1638773 - device-width conflict values in between initial-scale and width

Status: VERIFIED FIXED

(Core :: Panning and Zooming, defect, P1)

Description

[Karl Dubost💡 :karlcow]

There is a site with these values

<meta name="viewport"
      content="initial-scale=device-width, 
               maximum-scale=1.0, 
               user-scalable=no, 
               width=device-width">

The site is hugely blown out.

The current specification says:
https://drafts.csswg.org/css-device-adapt/#min-scale-max-scale

device-width and device-height are translated to 10

so we end up with

<meta name="viewport"
      content="initial-scale=10, 
               maximum-scale=1.0, 
               user-scalable=no, 
               width=device-width">

which should win?

• Chrome shows the site with width=device-width
• Firefox shows the site x10 zoom

This is yet another edge case.

note: can be reproduced on rdm.

see details on https://webcompat.com/issues/52856

Comment 1

[Hiroyuki Ikezoe (:hiro)]

I'd say the scale value should be 1.0.
Does the site work fine before bug 1598145?

Comment 2

[Release mgmt bot [:sylvestre / :calixte / :marco for bugbug]]

Set release status flags based on info from the regressing bug 1598145

Comment 3

[Brad Werth [:bradwerth]]

This is solvable by adding a clamp to the code introduced in Bug 1598145. I'll propose a patch with a fix and a web platform test.

Comment 4

[Brad Werth [:bradwerth]]

Attachment: Bug 1638773: Allow initial-scale clamping when user-scalable=no, add WPT.

This corrects the handling of user-scalable=no to first apply the clamping
of the initial-scale (whether specified or default) to the min and max scales.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0143fd91ba20
Allow initial-scale clamping when user-scalable=no, add WPT. r=hiro

Comment 6

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

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/23713 for changes under testing/web-platform/tests

Comment 7

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

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

Comment 8

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/0143fd91ba20

Comment 9

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

Upstream PR merged by moz-wptsync-bot

Comment 10

[Emily Toop (:fluffyemily)]

Thanks to :hiro for bringing this to the attention of the Fenix team. Could we please request this be uplifted to 77 so that we can get this fix for the Fenix product market fit experiment?

Comment 11

[Brad Werth [:bradwerth]]

Comment on attachment 9150299 [details]
Bug 1638773: Allow initial-scale clamping when user-scalable=no, add WPT.

Beta/Release Uplift Approval Request

• User impact if declined: Sites with meta viewport tags with user-scalable=no and very large or very small initial-scale will appear at unreadable sizes in GeckoView.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): The code change only applies when user-scalable=no, which is an uncommon pattern and noted as bad practice (though permitted by spec).
• String changes made/needed:

Comment 12

[Ryan VanderMeulen [:RyanVM]]

Comment on attachment 9150299 [details]
Bug 1638773: Allow initial-scale clamping when user-scalable=no, add WPT.

Fixes an important mobile web compat issue affecting Fenix. Approved for 77.0b9.

Comment 13

[Release mgmt bot [:sylvestre / :calixte / :marco for bugbug]]

Changing the priority to p1 as the bug is tracked by a release manager for the current beta.
See What Do You Triage for more information

Comment 14

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-beta/rev/d4b281989ea6

Comment 15

[Hiroyuki Ikezoe (:hiro)]

Thank you Brad and Emily!

Comment 16

[Oana Horvath]

Verified as fixed on the reported website, on Fenix Beta 5.1-beta2.