2055928 - Flex items overlapping in printout / print preview, with `flex-flow: column wrap` and table as flex item

Status: NEW

(Core :: Layout: Flexbox, defect)

Description

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

STR:

1. Print preview the attached testcase.
2. Scroll to the end and look at the orange-bordered box with "AM I OVERLAPPING?"

ACTUAL RESULTS:
It's overlapping the previous content (the text and the border)

EXPECTED RESULTS:
Should not be overlapping.

The testcase here was reduced from a privately-shared version of the (inaccessible-to-me) website described in bug 2052162, which reproduces the same problem.

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: screenshot of print-preview for testcase 1

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: testcase 2 (with small page-size, making the problem worse)

Here's a copy of testcase 1 where I added

  @page { size: 5in 3in }

...to force us to print to smaller pages.

In this version, that orange box doesn't just overlap; it also starts on the wrong page entirely. It should start on page 11 (after the table that precedes it) but instead it starts on page 9 and spills over onto page 10, overlapping the table on both of those pages.

Comment 3

[Daniel Holbert [:dholbert]]

Attachment: screenshot of print preview for testcase 2

Comment 4

[Daniel Holbert [:dholbert]]

This might be a version of bug 1806717 -- nsFlexContainerFrame.cpp has several comments referencing Bug 1806717 and saying we don't implement fragmentation for multi-line column-oriented flex container (flex-flow: column wrap).

I think we don't implement that because there's a fair bit of complexity, but maybe we can implement a simpler approach for the scenario in this bug, where our flex container does technically have flex-wrap: wrap (and so could theoretically be multi-line) but only actually has a single flex line...