COMMAND ENTRIES

The most common kind of menu entry is a command entry, which behaves much like a button widget. When a command entry is invoked, a callback is executed. The callback is specified with the -command option.

SEPARATOR ENTRIES

A separator is an entry that is displayed as a horizontal dividing line. A separator may not be activated or invoked, and it has no behavior other than its display appearance.

CHECKBUTTON ENTRIES

A checkbutton menu entry behaves much like a checkbutton widget. When it is invoked it toggles back and forth between the selected and deselected states. When the entry is selected, a particular value is stored in a particular global variable (as determined by the -onvalue and -variable options for the entry); when the entry is deselected another value (determined by the -offvalue option) is stored in the global variable. An indicator box is displayed to the left of the label in a checkbutton entry. If the entry is selected then the indicator's center is displayed in the color given by the -selectcolor option for the entry; otherwise the indicator's center is displayed in the background color for the menu. If a -command option is specified for a checkbutton entry, then its value is evaluated each time the entry is invoked; this happens after toggling the entry's selected state.

RADIOBUTTON ENTRIES

A radiobutton menu entry behaves much like a radiobutton widget. Radiobutton entries are organized in groups of which only one entry may be selected at a time. Whenever a particular entry becomes selected it stores a particular value into a particular global variable (as determined by the -value and -variable options for the entry). This action causes any previously-selected entry in the same group to deselect itself. Once an entry has become selected, any change to the entry's associated variable will cause the entry to deselect itself. Grouping of radiobutton entries is determined by their associated variables: if two entries have the same associated variable then they are in the same group. An indicator diamond is displayed to the left of the label in each radiobutton entry. If the entry is selected then the indicator's center is displayed in the color given by the -selectcolor option for the entry; otherwise the indicator's center is displayed in the background color for the menu. If a -command option is specified for a radiobutton entry, then its value is evaluated each time the entry is invoked; this happens after selecting the entry.

CASCADE ENTRIES

A cascade entry is one with an associated menu (determined by the -menu option). Cascade entries allow the construction of cascading menus. The postcascade method can be used to post and unpost the associated menu just next to of the cascade entry. The associated menu must be a child of the menu containing the cascade entry (this is needed in order for menu traversal to work correctly).

A cascade entry posts its associated menu by invoking

where menu is the path name of the associated menu, and x and y are the root-window coordinates of the upper-right corner of the cascade entry. On Unix, the lower-level menu is unposted by executing

where menu is the name of the associated menu. On other platforms, the platform's native code takes care of unposting the menu.

If a -command option is specified for a cascade entry then it is evaluated whenever the entry is invoked. This is not supported on Windows.

TEAR-OFF ENTRIES

A tear-off entry appears at the top of the menu if enabled with the tearOff option. It is not like other menu entries in that it cannot be created with the add method and cannot be deleted with the delete method. When a tear-off entry is created it appears as a dashed line at the top of the menu. Under the default bindings, invoking the tear-off entry causes a torn-off copy to be made of the menu and all of its submenus.

MENUBARS

Any menu can be set as a menubar for a toplevel window (see the Toplevel constructor for syntax). On the Macintosh, whenever the toplevel is in front, this menu's cascade items will appear in the menubar across the top of the main monitor. On Windows and Unix, this menu's items will be displayed in a menubar accross the top of the window. These menus will behave according to the interface guidelines of their platforms. For every menu set as a menubar, a clone menu is made. See "CLONES" for more information.

As noted, menubars may behave differently on different platforms. One example of this concerns the handling of checkbuttons and radiobuttons within the menu. While it is permitted to put these menu elements on menubars, they may not be drawn with indicators on some platforms, due to system restrictions.

SPECIAL MENUS IN MENUBARS

Certain menus in a menubar will be treated specially. On the Macintosh, access to the special Apple and Help menus is provided. On Windows, access to the Windows System menu in each window is provided. On X Windows, a special right-justified help menu is provided. In all cases, these menus must be created with the command name of the menubar menu concatenated with the special name. So for a menubar named .menubar, on the Macintosh, the special menus would be .menubar.apple and .menubar.help; on Windows, the special menu would be .menubar.system; on X Windows, the help menu would be .menubar.help.

When Tk sees an Apple menu on the Macintosh, that menu's contents make up the first items of the Apple menu on the screen whenever the window containing the menubar is in front. The menu is the first one that the user sees and has a title which is an Apple logo. After all of the Tk-defined items, the menu will have a separator, followed by all of the items in the user's Apple Menu Items folder. Since the System uses a different menu definition procedure for the Apple menu than Tk uses for its menus, and the system APIs do not fully support everything Tk tries to do, the menu item will only have its text displayed. No font attributes, images, bitmaps, or colors will be displayed. In addition, a menu with a tearoff item will have the tearoff item displayed as "(TearOff)".

When Tk see a Help menu on the Macintosh, the menu's contents are appended to the standard help menu on the right of the user's menubar whenever the user's menubar is in front. The first items in the menu are provided by Apple. Similar to the Apple Menu, cusomization in this menu is limited to what the system provides.

When Tk sees a System menu on Windows, its items are appended to the system menu that the menubar is attached to. This menu has an icon representing a spacebar, and can be invoked with the mouse or by typing Alt+Spacebar. Due to limitations in the Windows API, any font changes, colors, images, bitmaps, or tearoff images will not appear in the system menu.

