SDL: Fix GetSampler() bug for INDEX8 pixel format (#15099) (01d8b)

From 01d8bb5b7c7bc0c628c2758dcc60393ee0e69fc7 Mon Sep 17 00:00:00 2001
From: Void Star Caster <[EMAIL REDACTED]>
Date: Tue, 24 Feb 2026 17:05:30 +0100
Subject: [PATCH] Fix GetSampler() bug for INDEX8 pixel format (#15099)

(cherry picked from commit 4a4ae4a79d3522b9ba6b0f5cbfdcb825cdf959f7)
---
 src/render/direct3d11/SDL_render_d3d11.c | 12 ++++++------
 src/render/direct3d12/SDL_render_d3d12.c | 12 ++++++------
 src/render/gpu/SDL_render_gpu.c          | 18 ++++++++----------
 src/render/metal/SDL_render_metal.m      | 15 +++++++--------
 src/render/vulkan/SDL_render_vulkan.c    | 15 +++++++--------
 5 files changed, 34 insertions(+), 38 deletions(-)

diff --git a/src/render/direct3d11/SDL_render_d3d11.c b/src/render/direct3d11/SDL_render_d3d11.c
index 14d4f1e509ad3..4cfdf9bab6464 100644
--- a/src/render/direct3d11/SDL_render_d3d11.c
+++ b/src/render/direct3d11/SDL_render_d3d11.c
@@ -2423,6 +2423,11 @@ static bool D3D11_SetDrawState(SDL_Renderer *renderer, const SDL_RenderCommand *
 
 static ID3D11SamplerState *D3D11_GetSamplerState(D3D11_RenderData *data, SDL_PixelFormat format, SDL_ScaleMode scale_mode, SDL_TextureAddressMode address_u, SDL_TextureAddressMode address_v)
 {
+    if (format == SDL_PIXELFORMAT_INDEX8) {
+        // We'll do linear sampling in the shader if needed
+        scale_mode = SDL_SCALEMODE_NEAREST;
+    }
+
     Uint32 key = RENDER_SAMPLER_HASHKEY(scale_mode, address_u, address_v);
     SDL_assert(key < SDL_arraysize(data->samplers));
     if (!data->samplers[key]) {
@@ -2440,12 +2445,7 @@ static ID3D11SamplerState *D3D11_GetSamplerState(D3D11_RenderData *data, SDL_Pix
             break;
         case SDL_SCALEMODE_PIXELART:    // Uses linear sampling
         case SDL_SCALEMODE_LINEAR:
-            if (format == SDL_PIXELFORMAT_INDEX8) {
-                // We'll do linear sampling in the shader
-                samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_POINT;
-            } else {
-                samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
-            }
+            samplerDesc.Filter = D3D11_FILTER_MIN_MAG_MIP_LINEAR;
             break;
         default:
             SDL_SetError("Unknown scale mode: %d", scale_mode);
diff --git a/src/render/direct3d12/SDL_render_d3d12.c b/src/render/direct3d12/SDL_render_d3d12.c
index e86aed13dabf5..4eb2a926012d1 100644
--- a/src/render/direct3d12/SDL_render_d3d12.c
+++ b/src/render/direct3d12/SDL_render_d3d12.c
@@ -2863,6 +2863,11 @@ static bool D3D12_SetDrawState(SDL_Renderer *renderer, const SDL_RenderCommand *
 
