956781 - Meetup page causes fullpage invalidation while scrolling, with background-image & "background-attachment: fixed"

Status: RESOLVED DUPLICATE of bug 1039020

(Core :: Layout, defect, P4)

Description

[Benoit Girard (:BenWa)]

Scroll:
http://www.meetup.com/Bitcoin-Toronto/

Comment 1

[Daniel Holbert [:dholbert]]

I can reproduce this on 64-bit Linux nightly.

It only happens *after* the background image has loaded (which takes a few seconds, on my internet connection at home). Before that image has appeared, the page only invalidates thin stripes at the edges when I scroll, as I'd expect.

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: reduced testcase 1 (turn on paint flashing & scroll)

Here's a reduced testcase.

Basically, when you have a container-div with "background-attachment:fixed", we seem to think that all of its children need to be repainted on scroll.

We probably *would* need to repaint (or at least recomposite) if those children were something like text with a transparent background, because then the text would be moving to be over a different part of the image, and it'd need to be recomposited over that image.

But in this case, there child is one big opaque background (with text inside of it), so there's no reason it'd all need to be repainted when it's scrolled.

Comment 3

[Daniel Holbert [:dholbert]]

s/there child/the child/

Comment 4

[Markus Stange [:mstange]]

This was fixed in bug 1039020.