menu - Create and manipulate menu widgets

SYNOPSIS

Switch:  -postcommand  
Name: postCommand
Class: Command

If this option is specified then it provides a Tcl command to execute each time the menu is posted. The command is invoked by the post widget command before posting the menu.

Switch:  -selectcolor  
Name: selectColor
Class: Background

For menu entries that are check buttons or radio buttons, this option specifies the color to display in the indicator when the check button or radio button is selected.

Switch:  -tearoff  
Name: tearOff
Class: TearOff

This option must have a proper boolean value, which specifies whether or not the menu should include a tear-off entry at the top. If so, it will exist as entry 0 of the menu and the other entries will number starting at 1. The default menu bindings arrange for the menu to be torn off when the tear-off entry is invoked.

Switch:  -tearoffcommand  
Name: tearOffCommand
Class: TearOffCommand

If this option has a non-empty value, then it specifies a Tcl command to invoke whenever the menu is torn off. The actual command will consist of the value of this option, followed by a space, followed by the name of the menu window, followed by a space, followed by the name of the name of the torn off menu window. For example, if the option's is ``a b'' and menu .x.y is torn off to create a new menu .x.tearoff1, then the command ``a b .x.y .x.tearoff1'' will be invoked.

Switch:  -transient  
Name: transient
Class: Transient

This option must have a boolean value. True means that the menu is used on a transient basis, e.g. as a pop-up, pull-down, or cascaded menu. False means that the menu will be displayed on the screen continuously, for example as a torn-off menu. If the option is true, no window manager border will be displayed around the menu and redisplay will be optimized using X's ``save under'' facility.

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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. 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.

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. The postcascade widget command can be used to post and unpost the associated menu just to the right 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. 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.

If a -command option is specified for a cascade entry then it is evaluated as a Tcl command whenever the entry is invoked.

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.

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 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:

-activebackground value

Specifies a background color to use for displaying this entry when it is active. If this option is specified as an empty string (the default), then the activeBackground option for the overall menu is used. If the tk_strictMotif variable has been set to request strict Motif compliance, then this option is ignored and the -background option is used in its place. This option is not available for separator or tear-off entries.

-activeforeground value

Specifies a foreground color to use for displaying this entry when it is active. If this option is specified as an empty string (the default), then the activeForeground option for the overall menu is used. This option is not available for separator or tear-off entries.

-accelerator value

Specifies a string to display at the right side of the menu entry. Normally describes an accelerator keystroke sequence that may be typed to invoke the same function as the menu entry. This option is not available for separator or tear-off entries.

-background value

Specifies a background color to use for displaying this entry when it is in the normal state (neither active nor disabled). If this option is specified as an empty string (the default), then the background option for the overall menu is used. This option is not available for separator or tear-off entries.

-bitmap value

Specifies a bitmap to display in the menu instead of a textual label, in any of the forms accepted by Tk_GetBitmap. This option overrides the -label option but may be reset to an empty string to enable a textual label to be displayed. If a -image option has been specified, it overrides -bitmap. This option is not available for separator or tear-off entries.

-command value

Specifies a Tcl command to execute when the menu entry is invoked. Not available for separator or tear-off entries.

-font value

Specifies the font to use when drawing the label or accelerator string in this entry. If this option is specified as an empty string (the default) then the font option for the overall menu is used. This option is not available for separator or tear-off entries.

-foreground value

Specifies a foreground color to use for displaying this entry when it is in the normal state (neither active nor disabled). If this option is specified as an empty string (the default), then the foreground option for the overall menu is used. This option is not available for separator or tear-off entries.

-image value

Specifies an image to display in the menu instead of a text string or bitmap The image must have been created by some previous invocation of image create. This option overrides the -label and -bitmap options but may be reset to an empty string to enable a textual or bitmap label to be displayed. This option is not available for separator or tear-off entries.

-indicatoron value

Available only for checkbutton and radiobutton entries. Value is a boolean that determines whether or not the indicator should be displayed.

-label value

Specifies a string to display as an identifying label in the menu entry. Not available for separator or tear-off entries.

-menu value

Available only for cascade entries. Specifies the path name of the submenu associated with this entry. The submenu must be a child of the menu.

-offvalue value

Available only for checkbutton entries. Specifies the value to store in the entry's associated variable when the entry is deselected.

-onvalue value

Available only for checkbutton entries. Specifies the value to store in the entry's associated variable when the entry is selected.

-selectcolor value

Available only for checkbutton and radiobutton entries. Specifies the color to display in the indicator when the entry is selected. If the value is an empty string (the default) then the selectColor option for the menu determines the indicator color.

-selectimage value

Available only for checkbutton and radiobutton entries. Specifies an image to display in the entry (in place of the -image option) when it is selected. Value is the name of an image, which must have been created by some previous invocation of image create. This option is ignored unless the -image option has been specified.

-state value

Specifies one of three states for the entry: normal, active, or disabled. In normal state the entry is displayed using the foreground option for the menu and the background option from the entry or the menu. The active state is typically used when the pointer is over the entry. In active state the entry is displayed using the activeForeground option for the menu along with the activebackground option from the entry. Disabled state means that the entry should be insensitive: the default bindings will refuse to activate or invoke the entry. In this state the entry is displayed according to the disabledForeground option for the menu and the background option from the entry. This option is not available for separator entries.

-underline value

Specifies the integer index of a character to underline in the entry. This option is also queried by the default bindings and used to implement keyboard traversal. 0 corresponds to the first character of the text displayed in the entry, 1 to the next character, and so on. If a bitmap or image is displayed in the entry then this option is ignored. This option is not available for separator or tear-off entries.

-value value

Available only for radiobutton entries. Specifies the value to store in the entry's associated variable when the entry is selected.

-variable value

Available only for checkbutton and radiobutton entries. Specifies the name of a global value to set when the entry is selected. For checkbutton entries the variable is also set when the entry is deselected. For radiobutton entries, changing the variable causes the currently-selected entry to deselect itself.

The add widget command returns an empty string.

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 insert index type ?option value option value ...?

Same as the add widget command 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 command. It is not possible to insert new menu entries before the tear-off entry, if the menu has one.

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 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 pathName isn't posted, the command has no effect except to unpost any currently posted submenu.

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:

[1]
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.

[2]
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.

[3]
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.

[4]
The Space and Return keys invoke the active entry and unpost the menu.

[5]
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.

[6]
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.

[7]
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.

[8]
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.

[9]
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.

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