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The checkbutton command creates a new window (given by the pathName argument) and makes it into a check-button widget. Additional options, described above, may be specified on the command line or in the option database to configure aspects of the check button 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 check button is a widget that displays a textual string or bitmap and a square called a selector. A check button 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 check button.

In addition, check buttons can be selected. If a check button is selected then a special highlight appears in the selector, and a Tcl variable associated with the check button is set to a particular value (normally 1). If the check button is not selected, then the selector is drawn in a different fashion and the associated variable is set to a different value (typically 0). By default, the name of the variable associated with a check button is the same as the name used to create the check button. 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. By default a check button is configured to select and deselect itself on alternate button clicks. In addition, each check button monitors its associated variable and automatically selects and deselects itself when the variables value changes to and from the button's "on" value.

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