diff --git a/src/gpu/vulkan/SDL_gpu_vulkan.c b/src/gpu/vulkan/SDL_gpu_vulkan.c index 6e215b908..4a7d0aab9 100644 --- a/src/gpu/vulkan/SDL_gpu_vulkan.c +++ b/src/gpu/vulkan/SDL_gpu_vulkan.c @@ -4290,6 +4290,7 @@ static bool VULKAN_INTERNAL_CreateSwapchain( VkSemaphoreCreateInfo semaphoreCreateInfo; SwapchainSupportDetails swapchainSupportDetails; bool hasValidSwapchainComposition, hasValidPresentMode; + VkCompositeAlphaFlagsKHR compositeAlphaFlag = 0; Sint32 drawableWidth, drawableHeight; Uint32 i; SDL_VideoDevice *_this = SDL_GetVideoDevice(); @@ -4465,6 +4466,25 @@ static bool VULKAN_INTERNAL_CreateSwapchain( swapchainData->imageCount = SDL_max(swapchainData->imageCount, 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; @@ -4482,7 +4502,7 @@ static bool VULKAN_INTERNAL_CreateSwapchain( swapchainCreateInfo.queueFamilyIndexCount = 0; swapchainCreateInfo.pQueueFamilyIndices = NULL; swapchainCreateInfo.preTransform = swapchainSupportDetails.capabilities.currentTransform; - swapchainCreateInfo.compositeAlpha = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR; + swapchainCreateInfo.compositeAlpha = compositeAlphaFlag; swapchainCreateInfo.presentMode = swapchainData->presentMode; swapchainCreateInfo.clipped = VK_TRUE; swapchainCreateInfo.oldSwapchain = VK_NULL_HANDLE;