Fix ToolStripDropDownMenu scroll boundary handling to prevent out-of-range and unintended dropdown dismissal#14490
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…range and unintended dropdown dismissal
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Pull request overview
Fixes ToolStripDropDownMenu scrolling boundary behavior so scroll buttons reflect actual scrollability, prevent out-of-range scrolling at boundaries, and avoid unintended dropdown dismissal when interacting with scroll buttons.
Changes:
- Replaces edge-based
Rectangle.Contains(...)checks with explicit “fully visible” / “intersects viewport” checks. - Updates scroll button enable/disable logic and adds early-return guards to avoid invalid scrolling paths.
- Marks
ToolStripScrollButtonas navigation-only (SupportsItemClick = false) and adds regression unit tests.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.
| File | Description |
|---|---|
| src/System.Windows.Forms/System/Windows/Forms/Controls/ToolStrips/ToolStripDropDownMenu.cs | Adjusts visibility math, scroll boundary logic, and scroll-button status calculation. |
| src/System.Windows.Forms/System/Windows/Forms/Controls/ToolStrips/ToolStripScrollButton.cs | Prevents scroll buttons from participating in item-click routing to avoid AutoClose dismissal. |
| src/test/unit/System.Windows.Forms/ToolStripDropDownMenuTests.cs | Adds/updates unit tests covering scroll boundary and scroll-button click behavior. |
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Fixes #6650
Proposed changes
fully visible/intersects viewport) instead of edge-basedRectangle.Contains(...).ScrollInternal(bool up)when the target scroll button is already disabled.ToolStripScrollButtonas navigation-only (SupportsItemClick = false) so scrolling does not trigger dropdown auto-close behavior.Customer Impact
Regression?
Risk
Screenshots
Before
The ToolStripScrollDownButton is still enabled when displaying the last dropdown item, and in this case, an exception pops up when clicking that ToolStripScrollDownButton again
After
When go through the last dropdown item, the ToolStripScrollDownButton is disabled
AfterChanges.mp4
Test methodology
Test environment(s)
Microsoft Reviewers: Open in CodeFlow