 static D3D12_CPU_DESCRIPTOR_HANDLE *D3D12_GetSamplerState(D3D12_RenderData *data, SDL_PixelFormat format, SDL_ScaleMode scale_mode, SDL_TextureAddressMode address_u, SDL_TextureAddressMode address_v)
 {
+    if (format == SDL_PIXELFORMAT_INDEX8) {
+        // We'll do linear sampling in the shader if needed
+        scale_mode = SDL_SCALEMODE_NEAREST;
+    }
+
     Uint32 key = RENDER_SAMPLER_HASHKEY(scale_mode, address_u, address_v);
     SDL_assert(key < SDL_arraysize(data->samplers));
     if (!data->samplers_created[key]) {
@@ -2888,12 +2893,7 @@ static D3D12_CPU_DESCRIPTOR_HANDLE *D3D12_GetSamplerState(D3D12_RenderData *data
             break;
         case SDL_SCALEMODE_PIXELART:    // Uses linear sampling
         case SDL_SCALEMODE_LINEAR:
-            if (format == SDL_PIXELFORMAT_INDEX8) {
-                // We'll do linear sampling in the shader
-                samplerDesc.Filter = D3D12_FILTER_MIN_MAG_MIP_POINT;
-            } else {
-                samplerDesc.Filter = D3D12_FILTER_MIN_MAG_MIP_LINEAR;
-            }
+            samplerDesc.Filter = D3D12_FILTER_MIN_MAG_MIP_LINEAR;
             break;
         default:
             SDL_SetError("Unknown scale mode: %d", scale_mode);
diff --git a/src/render/gpu/SDL_render_gpu.c b/src/render/gpu/SDL_render_gpu.c
index 54aa35ab70880..b589333850bc2 100644
--- a/src/render/gpu/SDL_render_gpu.c
+++ b/src/render/gpu/SDL_render_gpu.c
@@ -774,6 +774,11 @@ static void SetViewportAndScissor(GPU_RenderData *data)
 
 static SDL_GPUSampler *GetSampler(GPU_RenderData *data, SDL_PixelFormat format, SDL_ScaleMode scale_mode, SDL_TextureAddressMode address_u, SDL_TextureAddressMode address_v)
 {
+    if (format == SDL_PIXELFORMAT_INDEX8) {
+        // We'll do linear sampling in the shader if needed
+        scale_mode = SDL_SCALEMODE_NEAREST;
+    }
+
     Uint32 key = RENDER_SAMPLER_HASHKEY(scale_mode, address_u, address_v);
     SDL_assert(key < SDL_arraysize(data->samplers));
     if (!data->samplers[key]) {
@@ -787,16 +792,9 @@ static SDL_GPUSampler *GetSampler(GPU_RenderData *data, SDL_PixelFormat format,
             break;
         case SDL_SCALEMODE_PIXELART:    // Uses linear sampling
         case SDL_SCALEMODE_LINEAR:
-            if (format == SDL_PIXELFORMAT_INDEX8) {
-                // We'll do linear sampling in the shader
-                sci.min_filter = SDL_GPU_FILTER_NEAREST;
-                sci.mag_filter = SDL_GPU_FILTER_NEAREST;
-                sci.mipmap_mode = SDL_GPU_SAMPLERMIPMAPMODE_NEAREST;
-            } else {
-                sci.min_filter = SDL_GPU_FILTER_LINEAR;
-                sci.mag_filter = SDL_GPU_FILTER_LINEAR;
-                sci.mipmap_mode = SDL_GPU_SAMPLERMIPMAPMODE_LINEAR;
-            }
+            sci.min_filter = SDL_GPU_FILTER_LINEAR;
+            sci.mag_filter = SDL_GPU_FILTER_LINEAR;
+            sci.mipmap_mode = SDL_GPU_SAMPLERMIPMAPMODE_LINEAR;
             break;
         default:
             SDL_SetError("Unknown scale mode: %d", scale_mode);
diff --git a/src/render/metal/SDL_render_metal.m b/src/render/metal/SDL_render_metal.m
index 36a4b5cc336dd..a5fb3bd233fee 100644
--- a/src/render/metal/SDL_render_metal.m
+++ b/src/render/metal/SDL_render_metal.m
@@ -1560,6 +1560,11 @@ static bool SetDrawState(SDL_Renderer *renderer, const SDL_RenderCommand *cmd, c
 
