From e2adaa082c219c4c5f2025ae4898d3711000cab9 Mon Sep 17 00:00:00 2001
From: MrTheShy <49885496+MrTheShy@users.noreply.github.com>
Date: Mon, 9 Mar 2026 04:16:58 +0100
Subject: Fix split-screen UI wrong positioning on window resize (#989)

* Fix split-screen UI wrong positioning on window resize

In vertical split at window heights below 1080, ComputeTileScale's min-scale clamp (>= 1.0) prevented the SWF from scaling down to fit, cropping the bottom and causing repositionHud to shift HUD elements downward. Chat and Tooltips additionally applied an offset from ComputeSplitContentOffset that only produced correct values at the 1920x1080 design resolution.

Override the scale for vertical split so the SWF fits the full window height when it is shorter than the movie. Remove the broken content offset from Chat and Tooltips -- the tile crop already positions the content correctly.

* Fix gamma post-process in split-screen

The gamma shader sampled the full backbuffer texture (UV 0..1) into each player's viewport, stretching the entire screen into every split region. Extended the shader constant buffer with per-viewport UV offset and scale so each pass samples only its own portion of the backbuffer.

ComputeViewportForPlayer was hardcoded to top/bottom for 2 players, ignoring the vertical split setting. Rewrote it to read each player's m_iScreenSection directly, which already accounts for the split orientation preference.

Secondary players have no Graphics menu and cannot change gamma. CachePlayerGammas now reads the primary player's setting and applies it uniformly to all viewports.
---
 Minecraft.Client/Windows64/PostProcesser.cpp | 50 ++++++++++++++++++----------
 1 file changed, 32 insertions(+), 18 deletions(-)

(limited to 'Minecraft.Client/Windows64')

diff --git a/Minecraft.Client/Windows64/PostProcesser.cpp b/Minecraft.Client/Windows64/PostProcesser.cpp
index 4c55d3d9..aabb1f67 100644
--- a/Minecraft.Client/Windows64/PostProcesser.cpp
+++ b/Minecraft.Client/Windows64/PostProcesser.cpp
@@ -21,13 +21,17 @@ const char* PostProcesser::g_gammaPSCode =
     "cbuffer GammaCB : register(b0)\n"
     "{\n"
     "    float gamma;\n"
-    "    float3 pad;\n"
+    "    float _pad;\n"
+    "    float2 uvOffset;\n"
+    "    float2 uvScale;\n"
+    "    float2 _pad2;\n"
     "};\n"
     "Texture2D sceneTex : register(t0);\n"
     "SamplerState sceneSampler : register(s0);\n"
     "float4 main(float4 pos : SV_Position, float2 uv : TEXCOORD0) : SV_Target\n"
     "{\n"
-    "    float4 color = sceneTex.Sample(sceneSampler, uv);\n"
+    "    float2 texUV = uvOffset + uv * uvScale;\n"
+    "    float4 color = sceneTex.Sample(sceneSampler, texUV);\n"
     "\n"
     "    color.rgb = max(color.rgb, 0.0);\n"
     "\n"
@@ -158,7 +162,7 @@ void PostProcesser::Init()
     cbDesc.BindFlags = D3D11_BIND_CONSTANT_BUFFER;
     cbDesc.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE;
 
-    GammaCBData initData = {1.0f, {0, 0, 0}};
+    GammaCBData initData = {1.0f, 0, 0.0f, 0.0f, 1.0f, 1.0f, {0, 0}};
     D3D11_SUBRESOURCE_DATA srData;
     srData.pSysMem = &initData;
     srData.SysMemPitch = 0;
@@ -237,6 +241,10 @@ void PostProcesser::Apply() const
     {
         GammaCBData *cb = static_cast<GammaCBData *>(mapped.pData);
         cb->gamma = m_gamma;
+        cb->uvOffsetX = 0.0f;
+        cb->uvOffsetY = 0.0f;
+        cb->uvScaleX = 1.0f;
+        cb->uvScaleY = 1.0f;
         ctx->Unmap(m_pGammaCB, 0);
     }
 
@@ -333,6 +341,21 @@ void PostProcesser::ApplyFromCopied() const
 
     ID3D11DeviceContext* ctx = g_pImmediateContext;
 
+    D3D11_VIEWPORT vp;
+    if (m_useCustomViewport)
+    {
+        vp = m_customViewport;
+    }
+    else
+    {
+        vp.Width = static_cast<FLOAT>(m_gammaTexWidth);
+        vp.Height = static_cast<FLOAT>(m_gammaTexHeight);
+        vp.MinDepth = 0.0f;
+        vp.MaxDepth = 1.0f;
+        vp.TopLeftX = 0;
+        vp.TopLeftY = 0;
+    }
+
     D3D11_MAPPED_SUBRESOURCE mapped;
     const D3D11_MAP mapType = m_wineMode ? D3D11_MAP_WRITE_NO_OVERWRITE : D3D11_MAP_WRITE_DISCARD;
     const HRESULT hr = ctx->Map(m_pGammaCB, 0, mapType, 0, &mapped);
@@ -340,6 +363,12 @@ void PostProcesser::ApplyFromCopied() const
     {
         const auto cb = static_cast<GammaCBData*>(mapped.pData);
         cb->gamma = m_gamma;
+        const float texW = static_cast<float>(m_gammaTexWidth);
+        const float texH = static_cast<float>(m_gammaTexHeight);
+        cb->uvOffsetX = vp.TopLeftX / texW;
+        cb->uvOffsetY = vp.TopLeftY / texH;
+        cb->uvScaleX = vp.Width / texW;
+        cb->uvScaleY = vp.Height / texH;
         ctx->Unmap(m_pGammaCB, 0);
     }
 
@@ -354,21 +383,6 @@ void PostProcesser::ApplyFromCopied() const
     ID3D11RenderTargetView* bbRTV = g_pRenderTargetView;
     ctx->OMSetRenderTargets(1, &bbRTV, nullptr);
 
-    D3D11_VIEWPORT vp;
-    if (m_useCustomViewport)
-    {
-        vp = m_customViewport;
-    }
-    else
-    {
-        vp.Width = static_cast<FLOAT>(m_gammaTexWidth);
-        vp.Height = static_cast<FLOAT>(m_gammaTexHeight);
-        vp.MinDepth = 0.0f;
-        vp.MaxDepth = 1.0f;
-        vp.TopLeftX = 0;
-        vp.TopLeftY = 0;
-    }
-
     ctx->RSSetViewports(1, &vp);
 
     ctx->IASetInputLayout(nullptr);
-- 
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