MenuBar Internals

Overview

Namespace: TheTechIdea.Beep.Winform.Controls.Menus
BeepMenuBar is a full-featured menu bar control decomposed across 13 partial files. It handles menu bar layout, popup submenus with drift-corrected hover persistence (via the SubmenuTriangleTracker), theming, accessibility, keyboard navigation with mnemonics, and high-contrast rendering. The SubmenuTriangleTracker is a classic Amazon-style drift heuristic based on Bret Victor's "Pull-Down Menus, Faster" (2005) research.

Partial File Layout (13 Files)

SubmenuTriangleTracker

Visibility: internal static in Menus/Helpers/SubmenuTriangleTracker.cs. A stateless geometry helper that solves the classic "submenu flicker" problem. When the cursor moves diagonally from a parent menu item toward an open submenu, this tracker determines whether the cursor is "heading toward" the submenu.

internal static class SubmenuTriangleTracker
{
    public static bool IsHeadingTowardSubmenu(
        Point lastPos,          // previous cursor position (screen coords)
        Point currentPos,       // current cursor position (screen coords)
        Point submenuTopLeft,   // submenu window top-left corner
        Point submenuBottomLeft // submenu window bottom-left corner
    );
    // Returns true when currentPos is inside the triangle formed by
    // lastPos, submenuTopLeft, and submenuBottomLeft
    // -> cursor is plausibly moving toward the submenu
    // -> should NOT dismiss the submenu
}

This is based on the same research used in WPF's MenuItem.IsSubmenuOpen heuristic and Amazon's retail mega-menu analysis. The tracker allows users to move the cursor diagonally to a submenu without the timer closing it prematurely.

  Menu Item        Submenu
  [File]----------+
  [Edit]       +--+  Open Recent
  [View]       |     +--------------+
               +---->| LastFile1.cs |
  cursor moves        | LastFile2.cs |
  diagonally ->       +--------------+
  Tracker keeps
  submenu open

Popup Management

BeepMenuBar.Popup.cs handles the complete submenu popup lifecycle:

• Hover to open -- After a configurable hover delay, the submenu form is created, positioned anchored to the parent item, and shown
• Leave to close -- On mouse-leave, a brief timeout starts before closing. The SubmenuTriangleTracker extends this timeout when the cursor plausibly heads toward the submenu
• Z-order -- Submenus are created as owned Forms with ShowWithoutActivation to avoid stealing focus
• Position anchoring -- Submenu position is calculated relative to the parent item's rectangle, adjusting to stay within screen bounds

Keyboard Navigation

BeepMenuBar.Keyboard.cs routes all keyboard input:

• Arrow keys -- Left/Right navigate between top-level items. Up/Down navigate within submenu items. Right on a parent item opens the submenu. Left on a submenu item closes it and returns to parent.
• Enter -- Invokes the active menu item command or opens its submenu
• Escape -- Closes the current submenu level, or dismisses the entire menu bar
• Mnemonics -- Alt+letter activates the menu item with matching mnemonic character
• Tab -- Cycles focus away from the menu bar

Helper Classes

High Contrast

BeepMenuBar.HighContrast.cs detects system high contrast mode via SystemInformation.HighContrast. When active:

• All theme colors are overridden with system-defined contrast colors
• Borders use SystemColors.ControlDark (2px thickness)
• Focus rectangles use SystemColors.Highlight
• Selection uses SystemColors.Highlight / SystemColors.HighlightText
• Icons are rendered in high-contrast-compatible mode (outline style)

Code Examples

var menu = new BeepMenuBar();
menu.Items.Add(new BeepMenuItem("File", null,
    new List<BeepMenuItem>
    {
        new BeepMenuItem("New", Icons.NewFile, () => NewFile()),
        new BeepMenuItem("Open", Icons.OpenFolder, () => OpenFile()),
        new BeepMenuSeparator(),
        new BeepMenuItem("Save", Icons.Save, () => SaveFile())
            { Shortcut = "Ctrl+S" },
        new BeepMenuItem("Exit", null, () => Application.Exit())
    }));
menu.Items.Add(new BeepMenuItem("Help", null,
    new List<BeepMenuItem>
    {
        new BeepMenuItem("About", Icons.Info, () => ShowAbout())
    }));