Create and manipulate button widgets

## NAME

button - Create and manipulate button widgets

## SYNOPSIS

$button = $parent->Button(?options?);

## STANDARD OPTIONS

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

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

## WIDGET-SPECIFIC OPTIONS

Name: command
Class: Command
Configure Option: -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.

Name: height
Class: Height
Configure Option: -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: state
Class: State
Configure Option: -state
  Specifies one of three states for the button: normal, active, or disabled. In normal state the button is displayed using the foreground and background options. The active state is typically used when the pointer is over the button. In active state the button is displayed using the activeForeground and activeBackground options. Disabled state means that the button 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 button is displayed.

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

A button is a widget that displays a textual string, bitmap or image. 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. 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; and it can be made to flash. When a user invokes the button (by pressing mouse button 1 with the cursor over the button), then the Tcl command specified in the -command option is invoked.

## WIDGET METHODS

The button command creates a widget object whose name is $widget. This command may be used to invoke various operations on the widget. It has the following general form:

    $button->method(?arg arg ...?)

Option and the args determine the exact behavior of the command. The following commands are possible for button widgets:

$button->cget(option)
  Returns the current value of the configuration option given by option. Option may have any of the values accepted by the button command.
$button->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 (see configure 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 button command.
$button->flash
  Flash the button. This is accomplished by redisplaying the button several times, alternating between active and normal colors. At the end of the flash the button is left in the same normal/active state as when the command was invoked. This command is ignored if the button's state is disabled.
$button->invoke
  Invoke the Tcl command associated with the button, 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 button. This command is ignored if the button's state is disabled.

## DEFAULT BINDINGS

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

1. A button activates whenever the mouse passes over it and deactivates whenever the mouse leaves the button.
2. A button's relief is changed to sunken whenever mouse button 1 is pressed over the button, and the relief is restored to its original value when button 1 is later released.
3. If mouse button 1 is pressed over a button and later released over the button, the button is invoked. However, if the mouse is not over the button when button 1 is released, then no invocation occurs.
4. When a button has the input focus, the space key causes the button to be invoked.

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

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

## KEYWORDS

button, widget