Wire up the system text scaler from `PlatformDispatcher` by LongCatIsLooong · Pull Request #159999 · flutter/flutter

LongCatIsLooong · 2024-12-09T22:24:55Z

The equality of 2 SystemTextScaler is determined by the platform's textScaleFactor scalar, because the scale method is always monotonically increasing wrt textScaleFactor.
On Android the scalar reflects the user configuration in system preference it seems: https://developer.android.com/reference/android/content/res/Configuration#fontScale

Pre-launch Checklist

I read the Contributor Guide and followed the process outlined there for submitting PRs.
I read the Tree Hygiene wiki page, which explains my responsibilities.
I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
I signed the CLA.
I listed at least one issue that this PR fixes in the description above.
I updated/added relevant documentation (doc comments with ///).
I added new tests to check the change I am making, or this PR is test-exempt.
I followed the breaking change policy and added Data Driven Fixes where supported.
All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.

Piinks · 2025-02-26T00:45:43Z

(Triage) Confirmed with @LongCatIsLooong this is still on their radar

This is for #159999. That PR breaks registered tests so a new matcher is added for soft transition & making it slightly easier to write tests that verify nothing is shadowing the system text scaler in the widget tree. If this approach sounds plausible & gets merged, I'm going to: 1. remake the breaking change announcement 2. update the migration guide with the new matcher, 3. migrate the registered tests and mark #159999 as ready for review. ## Pre-launch Checklist - [ ] I read the [Contributor Guide] and followed the process outlined there for submitting PRs. - [ ] I read the [Tree Hygiene] wiki page, which explains my responsibilities. - [ ] I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement]. - [ ] I signed the [CLA]. - [ ] I listed at least one issue that this PR fixes in the description above. - [ ] I updated/added relevant documentation (doc comments with `///`). - [ ] I added new tests to check the change I am making, or this PR is [test-exempt]. - [ ] I followed the [breaking change policy] and added [Data Driven Fixes] where supported. - [ ] All existing and new tests are passing. If you need help, consider asking for advice on the #hackers-new channel on [Discord].  [Contributor Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview [Tree Hygiene]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md [test-exempt]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests [Flutter Style Guide]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md [Features we expect every widget to implement]: https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement [CLA]: https://cla.developers.google.com/ [flutter/tests]: https://github.com/flutter/tests [breaking change policy]: https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes [Discord]: https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md [Data Driven Fixes]: https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

Flutter PR flutter/flutter#159999 (fixing a bug where MediaQuery provides an incorrect TextScaler) breaks this test; fix it with isSystemTextScaler. [chris: rewrote commit message; used package:legacy_checks]

Flutter PR flutter/flutter#159999 (fixing a bug where MediaQuery provides an incorrect TextScaler) breaks this test; fix it with isSystemTextScaler. Co-authored-by: Chris Bobbe <[email protected]>

chunhtai · 2025-03-20T19:04:19Z

packages/flutter/lib/src/painting/text_scaler.dart

    if (identical(this, other)) {
      return true;
    }
+    assert(minScale < maxScale);


If this is the only place to enforce this constraint, we should do it where these two values are set instead. a crash here won't help us much in tracing down the bug

This is enforced in the (private) constructor (if minScale == maxScale the public API will return a different type of TextScaler). The assert is to indicate this is a valid assumption one can make for readers. Does it make more sense to make this a code comment then?

as long as there is not the first fail safe point, I am fine either way.

I'm also fine either way, but maybe a comment is better to avoid the confusion that started this thread.

removed the assert.

chunhtai · 2025-03-20T19:05:51Z

packages/flutter/lib/src/painting/text_scaler.dart

      minScale == maxScale ? minScale.hashCode : Object.hash(scaler, minScale, maxScale);
+
+  @override
+  String toString() => '$scaler clamped [$minScale, $maxScale]';


consider use Diagnosticable

That doesn't seem to reduce the amount of code I have to write, are there other benefits of using Diagnosticable?

it provide a better api to fill in properties for printing the string representation. Besides that, I think devtools uses that api to get details about an object, but i am not too familiar with that part of the code.

