Backends: SDLRenderer3: added support for platform_io.DrawCallback_SetSamplerFromTex. (#9378)

backends/imgui_impl_sdlrenderer3.cpp

@@ -25,7 +25,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2026-09-17: Restore modified texture scale modes at the end of RenderDrawData(). Added CurrentScaleMode in ImGui_ImplSDLRenderer3_RenderState (#9543, #9378)
+//  2026-09-17: Restore modified texture scale modes at the end of RenderDrawData(). Added DrawCallback_SetSamplerFromTex support. Added CurrentScaleMode in ImGui_ImplSDLRenderer3_RenderState (#9543, #9378)
 //  2026-07-15: Fixed default sampler state to be linear (broken 2026-04-23). (#9470, #9378)
 //  2026-04-23: Added support for standard draw callbacks (in platform_io): DrawCallback_ResetRenderState, DrawCallback_SetSamplerLinear, DrawCallback_SetSamplerNearest. (#9378)
 //  2026-03-12: Fixed invalid assert in ImGui_ImplSDLRenderer3_UpdateTexture() if ImTextureID_Invalid is defined to be != 0, which became the default since 2026-03-12. (#9295)
@@ -122,6 +122,7 @@ static int SDL_RenderGeometryRaw8BitColor(SDL_Renderer* renderer, ImVector<SDL_F
 static void ImGui_ImplSDLRenderer3_DrawCallback_ResetRenderState(const ImDrawList*, const ImDrawCmd*)   {} // Intentionally empty. Used as an identifier for rendering loop to call its code. Simpler to implement this way.
 static void ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerLinear(const ImDrawList*, const ImDrawCmd*)   { ImGui_ImplSDLRenderer3_RenderState* render_state = ImGui_ImplSDLRenderer3_GetRenderState(); render_state->CurrentScaleMode = SDL_SCALEMODE_LINEAR; }
 static void ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerNearest(const ImDrawList*, const ImDrawCmd*)  { ImGui_ImplSDLRenderer3_RenderState* render_state = ImGui_ImplSDLRenderer3_GetRenderState(); render_state->CurrentScaleMode = SDL_SCALEMODE_NEAREST; }
+static void ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerFromTex(const ImDrawList*, const ImDrawCmd*)  { ImGui_ImplSDLRenderer3_RenderState* render_state = ImGui_ImplSDLRenderer3_GetRenderState(); render_state->CurrentScaleMode = SDL_SCALEMODE_INVALID; } // SDL_SCALEMODE_INVALID = use/keep value in texture.
 
 // SDLRenderer has various design issues which makes it hard to do it compared to regular graphics API.
 // - scale/filtering mode is tied to a texture.
@@ -129,18 +130,38 @@ static void ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerNearest(const ImDrawLi
 static void ImGui_ImplSDLRenderer3_TexScaleModeUpdate(SDL_Renderer* renderer, SDL_Texture* tex, SDL_ScaleMode desired_scale_mode)
 {
     ImGui_ImplSDLRenderer3_Data* bd = ImGui_ImplSDLRenderer3_GetBackendData();
+    if (desired_scale_mode != SDL_SCALEMODE_INVALID)
+    {
+        // Enforce a scale mode
         SDL_ScaleMode tex_scale_mode = desired_scale_mode;
         if (!SDL_GetTextureScaleMode(tex, &tex_scale_mode) || tex_scale_mode == desired_scale_mode)
             return;
         SDL_FlushRenderer(renderer);
         SDL_SetTextureScaleMode(tex, desired_scale_mode);
 
-    // Store backup of old scale mode
+        // Store backup of old scale mode (FIXME-OPT)
         for (ImGui_ImplSDLRenderer3_TexScaleModeEntry& entry : bd->TexScaleModeBackups)
             if (entry.Texture == tex)
+            {
+                if (entry.ScaleModeBackup == SDL_SCALEMODE_INVALID)
+                    entry.ScaleModeBackup = tex_scale_mode;
                 return;
+            }
         ImGui_ImplSDLRenderer3_TexScaleModeEntry entry = { tex, tex_scale_mode };
         bd->TexScaleModeBackups.push_back(entry);
+    }
+    else
+    {
+        // Use scale mode that was set in texture by user. If there is an entry, restore it and clear the entry.
+        for (ImGui_ImplSDLRenderer3_TexScaleModeEntry& entry : bd->TexScaleModeBackups)
+            if (entry.Texture == tex && entry.ScaleModeBackup != SDL_SCALEMODE_INVALID)
+            {
+                SDL_FlushRenderer(renderer);
+                SDL_SetTextureScaleMode(tex, entry.ScaleModeBackup);
+                entry.ScaleModeBackup = SDL_SCALEMODE_INVALID;
+                return;
+            }
+    }
 }
 
