diff --git a/src/gpu/vulkan/SDL_gpu_vulkan.c b/src/gpu/vulkan/SDL_gpu_vulkan.c index c63c4884b3..9986d48ac6 100644 --- a/src/gpu/vulkan/SDL_gpu_vulkan.c +++ b/src/gpu/vulkan/SDL_gpu_vulkan.c @@ -4430,6 +4430,7 @@ static Uint32 VULKAN_INTERNAL_CreateSwapchain( VkSemaphoreCreateInfo semaphoreCreateInfo; SwapchainSupportDetails swapchainSupportDetails; bool hasValidSwapchainComposition, hasValidPresentMode; + VkCompositeAlphaFlagsKHR compositeAlphaFlag = 0; Uint32 i; windowData->frameCounter = 0; @@ -4570,6 +4571,25 @@ static Uint32 VULKAN_INTERNAL_CreateSwapchain( requestedImageCount = SDL_max(requestedImageCount, 3); } + // Default to opaque, if available, followed by inherit, and overwrite with a value that supports transparency, if necessary. + if (swapchainSupportDetails.capabilities.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR) { + compositeAlphaFlag = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR; + } else if (swapchainSupportDetails.capabilities.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR) { + compositeAlphaFlag = VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR; + } + + if ((windowData->window->flags & SDL_WINDOW_TRANSPARENT) || !compositeAlphaFlag) { + if (swapchainSupportDetails.capabilities.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR) { + compositeAlphaFlag = VK_COMPOSITE_ALPHA_PRE_MULTIPLIED_BIT_KHR; + } else if (swapchainSupportDetails.capabilities.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR) { + compositeAlphaFlag = VK_COMPOSITE_ALPHA_POST_MULTIPLIED_BIT_KHR; + } else if (swapchainSupportDetails.capabilities.supportedCompositeAlpha & VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR) { + compositeAlphaFlag = VK_COMPOSITE_ALPHA_INHERIT_BIT_KHR; + } else { + SDL_LogWarn(SDL_LOG_CATEGORY_GPU, "SDL_WINDOW_TRANSPARENT flag set, but no suitable swapchain composite alpha value supported!"); + } + } + swapchainCreateInfo.sType = VK_STRUCTURE_TYPE_SWAPCHAIN_CREATE_INFO_KHR; swapchainCreateInfo.pNext = NULL; swapchainCreateInfo.flags = 0; @@ -4591,7 +4611,7 @@ static Uint32 VULKAN_INTERNAL_CreateSwapchain( #else swapchainCreateInfo.preTransform = swapchainSupportDetails.capabilities.currentTransform; #endif - swapchainCreateInfo.compositeAlpha = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR; + swapchainCreateInfo.compositeAlpha = compositeAlphaFlag; swapchainCreateInfo.presentMode = SDLToVK_PresentMode[windowData->presentMode]; swapchainCreateInfo.clipped = VK_TRUE; swapchainCreateInfo.oldSwapchain = VK_NULL_HANDLE;