This is what it looks like now:

'│└RichText(softWrap: wrapping at box width, textScaler: SystemTextScaler (no scaling), maxLines: unlimited, text: "A", dependencies: [Directionality], renderObject: RenderParagraph#00000 relayoutBoundary=up1)\n'

So that still works. I'd keep the class hierarchy simple for now in case someone wants to implement the class instead of extending.

yeah makes sense

For my own understanding I wonder if @kenzieschmoll has any thoughts on when to use Diagnosticable in cases like this? I've wondered about this before.

flutter/flutter#159999

LongCatIsLooong · 2025-03-24T20:16:07Z

@chunhtai @justinmc made a few changes after your last LGTM (diff). Does this still LGTY?

justinmc

Renewing my LGTM 👍

justinmc · 2025-03-29T00:01:28Z

packages/flutter/lib/src/painting/text_painter.dart

    )
    double textScaleFactor = 1.0,
-    TextScaler textScaler = TextScaler.noScaling,
+    TextScaler textScaler = const _UnspecifiedTextScaler(),


Excellent use of the sentinel pattern 💂

justinmc · 2025-03-29T00:10:40Z

packages/flutter/lib/src/widgets/media_query.dart

+      SystemTextScaler(:final double textScaleFactor) => this.textScaleFactor == textScaleFactor,
+      // When textScaleFactor is 1.0, the two TextScalers are extensionally
+      // equivalent.
+      TextScaler.noScaling => textScaleFactor == 1.0,


Good catch.

dkwingsmt · 2025-04-23T18:03:28Z

There are two Google test failures and are flakes. There are also a conflict.

LongCatIsLooong · 2025-05-12T19:51:23Z

Waiting for my CL to land before merging this.

auto-submit · 2025-05-13T08:20:31Z

autosubmit label was removed for flutter/flutter/159999, because - The status or check suite Google testing has failed. Please fix the issues identified (or deflake) before re-applying this label.

…tter/flutter#159999)

flutter/flutter@336a7ec...0b9f928 2025-05-14 [email protected] Fix Linux Impeller support broken by incorrect deletion of stencil buffer. (flutter/flutter#168668) 2025-05-14 [email protected] Roll Fuchsia Linux SDK from 6J81agNhuK4q255Jj... to fSvuEJgRmHxnewRJr... (flutter/flutter#168794) 2025-05-14 [email protected] Run `{Platform} flutter_packaging` builders on release candidates. (flutter/flutter#168762) 2025-05-14 [email protected] Remove `docs_deploy_beta`, fix `docs_publish`, add comments. (flutter/flutter#168754) 2025-05-14 [email protected] Add `titleAlignment` to `CheckboxListTile` and `RadioListTile` (flutter/flutter#168666) 2025-05-14 [email protected] Remove deprecated todo about caching (flutter/flutter#168534) 2025-05-13 [email protected] Replace hardcoded host and app level build.gradle paths with `AndroidProject`-level getters in `gradle_errors.dart` (flutter/flutter#167949) 2025-05-13 [email protected] Improve documentation for KeyedSubtree constructor (flutter/flutter#167198) 2025-05-13 [email protected] Wire up the system text scaler from `PlatformDispatcher` (flutter/flutter#159999) 2025-05-13 [email protected] Roll Dart SDK from 645d04a7a964 to b3520981e0f0 (3 revisions) (flutter/flutter#168721) 2025-05-13 [email protected] [a11y] Semanctis flag refactor step 3: framework part (flutter/flutter#167771) 2025-05-13 [email protected] Remove/replace the `team` label with `c: contributor-productivity`. (flutter/flutter#168702) 2025-05-13 98614782+auto-submit[bot]@users.noreply.github.com Reverts "Clip search artifacts in CupertinoSliverNavigationBar searchable-to-searchable transitions (#168510)" (flutter/flutter#168775) 2025-05-13 [email protected] Use live region in error text input decorator for Android (flutter/flutter#165531) 2025-05-13 [email protected] [tool] Fix deprecated API calls within tool (flutter/flutter#168200) 2025-05-13 [email protected] Clip search artifacts in CupertinoSliverNavigationBar searchable-to-searchable transitions (flutter/flutter#168510) 2025-05-13 [email protected] Fixes hero not shown when remove pages without animation (flutter/flutter#168617) 2025-05-13 [email protected] [iOS] Do not hide selection handles when platform hides system context menu (flutter/flutter#168678) 2025-05-13 [email protected] Updated execution path to silently include --start-paused and updated tests (flutter/flutter#168400) 2025-05-13 [email protected] Roll Packages from 6a28ad9 to 2e166de (2 revisions) (flutter/flutter#168736) 2025-05-13 [email protected] [web] Fix multiline input selection in Chrome. (flutter/flutter#168217) 2025-05-13 [email protected] Call xcode_backend.dart from macos_assemble.sh (flutter/flutter#168108) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

…tter/flutter#159999)

github-actions bot added a: tests "flutter test", flutter_test, or one of our tests a: text input Entering text in a text field or keyboard related problems framework flutter/packages/flutter repository. See also f: labels. labels Dec 9, 2024

wire up PlatformDispatcher text scaler

6f263bb

LongCatIsLooong force-pushed the text-scaler branch from 862c54c to 6f263bb Compare December 9, 2024 22:38