 static id<MTLSamplerState> GetSampler(SDL3METAL_RenderData *data, SDL_PixelFormat format, SDL_ScaleMode scale_mode, SDL_TextureAddressMode address_u, SDL_TextureAddressMode address_v)
 {
+    if (format == SDL_PIXELFORMAT_INDEX8) {
+        // We'll do linear sampling in the shader if needed
+        scale_mode = SDL_SCALEMODE_NEAREST;
+    }
+
     NSNumber *key = [NSNumber numberWithInteger:RENDER_SAMPLER_HASHKEY(scale_mode, address_u, address_v)];
     id<MTLSamplerState> mtlsampler = data.mtlsamplers[key];
     if (mtlsampler == nil) {
@@ -1572,14 +1577,8 @@ static bool SetDrawState(SDL_Renderer *renderer, const SDL_RenderCommand *cmd, c
             break;
         case SDL_SCALEMODE_PIXELART:    // Uses linear sampling
         case SDL_SCALEMODE_LINEAR:
-            if (format == SDL_PIXELFORMAT_INDEX8) {
-                // We'll do linear sampling in the shader
-                samplerdesc.minFilter = MTLSamplerMinMagFilterNearest;
-                samplerdesc.magFilter = MTLSamplerMinMagFilterNearest;
-            } else {
-                samplerdesc.minFilter = MTLSamplerMinMagFilterLinear;
-                samplerdesc.magFilter = MTLSamplerMinMagFilterLinear;
-            }
+            samplerdesc.minFilter = MTLSamplerMinMagFilterLinear;
+            samplerdesc.magFilter = MTLSamplerMinMagFilterLinear;
             break;
         default:
             SDL_SetError("Unknown scale mode: %d", scale_mode);
diff --git a/src/render/vulkan/SDL_render_vulkan.c b/src/render/vulkan/SDL_render_vulkan.c
index cd7bed413b659..692dea7dbc540 100644
--- a/src/render/vulkan/SDL_render_vulkan.c
+++ b/src/render/vulkan/SDL_render_vulkan.c
@@ -3874,6 +3874,11 @@ static bool VULKAN_SetDrawState(SDL_Renderer *renderer, const SDL_RenderCommand
 
 static VkSampler VULKAN_GetSampler(VULKAN_RenderData *data, SDL_PixelFormat format, SDL_ScaleMode scale_mode, SDL_TextureAddressMode address_u, SDL_TextureAddressMode address_v)
 {
+    if (format == SDL_PIXELFORMAT_INDEX8) {
+        // We'll do linear sampling in the shader if needed
+        scale_mode = SDL_SCALEMODE_NEAREST;
+    }
+
     Uint32 key = RENDER_SAMPLER_HASHKEY(scale_mode, address_u, address_v);
     SDL_assert(key < SDL_arraysize(data->samplers));
     if (!data->samplers[key]) {
@@ -3893,14 +3898,8 @@ static VkSampler VULKAN_GetSampler(VULKAN_RenderData *data, SDL_PixelFormat form
             break;
         case SDL_SCALEMODE_PIXELART:    // Uses linear sampling
         case SDL_SCALEMODE_LINEAR:
-            if (format == SDL_PIXELFORMAT_INDEX8) {
-                // We'll do linear sampling in the shader
-                samplerCreateInfo.magFilter = VK_FILTER_NEAREST;
-                samplerCreateInfo.minFilter = VK_FILTER_NEAREST;
-            } else {
-                samplerCreateInfo.magFilter = VK_FILTER_LINEAR;
-                samplerCreateInfo.minFilter = VK_FILTER_LINEAR;
-            }
+            samplerCreateInfo.magFilter = VK_FILTER_LINEAR;
+            samplerCreateInfo.minFilter = VK_FILTER_LINEAR;
             break;
         default:
             SDL_SetError("Unknown scale mode: %d", scale_mode);