_FragCoord,
+            // so there's no need to update it in other cases.
+            if (yNegate && _fsReadsFragCoord)
+            {
+                UpdateSupportBufferViewportSize();
+            }
+
             _currentSpecState.SetViewportTransformDisable(disableTransform);
             _currentSpecState.SetDepthMode(GetDepthMode() == DepthMode.MinusOneToOne);
+            _currentSpecState.SetYNegateEnabled(yNegate);
         }
 
         /// <summary>
@@ -1415,9 +1424,41 @@ namespace Ryujinx.Graphics.Gpu.Engine.Threed
                 _currentProgramInfo[stageIndex] = info;
             }
 
+            if (gs.Shaders[5]?.Info.UsesFragCoord == true)
+            {
+                // Make sure we update the viewport size on the support buffer if it will be consumed on the new shader.
+
+                if (!_fsReadsFragCoord && _state.State.YControl.HasFlag(YControl.NegateY))
+                {
+                    UpdateSupportBufferViewportSize();
+                }
+
+                _fsReadsFragCoord = true;
+            }
+            else
+            {
+                _fsReadsFragCoord = false;
+            }
+
             _context.Renderer.Pipeline.SetProgram(gs.HostProgram);
         }
 
+        /// <summary>
+        /// Updates the viewport size on the support buffer for fragment shader access.
+        /// </summary>
+        private void UpdateSupportBufferViewportSize()
+        {
+            ref var transform = ref _state.State.ViewportTransform[0];
+
+            float scaleX = MathF.Abs(transform.ScaleX);
+            float scaleY = transform.ScaleY;
+
+            float width = scaleX * 2;
+            float height = scaleY * 2;
+
+            _context.SupportBufferUpdater.SetViewportSize(width, MathF.Abs(height));
+        }
+
         /// <summary>
         /// Updates bindings consumed by the shader on the texture and buffer managers.
         /// </summary>
-- 
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