menu - Create and manipulate menu widgets

SYNOPSIS

menu pathName ?options?

STANDARD OPTIONS

activeBackground	background	disabledForeground	relief
activeBorderWidth	borderWidth	font
activeForeground	cursor	foreground

See the options manual entry for details on the standard options.

WIDGET-SPECIFIC OPTIONS

Name:	postCommand
Class:	Command
Command-Line Switch:	-postcommand

Name:	selectColor
Class:	Background
Command-Line Switch:	-selectcolor

Name:	tearOff
Class:	TearOff
Command-Line Switch:	-tearoff

INTRODUCTION

The menu command creates a new top-level window (given by the pathName argument) and makes it into a menu widget. Additional options, described above, may be specified on the command line or in the option database to configure aspects of the menu such as its colors and font. The menu command returns its pathName argument. At the time this command is invoked, there must not exist a window named pathName, but pathName's parent must exist.

A menu is a widget that displays a collection of one-line entries arranged in a column. 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. A disabled entry cannot be activated or invoked. Disabled entries may be re-enabled, at which point it becomes possible to activate and invoke them again.

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 Tcl command is executed. The Tcl command 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 as a Tcl command 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 as a Tcl command 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. When the entry is activated, the associated menu is posted just to the right of the entry; that menu remains posted until the higher-level menu is unposted or until some other entry is activated in the higher-level menu. The associated menu should normally be a child of the menu containing the cascade entry, in order for menu traversal to work correctly.

A cascade entry posts its associated menu by invoking a Tcl command of the form

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. The lower-level menu is unposted by executing a Tcl command with the form

where menu is the name of the associated menu.

If a -command option is specified for a cascade entry then it is evaluated as a Tcl command each time the associated menu is posted (the evaluation occurs before the menu is posted).

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.

WIDGET COMMAND

The menu command creates a new Tcl command whose name is pathName. This command may be used to invoke various operations on the widget. It has the following general form:

pathName option ?arg arg ...?
Option and the args determine the exact behavior of the command.

Many of the widget commands 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.
last
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.
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 widget command. 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. The rules of Tcl_StringMatch are used.

The following widget commands are possible for menu widgets:

pathName 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.
pathName 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:
pathName cget option
Returns the current value of the configuration option given by option. Option may have any of the values accepted by the menu command.
pathName configure ?option? ?value option value ...?
Query or modify the configuration options of the widget. If no option is specified, returns a list describing all of the available options for pathName (see Tk_ConfigureInfo for information on the format of this list). If option is specified with no value, then the command returns a list describing the one named option (this list will be identical to the corresponding sublist of the value returned if no option is specified). If one or more option-value pairs are specified, then the command modifies the given widget option(s) to have the given value(s); in this case the command returns an empty string. Option may have any of the values accepted by the menu command.
pathName 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).
pathName 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 widget command.
pathName entryconfigure index ?options?
This command is similar to the configure command, 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 widget command. If options are specified, options are modified as indicated in the command and the command returns an empty string. If no options are specified, returns a list describing the current options for entry index (see Tk_ConfigureInfo for information on the format of this list).
pathName index index
Returns the numerical index corresponding to index, or none if index was specified as none.
pathName 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 command associated with it then the result of that command is returned as the result of the invoke widget command. 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 widget command.
pathName 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 command normally returns an empty string. If the postCommand option has been specified, then its value is executed as a Tcl script before posting the menu and the result of that script is returned as the result of the post widget command. If an error returns while executing the command, then the error is returned without posting the menu.
pathName type index
Returns the type of the menu entry given by index. This is the type argument passed to the add widget command when the entry was created, such as command or separator, or tearoff for a tear-off entry.
pathName 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.
pathName yposition index
Returns a decimal string giving the y-coordinate within the menu window of the topmost pixel in the entry specified by index.

MENU CONFIGURATIONS

The default bindings support four different ways of using menus:

Pulldown Menus
This is the most common case. 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.

DEFAULT BINDINGS

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

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

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

BUGS

At present it isn't possible to use the option database to specify values for the options to individual entries.

KEYWORDS

menu, widget