1766685 - Consider class A breakpoints when performing named page fragmentation

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[Emily McDonough [:alaskanemily]]

Our current logic implemented in bug 1740366 does not consider whether a frame satisfies the spec's definition of whether the page property applies to the frame: https://www.w3.org/TR/css-page-3/#using-named-pages

This requires that the frame satisfies the requirements to be able to cause class A breakpoints, as defined in: https://www.w3.org/TR/css-break-3/#btw-blocks

This requires that the frame be block-level for the page property to be read and propagated. We have a few tests implemented in bug 1740366 (page-name-{img,canvas}-00[1-2].html) which should fail when this is correctly implemented. Tests should also be added to check for other elements, like span which generates an anonymous containing frame.

Comment 1

[Emily McDonough [:alaskanemily]]

Attachment: Bug 1766685 - Do not perform page-breaks in the destructor of the page name tracker RAII struct

Instead, do this just before we actually construct frames for items.

This has issues with replaced frames currently, as either the
insert-page-break function isn't happening for these elements or it is being
called and child elements of replaced frames are cleared/ignored. This is the
main TODO remaining.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/97613a0619b2
Do not perform page-breaks in the destructor of the page name tracker RAII struct r=dholbert

Comment 3

[Iulian Moraru]

https://hg.mozilla.org/mozilla-central/rev/97613a0619b2

Comment 4

[Daniel Holbert [:dholbert]]

Attachment: testcase 1 ("break test"), testing page-name-disagreements between various siblings

Here's the "break test" testcase that I referenced on phabricator here: https://phabricator.services.mozilla.com/D152701#5068339

Chrome only seems to introduce a page-break at the very bottom of this test, for the block container, and nowhere else.

vs. Firefox-with-the-attached-patch fatally aborts as noted in the referenced phabricator comment, when trying to handle a case with page-name-induced fragmentation on children of a grid.

Maybe we can simplify here and only attempt to make this work for block containers for the time being? (which would get us feature parity, it seems)

Comment 5

[Daniel Holbert [:dholbert]]

Gah, sorry, comment 4 was intended for another bug (Bug 1779645). Reposting there.