644362 - Make -moz-element fast

Status: NEW

(Core :: Layout, enhancement)

Description

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

The inchoate plan as I understand so far is, if a -moz-element source is large/interesting enough, ensure that it gets its own layer, then where the -moz-element is used, insert some kind of reference layer into the layer tree that refers to the source layer.  Then at compositing time, we would adjust the source layer somehow at its reference and composite it directly to screen.  That adjustment could probably just be a transform+clip.

Things get a bit interesting if a -moz-element source itself refers to content that includes a -moz-element.  Shouldn't pose too many problems I wouldn't imagine.

Comment 1

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

I don't think -moz-element usage is particularly widespread, so for now this is a nice-to-have optimization for content use case.

Comment 2

[Tobias Schneider [:tobytailor]]

Attachment: -moz-element test case

Extracted a test case from current experiments with DOM based compositing for Shumway. Having multiple instances of a shape placed on the screen is a frequently used feature in SWF files. Using -moz-element results in pretty poor performance. This should be optimized.

Comment 3

[jsnkuhn]

FYI, Google's paintAPI polyfill (https://github.com/GoogleChromeLabs/css-paint-polyfill) uses -moz-element() for implementation in Firefox. A performance boost to -moz-element would be useful for this.