Fix PropertyGrid Tab navigation regression caused by ToolStrip keyboard focus changes

[LeafShi1]

Fixes #14421

Root cause

• PR 13034 changed ToolStrip so that whenever a ToolStrip receives focus (WM_SETFOCUS), it becomes the active ToolStrip in ToolStripManager.ModalMenuFilter.
• For normal top-level menu/toolbar strips this is desired (to fix 12916), but for the inner PropertyGridToolStrip it means:
  • Entering / staying in menu mode when focus moves to the PropertyGrid toolbar.
  • Dialog-level focus routing and Tab handling start to respect this active ToolStrip state.
• With a PropertyGrid on the form, this extra menu-mode/ActiveToolStrip state causes the second and subsequent Tab cycles to be biased toward the PropertyGrid and its toolbar, so some sibling controls (e.g. Button, ComboBox) are skipped — a regression vs .NET Framework and .NET 8/9.

Proposed changes

• In PropertyGridToolStrip (the inner ToolStrip used by PropertyGrid), override WndProc and, on WM_SETFOCUS, remove this ToolStrip from ToolStripManager.ModalMenuFilter’s active ToolStrip list and exit menu mode if it was the active one.
• This isolates PropertyGrid’s internal toolbar from the global menu-mode / ActiveToolStrip mechanics introduced in PR 13034 , while leaving all other ToolStrips (including the ones involved in 12916) using the existing behavior unchanged.

Customer Impact

• PropertyGrid no longer interferes with the form’s Tab cycle, all TabStop controls (Buttons, ComboBox, PropertyGrid, etc.) are visited in order on every Tab cycle

Regression?

• Yes

Risk

• minimal

Screenshots

Before

• First Tab cycle: all controls are reachable ✔
• Second and subsequent cycles:

Some controls (e.g., ComboBox, one Button) are skipped ❌
Focus repeatedly lands on PropertyGrid and a subset of controls ❌

PropertyGridIssue.mp4

After

All TabStop controls (Buttons, PropertyGrid, etc.) are visited in order on every Tab cycle

AfterChanges.mp4

Test methodology

• Manually

Test environment(s)

• .net 11.0.0-preview.3.26174.112

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

Fixes a WinForms PropertyGrid Tab navigation regression introduced by global ToolStrip “active ToolStrip / menu mode” focus handling changes, by preventing the inner PropertyGridToolStrip from remaining active in ToolStripManager.ModalMenuFilter when it receives focus.

Changes:

• Override PropertyGridToolStrip.WndProc to detect WM_SETFOCUS and remove the inner ToolStrip from ModalMenuFilter’s active ToolStrip queue.
• Exit menu mode when the PropertyGridToolStrip was the active ToolStrip and no other active ToolStrip remains.

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