645563 - Implement scrollbars using a single anonymous element, instead of nested XUL NAC

Status: NEW

(Core :: Layout, defect)

Description

[(no longer active)]

From bug 237842 comment 31:

> We could probably win quite a lot of performance for all kinds of things by
> creating a single anonymous element that implements a complete scrollbar
> (instead of the complex XBL binding we currently use), and simplify a lot of
> stuff too. We could give that element a proper non-element-based API and move
> the thumb without having to do reflow. I thought there was a bug for this but I
> can't find it.

Comment 1

[Florian Bender]

See Bug 793942.

Comment 2

[Alfred Kayser]

As long as we can theme it, it would be a great performance improvement probably.

Comment 3

[Brian Grinstead [:bgrins]]

We're going to remove the XBL in Bug 1431246, replicating the markup that's currently in XBL anon content into XUL NAC. That doesn't change anything about the benefits from Comment 0 - just going to mark this as dependent since it'll move around where the DOM gets created.

Comment 4

[Brian Grinstead [:bgrins]]

Implementing this should at least save the memory cost of scrollbars.css (https://bugzilla.mozilla.org/show_bug.cgi?id=1474793#c8), some styles out of minimal-xul.css, and also whatever the NAC uses.

Comment 5

[Chris Peterson [:cpeterson]]

Emilio, will non-native theming make this XUL scrollbar bug obsolete?

Comment 6

[Emilio Cobos Álvarez (:emilio)]

No