[Mesa-dev] [PATCH v2 2/3] vulkan/wsi: Report the correct min/maxImageCount

Neil Roberts bpeeluk at yahoo.co.uk
Mon Oct 2 16:57:13 UTC 2017

Jason Ekstrand <jason at jlekstrand.net> writes:

> I wish...  Unfortunately, the spec says:
> Let *n* be the total number of images in the swapchain, *m* be the
> value of VkSurfaceCapabilitiesKHR::minImageCount, and *a* be the
> number of presentable images that the application has currently
> acquired (i.e. images acquired with vkAcquireNextImageKHR, but not yet
> presented with vkQueuePresentKHR). vkAcquireNextImageKHR *can* always
> succeed if a ≤ n - m at the time vkAcquireNextImageKHR is called.
> vkAcquireNextImageKHR *should* not be called if a > n - m with a
> timeout of UINT64_MAX; in such a case, vkAcquireNextImageKHR *may*
> block indefinitely.
> Because this is based on the number of images in the swapchain and the
> VkSurfaceCapabilitiesKHR field, if we return a swapchain with more
> images, n will be larger but not m so that just means that they can
> acquire more images, not that we've reserved more. Arguably, that's a
> spec bug and I'll file one and see where it goes. However, it's
> definitely what the spec says today. :-(

Fair enough. Thanks for the explanation.

- Neil


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