graphics: preserve logical alpha when blending reordered targets (PPSA02721)

Co-authored-by: EmK530 <admin@emk530.net>

src/graphics/host_gpu/renderer/pipeline/blendMapping.h

@@ -0,0 +1,27 @@
+#ifndef EMULATOR_SRC_GRAPHICS_HOST_GPU_RENDERER_PIPELINE_BLENDMAPPING_H_
+#define EMULATOR_SRC_GRAPHICS_HOST_GPU_RENDERER_PIPELINE_BLENDMAPPING_H_
+
+#include <cstdint>
+
+namespace Libs::Graphics {
+
+namespace HW {
+struct BlendControl;
+}
+namespace Prospero {
+struct ColorComponentMapping;
+}
+
+enum class BlendMappingSupport {
+	Direct,
+	SourceAlpha, // Requires logical alpha in the second blend source.
+	Unsupported,
+};
+
+bool                BlendFactorIsDualSource(uint8_t factor);
+BlendMappingSupport ClassifyBlendMapping(const HW::BlendControl&                blend,
+                                         const Prospero::ColorComponentMapping& mapping);
+
+} // namespace Libs::Graphics
+
+#endif // EMULATOR_SRC_GRAPHICS_HOST_GPU_RENDERER_PIPELINE_BLENDMAPPING_H_