Pictures in the UI read as ImGui's colours are: an sRGB picture was turned linear and showed too dark (the logo in About, the Picture panel's paint) — a UNORM view on Vulkan, a skip-decode sampler on OpenGL 4.6 and 4.0, the texture's own setting before 3.3

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

engine/render/backend.h

@@ -14,8 +14,20 @@
 #include <string>
 #include <vector>
 
+struct ImDrawList;
+struct ImDrawCmd;
+
 namespace keel {
 
+// Draw callbacks round an sRGB picture drawn in the UI, so it's read as the plain numbers ImGui's
+// own colours are (read as sRGB it turns linear, and looks too dark). None when uiTexture already
+// gives such a view (Vulkan).
+struct UiRawRead {
+    void (*begin)(const ImDrawList*, const ImDrawCmd*) = nullptr;
+    void (*end)(const ImDrawList*, const ImDrawCmd*) = nullptr;
+    void* data = nullptr;
+};
+
 class Window;
 using TextureId = uint32_t;
 
@@ -217,6 +229,7 @@ public:
     virtual void uploadModel(uint32_t model, const KmdlModel& kmdl) = 0;
     // A texture as Dear ImGui's ImTextureID, for drawing it in the UI (0 = none).
     virtual uint64_t uiTexture(TextureId slot) = 0;
+    virtual UiRawRead uiRawRead(TextureId) { return {}; }
     // Starts a frame; false when nothing can be drawn (minimised). Sets the drawable size.
     virtual bool beginFrame(uint32_t& width, uint32_t& height) = 0;
     // Renders the packet, then ImGui's draw data, and presents.

engine/render/renderer.h

@@ -76,6 +76,7 @@ public:
 
     // A loaded texture for ImGui::Image (ImTextureID); 0 if it isn't one.
     uint64_t uiTexture(TextureId texture) { return backend_ ? backend_->uiTexture(texture) : 0; }
+    UiRawRead uiRawRead(TextureId texture) { return backend_ ? backend_->uiRawRead(texture) : UiRawRead{}; }
     // Pixel size of a loaded texture.
     glm::ivec2 textureSize(TextureId texture) const {
         const auto it = textureSizes_.find(texture);