LongCatIsLooong mentioned this pull request Dec 11, 2024

Add a isSystemTextScaler matcher #160120

Merged

9 tasks

Merge remote-tracking branch 'upstream/master' into text-scaler

794eb9b

LongCatIsLooong added 5 commits March 3, 2025 12:36

Merge remote-tracking branch 'upstream/master' into text-scaler

43370ad

buh

410dfd6

cuh

30e1a25

Merge remote-tracking branch 'upstream/master' into text-scaler

c762d89

fix tests

f1daf7b

github-actions bot added f: material design flutter/packages/flutter/material repository. f: scrolling Viewports, list views, slivers, etc. labels Mar 19, 2025

LongCatIsLooong added 5 commits March 19, 2025 13:01

_ClampedTextScaler.toString

5d52807

fix tests

7c253a2

format

ef62ab2

fix tests

350dbe0

format

b583bb8

LongCatIsLooong marked this pull request as ready for review March 19, 2025 23:12

LongCatIsLooong requested review from chunhtai and justinmc March 19, 2025 23:12

LongCatIsLooong mentioned this pull request Mar 19, 2025

[Flutter Migration] migrate emoji_reaction_test.dart zulip/zulip-flutter#1424

Merged

chunhtai reviewed Mar 20, 2025

View reviewed changes

LongCatIsLooong added a commit to flutter/tests that referenced this pull request Mar 20, 2025

bump zulip.test to2117fe176aa740d00ff4e6be5ac38bd98eab8a3d

ec1d8c0

flutter/flutter#159999

LongCatIsLooong mentioned this pull request Mar 20, 2025

Bump zulip.test to2117fe176aa740d00ff4e6be5ac38bd98eab8a3d flutter/tests#449

Merged

8 tasks

github-actions bot added the d: examples Sample code and demos label Mar 24, 2025

Merge branch 'master' into text-scaler

33b34b1

justinmc approved these changes Mar 29, 2025

View reviewed changes

matanlurey removed their request for review April 2, 2025 15:28

Merge branch 'master' into text-scaler

961dba2

Merge branch 'master' into text-scaler

56732e5

LongCatIsLooong added the autosubmit Merge PR when tree becomes green via auto submit App label May 13, 2025

auto-submit bot removed the autosubmit Merge PR when tree becomes green via auto submit App label May 13, 2025

LongCatIsLooong added the autosubmit Merge PR when tree becomes green via auto submit App label May 13, 2025

auto-submit bot added this pull request to the merge queue May 13, 2025

Merged via the queue into flutter:master with commit 30fe6e7 May 14, 2025
76 of 77 checks passed

flutter-dashboard bot removed the autosubmit Merge PR when tree becomes green via auto submit App label May 14, 2025

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request May 14, 2025

30fe6e7 Wire up the system text scaler from PlatformDispatcher (flu…

d5028a3

…tter/flutter#159999)

engine-flutter-autoroll mentioned this pull request May 14, 2025

Roll Flutter from 336a7ecf7b40 to 0b9f9288caf3 (22 revisions) flutter/packages#9251

Merged

LongCatIsLooong deleted the text-scaler branch May 14, 2025 16:14

Piinks mentioned this pull request May 16, 2025

Flutter Notable Commits - 2025 #161460

Closed

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 14, 2025

30fe6e7 Wire up the system text scaler from PlatformDispatcher (flu…

7039a0e

…tter/flutter#159999)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 14, 2025

30fe6e7 Wire up the system text scaler from PlatformDispatcher (flu…

eaa9524

…tter/flutter#159999)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 15, 2025

30fe6e7 Wire up the system text scaler from PlatformDispatcher (flu…

4cf5244

…tter/flutter#159999)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 15, 2025

30fe6e7 Wire up the system text scaler from PlatformDispatcher (flu…

ceea9ff

…tter/flutter#159999)

engine-flutter-autoroll added a commit to engine-flutter-autoroll/packages that referenced this pull request Aug 16, 2025

30fe6e7 Wire up the system text scaler from PlatformDispatcher (flu…

66cae48

…tter/flutter#159999)

justinmc mentioned this pull request Sep 23, 2025

textScalar.clamp throws Failed assertion: line 118 pos 80: 'maxScale > minScale': is not true. #174828

Closed

Conversation

LongCatIsLooong commented Dec 9, 2024 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Pre-launch Checklist

Uh oh!

Piinks commented Feb 26, 2025

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

LongCatIsLooong commented Mar 24, 2025

Uh oh!

justinmc left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

dkwingsmt commented Apr 23, 2025

Uh oh!

LongCatIsLooong commented May 12, 2025

Uh oh!

auto-submit bot commented May 13, 2025

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

LongCatIsLooong commented Dec 9, 2024 •

edited

Loading

justinmc left a comment •

edited

Loading