tree 4c720325cd2091b4c75554cfc38e452f563712a4
parent 806ae8875bea1b8380081b0da8fd416337ea447f
author Morten Stenshorne <mstensho@chromium.org> 1613601002 -0800
committer Blink WPT Bot <blink-w3c-test-autoroller@chromium.org> 1613603407 -0800

Allow fragmentainers with zero block-size.

The spec [1] says that fragmentainers are assumed to have a minimum
block-size of 1px regardless of their used size, in order to guarantee
content progress. We implemented this by simply making sure that the
used block-size of a fragmentainer would never become less than 1px. But
this wasn't ideal, as that would contribute to unwanted layout overflow
in cases where the content of the multicol container was shorter than
1px.

We'll now still accept at least 1px of content into each fragmentainer,
but don't stretch the fragmentainer itself (just allow the actual column
fragments to become that short as they want, and instead let the content
overflow the columns if necessary).

We still need to fill at least 1px of content before moving to the next
fragmentainer, and fast/multicol/zero-height-with-children.html is a
good test for this.

[1] https://www.w3.org/TR/css-break-3/#breaking-rules

Bug: 829028
Change-Id: I7b4e69524288dad8bb10fd10c715339d1769815a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2698554
Reviewed-by: Alison Maher <almaher@microsoft.com>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#854974}