## checkbutton

Create and manipulate checkbutton widgets

### SYNOPSIS

(checkbutton widget-name ?options?)

### STANDARD OPTIONS

    :activebackground                      :activeforeground
    :anchor                                :background
    :bitmap                                :borderwidth
    :cursor                                :disabledforeground
    :font                                  :foreground
    :highlightbackground                   :highlightcolor
    :highlightthickness                    :image
    :justify                               :padx
    :pady                                  :relief
    :takefocus                             :text
    :textvariable                          :underline
    :wraplength

### WIDGET-SPECIFIC OPTIONS

Name: command
Class: Command
Option keyword: :command
STklos slot name: command
  Specifies a STk procedure to associate with the button. This procedure is typically invoked when mouse button 1 is released over the button window. The button's global variable (:variable option) will be updated before the procedure is invoked.

Name: environment
Class: Environment
Option keyword: :environment
STklos slot name: environment
  Specifies the environment in which the :textvariable must be taken. By default, the value of this option is the STk global environment.

Name: height
Class: Height
Option keyword: :height
STklos slot name: height
  Specifies a desired height for the button. If an image or bitmap is being displayed in the button then the value is in screen units (i.e. any of the forms acceptable to Tk_GetPixels); for text it is in lines of text. If this option isn't specified, the button's desired height is computed from the size of the image or bitmap or text being displayed in it.

Name: indicatorOn
Class: IndicatorOn
Option keyword: :indicatoron
STklos slot name: indicator-on
  Specifies whether or not the indicator should be drawn. Must be a proper boolean value. If false, the relief option is ignored and the widget's relief is always sunken if the widget is selected and raised otherwise.

Name: offValue
Class: Value
Option keyword: :offvalue
STklos slot name: off-value
  Specifies value to store in the button's associated variable whenever this button is deselected. Defaults to #f.

Name: onValue
Class: Value
Option keyword: :onvalue
STklos slot name: on-value
  Specifies value to store in the button's associated variable whenever this button is selected. Defaults to #t.

Name: selectColor
Class: Background
Option keyword: :selectcolor
STklos slot name: select-color
  Specifies a background color to use when the button is selected. If indicatorOn is true then the color applies to the indicator. Under Windows, this color is used as the background for the indicator regardless of the select state. If indicatorOn is false, this color is used as the background for the entire widget, in place of background or activeBackground, whenever the widget is selected. If specified as an empty string then no special color is used for displaying when the widget is selected.

Name: selectImage
Class: SelectImage
Option keyword: :selectimage
STklos slot name: select-image
  Specifies an image to display (in place of the image option) when the checkbutton is selected. This option is ignored unless the image option has been specified.

Name: state
Class: State
Option keyword: :state
STklos slot name: state
  Specifies one of three states for the checkbutton: normal, active, or disabled. In normal state the checkbutton is displayed using the foreground and background options. The active state is typically used when the pointer is over the checkbutton. In active state the checkbutton is displayed using the activeForeground and activeBackground options. Disabled state means that the checkbutton should be insensitive: the default bindings will refuse to activate the widget and will ignore mouse button presses. In this state the disabledForeground and background options determine how the checkbutton is displayed.

Name: stringvalue
Class: StringValue
Option keyword: :stringvalue
STklos slot name: string-value
  Specifies if the value set to variable by :offvalue or :onvalue must be stringified. For instance, with

    (checkbutton '.c :text "Try" :variable 'x :stringvalue #t
                     :onvalue 10 :offvalue 20)

the variabe x var is set to "10" or "20", whereas with

    (checkbutton '.c :text "Try" :variable 'x :stringvalue #f
                     :onvalue 10 :offvalue 20)

it is set to 10 or 20. Default value for :stringvalue is #t.

Name: variable
Class: Variable
Option keyword: :variable
STklos slot name: variable
  Specifies name of global variable to set to indicate whether or not this button is selected. Defaults to the name of the button within its parent (i.e. the last element of the button window's path name).

Name: width
Class: Width
Option keyword: :width
STklos slot name: width
  Specifies a desired width for the button. If an image or bitmap is being displayed in the button then the value is in screen units (i.e. any of the forms acceptable to Tk_GetPixels); for text it is in characters. If this option isn't specified, the button's desired width is computed from the size of the image or bitmap or text being displayed in it.

