PSA: Browser text zoom on Android will now work like it does on desktop

[Jonathan Bernal]

Contact emails

mschi...@google.com, rayjon...@google.com, p...@google.com, ikilp...@google.com, ald...@google.com, chri...@google.com

Explainer

https://docs.google.com/document/d/1vRVRJFaY3TWRFkrKvLhhiBemTfFxUzI_co4YZq_kB0E/edit

Summary

Browser text zoom on Android will now work like it does on desktop. See https://blog.google/products/android/new-android-features-february-2023/ for a blog post about it. The default rendered zoom value of a given page will transparently account for a user’s OS-level font size setting. This means that any user on Android who has a non-default OS-level font size setting (~40% of users), will use a non-100% zoom on Android Chrome by default. This feature is currently released to 10% of stable users.

How to opt into the feature:

1. Go to chrome://flags

2. Search for "Accessibility Page Zoom”

3. Use the dropdown box to switch the feature from “Default” to “Enabled”

4. Restart Chrome (force quit)

How to use the feature: https://support.google.com/chrome/answer/96810?co=GENIE.Platform%3DAndroid&oco=1

Blink component

Compositor 

Risks

• This will change the overall distribution of window.innerWidth values a website sees, which may be unexpected.

• Don't currently have any provision for opting out specific origins (eg. overriding the default zoom level back to 100%) if breakage is discovered.

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

Android and Android WebView

Is this feature fully tested by web-platform-tests?

No

Flag name

Accessibility Page Zoom

Requires code in //chrome?

Yes

Tracking bug

https://bugs.chromium.org/p/chromium/issues/detail?id=645717

Launch bug

https://launch.corp.google.com/launch/4206588 (sorry, Googlers only)

Estimated milestones

M113

Link to entry on the Chrome Platform Status

N/A

Links to previous Intent discussions

N/A

[Torne (Richard Coles)]

This mentions it's supported in Android WebView, but WebView has always used the font size specified in the OS to scale text specifically (*not* to scale CSS pixels): https://source.chromium.org/chromium/chromium/src/+/main:android_webview/java/src/org/chromium/android_webview/AwSettings.java;l=296;drc=334d01268df246e959b238956ab956413562edfb

Does this change actually affect WebView? If so, how? If it ends up stacking with the text zoom we are already doing then the results may not be desirable.

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[Torne (Richard Coles)]

This mentions it's supported in Android WebView, but WebView has always used the font size specified in the OS to scale text specifically (*not* to scale CSS pixels): https://source.chromium.org/chromium/chromium/src/+/main:android_webview/java/src/org/chromium/android_webview/AwSettings.java;l=296;drc=334d01268df246e959b238956ab956413562edfb

Does this change actually affect WebView? If so, how? If it ends up stacking with the text zoom we are already doing then the results may not be desirable.

On Wed, 2 Aug 2023 at 13:27, 'Jonathan Bernal' via blink-dev <blin...@chromium.org> wrote:

[Rick Byers]

Hi Jonathan,

In doing bug triage, I'm randomly coming across multiple web developers confused by this behavior. Do we need a blog post perhaps to help raise awareness and provide a better announcement to the community than a blink-dev thread?

Thanks,

   Rick

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAEV-rjfS8HbqdveWr9ve3k0E6QOW93umXc%3DWFNbSDFGgbk%3Dshg%40mail.gmail.com.

[Daniel Herr]

I would like to point out that at least on Chrome OS, the font scale does not affect the display scale. Personally I consider that to be the correct behavior.

The argument that scaling only the size of text but not zooming the page would cause issues due to developers hardcoding UI elements containing text using nonresponsive sizes is true, but no more so that is already the case on CrOS/Win/Mac/Linux using the browser specific font size settings.

[Mark Schillaci]

Just to loop back on this - Page Zoom does not affect WebView. The custom text zoom of WebView was not changed.

Sorry for the delay :p.