emscripten-core/emscripten

Support `desynchronized` canvas context attribute

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#8,406 opened on Apr 5, 2019

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Description

Chrome has recently added a desynchronized canvas context attribute that disables double buffering for canvases to achieve lower latency. It will be available by default on Chrome 75 (currently on Canary), it's possible to make it available in Chrome 73 by enabling chrome://flags/#enable-experimental-web-platform-features.

We should add desynchronized to EmscriptenWebGLContextAttributes, and if true, set both desynchronized and lowLatency properties to true in the getContext call that creates the context. lowLatency is the old name for this feature, used up until Chrome 74.

If needed for debugging and writing unit tests, ctx.getContextAttributes() can be called on the created context to check if the flag is supported and was accepted.

See https://www.chromestatus.com/feature/6360971442388992 and https://docs.google.com/document/d/1-Z_dj9AQ4SjgDLAEY3ELR0YrlHR3JZyJPhaHAstS5WU/edit# (this link focuses mostly on ChromeOS).

Contributor guide

Research direction
Examine the Emscripten source code for WebGL context creation, focusing on the struct `EmscriptenWebGLContextAttributes` and the function that calls `getContext`. The issue specifies setting both `desynchronized` and `lowLatency` properties to true if the attribute is true. Review the linked Chrome documentation for details. Also check the 3 comments on the issue for any additional guidance or clarifications.
Tech stack
javascriptcpp
Domain
frontendperformance
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
basic knowledge of WebGL canvasfamiliarity with Emscripten codebaseunderstanding of C++ and JavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75