GCL TK Manual: menu

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### 2.5 menu

menu \- Create and manipulate menu widgets

#### Synopsis

menu pathName ?options?

#### Standard Options

    activeBackground       background       disabledForeground
    activeBorderWidth      borderWidth      font
    activeForeground       cursor           foreground

See options, for more information.

#### Arguments for Menu

`: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.

`:selector`

  Name=`"selector" Class=`"`Foreground"`

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

#### 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 text or a bitmap, which is determined by the :label or :bitmap option 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 a selector. The selector is present only for check-button or radio-button 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.

#### Check-Button Entries

A check-button menu entry behaves much like a check-button 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. A selector box is displayed to the left of the label in a check-button entry. If the entry is selected then the box’s center is displayed in the color given by the selector option for the menu; otherwise the box’s center is displayed in the background color for the menu. If a :command option is specified for a check-button 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.

#### Radio-Button Entries

A radio-button menu entry behaves much like a radio-button widget. Radio-button 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 radio-button entries is determined by their associated variables: if two entries have the same associated variable then they are in the same group. A selector diamond is displayed to the left of the label in each radio-button entry. If the entry is selected then the diamond’s center is displayed in the color given by the selector option for the menu; otherwise the diamond’s center is displayed in the background color for the menu. If a :command option is specified for a radio-button 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

menu :post x y

  where menu is the path name of the associated menu, x and y are the root-window coordinates of the upper-right corner of the cascade entry, and group is the name of the menu’s group (as determined in its last post widget command). 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 each time the associated menu is posted (the evaluation occurs before the menu is posted).

#### A Menu Widget’s Arguments

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 spanning that y-coordinate is used. For example, “@0” indicates the top-most entry in the window. If number is outside the range of the window then this form is equivalent to none.

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. This option is not available for separator 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 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 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. This option is not available for separator entries.

  :command value

    For command, checkbutton, and radiobutton entries, specifies a Tcl command to execute when the menu entry is invoked. For cascade entries, specifies a Tcl command to execute when the entry is activated (i.e. just before its submenu is posted). Not available for separator 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 entries.

  :label value

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

  :menu value

    Available only for cascade entries. Specifies the path name of the menu associated with this entry.

  :offvalue value

    Available only for check-button entries. Specifies the value to store in the entry’s associated variable when the entry is deselected.

  :onvalue value

    Available only for check-button entries. Specifies the value to store in the entry’s associated variable when the entry is selected.

  :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 is insensitive: it doesn’t activate and doesn’t respond to mouse button presses or releases. 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 typically used to indicate keyboard traversal characters. 0 corresponds to the first character of the text displayed in the entry, 1 to the next character, and so on. If a bitmap is displayed in the entry then this option is ignored. This option is not available for separator entries.

  :value value

    Available only for radio-button entries. Specifies the value to store in the entry’s associated variable when the entry is selected.

  :variable value

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

The add widget command returns an empty string.

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. Returns an empty string.

pathName :disable index

  Change the state of the entry given by index to disabled and redisplay the entry using its disabled colors. Returns an empty string. This command is obsolete and will eventually be removed; use “pathName :entryconfigure index :state disabled” instead.

pathName :enable index

  Change the state of the entry given by index to normal and redisplay the entry using its normal colors. Returns an empty string. This command is obsolete and will eventually be removed; use “pathName :entryconfigure index :state normal” instead.

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. Normally the associated menubutton will take care of unposting the menu.

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 :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.

#### Default Bindings

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

- [1] When the mouse cursor enters a menu, the entry underneath the mouse cursor is activated; as the mouse moves around the menu, the active entry changes to track the mouse.
- [2] When button 1 is released over a menu, the active entry (if any) is invoked.
- [3] A menu can be repositioned on the screen by dragging it with mouse button 2.
- [4] A number of other bindings are created to support keyboard menu traversal. See the manual entry for tk_bindForTraversal for details on these bindings.

Disabled menu entries are non-responsive: they don’t activate and 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

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