Hi, So today I was looking at a bug[1] that happens to be a combination of edge cases (as usual) ending up badly. In particular, a columnset frame removing a not-first-in-flow frame via DeleteNextInFlow that happens to hold the pseudo-elements of a nested display: contents element, thus unbinding them from the tree and breaking the counter manager invariants.
I've noticed recently in other bug I've recently fixed a similar pattern (that bug crashed creating a first-letter continuation during bidi resolution, though the underlying issue ended up being other). I think the frame tree would be much easier to reason about and manage if it didn't mutate during reflow, though there seem to be a bunch of places that do that (grepping for StealFrame, CreateContinuation, ...). Note: I mean mutate as "creating / destroying frames", not as in "not change any member variable of any frame", obviously. My questions are (for those who know more about Gecko layout than me): * Do you think it is reasonably doable to stop mutating the frame tree from layout? * Would it be worth it? (I think it would!) * Would it be reasonable to spend some time on it? (perhaps in the medium / long term, given right now everyone has other important things to do :P) I could believe that most of these changes may require some rework of some parts of layout and frame construction (I'm looking at float / out-of-flows / first-letters, etc), but I also think some of those are the ones where the frame constructor handles dynamic changes poorly (ib-splits certainly enter in this category, though I'm not sure that we mutate those during reflow). Anyway I could believe that if we refactor things with this in mind we could make frame construction better for dynamic changes. There are also a few CreateContinuationFor calls in block layout that could also be hard to replace, haven't checked in detail yet... Anyway, just wanted to know if other people think this goal would be reasonable / worth it. Thanks in advance, -- Emilio [1]: https://bugzilla.mozilla.org/show_bug.cgi?id=1381134 _______________________________________________ dev-tech-layout mailing list dev-tech-layout@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-tech-layout
