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1. Tkinter.Menu - create and manipulate menu widgets

The menu command creates a new top-level window and makes it into a menu widget. Additional options may be specified in the constructor or in the option database to configure aspects of the menu such as its colors and font.

A menu is a widget that displays a collection of one-line entries arranged in one or more columns. There exist several different types of entries, each with different properties. Entries of different types may be combined in a single menu. Menu entries are not the same as entry widgets. In fact, menu entries are not even distinct widgets; the entire menu is one widget.

Menu entries are displayed with up to three separate fields. The main field is a label in the form of a text string, a bitmap, or an image, controlled by the label, bitmap, and image options for the entry. If the accelerator option is specified for an entry then a second textual field is displayed to the right of the label. The accelerator typically describes a keystroke sequence that may be typed in the application to cause the same result as invoking the menu entry. The third field is an indicator. The indicator is present only for checkbutton or radiobutton entries. It indicates whether the entry is selected or not, and is displayed to the left of the entry's string.

In normal use, an entry becomes active (displays itself differently) whenever the mouse pointer is over the entry. If a mouse button is released over the entry then the entry is invoked. The effect of invocation is different for each type of entry; these effects are described below in the sections on individual entries.

Entries may be disabled, which causes their labels and accelerators to be displayed with dimmer colors. The default menu bindings will not allow a disabled entry to be activated or invoked. Disabled entries may be re-enabled, at which point it becomes possible to activate and invoke them again.

Whenever a menu's active entry is changed, a <<MenuSelect>> virtual event is sent to the menu. The active item can then be queried from the menu, and an action can be taken, such as setting context-sensitive help text for the entry.

1.1. 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 command is executed. The command is specified with the command option, which can be a Python callable or a string containing a Tcl command.

1.2. 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.

1.3. 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 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 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 it is called each time the entry is invoked; this happens after toggling the entry's selected state.

1.4. 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 it is called each time the entry is invoked; this happens after selecting the entry.

1.5. 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 widget command 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 a Tcl command of the form

menu post x y

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 a Tcl command with the form

menu unpost

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 called whenever the entry is invoked. This is not supported on Windows.

1.6. 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 widget command and cannot be deleted with the delete widget command. 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.

1.7. Menubars

Any menu can be set as a menubar for a toplevel window (see toplevel command 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 the CLONES section 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.

1.8. 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. [XXX how to create widgets with these names in Tkinter]

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.

1.9. 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.

= Menu Configurations =

The default bindings support four different ways of using menus:

Pulldown Menus in Menubar

This is the most command case. You create a menu widget that will become the menu bar. You then add cascade entries to this menu, specifying the pull down menus you wish to use in your menu bar. You then create all of the pulldowns. Once you have done this, specify the menu using the -menu option of the toplevel's widget command. See the toplevel manual entry for details.

Pulldown Menus in Menu Buttons

This is the compatable way to do menu bars. You create one menubutton widget for each top-level menu, and typically you arrange a series of menubuttons in a row in a menubar window. You also create the top-level menus and any cascaded submenus, and tie them together with -menu options in menubuttons and cascade menu entries. The top-level menu must be a child of the menubutton, and each submenu must be a child of the menu that refers to it. Once you have done this, the default bindings will allow users to traverse and invoke the tree of menus via its menubutton; see the menubutton manual entry for details.

Popup Menus

Popup menus typically post in response to a mouse button press or keystroke. You create the popup menus and any cascaded submenus, then you call the tk_popup procedure at the appropriate time to post the top-level menu.

Option Menus

An option menu consists of a menubutton with an associated menu that allows you to select one of several values. The current value is displayed in the menubutton and is also stored in a global variable. Use the tk_optionMenu procedure to create option menubuttons and their menus.

Torn-off Menus

You create a torn-off menu by invoking the tear-off entry at the top of an existing menu. The default bindings will create a new menu that is a copy of the original menu and leave it permanently posted as a top-level window. The torn-off menu behaves just the same as the original menu.

2. Default Bindings

Tk automatically creates class bindings for menus that give them the following default behavior:

When the mouse enters a menu, the entry underneath the mouse cursor activates; as the mouse moves around the menu, the active entry changes to track the mouse.
When the mouse leaves a menu all of the entries in the menu deactivate, except in the special case where the mouse moves from a menu to a cascaded submenu.
When a button is released over a menu, the active entry (if any) is invoked. The menu also unposts unless it is a torn-off menu.
The Space and Return keys invoke the active entry and unpost the menu.
If any of the entries in a menu have letters underlined with with -underline option, then pressing one of the underlined letters (or its upper-case or lower-case equivalent) invokes that entry and unposts the menu.
The Escape key aborts a menu selection in progress without invoking any entry. It also unposts the menu unless it is a torn-off menu.
The Up and Down keys activate the next higher or lower entry in the menu. When one end of the menu is reached, the active entry wraps around to the other end.
The Left key moves to the next menu to the left. If the current menu is a cascaded submenu, then the submenu is unposted and the current menu entry becomes the cascade entry in the parent. If the current menu is a top-level menu posted from a menubutton, then the current menubutton is unposted and the next menubutton to the left is posted. Otherwise the key has no effect. The left-right order of menubuttons is determined by their stacking order: Tk assumes that the lowest menubutton (which by default is the first one created) is on the left.
The Right key moves to the next menu to the right. If the current entry is a cascade entry, then the submenu is posted and the current menu entry becomes the first entry in the submenu. Otherwise, if the current menu was posted from a menubutton, then the current menubutton is unposted and the next menubutton to the right is posted.

Disabled menu entries are non-responsive: they don't activate and they ignore mouse button presses and releases.

Several of the bindings make use of the command tk_menuSetFocus. It saves the current focus and sets the focus to its pathName argument, which is a menu widget.

The behavior of menus can be changed by defining new bindings for individual widgets or by redefining the class bindings.

3. Base Classes

?../Widget ?../BaseWidget ?../Misc ?../Pack ?../Place ?../Grid

4. Gotchas

In addition to the system-specific limitations mentioned in the menu manpage, Changes to the font or color are ignored if the menu is an instance of the Menu class and the -menu of a ?Tk or ?Toplevel window on Microsoft Windows and possibly Apple Mac. If you require a menu with a different font or foreground color you may consider using the ?Menubutton

[Would someone like to re-word this?] - I'll try MF Original thread: http://mail.python.org/pipermail/tkinter-discuss/2004-September/000164.html

5. References

pydoc Tkinter.Menu

http://www.pythonware.com/library/tkinter/introduction/menu.htm

http://wiki.tcl.tk/menu

http://www.purl.org/tcl/home/man/tcl8.4/TkCmd/menu.htm

Immutable page [current page size 15305 bytes] (last edited 2007-03-26 13:49:46 by JeffEpler)
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