1978106 - Intrinsic sizing of SVG breaks with `box-sizing: border-box` and `border`.

Status: VERIFIED FIXED

(Core :: SVG, defect)

Description

[David Shin[:dshin]]

Attachment: Minimum Reproducible Case

(Discovered in a session of virtual escape room from)

STR: Load attached testcase
Expected: Black circle in the grey square (SVG border) should fit within black square (Containing div border)
Actual: SVG is sized bigger than the containing div

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: testcase 2 (less minimal, more-complete reproduction of the full widget on the site)

For posterity / testing, here's a more complete copy of the "timer" widget that's affected by this on the original site.

The issue here is that -- in Firefox -- the outer border looks thicker on the top-left corner as compared to the bottom-right corner.

Comment 2

[Daniel Holbert [:dholbert]]

This goes back ~forever; I can reproduce in Nightly 2013-12-15 if I add a prefixed version of box-sizing (which we needed back then), i.e. -moz-box-sizing:border-box;

Comment 3

[Emilio Cobos Álvarez (:emilio)]

I think I know where this is going wrong.

Comment 4

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1978106 - Fix size to fill the containing block in intrinsic sizing. r=dholbert,#layout

This matches iSizeToFillCb.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/1ff5e09219ad
https://hg.mozilla.org/integration/autoland/rev/b4f1a04f796f
Fix size to fill the containing block in intrinsic sizing. r=dholbert,dshin

Comment 6

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/53854 for changes under testing/web-platform/tests

Comment 7

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/b4f1a04f796f

Comment 8

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

Upstream PR merged by moz-wptsync-bot

Comment 9

[Ardelean Oana, Desktop Test Engineering [:oardelean]]

Issue is reproducible on a 2025-07-18 Firefox Nightly build on Windows 10, using the testcases from Comment 0 and Comment 1.
Verified as fixed on Firefox Nightly 143.0a1 and Firefox 142.0b4 on Windows 10, Ubuntu 22, macOS 15.