Fix semaphore reuse validation error by waiting on all fences

[0xKitKoi]

While creating my own application with Walnut, my terminal was spammed with a Vulkan Validation Error:

[vulkan] Debug report from ObjectType: 5
Message: Validation Error: [ VUID-vkAcquireNextImageKHR-semaphore-01779 ] Object 0: handle = 0xdcc8fd0000000012, type = VK_OBJECT_TYPE_SEMAPHORE; | MessageID = 0x5717e75b | vkAcquireNextImageKHR():  Semaphore must not have any pending operations. The Vulkan spec states: If semaphore is not VK_NULL_HANDLE it must not have any uncompleted signal or wait operations pending (https://vulkan.lunarg.com/doc/view/1.3.283.0/windows/1.3-extensions/vkspec.html#VUID-vkAcquireNextImageKHR-semaphore-01779)

After some debugging line by line, digging into the Application.cpp file in the Application::Run() function I found the lines that triggered my console to be spammed

			// Update and Render additional Platform Windows
			if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
			{
				ImGui::UpdatePlatformWindows();
				ImGui::RenderPlatformWindowsDefault();
			}

When calling vkAcquireNextImageKHR, you pass in a semaphore and it expects that this semaphore is not already in use, meaning it is still pending in some queue operation. This violates the Vulkan spec.
A simple fix is to just wait for the semaphore to finish:

			// Wait for all fences to avoid semaphore reuse issues in multi-viewport mode
			for (uint32_t i = 0; i < g_MainWindowData.ImageCount; i++)
			{
				ImGui_ImplVulkanH_Frame* frame = &g_MainWindowData.Frames[i];
				if (frame->Fence != VK_NULL_HANDLE)
				{
					vkWaitForFences(g_Device, 1, &frame->Fence, VK_TRUE, UINT64_MAX);
				}
			}

			// Update and Render additional Platform Windows
			if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
			{
				ImGui::UpdatePlatformWindows();
				ImGui::RenderPlatformWindowsDefault();
			}

This is also my first ever open source contribution so be brutal

[coderabbitai]

Walkthrough

A synchronization step was added after the main frame rendering in the application's run loop. The code now waits for all Vulkan fences associated with each frame of the main window to ensure GPU operations are complete before continuing.

Changes

File(s)	Change Summary
Walnut/src/Walnut/Application.cpp	Added Vulkan fence synchronization after frame rendering by waiting on each frame's fence to ensure GPU operations complete

Poem

A fence for each frame, a wait in the night,
Ensuring the semaphores don’t cause a fright.
With Vulkan in tow, our windows align,
Multi-viewports now work just fine.
The GPU’s in sync, the code’s feeling bright—
Another small hop towards rendering right!
🐇✨

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📒 Files selected for processing (1)

• Walnut/src/Walnut/Application.cpp (1 hunks)

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• Walnut/src/Walnut/Application.cpp

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• 📝 Generate Docstrings

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

Walnut/src/Walnut/Application.cpp (1)

666-667: Remove unnecessary blank lines.

The extra whitespace doesn't follow the existing code style in the file.

-			
-				
+

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3b8e414 and e51a94b.

📒 Files selected for processing (1)

• Walnut/src/Walnut/Application.cpp (1 hunks)

[0xKitKoi]

Oh this should also fix #81