Fix issue 14693: TrackBar UI control doesn't reflect properties

[SimonZhao888]

Fixes #14693

Root Cause

This regression came from the manual tick-rendering path introduced in #8060.
When TrackBar falls back to DrawTicksManually(), the tick math had two issues:

• The interior tick loop in DrawTicksManually() had an off-by-one boundary (<), so the last valid interior tick could be skipped.
• Tick rendering was not refreshed on size changes when using manual ticks, so the UI could become stale after resize/property updates.

Proposed changes

• Fixed the manual tick loop boundary in DrawTicksManually() from < to <= so the final valid interior tick is included.
• Added TrackBar.OnSizeChanged(EventArgs) override to refresh ticks on resize。
  • Recreate the handle when auto/manual tick mode decision changes.
  • Otherwise redraw manual ticks and invalidate.
• Added public API baseline entry for the new override:
  • override System.Windows.Forms.TrackBar.OnSizeChanged(System.EventArgs! e) -> void in PublicAPI.Unshipped.txt.

Customer Impact

• The TrackBar UI control correctly reflects the properties.

Regression?

• Yes

Risk

• Mini

Screenshots

Before

After

14693.mp4

14693-1.mp4

14693-2.mp4

Test methodology

• Manually

Test environment(s)

• 11.0.0-preview.6.26317

Microsoft Reviewers: Open in CodeFlow

[LeafShi1]

Thanks for the fix — the off-by-one in the tick loop is real and worth fixing. A few concerns to consider before merge:

1. PR description vs. code mismatch. The description says "Override the OnSizeChanged() method...", but there is no OnSizeChanged/OnResize override in the diff. The resize scenario (issue #2 in #14693) actually appears to be fixed as a side effect of making the tick count size-independent (the native control rescales stored logical tick positions on resize). Please update the description to match the code, or clarify how the resize case is covered.

2. No regression test. Since this is a runtime-only visual bug, please add a test asserting the tick count / last-interior-tick for the repro (Max=500, TickFrequency=50) so this doesn't regress again.

See inline comments for the specifics on the tick math.

[Copilot]

Pull request overview

Fixes a regression in WinForms TrackBar tick rendering when falling back to the manual tick-rendering path, aiming to make drawn ticks consistently reflect TickFrequency across range/size changes.

Changes:

• Adds validation/message resources for invalid TickFrequency values (rejects negatives; intends to allow 0).
• Reworks DrawTicksManually() to compute tick positions deterministically and adjust drawing based on control size.
• Adds localized resource entries for the new TickFrequency error string.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/System.Windows.Forms/System/Windows/Forms/Controls/TrackBar/TrackBar.cs	Updates TickFrequency validation and revises manual tick calculation/loop.
src/System.Windows.Forms/Resources/SR.resx	Adds TrackBarTickFrequencyError string.
src/System.Windows.Forms/Resources/xlf/SR.cs.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.de.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.es.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.fr.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.it.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.ja.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.ko.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.pl.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.pt-BR.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.ru.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.tr.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.zh-Hans.xlf	Adds localized entry for TrackBarTickFrequencyError.
src/System.Windows.Forms/Resources/xlf/SR.zh-Hant.xlf	Adds localized entry for TrackBarTickFrequencyError.

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