Tk Built-In Commands - button manual page

## button

Create and manipulate button widgets

### SYNOPSIS

(button 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. OP :default default Default default Specifies one of three states for the default ring: "normal", "active", or "disabled". In active state, the button is drawn with the platform specific appearance for a default button. In normal state, the button is drawn with the platform specific appearance for a non-default button, leaving enough space to draw the default button appearance. The normal and active states will result in buttons of the same size. In disabled state, the button is drawn with the non-default button appearance without leaving space for the default appearance. The disabled state may result in a smaller button than the active state. ring.

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: state
Class: State
Option keyword: :state
STklos slot name: 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
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 button procedure creates a new window (given by the widget-name argument) and makes it into a button widget. Additional options, described above, may be specified on the procedure line or in the option database to configure aspects of the button such as its colors, font, text, and initial relief. The button 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 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 STk procedure specified in the :command option is invoked.

### WIDGET PROCEDURE

The button 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 button 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 button 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 string. Option may have any of the values accepted by the button procedure.

(widget-name '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 procedure was invoked. This procedure is ignored if the button's state is disabled.

(widget-name 'invoke)
  Invoke the STk procedure associated with the button, if there is one (return value is undefined). This procedure is ignored if the button's state is disabled.

### DEFAULT BINDINGS

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

{[1]}
  A button activates whenever the mouse passes over it and deactivates whenever the mouse leaves the button. Under Windows, this binding is only active when mouse button 1 has been pressed over 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.

### SEE ALSO

checkbutton, radiobutton

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