[material_ui] Port flutter/flutter #185149 "Slider label clips the screen"

[mbcorona]

Ports flutter/flutter#185149 from flutter/flutter to flutter/packages, following the porting instructions in flutter/flutter#188444.

Long text in a Slider or RangeSlider label clipped off the edges of the screen. This limits the label's maxWidth to the screen width minus a calculated horizontal buffer (_kValueIndicatorHorizontalBuffer), forces maxLines = 1, and applies the Unicode ellipsis (\u2026), so the text no longer expands past the screen boundary and the bubble shape no longer breaks vertically. A screenSize.width.isFinite && screenSize.width > 0 guard keeps the constraint inert when no valid size is available.

The original PR was reviewed and approved by @QuncCccccc. No merge commits were included; the five commits cherry-picked onto material_ui with no conflicts.

Validation:

• dart format --set-exit-if-changed on the four changed files
• git diff --check
• flutter test test/slider_test.dart test/range_slider_test.dart

Fixesflutter/flutter#63293

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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

Note: The Flutter team is currently trialing the use of Gemini Code Assist for GitHub. Comments from the gemini-code-assist bot should not be taken as authoritative feedback from the Flutter team. If you find its comments useful you can update your code accordingly, but if you are unsure or disagree with the feedback, please feel free to wait for a Flutter team member's review for guidance on which automated comments should be addressed.

Footnotes

1. Regular contributors who have demonstrated familiarity with the repository guidelines only need to comment if the PR is not auto-exempted by repo tooling. ↩↩²

[gemini-code-assist]

Code Review

This pull request introduces a horizontal buffer of 64.0 logical pixels for the value indicators of both Slider and RangeSlider to prevent them from bleeding off the screen edges. The label painters are updated to apply this buffer as a maxWidth constraint, restrict the text to a single line with an ellipsis on overflow, and migrate to textScaler. Corresponding tests are added to verify this behavior. The review feedback suggests explicitly setting a smaller physical size for the test views in the new tests to ensure that the layout constraints and ellipsis behavior are actually triggered and verified.

[gemini-code-assist]

The test might pass even if the maxWidth constraint is not applied. The default screen width in WidgetTester is 800.0 logical pixels, and the test strings are likely shorter than 800.0 - 64.0 = 736.0 logical pixels. To ensure the constraint and ellipsis behavior are actually triggered and verified, consider setting a smaller physical size for the test view.

Suggested change

	testWidgets('RangeSlider labels respect horizontal buffer and avoid screen overflow', (
	WidgetTester tester,
	) async {
	final logPainters =<TextPainter>[];
	final shape =LoggingRangeSliderValueIndicatorShape(<InlineSpan>[], logPainters);
	testWidgets('RangeSlider labels respect horizontal buffer and avoid screen overflow', (
	WidgetTester tester,
	) async {
	tester.view.physicalSize =constSize(300.0, 600.0);
	tester.view.devicePixelRatio =1.0;
	addTearDown(() {
	tester.view.resetPhysicalSize();
	tester.view.resetDevicePixelRatio();
	});
	final logPainters =<TextPainter>[];
	final shape =LoggingRangeSliderValueIndicatorShape(<InlineSpan>[], logPainters);

[gemini-code-assist]

The test might pass even if the maxWidth constraint is not applied. The default screen width in WidgetTester is 800.0 logical pixels, and the test string is likely shorter than 800.0 - 64.0 = 736.0 logical pixels. To ensure the constraint and ellipsis behavior are actually triggered and verified, consider setting a smaller physical size for the test view.

Suggested change

	testWidgets('Slider label respects horizontal buffer and avoids screen overflow', (
	WidgetTester tester,
	) async {
	final logPainters =<TextPainter>[];
	final shape =LoggingValueIndicatorShape(<InlineSpan>[], logPainters);
	testWidgets('Slider label respects horizontal buffer and avoid screen overflow', (
	WidgetTester tester,
	) async {
	tester.view.physicalSize =constSize(300.0, 600.0);
	tester.view.devicePixelRatio =1.0;
	addTearDown(() {
	tester.view.resetPhysicalSize();
	tester.view.resetDevicePixelRatio();
	});
	final logPainters =<TextPainter>[];
	final shape =LoggingValueIndicatorShape(<InlineSpan>[], logPainters);

[mbcorona]

Not applicable: flutter_test uses the fixed-advance FlutterTest font
(1 em per glyph), so this 86-character label at textTheme.bodyLarge (16px)
lays out at ~1376 logical pixels, well past the 736 limit at the default
800px viewport. The constraint is exercised — removing the maxWidth fails
this assertion.

Test unchanged; this PR is a straight port of flutter/flutter#185149.

[mbcorona]

@QuncCccccc this is the port of flutter/flutter#185149 that you approve.
The code is unchanged from what you signed off on, just relocated to
material_ui with a pending changelog entry added.

[QuncCccccc]

LGTM. Thank you!