# checkbutton - Create and manipulate checkbutton widgets

## SYNOPSIS

checkbutton pathName ?options?

## STANDARD OPTIONS

    activeBackground	cursor	highlightThickness	takeFocus
    activeForeground	disabledForeground	image	text
    anchor	font	justify	textVariable
    background	foreground	padX	underline
    bitmap	highlightBackground	padY	wrapLength
    borderWidth	highlightColor	relief

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

## WIDGET-SPECIFIC OPTIONS

    Name:	command
    Class:	Command
    Command-Line Switch:	-command

Specifies a Tcl command to associate with the button. This command 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 command is invoked.

    Name:	height
    Class:	Height
    Command-Line Switch:	-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
    Command-Line Switch:	-indicatoron

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
    Command-Line Switch:	-offvalue

Specifies value to store in the button's associated variable whenever this button is deselected. Defaults to ``0''.

    Name:	onValue
    Class:	Value
    Command-Line Switch:	-onvalue

Specifies value to store in the button's associated variable whenever this button is selected. Defaults to ``1''.

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

Specifies a background color to use when the button is selected. If indicatorOn is true then the color applicies to the indicator. 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
    Command-Line Switch:	-selectimage

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
    Command-Line Switch:	-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:	variable
    Class:	Variable
    Command-Line Switch:	-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
    Command-Line Switch:	-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 command creates a new window (given by the pathName argument) and makes it into a checkbutton widget. Additional options, described above, may be specified on the command line or in the option database to configure aspects of the checkbutton such as its colors, font, text, and initial relief. The checkbutton 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 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 Tcl command 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 sunken relief and a special color, and a Tcl variable associated with the checkbutton is set to a particular value (normally 1). If the checkbutton is not selected, then the indicator is drawn with a raised relief and no special color, and the associated variable is set to a different value (typically 0). 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 command 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 COMMAND

The checkbutton 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. The following commands are possible for checkbutton widgets:

pathName cget option
  Returns the current value of the configuration option given by option. Option may have any of the values accepted by the checkbutton 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 checkbutton command.

pathName deselect
  Deselects the checkbutton and sets the associated variable to its ``off'' value.

pathName 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 command was invoked. This command is ignored if the checkbutton's state is disabled.

pathName 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 Tcl command associated with the checkbutton, if there is one. The return value is the return value from the Tcl command, or an empty string if there is no command associated with the checkbutton. This command is ignored if the checkbutton's state is disabled.

pathName select
  Selects the checkbutton and sets the associated variable to its ``on'' value.

pathName 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]
A checkbutton activates whenever the mouse passes over it and deactivates whenever the mouse leaves the checkbutton.

[2]
When mouse button 1 is pressed over a checkbutton it is invoked (its selection state toggles and the command 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.

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.

## KEYWORDS

checkbutton, widget