737450 - Checkerboarding is worse at the top or bottom of pages (or maybe when switching directions)

Status: RESOLVED WORKSFORME

(Firefox for Android Graveyard :: General, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

I haven't quantified this yet. But jpr saw it and I've seen something like this too.

Comment 1

[JP Rosevear [:jpr]]

For instance on http://www.cnn.com/2012/03/15/tech/web/firefox-new-browser-plans/index.html?hpt=hp_bn8 on a Galaxy Nexus scroll down with just enough velocity to reach the bottom in one finger swipe.  Checkboarding is not that bad until the bottom is reached, at which point there seems to be 1-2 big blocks of checker board drawing that take a couple hundred ms to redraw.

Comment 2

[Chris Lord [:cwiiis]]

At the top and bottom of the page, the displayport margins change so that we don't waste any of the display port on bits of the page that aren't there, and so that Gecko doesn't draw into area that should be blank (where the background will be drawn).

Perhaps there are costs associated with this displayport change, or rounding areas that are causing full invalidations?

Comment 3

[Brad Lassey [:blassey] (use needinfo?)]

(In reply to Chris Lord [:cwiiis] from comment #2)
> At the top and bottom of the page, the displayport margins change so that we
> don't waste any of the display port on bits of the page that aren't there,
> and so that Gecko doesn't draw into area that should be blank (where the
> background will be drawn).
> 
> Perhaps there are costs associated with this displayport change, or rounding
> areas that are causing full invalidations?

you touch it, you own it :-)

Comment 4

[Chris Lord [:cwiiis]]

I can't say I notice this anymore, and I'd have thought if there were any issues here, tiling would have alleviated them. Marking as worksforme.