742128 - Use a more efficient mechanism for notify Gecko about viewport changes

Status: RESOLVED INVALID

(Firefox for Android Graveyard :: General, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

On a page that is quick to paint (13ms) we spend 10% of our time under NotifyObservers() handling "Viewport:Changed"

Comment 1

[Jeff Muizelaar [:jrmuizel]]

In total about 3-5ms

Comment 2

[Kartikaya Gupta (email:[e-mail])]

So then this doesn't include the JSON serialization of the viewport in java. There isn't a whole lot we can trim out of the browser.js Viewport:Changed handler. There are three main operations - scrollTo, setResolution, and setDisplayPortForElement. Do you know which of those three is taking the most time? Or is it something else?

Comment 3

[Jeff Muizelaar [:jrmuizel]]

(In reply to Kartikaya Gupta (:kats) from comment #2)
> So then this doesn't include the JSON serialization of the viewport in java.
> There isn't a whole lot we can trim out of the browser.js Viewport:Changed
> handler. There are three main operations - scrollTo, setResolution, and
> setDisplayPortForElement. Do you know which of those three is taking the
> most time? Or is it something else?

I don't know anything more currently.

Comment 4

[Joe Drew (not getting mail)]

We need more information before we can figure out whether to block on this. Jeff, can you profile or otherwise gather that information?

Comment 5

[Jeff Muizelaar [:jrmuizel]]

A thought: how many times are handling the Viewport:Changed event in Gecko after a paint? Do we have a queue of a lot of these?

Comment 6

[Kartikaya Gupta (email:[e-mail])]

So with the code that's currently in m-c we do very aggressive coalescing of Viewport:Changed events (aggressive to the point of being wrong) so we shouldn't have very many of these events actually being processed by Gecko. I have a couple of patches in bug 740883 that cleans up the coalescing behaviour; this results in slightly more Viewport:Changed events being processed while the user's finger is actually on the screen (because the Viewport:Changed events are being interleaved with touch events and we can't coalesce them). Once the user's finger is lifted we coalesce them more.

Comment 7

[Jan Henning [:JanH]]

Superseded by APZ?