1883699 - Rewrite table percent bsize code to work more like grid / flexbox.

Status: NEW

(Core :: Layout: Tables, task, P2)

Description

[Emilio Cobos Álvarez (:emilio)]

Quoting from matrix for reference. My understanding is that the table code is doing something very similar to grid / flex:

• We need the "desired" bsize of the table cells to compute the row heights.
• But once we know that, we have a "final" row bsize that we need to propagate to all cells.
• So to do it in general, we'd need two reflows. The "special bsize reflow" is basically trying to optimize out one of them if there are no percentage bsizes.

Reason for me looking into this is that the fundamental issue with https://bugzilla.mozilla.org/show_bug.cgi?id=1877719 is that vertical alignment doesn't work for scrollable table cells. To make overflow work on table cells sanely, we'd need to make the scrollframe take all the space of the cell. But that's basically a relative bsize, so doing that the naive way will break all this "special bsize reflow" optimization mess.

So I think I want to change tables to work more like grid / flex (so, cache their "measuring" reflow metrics, and avoid that measuring reflow when the cache is still valid).

Daniel pointed out that doing this will most likely help with / fix bug 1725781.