1365806 - empty element has an offsetheight if given overflow-y:scroll, unlike other browsers

Status: RESOLVED FIXED

(Core :: Layout: Scrolling and Overflow, defect, P3)

Description

[Thomas Wisniewski]

Attachment: testcase.html

As per the attached testcase, giving an otherwise-empty element overflow-y:scroll will forcefully give it an offsetHeight (the actual value varies from theme to theme).

Other browsers all give the element a zero offsetHeight (I have tested Chrome, Safari, Edge, and Internet Explorer 11).

This currently affects the UK Labor Party's website, as it expects the offsetHeight of such an element to be === 0, and otherwise leaves its height alone, making a section of the site's content appear much smaller than it otherwise would be (as shown in the related webcompat.com issue #6353).

Comment 1

[Mats Palmgren (inactive)]

I'm guessing that's because we impose a minimum size on the scrollbar,
and other UAs don't?
data:text/html,<div style="overflow-y:scroll; border:1px solid"></div>

I think that comes from the Widget layer, e.g.:
http://searchfox.org/mozilla-central/rev/f55349994fdac101d121b11dac769f3f17fbec4b/widget/gtk/nsNativeThemeGTK.cpp#1486-1500

Comment 2

[Thomas Wisniewski]

Yes, this seems to be the culprit. When I remove that switch-case, the rendering is similar to other browsers. But I'm not sure if the problem in bug 513006 that case fixed is still a concern. Thoughts?

Comment 3

[Karl Dubost💡 :karlcow]

In Chrome the box is      0px high 
and in Firefox, this is  16px high
data:text/html,<div style="height:auto;overflow-y:scroll;background-color:pink"></div>

Visible on Rakuten on Android
https://webcompat.com/issues/22960

Comment 4

[Firefox Bug Husbandry Bot]

Migrating Webcompat whiteboard priorities to project flags. See bug 1547409.

Comment 5

[Firefox Bug Husbandry Bot]

See bug 1547409. Migrating whiteboard priority tags to program flags.

Comment 6

[Sid Vishnoi :sidvishnoi]

To add, this is causing issues on https://console.cloud.google.com with a persistent bar floating on screen. (Although they should be using overflow: auto there instead)
Comparison between Firefox and Chrome behavior: https://i.imgur.com/8LmpOKz.png

Comment 8

[Emilio Cobos Álvarez (:emilio)]

Fwiw, this is the widget-imposed min size of the scrollbar element.

Comment 9

[Jeff Muizelaar [:jrmuizel]]

Should we change that imposition?

Comment 10

[Emilio Cobos Álvarez (:emilio)]

Probably... I can look into it, just not right now.

Comment 12

[Emilio Cobos Álvarez (:emilio)]

Attachment: Bug 1365806 - Make scrollbars not impose a minimum size on the scroller. r=dholbert

Also, don't suppress scrollbars if the scrollport is less than their
width, as that can happen now :)

Scrollbars code is tricky, so I'll wait until the soft freeze is over to
land this.

Comment 15

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/842955b61f01
Make scrollbars not impose a minimum size on the scroller. r=dholbert

Comment 16

[Narcis Beleuzu [:NarcisB]]

Backed out for wr failures on contain-size-scrollbars-002.html

Backout link: https://hg.mozilla.org/integration/autoland/rev/ad7eed76c065f345ba7f4136c81564a4ad2de95e
Log link: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=301009550&repo=autoland&lineNumber=5368

Also on contain-size-flexbox-002.html : https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=301010389&repo=autoland&lineNumber=17613

Comment 17

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/012f25fede5c
Make scrollbars not impose a minimum size on the scroller. r=dholbert

Comment 18

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/23466 for changes under testing/web-platform/tests

Comment 19

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

Upstream web-platform-tests status checks passed, PR will merge once commit reaches central.

Comment 20

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/012f25fede5c

Comment 21

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

Upstream PR merged by moz-wptsync-bot