GPU: Vulkan backend flags command buffer for cleanup when swapchain is requested

When skipping presentation due to the window being hidden, presentDataCount is not incremented on the command buffer, and subsequently the submitted command buffers will not be cleaned up as long as the window is hidden. This results in a lag spike when showing the window due to all previously submitted command buffers suddenly being cleaned up at once, and lag at shutdown due to an equivalent number of fences needing to be destroyed.

Instead of relying on presentDataCount to determine whether a command buffer should be cleaned up, use a flag, which is set under the appropriate circumstances.

Author: Kontrabant

src/gpu/vulkan/SDL_gpu_vulkan.c

@@ -1079,6 +1079,7 @@ typedef struct VulkanCommandBuffer
     VulkanFenceHandle *inFlightFence;
     bool autoReleaseFence;
 
+    bool swapchainRequested;
     bool isDefrag; // Whether this CB was created for defragging
 } VulkanCommandBuffer;
 
@@ -9934,6 +9935,9 @@ static bool VULKAN_INTERNAL_AcquireSwapchainTexture(
         SET_STRING_ERROR_AND_RETURN("Cannot acquire a swapchain texture from an unclaimed window!", false);
     }
 
+    // The command buffer is flagged for cleanup when the swapchain is requested as a cleanup timing mechanism
+    vulkanCommandBuffer->swapchainRequested = true;
+
     if (window->flags & SDL_WINDOW_HIDDEN) {
         // Edge case, texture is filled in with NULL but not an error
         return true;
@@ -10392,6 +10396,7 @@ static void VULKAN_INTERNAL_CleanCommandBuffer(
     commandBuffer->presentDataCount = 0;
     commandBuffer->waitSemaphoreCount = 0;
     commandBuffer->signalSemaphoreCount = 0;
+    commandBuffer->swapchainRequested = false;
 
     // Reset defrag state
 
@@ -10548,7 +10553,7 @@ static bool VULKAN_Submit(
     VulkanTextureSubresource *swapchainTextureSubresource;
     VulkanMemorySubAllocator *allocator;
     bool performCleanups =
-        (renderer->claimedWindowCount > 0 && vulkanCommandBuffer->presentDataCount > 0) ||
+        (renderer->claimedWindowCount > 0 && vulkanCommandBuffer->swapchainRequested) ||
         renderer->claimedWindowCount == 0;
 
     SDL_LockMutex(renderer->submitLock);