MudTabs: Fix scroll buttons inside disabled form

[redgp0g]

There's a bug that if a Disabled Form wrap MudTabs the scroll buttons are disabled because of the CascadingValue ParentDisabled, so I added around only the scroll buttons an fixed CascadingValue ParentDisabled with value false to prevent this bug to happens, the issue

fixes #12366

• Create ScrollButtons viewer test and unit test for the bug
• Add fixed CascadingValue ParentDisabled with false value aroud the scroll buttons

video.mp4

Checklist:

• I've read the contribution guidelines

• My code follows the style of this project

• I've added or updated relevant unit tests

• Verified tabs are considered navigation and general consensus is not to be disabled per MUI standards. There was not a hard and fast standard for it but that seems to be the generally accepted practice.

[Copilot]

Pull request overview

Fixes a MudTabs regression where tab scroll buttons become disabled when MudTabs is wrapped in a disabled MudForm (via the ParentDisabled cascading value), ensuring scroll navigation remains usable.

Changes:

• Wrap MudTabs scroll buttons with a fixed CascadingValue Name="ParentDisabled" set to false to prevent form-level disabled state from disabling them.
• Add a unit test covering the regression scenario.
• Add a new UnitTests.Viewer repro component to demonstrate the issue.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
src/MudBlazor/Components/Tabs/MudTabs.razor	Overrides ParentDisabled cascade for scroll buttons so they remain interactive inside disabled forms.
src/MudBlazor.UnitTests/Components/TabsTests.cs	Adds a regression test intended to verify scroll buttons remain enabled under a disabled parent form.
src/MudBlazor.UnitTests.Viewer/TestComponents/Tabs/TabScrollButtonsEnabledInsideFormTest.razor	Adds a viewer repro for scroll-button behavior inside a disabled MudForm.

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[Copilot]

The new test assumes both scroll buttons are enabled (Disabled == false) initially and after toggling the form. In MudTabs, the previous button is legitimately disabled when the scroll position is at the start (see SetScrollabilityStates: _prevButtonDisabled = Math.Abs(_scrollPosition) < 0.01), so this assertion can fail even when the ParentDisabled regression is fixed. Instead, capture the buttons' Disabled states before disabling the form and assert the states do not change when the parent form toggles, or move the scroll position (e.g., click Next once) so the button-under-test is enabled due to scroll state and then verify it remains enabled under a disabled form.

Suggested change

	scrollButtons.First().Instance.Disabled.Should().BeFalse("scroll button should be enabled initially");
	scrollButtons.Last().Instance.Disabled.Should().BeFalse("scroll button should be enabled initially");
	var toggleFormDisabledButton = comp.Find("button.mud-button-root:not(.mud-icon-button)");
	await toggleFormDisabledButton.ClickAsync();
	scrollButtons = comp.FindComponents<MudIconButton>();
	scrollButtons.First().Instance.Disabled.Should().BeFalse("scroll button should remain enabled even when form is disabled");
	scrollButtons.Last().Instance.Disabled.Should().BeFalse("scroll button should remain enabled even when form is disabled");
	await toggleFormDisabledButton.ClickAsync();
	scrollButtons = comp.FindComponents<MudIconButton>();
	scrollButtons.First().Instance.Disabled.Should().BeFalse("scroll button should be enabled when form is re-enabled");
	scrollButtons.Last().Instance.Disabled.Should().BeFalse("scroll button should be enabled when form is re-enabled");
	var initialPrevDisabled = scrollButtons.First().Instance.Disabled;
	var initialNextDisabled = scrollButtons.Last().Instance.Disabled;
	var toggleFormDisabledButton = comp.Find("button.mud-button-root:not(.mud-icon-button)");
	await toggleFormDisabledButton.ClickAsync();
	scrollButtons = comp.FindComponents<MudIconButton>();
	scrollButtons.First().Instance.Disabled.Should().Be(initialPrevDisabled, "scroll button disabled state should not change when form is disabled");
	scrollButtons.Last().Instance.Disabled.Should().Be(initialNextDisabled, "scroll button disabled state should not change when form is disabled");
	await toggleFormDisabledButton.ClickAsync();
	scrollButtons = comp.FindComponents<MudIconButton>();
	scrollButtons.First().Instance.Disabled.Should().Be(initialPrevDisabled, "scroll button disabled state should not change when form is re-enabled");
	scrollButtons.Last().Instance.Disabled.Should().Be(initialNextDisabled, "scroll button disabled state should not change when form is re-enabled");

[redgp0g]

I don't think the suggestion is the best, maybe the point can make sense, but I think with de MudContainer with a extra small max width, and if I add more tab panels, I can guarantee the scroll buttons are gone be enabled by default

[versile2]

good work