2003822 - container queries don't work when printing (aside from paint-time effects), due to nsPageSequenceFrame refusuing to reflow more than once

Status: NEW

(Core :: Printing: Output, defect)

Description

[pinage404+bugzilla.mozilla.org]

Attachment: bug.html

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:145.0) Gecko/20100101 Firefox/145.0

Steps to reproduce:

I have a container query that add a display grid

I attached a file to reproduce

Actual results:

Everything is fine on a screen but the element with a display: grid; appears empty in print mode

I tried on Firefox 145.0.1 (64 bits) and Zen Browser 1.17.9b (Firefox 145.0.1) (64 bits) on :

• system: "x86_64-linux"
• host os: Linux 6.12.58, NixOS, 25.05 (Warbler), 25.05.20251124.1c8ba8d
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.28.5
• nixpkgs: /nix/store/79nihxkkd2gix5y4ijf0zmyznx04lghn-source

Expected results:

The print mode should display like the screen mode

Comment 1

[pinage404+bugzilla.mozilla.org]

Attachment: Screenshot on screen mode, there is a big black rectangle which contains 2 blues rectangles with text

Comment 2

[pinage404+bugzilla.mozilla.org]

Attachment: Screenshot of the print mode, there is an empty big black rectangle, without the blue rectangle, without the text

Comment 3

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Printing: Output' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Comment 4

[Daniel Holbert [:dholbert]]

I suspect this has to do with how container-queries work with layout/restyle/layout interleaving, mixed with the fact that our print-reflow codepath avoids incremental reflow entirely -- specifically this early-return where nsPageSequenceFrame::Reflow bails if it's been reflowed previously:
https://searchfox.org/firefox-main/rev/5a5b3741981250310f4327537f18879559779f9c/layout/generic/nsPageSequenceFrame.cpp#294-299

Comment 5

[Daniel Holbert [:dholbert]]

Attachment: testcase 2

Here's a testcase with a container-query that has some paint effects (changing color/background) as well as some layout effects (changing height/width)

We successfully apply the paint effects but not the layout effects. So this is a good clue that we're successfully restyling but not managing to make it through another reflow to update the frame tree sizes, as suspected in my previous comment.