 static void ImGui_ImplSDLRenderer3_TexScaleModeRestoreBackups(SDL_Renderer* renderer)
@@ -345,6 +366,7 @@ bool ImGui_ImplSDLRenderer3_Init(SDL_Renderer* renderer)
     platform_io.DrawCallback_ResetRenderState = ImGui_ImplSDLRenderer3_DrawCallback_ResetRenderState;
     platform_io.DrawCallback_SetSamplerLinear = ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerLinear;
     platform_io.DrawCallback_SetSamplerNearest = ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerNearest;
+    platform_io.DrawCallback_SetSamplerFromTex = ImGui_ImplSDLRenderer3_DrawCallback_SetSamplerFromTex;
 
     bd->Renderer = renderer;
 

backends/imgui_impl_sdlrenderer3.h

@@ -49,7 +49,7 @@ IMGUI_IMPL_API void     ImGui_ImplSDLRenderer3_UpdateTexture(ImTextureData* tex)
 struct ImGui_ImplSDLRenderer3_RenderState
 {
     SDL_Renderer*       Renderer;
-    SDL_ScaleMode       CurrentScaleMode;   // Current scale mode during render.
+    SDL_ScaleMode       CurrentScaleMode;   // Current scale mode during render. Set to SDL_SCALEMODE_INVALID to use "SetSamplerFromTex" mode.
 };
 
 static inline ImGui_ImplSDLRenderer3_RenderState* ImGui_ImplSDLRenderer3_GetRenderState() { return (ImGui_ImplSDLRenderer3_RenderState*)ImGui::GetPlatformIO().Renderer_RenderState; }

docs/CHANGELOG.txt

@@ -100,6 +100,9 @@ Other Changes:
   - Reworked assert in PushTexture() to allow convenience grace period of using a
     texture that was queue for destroy during the frame. Make it safe to stick to
     an existing texture during the frame. (#9528, #8465)
+  - Added optional `platform_io.DrawCallback_SetSamplerFromTex` standard backend-agnostic
+    draw callback for requesting to use the sampler associated already associated to a texture.
+    Currently only supported by the SDLRenderer3 backend. (#9378)
 - Demo:
   - Added `Widgets->Mixed Values` section. (#5518, #5677, #6865)
 - Backends:
@@ -108,6 +111,11 @@ Other Changes:
     going through a SDL_Renderer. (#5592) [@lailoken]
   - SDLRenderer3: restore any temporarily modified texture scale modes at the of `RenderDrawData()`. (#9378)
   - SDLRenderer3: expose CurrentScaleMode in ImGui_ImplSDLRenderer3_RenderState. (#9543, #9378) [@Clownacy]
+  - SDLRenderer3: added support for `platform_io.DrawCallback_SetSamplerFromTex` draw callback to request
+    using the sampler associated already associated to a texture via `SDL_SetTextureScaleMode()`. (#9378)
+    It is equivalent to setting `render_state->CurrentScaleMode = SDL_SCALEMODE_INVALID`.
+    Note: this  callback is only supported by selected rendering backends: most other graphics API
+    don't have the equivalent of `SDL_SetTextureScaleMode()` and the callback won't work with them.
   - Vulkan: added for support for multiple Vulkan contexts with custom loaders. (#6616) [@lstalmir]
   - WebGPU: fixed passing non-integer sizes to `wgpuRenderPassEncoderSetViewport()`
     when when `FramebufferScale` is >1.0f. (#9515, #8628) [@WayU]

imgui.cpp

@@ -16111,7 +16111,7 @@ void ImGuiPlatformIO::ClearRendererHandlers()
 {
     Renderer_TextureMaxWidth = Renderer_TextureMaxHeight = 0;
     Renderer_RenderState = NULL;
-    DrawCallback_ResetRenderState = DrawCallback_SetSamplerLinear = DrawCallback_SetSamplerNearest = NULL;
+    DrawCallback_ResetRenderState = DrawCallback_SetSamplerLinear = DrawCallback_SetSamplerNearest = DrawCallback_SetSamplerFromTex = NULL;
 }
 
 ImGuiViewport* ImGui::GetMainViewport()

imgui.h

@@ -4114,6 +4114,7 @@ struct ImGuiPlatformIO
     ImDrawCallback  DrawCallback_ResetRenderState;      // Request to reset the graphics/render state.
     ImDrawCallback  DrawCallback_SetSamplerLinear;      // Request backend to set texture sampling to Linear.
     ImDrawCallback  DrawCallback_SetSamplerNearest;     // Request backend to set texture sampling to Nearest/Point.
+    ImDrawCallback  DrawCallback_SetSamplerFromTex;     // Request backend to use sampler associated to texture - only available in some backends: SDLRenderer3.
     //ImDrawCallback  DrawCallback_SetSamplerCustom;    // Request backend to set texture sampling using Backend Specific data.
 
     //------------------------------------------------------------------