SDL: vulkan: Don't set the opaque bit on transparent windows

SDL Commits
1 
From 44ec57626fe82dc5f4671792a7de2fdcf577ed73 Mon Sep 17 00:00:00 2001
From: Frank Praznik <[EMAIL REDACTED]>
Date: Fri, 28 Jun 2024 13:53:37 -0400
Subject: [PATCH] vulkan: Don't set the opaque bit on transparent windows

If window transparency was requested via the SDL_WINDOW_TRANSPARENT flag, don't set the opaque bit on the swapchain composite alpha value. Fixes transparent windows when using the Vulkan renderer (e.g. testsprite --transparent).
---
 src/render/vulkan/SDL_render_vulkan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/render/vulkan/SDL_render_vulkan.c b/src/render/vulkan/SDL_render_vulkan.c
index a7dba54ab7230..0454e80ad99de 100644
--- a/src/render/vulkan/SDL_render_vulkan.c
+++ b/src/render/vulkan/SDL_render_vulkan.c
@@ -2150,7 +2150,7 @@ static VkResult VULKAN_CreateSwapChain(SDL_Renderer *renderer, int w, int h)
     swapchainCreateInfo.imageUsage = VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT | VK_IMAGE_USAGE_TRANSFER_DST_BIT;
     swapchainCreateInfo.imageSharingMode = VK_SHARING_MODE_EXCLUSIVE;
     swapchainCreateInfo.preTransform = rendererData->surfaceCapabilities.currentTransform;
-    swapchainCreateInfo.compositeAlpha = VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
+    swapchainCreateInfo.compositeAlpha = (renderer->window->flags & SDL_WINDOW_TRANSPARENT) ? 0 : VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR;
     swapchainCreateInfo.presentMode = presentMode;
     swapchainCreateInfo.clipped = VK_TRUE;
     swapchainCreateInfo.oldSwapchain = rendererData->swapchain;