NAME¶
Tk::Checkbutton - Create and manipulate Checkbutton widgets
SYNOPSIS¶
$checkbutton =
$parent->
Checkbutton(?
options?);
STANDARD OPTIONS¶
-activebackground -activeforeground -anchor
-background -bitmap -borderwidth -compound
-cursor -disabledforeground -font -foreground
-highlightbackground -highlightcolor -highlightthickness
-image -justify -padx -pady -relief
-takefocus -text -textvariable -underline
-wraplength
See Tk::options for details of the standard 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. The button's global variable ( -variable option)
will be updated before the command is invoked.
- 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.
- Name: indicatorOn
- Class: IndicatorOn
- Switch: -indicatoron
- Specifies whether or not the indicator should be drawn.
Must be a proper boolean value. If false, the relief option is
ignored and the widget's relief is always sunken if the widget is selected
and raised otherwise.
- Command-Line Name: -offrelief
- Database Name: offRelief
- Database Class: OffRelief
- Specifies the relief for the checkbutton when the indicator
is not drawn and the checkbutton is off. The default value is
raised. By setting this option to flat and setting
-indicatoron false -overrelief raised, the effect is achieved of
having a flat button that raises on mouse-over and which is depressed when
activated. This is the behavior typically exhibited by the Bold, Italic,
and Underline checkbuttons on the toolbar of a word-processor, for
example.
- Name: offValue
- Class: Value
- Switch: -offvalue
- Specifies value to store in the button's associated
variable whenever this button is deselected. Defaults to ``0''.
- Name: onValue
- Class: Value
- Switch: -onvalue
- Specifies value to store in the button's associated
variable whenever this button is selected. Defaults to ``1''.
- 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: selectColor
- Class: Background
- Switch: -selectcolor
- Specifies a background color to use when the button is
selected. If indicatorOn is true then the color applies to the
indicator. Under Windows, this color is used as the background for the
indicator regardless of the select state. If indicatorOn is false,
this color is used as the background for the entire widget, in place of
background or activeBackground, whenever the widget is
selected. If specified as an empty string then no special color is used
for displaying when the widget is selected.
- Name: selectImage
- Class: SelectImage
- Switch: -selectimage
- Specifies an image to display (in place of the image
option) when the checkbutton is selected. This option is ignored unless
the image option has been specified.
- Name: state
- Class: State
- Switch: -state
- Specifies one of three states for the checkbutton:
normal, active, or disabled. In normal state the
checkbutton is displayed using the foreground and background
options. The active state is typically used when the pointer is over the
checkbutton. In active state the checkbutton is displayed using the
activeForeground and activeBackground options. Disabled
state means that the checkbutton 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 checkbutton is displayed.
- Name: variable
- Class: Variable
- Switch: -variable
- Specifies reference to a variable to set to indicate
whether or not this button is selected. Defaults to
"\$widget->{'Value'}" member of the widget's hash. In general
perl variables are "undef" unless specifically initialized which
will not match either default -onvalue or default
-offvalue.
- 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
Checkbutton method creates a new window (given by the $widget
argument) and makes it into a checkbutton widget. Additional options,
described above, may be specified on the command line or in the option
database to configure aspects of the checkbutton such as its colors, font,
text, and initial relief. The
checkbutton 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 checkbutton is a widget that displays a textual string, bitmap or image and a
square called an
indicator. 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. A checkbutton has all of the behavior of a simple button, including
the following: 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 perl/Tk callback whenever
mouse button 1 is clicked over the checkbutton.
In addition, checkbuttons can be
selected. If a checkbutton is selected
then the indicator is normally drawn with a selected appearance, and a Tcl
variable associated with the checkbutton is set to a particular value
(normally 1). Under Unix, the indicator is drawn with a sunken relief and a
special color. Under Windows, the indicator is drawn with a check mark inside.
If the checkbutton is not selected, then the indicator is drawn with a
deselected appearance, and the associated variable is set to a different value
(typically 0). Under Unix, the indicator is drawn with a raised relief and no
special color. Under Windows, the indicator is drawn without a check mark
inside. By default, the name of the variable associated with a checkbutton is
the same as the
name used to create the checkbutton. The variable name,
and the ``on'' and ``off'' values stored in it, may be modified with options
on the command line or in the option database. Configuration options may also
be used to modify the way the indicator is displayed (or whether it is
displayed at all). By default a checkbutton is configured to select and
deselect itself on alternate button clicks. In addition, each checkbutton
monitors its associated variable and automatically selects and deselects
itself when the variables value changes to and from the button's ``on'' value.
The
Checkbutton 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 checkbutton widgets:
- $checkbutton->deselect
- Deselects the checkbutton and sets the associated variable
to its ``off'' value.
- $checkbutton->flash
- Flashes the checkbutton. This is accomplished by
redisplaying the checkbutton several times, alternating between active and
normal colors. At the end of the flash the checkbutton is left in the same
normal/active state as when the command was invoked. This command is
ignored if the checkbutton's state is disabled.
- $checkbutton->invoke
- Does just what would have happened if the user invoked the
checkbutton with the mouse: toggle the selection state of the button and
invoke the perl/Tk callback associated with the checkbutton, if there is
one. The return value is the return value from the perl/Tk callback, or an
empty string if there is no command associated with the checkbutton. This
command is ignored if the checkbutton's state is disabled.
- $checkbutton->select
- Selects the checkbutton and sets the associated variable to
its ``on'' value.
- $checkbutton->toggle
- Toggles the selection state of the button, redisplaying it
and modifying its associated variable to reflect the new state.
BINDINGS¶
Tk automatically creates class bindings for checkbuttons that give them the
following default behavior:
- [1]
- On Unix systems, a checkbutton activates whenever the mouse
passes over it and deactivates whenever the mouse leaves the checkbutton.
On Mac and Windows systems, when mouse button 1 is pressed over a
checkbutton, the button activates whenever the mouse pointer is inside the
button, and deactivates whenever the mouse pointer leaves the button.
- [2]
- When mouse button 1 is pressed over a checkbutton, it is
invoked (its selection state toggles and the command associated with the
button is invoked, if there is one).
- [3]
- When a checkbutton has the input focus, the space key
causes the checkbutton to be invoked. Under Windows, there are additional
key bindings; plus (+) and equal (=) select the button, and minus (-)
deselects the button.
If the checkbutton's state is disabled then none of the above actions
occur: the checkbutton is completely non-responsive.
The behavior of checkbuttons can be changed by defining new bindings for
individual widgets or by redefining the class bindings.
KEYWORDS¶
checkbutton, widget