Tutorial Issue - 20-rendering-presentation - Semaphore might still be in use.

[Duumbo]

Hi,
I am working on your tutorial (thanks for this resource, it has been very informative.) I came across a validation layer error after completing the chapter 20. Using the code from the completed chapter,
I get multiple validation errors that all read like

ERROR 15_hello_triangle > (VALIDATION) vkQueueSubmit(): pSubmits[0].pSignalSemaphores[0] (VkSemaphore 0x1a000000001a) is being signaled by VkQueue 0x55f6b4a2e0f0, but it may still be in use by VkSwapchainKHR 0x30000000003.
Most recently acquired image indices: [0], 1, 2.
(Brackets mark the last use of VkSemaphore 0x1a000000001a in a presentation operation.)
Swapchain image 0 was presented but was not re-acquired, so VkSemaphore 0x1a000000001a may still be in use and cannot be safely reused with image index 2.
Vulkan insight: See https://docs.vulkan.org/guide/latest/swapchain_semaphore_reuse.html for details on swapchain semaphore reuse. Examples of possible approaches:
   a) Use a separate semaphore per swapchain image. Index these semaphores using the index of the acquired image.
   b) Consider the VK_KHR_swapchain_maintenance1 extension. It allows using a VkFence with the presentation operation.
The Vulkan spec states: Each binary semaphore element of the pSignalSemaphores member of any element of pSubmits must be unsignaled when the semaphore signal operation it defines is executed on the device (https://docs.vulkan.org/spec/latest/chapters/cmdbuffers.html#VUID-vkQueueSubmit-pSignalSemaphores-00067)

So I dug into it and came across this frequent problem with swapchain semaphore reuse. Reading this, I was able to fix these validation errors by doing the following:

• Save the min_image_count while we are creating the swapchain.
• In fn create_sync_objects, create semaphores for each min_image_count of the swapchain

    for _ in 0..data.swapchain_min_image_count {
        data.image_available_semaphore.push(device.create_semaphore(&semaphore_info, None)?);
        data.render_finished_semaphore.push(device.create_semaphore(&semaphore_info, None)?);
    }

• In fn render, signal the semaphore of the acquired image index

    let signal_semaphores = &[self.data.render_finished_semaphore[image_index]];

As I am quite new to Vulkan, I don't really know if this is the right way to do what we are doing in this tutorial, but it makes sense. Let me know if I am not mistaken and I will submit a pull request.
Thanks a lot

[KyleMayes]

Sorry for the long delay, this is a real problem with the tutorial.

If you still want to make the necessary changes, I'd be happy to approve them.
If not, I will make the changes in the next week or so.

Thanks!

[KyleMayes]

I've made the code changes, I now just need to update the text of the tutorial to reflect the changes before I can push the fix for this. Should be done pretty soon.