Tk::Button (3)

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NAME

Tk::Button - Create and manipulate Button widgets

SYNOPSIS

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

STANDARD OPTIONS

-activebackground -activeforeground -anchor -background -bitmap -borderwidth -compound -cursor -disabledforeground -font -foreground -highlightbackground -highlightcolor -highlightthickness -image -justify -padx -pady -relief -repeatdelay -repeatinterval -takefocus -text -textvariable -underline -wraplength

See Tk::options for details of the standard options.

WIDGET-SPECIFIC OPTIONS

Name:        command

Class:      Command

Switch:      -command

Specifies a Perl/Tk callback to associate with the
button. This command is typically invoked when mouse button 1 is released over the button window.

Command-Line Name: -compound

Database Name: compound

Database Class: Compound

Specifies whether the button should display both an image and text, and if so, where the image should be placed relative to the text. Valid values for this option are bottom, center, left, none, right and top. The default value is none, meaning that the button will display either an image or text, depending on the values of the -image and -bitmap options.

Name:  default

Class:      Default

Switch:      -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:  height

Class:      Height

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.

Command-Line Name: -overrelief

Database Name: overRelief

Database Class: OverRelief

Specifies an alternative relief for the button, to be used when the mouse cursor is over the widget. This option can be used to make toolbar buttons, by configuring -relief flat -overrelief raised. If the value of this option is the empty string, then no alternative relief is used when the mouse cursor is over the button. The empty string is the default value.

Name:  state

Class:      State

Switch:      -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

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 Button method 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 perl/Tk callback specified in the -command option is invoked.

WIDGET METHODS

The Button method creates a widget object. This object supports the configure and cget methods described in Tk::options which can be used to enquire and modify the options described above. The widget also inherits all the methods provided by the generic Tk::Widget class.

The following additional methods are available for button widgets:

$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 callback associated with the buttons -command option, if there is one. The return value is the return value from the callback, or the undefined value if there is no callback 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 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.

KEYWORDS

button, widget