Provided by: perl-tk_804.033-2build1_amd64 
NAME
Tk::Scrollbar - Create and manipulate Scrollbar widgets
SYNOPSIS
$scrollbar = $parent->Scrollbar(?options?);
STANDARD OPTIONS
-activebackground -highlightbackground -orient -takefocus
-background -highlightcolor -relief -troughcolor -borderwidth -highlightthickness -repeatdelay
-cursor -jump -repeatinterval
See Tk::options for details of the standard options.
WIDGET-SPECIFIC OPTIONS
Name: activeRelief
Class: ActiveRelief
Switch: -activerelief
Specifies the relief to use when displaying the element that is active, if any. Elements other than
the active element are always displayed with a raised relief.
Name: command
Class: Command
Switch: -command
Specifies a callback to invoke to change the view in the widget associated with the scrollbar. When
a user requests a view change by manipulating the scrollbar, the callback is invoked. The callback
is passed additional arguments as described later. This option almost always has a value such as
[xview => $widget] or [yview => $widget], consisting of the a widget object and either xview (if the
scrollbar is for horizontal scrolling) or yview (for vertical scrolling). All scrollable widgets
have xview and yview methods that take exactly the additional arguments appended by the scrollbar as
described in "SCROLLING COMMANDS" below.
Name: elementBorderWidth
Class: BorderWidth
Switch: -elementborderwidth
Specifies the width of borders drawn around the internal elements of the scrollbar (the two arrows
and the slider). The value may have any of the forms acceptable to Tk_GetPixels. If this value is
less than zero, the value of the borderWidth option is used in its place.
Name: width
Class: Width
Switch: -width
Specifies the desired narrow dimension of the scrollbar window, not including 3-D border, if any.
For vertical scrollbars this will be the width and for horizontal scrollbars this will be the height.
The value may have any of the forms acceptable to Tk_GetPixels.
DESCRIPTION
The Scrollbar method creates a new window (given by the $widget argument) and makes it into a scrollbar
widget. Additional options, described above, may be specified on the command line or in the option
database to configure aspects of the scrollbar such as its colors, orientation, and relief. The
scrollbar 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 scrollbar is a widget that displays two arrows, one at each end of the scrollbar, and a slider in the
middle portion of the scrollbar. It provides information about what is visible in an associated window
that displays an document of some sort (such as a file being edited or a drawing). The position and size
of the slider indicate which portion of the document is visible in the associated window. For example,
if the slider in a vertical scrollbar covers the top third of the area between the two arrows, it means
that the associated window displays the top third of its document.
Scrollbars can be used to adjust the view in the associated window by clicking or dragging with the
mouse. See "BINDINGS" below for details.
ELEMENTS
A scrollbar displays five elements, which are referred to in the methods for the scrollbar:
arrow1
The top or left arrow in the scrollbar.
trough1
The region between the slider and arrow1.
slider
The rectangle that indicates what is visible in the associated widget.
trough2
The region between the slider and arrow2.
arrow2
The bottom or right arrow in the scrollbar.
WIDGET METHODS
The Scrollbar 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 scrollbar widgets:
$scrollbar->activate(?element?)
Marks the element indicated by element as active, which causes it to be displayed as specified by the
activeBackground and activeRelief options. The only element values understood by this command are
arrow1, slider, or arrow2. If any other value is specified then no element of the scrollbar will be
active. If element is not specified, the command returns the name of the element that is currently
active, or an empty string if no element is active.
$scrollbar->delta(deltaX, deltaY)
Returns a real number indicating the fractional change in the scrollbar setting that corresponds to a
given change in slider position. For example, if the scrollbar is horizontal, the result indicates
how much the scrollbar setting must change to move the slider deltaX pixels to the right (deltaY is
ignored in this case). If the scrollbar is vertical, the result indicates how much the scrollbar
setting must change to move the slider deltaY pixels down. The arguments and the result may be zero
or negative.
$scrollbar->fraction(x, y)
Returns a real number between 0 and 1 indicating where the point given by x and y lies in the trough
area of the scrollbar. The value 0 corresponds to the top or left of the trough, the value 1
corresponds to the bottom or right, 0.5 corresponds to the middle, and so on. X and y must be pixel
coordinates relative to the scrollbar widget. If x and y refer to a point outside the trough, the
closest point in the trough is used.
$scrollbar->get
Returns the scrollbar settings in the form of a list whose elements are the arguments to the most
recent set method.
$scrollbar->identify(x, y)
Returns the name of the element under the point given by x and y (such as arrow1), or an empty string
if the point does not lie in any element of the scrollbar. X and y must be pixel coordinates
relative to the scrollbar widget.
