Deprecate `textScaleFactor` in favor of `textScaler`, in preparation for Android 14 [Non-linear font scaling to 200%](https://developer.android.com/about/versions/14/features#non-linear-font-scaling). The `TextScaler` class can be moved to `dart:ui` in the future, if we decide to use the Android platform API or AndroidX to get the scaling curve instead of hard coding the curve in the framework.
I haven't put the Flutter version in the deprecation message so the analyzer checks are failing. Will do so after I finish the migration guide.
**Why `TextScaler.textScaleFactor`**
The author of a `TextScaler` subclass should provide a fallback `textScaleFactor`. By making `TextScaler` also contain the `textScaleFactor` information it also makes it easier to migrate: if a widget overrides `MediaQueryData.textScaler` in the tree, for unmigrated widgets in the subtree it would also have to override `MediaQueryData.textScaleFactor`, and that makes it difficult to remove `MediaQueryData.textScaleFactor` in the future.
## A full list of affected APIs in this PR
Deprecated: The method/getter/setter/argument is annotated with a `@Deprecated()` annotation in this PR, and the caller should replace it with `textScaler` instead. Unless otherwise specified there will be a Flutter fix available to help with migration but it's still recommended to migrate case-by-case.
**Replaced**: The method this `textScaleFactor` argument belongs to is rarely called directly by user code and is not overridden by any of the registered custom tests, so the argument is directly replaced by `TextScaler`.
**To Be Deprecated**: The method/getter/setter/argument can't be deprecated in this PR because a registered customer test depends on it and a Flutter fix isn't available (or the test was run without applying flutter fixes first). This method/getter/setter/argument will be deprecated in a followup PR once the registered test is migrated.
### `Painting` Library
| Affected API | State of `textScaleFactor` | Comment |
| --- | --- | --- |
| `InlineSpan.build({ double textScaleFactor = 1.0 })` argument | **Replaced** | |
| `TextStyle.getParagraphStyle({ double TextScaleFactor = 1.0 })` argument | **Replaced** | |
| `TextStyle.getTextStyle({ double TextScaleFactor = 1.0 })` argument| Deprecated | Can't replace: c47fd38dca/super_editor/lib/src/infrastructure/super_textfield/desktop/desktop_textfield.dart (L1903-L1905)|
| `TextPainter({ double TextScaleFactor = 1.0 })` constructor argument | Deprecated | |
| `TextPainter.textScaleFactor` getter and setter | Deprecated | No Flutter Fix, not expressible yet |
| `TextPainter.computeWidth({ double TextScaleFactor = 1.0 })` argument | Deprecated | |
| `TextPainter.computeMaxIntrinsicWidth({ double TextScaleFactor = 1.0 })` argument | Deprecated | |
### `Rendering` Library
| Affected API | State of `textScaleFactor` | Comment |
| --- | --- | --- |
| `RenderEditable({ double TextScaleFactor = 1.0 })` constructor argument | Deprecated | |
| `RenderEditable.textScaleFactor` getter and setter | Deprecated | No Flutter Fix, not expressible yet |
| `RenderParagraph({ double TextScaleFactor = 1.0 })` constructor argument | Deprecated | |
| `RenderParagraph.textScaleFactor` getter and setter | Deprecated | No Flutter Fix, not expressible yet |
### `Widgets` Library
| Affected API | State of `textScaleFactor` | Comment |
| --- | --- | --- |
| `MediaQueryData({ double TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | cd7b93532e/packages/flutter_markdown/test/text_scale_factor_test.dart (LL39C21-L39C35) |
| `MediaQueryData.textScaleFactor` getter | Deprecated | |
| `MediaQueryData.copyWith({ double? TextScaleFactor })` argument | Deprecated | |
| `MediaQuery.maybeTextScaleFactorOf(BuildContext context)` static method | Deprecated | No Flutter Fix, not expressible yet |
| `MediaQuery.textScaleFactorOf(BuildContext context)` static method | **To Be Deprecated** | cd7b93532e/packages/flutter_markdown/lib/src/_functions_io.dart (L68-L70), No Flutter Fix, not expressible yet |
| `RichText({ double TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | cd7b93532e/packages/flutter_markdown/lib/src/builder.dart (L829-L843) |
| `RichText.textScaleFactor` getter | **To Be Deprecated** | A constructor argument can't be deprecated right away|
| `Text({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | 914d120da1/packages/rfw/lib/src/flutter/core_widgets.dart (L647) , No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `Text.rich({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | The default constructor has an argument that can't be deprecated right away. No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `Text.textScaleFactor` getter | **To Be Deprecated** | A constructor argument can't be deprecated right away |
| `EditableText({ double? TextScaleFactor = 1.0 })` constructor argument | Deprecated | No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `EditableText.textScaleFactor` getter | Deprecated | |
### `Material` Library
| Affected API | State of `textScaleFactor` | Comment |
| --- | --- | --- |
| `SelectableText({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | cd7b93532e/packages/flutter_markdown/lib/src/builder.dart (L829-L843), No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `SelectableText.rich({ double? TextScaleFactor = 1.0 })` constructor argument | **To Be Deprecated** | The default constructor has an argument that can't be deprecated right away. No Flutter Fix because of https://github.com/dart-lang/sdk/issues/52664 |
| `SelectableText.textScaleFactor` getter | **To Be Deprecated** | A constructor argument can't be deprecated right away |
A lot of material widgets (`Slider`, `RangeSlider`, `TimePicker`, and different types of buttons) also change their layout based on `textScaleFactor`. These need to be handled in a case-by-case fashion and will be migrated in follow-up PRs.
Move Flutter Gallery to dev/integration_tests/ as it is an older copy used only for testing. The current version of the Flutter Gallery now lives in https://github.com/flutter/gallery.
