1890238 - Implement forced page break on flex items

Status: RESOLVED FIXED

(Core :: Layout: Flexbox, enhancement)

Description

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

We haven't implement any forced break on flex item yet. Specifically, we want to implement break-before and break-after on flex items for those values currently supported by gecko. Firefox's lacks any forced break support for multicol (bug 1840944), so we can start from paginated mode.

Relevant spec:

1. https://drafts.csswg.org/css-break-3/#break-between
2. https://drafts.csswg.org/css-flexbox-1/#pagination

Comment 1

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1890238 Part 1 - Rename childReflowStatus to childStatus. r?dholbert,#layout

Flex container is the only frame type in layout using childReflowStatus when
naming the nsReflowStatus variable for child. Drop "Reflow" for brevity and
for the consistency with childrenStatus in ReflowChildren().

Comment 2

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1890238 Part 2 - Honor forced break values on flex items. r?dholbert

This patch stops the frame constructor from inserting nsPageBreakFrame as a flex
item, because flex container does not rely on it to do forced page break at all,
and nsPageBreakFrame can produce wrong layout result.

The majority of this patch is to honor forced break values on flex items in
nsFlexContainerFrame::ReflowChildren(). In this patch, we don't handle avoid
break values such as break-before:avoid and break-after:avoid since they are
not handled in other frame types yet.

WPTs are added in later parts.

Comment 3

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1890238 Part 3 - Add WPT for forced break value on flex items in printing. r?dholbert

The flex items in 068 variants have no border because they can have some
fuzziness on the column-reverse flex container.

Comment 4

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1890238 Part 4 - Add WPT for forced break value propagation from flex items in printing. r?dholbert

Comment 5

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1890238 Part 5 - Add WPT for forced break value propagation from flex items in multicol. r?dholbert

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/31b65c4aa8e6
Part 1 - Rename childReflowStatus to childStatus. r=dholbert
https://hg.mozilla.org/integration/autoland/rev/3f8e6f37ef78
Part 2 - Honor forced break values on flex items. r=dholbert
https://hg.mozilla.org/integration/autoland/rev/30ff87c59be6
Part 3 - Add WPT for forced break value on flex items in printing. r=dholbert
https://hg.mozilla.org/integration/autoland/rev/93734abeec9d
Part 4 - Add WPT for forced break value propagation from flex items in printing. r=dholbert
https://hg.mozilla.org/integration/autoland/rev/de885bd06d1e
Part 5 - Add WPT for forced break value propagation from flex items in multicol. r=dholbert

Comment 7

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/46063 for changes under testing/web-platform/tests

Comment 8

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/31b65c4aa8e6
https://hg.mozilla.org/mozilla-central/rev/3f8e6f37ef78
https://hg.mozilla.org/mozilla-central/rev/30ff87c59be6
https://hg.mozilla.org/mozilla-central/rev/93734abeec9d
https://hg.mozilla.org/mozilla-central/rev/de885bd06d1e

Comment 9

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot