Bug 289876

Summary:

`position: absolute` with inner `max-height: 100%` makes `height: max-content` resolve to 0

Product:

WebKit

Reporter:

Benoît Rouleau <benoit.rouleau>

Component:

Layout and Rendering

Assignee:

Yulun Wu <yulun_wu>

Status:

RESOLVED FIXED

Severity:

Major

CC:

bfulgham, brandonstewart, karlcow, koivisto, simon.fraser, webkit-bug-importer, zalan

Priority:

Keywords:

BrowserCompat, InRadar

Version:

Safari Technology Preview

Hardware:

All

OS:

All

See Also:

https://bugs.webkit.org/show_bug.cgi?id=264448
https://github.com/web-platform-tests/wpt/pull/59425

Attachments:

Description	Flags
Test case	none
Patch	none
[fast-cq]Patch	none

Benoît Rouleau

Reported 2025-03-16 15:35:26 PDT

Created attachment 474584 [details] Test case See the attached test case and compare the result between Chrome, Firefox, and Safari. Only Safari doesn't show the red background (indicating that the box has a 0 height). What makes me think it's a bug is that if you remove the `position: absolute`, the height is the same as other browsers; I don't think the height of an element should ever be affected by whether it is absolute-positioned (unless it's the child of a flex or grid container that stretched it, but it's not the case here).

Attachments
Test case (574 bytes, text/html) 2025-03-16 15:35 PDT, Benoît Rouleau	no flags	Details
Patch (20.49 KB, patch) 2026-04-11 15:08 PDT, alan	no flags	Details Formatted Diff Diff
[fast-cq]Patch (25.85 KB, patch) 2026-04-11 15:23 PDT, alan	no flags	Details Formatted Diff Diff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.

Karl Dubost

Comment 1 2025-03-16 22:25:26 PDT

confirmed. Firefox and Chrome have a red background <div class="box"> <div class="box-inner">This text should have a red background.</div> </div> .box { background-color: red; height: max-content; position: absolute; } .box-inner { max-height: 100%; } # HEIGHT Safari: body: 0 .box: 0 .box-inner 0 Firefox: body: 0 .box: 19.2px .box-inner: 19.2px Chrome: body: 0 .box: 18.5 .box-inner 18.5

Radar WebKit Bug Importer

Comment 2 2025-03-18 11:20:19 PDT

<rdar://problem/147333178>

Yulun Wu

Comment 3 2026-03-03 14:49:32 PST

Pull request: https://github.com/WebKit/WebKit/pull/59834

alan

Comment 4 2026-04-11 15:08:18 PDT

Created attachment 479022 [details] Patch

alan

Comment 5 2026-04-11 15:23:01 PDT

Created attachment 479023 [details] [fast-cq]Patch