2002789 - Fix `AnchorPositioningUtils::GetScrollOffsetFor` and `GetOffsetToIgnoringScrolling` to handle sticky & chain-anchored frames

Status: ASSIGNED

(Core :: CSS Parsing and Computation, defect)

Description

[David Shin[:dshin]]

See bug 1999954 for context - anchor position we resolve against have partial scroll offset taken into account, even though it's not supposed to, and as a result, it's impossible to properly apply scroll offsets for these frames right now.

Scroll offset computation in AnchorPositioningUtils::GetScrollOffsetFor currently does not have any special handling for these frames either, which will need to be added at the same time for a proper fix.

Comment 1

[Jonathan Watt [:jwatt]]

There may be some risk here to changing these functions since non-anchor code uses them.

Comment 2

[David Shin[:dshin]]

(In reply to Jonathan Watt [:jwatt] from comment #1)

There may be some risk here to changing these functions since non-anchor code uses them.

You're right, regarding nsIFrame::GetOffsetToIgnoringScrolling. It may be worth hacking around nsIFrame::GetPositionIgnoringScrolling and nsIFrame::GetPositionOfChildIgnoringScrolling to return normal position for sticky & chained anchors, and see what breaks (Aside from anchor positioning scroll offset, which is expected to break)