GCL TK Manual: radiobutton

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### 2.14 radiobutton

radiobutton \- Create and manipulate radio-button widgets

#### Synopsis

radiobutton pathName ?options?

#### Standard Options

    activeBackground  bitmap              font        relief
    activeForeground  borderWidth         foreground  text
    anchor            cursor              padX        textVariable
    background        disabledForeground  padX

See options, for more information.

#### Arguments for Radiobutton

`:command`

  Name=`"command" Class=`"`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.

`:height`

  Name=`"height" Class=`"`Height"`

  Specifies a desired height for the button. If a 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 bitmap or text being displayed in it.

`:selector`

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

  Specifies the color to draw in the selector when this button is selected. If specified as an empty string then no selector is drawn for the button.

`:state`

  Name=`"state" Class=`"`State"`

  Specifies one of three states for the radio button: normal, active, or disabled. In normal state the radio button is displayed using the foreground and background options. The active state is typically used when the pointer is over the radio button. In active state the radio button is displayed using the activeForeground and activeBackground options. Disabled state means that the radio button is insensitive: it doesn’t activate and doesn’t respond to mouse button presses. In this state the disabledForeground and background options determine how the radio button is displayed.

`:value`

  Name=`"value" Class=`"`Value"`

  Specifies value to store in the button’s associated variable whenever this button is selected. Defaults to the name of the radio button.

`:variable`

  Name=`"variable" Class=`"`Variable"`

  Specifies name of global variable to set whenever this button is selected. Changes in this variable also cause the button to select or deselect itself. Defaults to the value selectedButton.

`:width`

  Name=`"width" Class=`"`Width"`

  Specifies a desired width for the button. If a 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 bitmap or text being displayed in it.

#### Description

The radiobutton command creates a new window (given by the pathName argument) and makes it into a radiobutton widget. Additional options, described above, may be specified on the command line or in the option database to configure aspects of the radio button such as its colors, font, text, and initial relief. The radiobutton 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 radio button is a widget that displays a textual string or bitmap and a diamond called a selector. A radio button has all of the behavior of a simple button: 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, radio buttons can be selected. If a radio button is selected then a special highlight appears in the selector and a Tcl variable associated with the radio button is set to a particular value. If the radio button is not selected then the selector is drawn in a different fashion. Typically, several radio buttons share a single variable and the value of the variable indicates which radio button is to be selected. When a radio button is selected it sets the value of the variable to indicate that fact; each radio button also monitors the value of the variable and automatically selects and deselects itself when the variable’s value changes. By default the variable selectedButton is used; its contents give the name of the button that is selected, or the empty string if no button associated with that variable is selected. The name of the variable for a radio button, plus the variable to be stored into it, may be modified with options on the command line or in the option database. By default a radio button is configured to select itself on button clicks.

#### A Radiobutton Widget’s Arguments

The radiobutton 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 radio-button widgets:

pathName :activate

  Change the radio button’s state to active and redisplay the button using its active foreground and background colors instead of normal colors. This command is ignored if the radio button’s state is disabled. This command is obsolete and will eventually be removed; use “pathName :configure :state active” instead.

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 radiobutton command.

pathName :deactivate

  Change the radio button’s state to normal and redisplay the button using its normal foreground and background colors. This command is ignored if the radio button’s state is disabled. This command is obsolete and will eventually be removed; use “pathName :configure :state normal” instead.

pathName :deselect

  Deselect the radio button: redisplay it without a highlight in the selector and set the associated variable to an empty string. If this radio button was not currently selected, then the command has no effect.

pathName :flash

  Flash the radio button. This is accomplished by redisplaying the radio button several times, alternating between active and normal colors. At the end of the flash the radio button is left in the same normal/active state as when the command was invoked. This command is ignored if the radio button’s state is disabled.

pathName :invoke

  Does just what would have happened if the user invoked the radio button with the mouse: select the button and invoke its associated Tcl command, 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 radio button. This command is ignored if the radio button’s state is disabled.

pathName :select

  Select the radio button: display it with a highlighted selector and set the associated variable to the value corresponding to this widget.

#### Bindings

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

- [1] The radio button activates whenever the mouse passes over it and deactivates whenever the mouse leaves the radio button.
- [2] The radio button’s relief is changed to sunken whenever mouse button 1 is pressed over it, and the relief is restored to its original value when button 1 is later released.
- [3] If mouse button 1 is pressed over the radio button and later released over the radio button, the radio button is invoked (i.e. it is selected and the command associated with the button is invoked, if there is one). However, if the mouse is not over the radio button when button 1 is released, then no invocation occurs.

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

#### Keywords

radio button, widget

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