Tk::Button - Create and manipulate Button widgets
$button =
$parent->Button(?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.
- 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.
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.
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.
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.