Use OffscreenCanvas if available

[aaronshaf]

"Now you can render your graphics off the main thread with OffscreenCanvas"

https://developers.google.com/web/updates/2018/08/offscreen-canvas

[timvandermeij]

Interesting find. If we can feature-detect this, we could try benchmarking this.

[websirnik]

@timvandermeij it is feature-detectable, see example here: https://developers.google.com/web/updates/2018/08/offscreen-canvas#use_with_popular_libraries

[phal0r]

This should give a performance boost for Chrome since in my observations rendering takes some time, especially when rendering many different pdfs including changing zoom levels. Is there already a plan to integrate this feature?

[benbro]

OffscreenCanvas is in origin trial in Firefox.

[timvandermeij]

Closing since we now use OffscreenCanvas if it's available (by feature detection). This was introduced by PR #14754 for image rendering performance improvements and enabled upstream in Firefox for PDF.js in https://bugzilla.mozilla.org/show_bug.cgi?id=1763330. If it's useful to use in more places, individual issues should be opened for those.