[Webkit-unassigned] [Bug 212505] When a figure exactly reaches the bottom of a column, its margin affects the subsequent column

Tue Jul 12 15:21:01 PDT 2022

https://bugs.webkit.org/show_bug.cgi?id=212505

--- Comment #5 from Brad Andalman <bya at 180g.co> ---
Actually, in Safari, the new "test case" attachment moves the image to the next column as well (as it does in Chrome and Firefox).

This is because the "test case" attachment doesn't just remove the "-webkit" prefixes from a few properties, but adds other things as well. In particular, it adds "<!DOCTYPE html>" at the beginning, which causes the browser to use Standards mode (as opposed to Quirks mode). This is why we see different behavior between the first attachment and the second. And this is likely why Karl couldn't repro in his animation.

In Quirks mode, when the image reaches the bottom of a column (exactly), then the margin-bottom affects the next column. I will add another attachment ("quirky test case") that illustrates this, and doesn't use properties with "-webkit" prefixes. If you change the figure's margin-top from 15px to 14px in this example, you'll see that the margin-bottom no longer affects the next column (as in my original report).

The behavior in Standards mode is different. In Standards mode, the figure will *never* reach the very bottom of the column. I will add another attachment ("standard test case") that shows this. In that example, if you change the figure's margin-top from 11px to 12px, then the image will move to the next column. I think the fact that the figure can't ever reach the very bottom of the column is another bug. The figure's margin-top should be able to be 15px without it being forced to the next column.

In both Chrome and Firefox, the behavior is the same in both Quirks and Standards modes. However, since the text layout is different (see attached "Safari vs Chrome Layout with Guides"), the image will reach the very bottom of the column when the figure's margin-top is only 11px, and switch when margin-top is changed to 12px. This is the same inflection point as the "standard test case" in Safari — is that a coincidence?

In short, there's a Safari bug in either mode. In Quirks mode, the margin-bottom affects the next column when it shouldn't; in Standards mode, the figure won't ever reach the bottom of the column.

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