Editing Macintosh Toolbox (section)

=== Menu Manager ===
The Menu Manager maintains hierarchical menus with a sophisticated caching and drawing system:

'''Menu Structure:'''
<pre>
TYPE MenuInfo = RECORD
    menuID:     INTEGER;        {Unique menu identifier}
    menuWidth:  INTEGER;        {Pixel width when drawn}
    menuHeight: INTEGER;        {Pixel height when drawn}
    menuProc:   Handle;         {MDEF resource handle}
    enableFlags: LONGINT;       {Item enable bits}
    menuData:   Str255;         {Pascal string menu items}
END;
</pre>

'''Menu Bar Structure:'''
The menu bar is stored as a relocatable block containing:
# Number of menus (2 bytes)
# Array of menu handles (4 bytes each)
# Total width calculation cache

'''Menu Definition Procedures (MDEFs):'''
* '''MDEF 0''': Standard text menu
* '''MDEF 1''': Scrolling menu (System 7)
* '''MDEF 2''': Popup menu variant