1793322 - Deal with column-reverse flexbox in nsFlexContainerFrame's nsILineIterator implementation.

Status: NEW

(Core :: Layout: Flexbox, enhancement, P3)

Description

[Emilio Cobos Álvarez (:emilio)]

For flex-direction: column-reverse flex containers (where we hit this code with info.mIsMainAxisReversed == true), I think this code will be wrong. In that scenario, I'd guess that we might want f to be mFrames.FrameAt(mFrames.GetLength() - aLineNumber) or something like that, assuming we want "line 0" to be the thing at the BStart edge?

I suspect this would need special-handling elsewhere, too; e.g. in the next function, FindLineContaining, we would probably need to account for this as well by subtracting index from the total child count so that the last child is treated as the 0th line. So: might involve a handful of changes throughout this file.

I agree with that and should be easy to test.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: WIP: Bug 1793322 - Deal with column-reversed flex container in nsILineIterator.

Not super-convinced this is useful, tho, because the behavior is rather
unintuitive either way.

Comment 2

[Emilio Cobos Álvarez (:emilio)]

Daniel, see comment 1. I think our behavior with the patch might be marginally better, but not too much in practice... Thoughts?

Comment 3

[Daniel Holbert [:dholbert]]

Thanks for the quick fix!

I'd like to spend a little time testing this out to get a feel for it; I probably won't have time for that until I'm back from PTO later this week (Thurs or Fri). Given this is lowish priority and it sounds like not a huge win, I suspect that's fine. :)