perf: smoother scrolling ...

[mmeeks]

Just wondering what's up with scrolling in writer - I load our writer sample document from make run and go to the nice big purple image which gives a good view of what's up.

Then I scroll with the touch-pad up and down - it 'feels' not entirely smooth; profile here:

And I wonder ;-) but need someone clueful to comment. Is it possible that:

• touchpad has a certain typematic rate - and we get a series of 'jerks' as the display moves from the events, and we would do well to animate between them for a more fluid look.
• there are a load of overlapping 'Animation' things - is this for the 'comments' that sit on top of the writer document and seem to move (nicely) but out of sync with the document ;-)
• The CollectAutofillContentService.processMutations stuff from (I guess) this 'bootstrap' code - seems to take a surprising amount of time - I've seen some chunks of profile that have a millisecond of JS doing (who knows what) in 'processMutations' - is it possible that our attempts to touch the DOM / do changes at a co-ordinated time are somewhat stymied by this well hidden 'Idle' event processing ? would adding a forced processMutations at the end of some 'resumeDrawing()' method or "messagesdone" event be useful ?

Would be great to have a poke about to see if there's something up there; I fear we have some self-inflicted paper-cuts there that perhaps we could fix easily ;-)

[mmeeks]

Interestingly it seems like various overlays / sections are particularly expensive to update - it's also notable that the comment bubbles seem to wander wrt. their position vs. the document - might be nice to render them on the canvas itself somehow if that's possible (?)

And of course there is a chunk of low hanging waste here: that #10441 should help with the comments above.