### DESCRIPTION

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

A checkbutton is a widget that displays a textual string, bitmap or image and a square called an indicator. If text is displayed, it must all be in a single font, but it can occupy multiple lines on the screen (if it contains newlines or if wrapping occurs because of the wrapLength option) and one of the characters may optionally be underlined using the underline option. A checkbutton has all of the behavior of a simple button, including the following: it can display itself in either of three different ways, according to the state option; it can be made to appear raised, sunken, or flat; it can be made to flash; and it invokes a STk procedure whenever mouse button 1 is clicked over the checkbutton.

In addition, checkbuttons can be selected. If a checkbutton is selected then the indicator is normally drawn with a selected appearance, and a STk variable associated with the checkbutton is set to a particular value (normally #t). Under Unix, the indicator is drawn with a sunken relief and a special color. Under Windows, the indicator is drawn with a check mark inside. If the checkbutton is not selected, then the indicator is drawn with a deselected appearance, and the associated variable is set to a different value (typically #f). Under Unix, the indicator is drawn with a raised relief and no special color. Under Windows, the indicator is drawn without a check mark inside. By default, the name of the variable associated with a checkbutton is the same as the name used to create the checkbutton. The variable name, and the ``on'' and ``off'' values stored in it, may be modified with options on the procedure line or in the option database. Configuration options may also be used to modify the way the indicator is displayed (or whether it is displayed at all). By default a checkbutton is configured to select and deselect itself on alternate button clicks. In addition, each checkbutton monitors its associated variable and automatically selects and deselects itself when the variables value changes to and from the button's ``on'' value.

### WIDGET PROCEDURE

The checkbutton procedure creates a new STk procedure whose name is widget-name. This procedure may be used to invoke various operations on the widget. It has the following general form:

    (widget-name option ?arg arg ...?)

Option and the args determine the exact behavior of the procedure. The following procedures are possible for checkbutton widgets:

(widget-name 'cget option)
  Returns the current value of the configuration option given by option. Option may have any of the values accepted by the checkbutton procedure.

(widget-name '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 widget-name (see Tk_ConfigureInfo for information on the format of this list). If option is specified with no value, then the procedure 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 procedure modifies the given widget option(s) to have the given value(s); in this case the procedure returns an empty list. Option may have any of the values accepted by the checkbutton procedure.

(widget-name 'deselect)
  Deselects the checkbutton and sets the associated variable to its ``off'' value.

(widget-name 'flash)
  Flashes the checkbutton. This is accomplished by redisplaying the checkbutton several times, alternating between active and normal colors. At the end of the flash the checkbutton is left in the same normal/active state as when the procedure was invoked. This procedure is ignored if the checkbutton's state is disabled.

(widget-name 'invoke)
  Does just what would have happened if the user invoked the checkbutton with the mouse: toggle the selection state of the button and invoke the STk procedure associated with the checkbutton, if there is one (return value is undefined) This procedure is ignored if the checkbutton's state is disabled.

(widget-name 'select)
  Selects the checkbutton and sets the associated variable to its ``on'' value.

(widget-name 'toggle)
  Toggles the selection state of the button, redisplaying it and modifying its associated variable to reflect the new state.

### BINDINGS

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

{[1]}
  On Unix systems, a checkbutton activates whenever the mouse passes over it and deactivates whenever the mouse leaves the checkbutton. On Windows systems, when mouse button 1 is pressed over a checkbutton, the button activates whenever the mouse pointer is inside the button, and deactivates whenever the mouse pointer leaves the button.

{[2]}
  When mouse button 1 is pressed over a checkbutton, it is invoked (its selection state toggles and the procedure associated with the button is invoked, if there is one).

{[3]}
  When a checkbutton has the input focus, the space key causes the checkbutton to be invoked. Under Windows, there are additional key bindings; plus (+) and equal (=) select the button, and minus (-) deselects the button.

If the checkbutton's state is disabled then none of the above actions occur: the checkbutton is completely non-responsive.

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

### SEE ALSO

button, radiobutton

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