When Tk see a Help menu on X Windows, the menu is moved to be last in the menubar and is right justified.

CLONES

When a menu is set as a menubar for a toplevel window, or when a menu is torn off, a clone of the menu is made. This clone is a menu widget in its own right, but it is a child of the original. Changes in the configuration of the original are reflected in the clone. Additionally, any cascades that are pointed to are also cloned so that menu traversal will work right. Clones are destroyed when either the tearoff or menubar goes away, or when the original menu is destroyed.

WIDGET METHODS

The Menu method creates a widget object. This object supports the configure and cget methods described in Tk::options which can be used to enquire and modify the options described above. The widget also inherits all the methods provided by the generic Tk::Widget class, and the Tk::Wm class.

Many of the methods for a menu take as one argument an indicator of which entry of the menu to operate on. These indicators are called indexes and may be specified in any of the following forms:

number

Specifies the entry numerically, where 0 corresponds to the top-most entry of the menu, 1 to the entry below it, and so on.

active

Indicates the entry that is currently active. If no entry is active then this form is equivalent to none. This form may not be abbreviated.

end

Indicates the bottommost entry in the menu. If there are no entries in the menu then this form is equivalent to none. This form may not be abbreviated.

last

Same as end.

none

Indicates ``no entry at all''; this is used most commonly with the activate option to deactivate all the entries in the menu. In most cases the specification of none causes nothing to happen in the method. This form may not be abbreviated.

@number

In this form, number is treated as a y-coordinate in the menu's window; the entry closest to that y-coordinate is used. For example, ``@0'' indicates the top-most entry in the window.

pattern

If the index doesn't satisfy one of the above forms then this form is used. Pattern is pattern-matched against the label of each entry in the menu, in order from the top down, until a matching entry is found. (In perl/Tk the matching is under review, but exact match should work.)

The following methods are possible for menu widgets:

$menu->activate(index)

Change the state of the entry indicated by index to active and redisplay it using its active colors. Any previously-active entry is deactivated. If index is specified as none, or if the specified entry is disabled, then the menu ends up with no active entry. Returns an empty string.

$menu->add(type, ?option, value, option, value, ...?)

Add a new entry to the bottom of the menu. The new entry's type is given by type and must be one of cascade, checkbutton, command, radiobutton, or separator, or a unique abbreviation of one of the above. If additional arguments are present, they specify any of the following options:

$menu->clone($parent ?, cloneType?)

Makes a clone of the current menu as a child of $parent. This clone is a menu in its own right, but any changes to the clone are propogated to the original menu and vice versa. cloneType can be normal, menubar, or tearoff. Should not normally be called outside of the Tk library. See "CLONES" for more information.

$menu->delete(index1?, index2?)

Delete all of the menu entries between index1 and index2 inclusive. If index2 is omitted then it defaults to index1. Attempts to delete a tear-off menu entry are ignored (instead, you should change the tearOff option to remove the tear-off entry).

$menu->entrycget(index, option)

Returns the current value of a configuration option for the entry given by index. Option may have any of the values accepted by the add method.

$menu->entryconfigure(index ?,options?)

This method is similar to the configure method, except that it applies to the options for an individual entry, whereas configure applies to the options for the menu as a whole. Options may have any of the values accepted by the add method. If options are specified, options are modified as indicated in the method call and the method returns an empty string. If no options are specified, returns a list describing the current options for entry index (see Tk::options for information on the format of this list).

$menu->index(index)

Returns the numerical index corresponding to index, or none if index was specified as none.

$menu->insert(index, type?, -option=>value, ...?)

Same as the add method except that it inserts the new entry just before the entry given by index, instead of appending to the end of the menu. The type, -option, and value arguments have the same interpretation as for the add widget method. It is not possible to insert new menu entries before the tear-off entry, if the menu has one.

$menu->invoke(index)

Invoke the action of the menu entry. See the sections on the individual entries above for details on what happens. If the menu entry is disabled then nothing happens. If the entry has a callback associated with it then the result of that callback is returned as the result of the invoke widget method. Otherwise the result is an empty string. Note: invoking a menu entry does not automatically unpost the menu; the default bindings normally take care of this before invoking the invoke method.

$menu->post(x, y)

Arrange for the menu to be displayed on the screen at the root-window coordinates given by x and y. These coordinates are adjusted if necessary to guarantee that the entire menu is visible on the screen. This method normally returns an empty string. If the postCommand option has been specified, then its value is executed before posting the menu and the result of that callback is returned as the result of the post widget method. If an error returns while executing the method, then the error is returned without posting the menu.

$menu->postcascade(index)

Posts the submenu associated with the cascade entry given by index, and unposts any previously posted submenu. If index doesn't correspond to a cascade entry, or if $menu isn't posted, the method has no effect except to unpost any currently posted submenu.

$menu->type(index)

Returns the type of the menu entry given by index. This is the type argument passed to the add widget method when the entry was created, such as command or separator, or tearoff for a tear-off entry.

$menu->unpost

Unmap the window so that it is no longer displayed. If a lower-level cascaded menu is posted, unpost that menu. Returns an empty string. This method does not work on Windows and the Macintosh, as those platforms have their own way of unposting menus.

$menu->yposition(index)

Returns a decimal string giving the y-coordinate within the menu window of the topmost pixel in the entry specified by index.