button - Create and manipulate button widgets

SYNOPSIS

Switch:  -command  
Name: command
Class: Command

Switch:  -height  
Name: height
Class: 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.

Switch:  -state  
Name: state
Class: 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.

Switch:  -width  
Name: width
Class: 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.

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DESCRIPTION

The button command creates a new window (given by the pathName 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 pathName argument. At the time this command is invoked, there must not exist a window named pathName, but pathName'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 COMMAND

The button 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 button widgets:

pathName 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.

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 button command.

pathName 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.

pathName 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