VK_KHR_present_wait2

Table of Contents

1. Problem Statement
2. Solution Space
3. Proposal

This document details the proposed design for a replacement for the VK_KHR_present_wait extension providing the same functionality, but being queryable per surface instead of per device.

1. Problem Statement

Vulkan WSI needs a way to wait until after a specified image has been presented to allow applications to control latency and pace frames.

2. Solution Space

The VK_KHR_present_wait extension already exists to solve this problem, however it is exposed via device capability. This leads to problems on some platforms where feature presence is not known at the device level.

Without knowing if a device can support the extension or not, the extension must be universally disabled, limiting its usability.

This proposal aims to fix this shortcoming in VK_KHR_present_wait.

3. Proposal

Deprecate the existing VK_KHR_present_wait extension and replace it with an almost identical extension, except this time make it queryable per surface instead of per device.

At the same time, reconsider some of the VK_KHR_present_wait language regarding when the wait finishes, allowing it to be implementation-dependent, instead of using terms like "time to light" and "first pixel", which would incidentally specify API behavior that is difficult to implement and less useful for dominant use cases.

API related to "time to light" and "first pixel" is deferred to a future extension.