$scrollbar->set(first, last)
This command is invoked by the scrollbar's associated widget to tell the scrollbar about the current
view in the widget. The command takes two arguments, each of which is a real fraction between 0 and
1. The fractions describe the range of the document that is visible in the associated widget. For
example, if first is 0.2 and last is 0.4, it means that the first part of the document visible in the
window is 20% of the way through the document, and the last visible part is 40% of the way through.
SCROLLING COMMANDS
When the user interacts with the scrollbar, for example by dragging the slider, the scrollbar notifies
the associated widget that it must change its view. The scrollbar makes the notification by evaluating a
callback specified as the scrollbar's -command option. The callback may take several forms. In each
case, the initial arguments passed are those specified in the -command callback itself, which usually has
a form like [yview => $widget]. (Which will invoke $widget->yview(...) where the ... part is as below.
See Tk::callbacks for details.) The callback is passed additional arguments as follows:
moveto,fraction
Fraction is a real number between 0 and 1. The widget should adjust its view so that the point given
by fraction appears at the beginning of the widget. If fraction is 0 it refers to the beginning of
the document. 1.0 refers to the end of the document, 0.333 refers to a point one-third of the way
through the document, and so on.
scroll,number,units
The widget should adjust its view by number units. The units are defined in whatever way makes sense
for the widget, such as characters or lines in a text widget. Number is either 1, which means one
unit should scroll off the top or left of the window, or -1, which means that one unit should scroll
off the bottom or right of the window.
scroll,number,page
The widget should adjust its view by number pages. It is up to the widget to define the meaning of a
page; typically it is slightly less than what fits in the window, so that there is a slight overlap
between the old and new views. Number is either 1, which means the next page should become visible,
or -1, which means that the previous page should become visible.
OLD COMMAND SYNTAX
In versions of Tk before 4.0, the set and get widget commands used a different form. This form is still
supported for backward compatibility, but it is deprecated. In the old command syntax, the set method
has the following form:
$scrollbar->set(totalUnits, windowUnits, firstUnit, lastUnit)
In this form the arguments are all integers. TotalUnits gives the total size of the object being
displayed in the associated widget. The meaning of one unit depends on the associated widget; for
example, in a text editor widget units might correspond to lines of text. WindowUnits indicates the
total number of units that can fit in the associated window at one time. FirstUnit and lastUnit give
the indices of the first and last units currently visible in the associated window (zero corresponds
to the first unit of the object).
Under the old syntax the get method returns a list of four integers, consisting of the totalUnits,
windowUnits, firstUnit, and lastUnit values from the last set method.
The callbacks generated by scrollbars also have a different form when the old syntax is being used, the
callback is passed a single argument:
unit
Unit is an integer that indicates what should appear at the top or left of the associated widget's
window. It has the same meaning as the firstUnit and lastUnit arguments to the set method.
The most recent set method determines whether or not to use the old syntax. If it is given two real
arguments then the new syntax will be used in the future, and if it is given four integer arguments then
the old syntax will be used.
BINDINGS
Tk automatically creates class bindings for scrollbars that give them the following default behavior. If
the behavior is different for vertical and horizontal scrollbars, the horizontal behavior is described in
parentheses.
[1] Pressing button 1 over arrow1 causes the view in the associated widget to shift up (left) by one unit
so that the document appears to move down (right) one unit. If the button is held down, the action
auto-repeats.
[2] Pressing button 1 over trough1 causes the view in the associated widget to shift up (left) by one
screenful so that the document appears to move down (right) one screenful. If the button is held
down, the action auto-repeats.
[3] Pressing button 1 over the slider and dragging causes the view to drag with the slider. If the jump
option is true, then the view doesn't drag along with the slider; it changes only when the mouse
button is released.
[4] Pressing button 1 over trough2 causes the view in the associated widget to shift down (right) by one
screenful so that the document appears to move up (left) one screenful. If the button is held down,
the action auto-repeats.
[5] Pressing button 1 over arrow2 causes the view in the associated widget to shift down (right) by one
unit so that the document appears to move up (left) one unit. If the button is held down, the action
auto-repeats.
[6] If button 2 is pressed over the trough or the slider, it sets the view to correspond to the mouse
position; dragging the mouse with button 2 down causes the view to drag with the mouse. If button 2
is pressed over one of the arrows, it causes the same behavior as pressing button 1.
[7] If button 1 is pressed with the Control key down, then if the mouse is over arrow1 or trough1 the
view changes to the very top (left) of the document; if the mouse is over arrow2 or trough2 the view
changes to the very bottom (right) of the document; if the mouse is anywhere else then the button
press has no effect.
[8] In vertical scrollbars the Up and Down keys have the same behavior as mouse clicks over arrow1 and
arrow2, respectively. In horizontal scrollbars these keys have no effect.
[9] In vertical scrollbars Control-Up and Control-Down have the same behavior as mouse clicks over
trough1 and trough2, respectively. In horizontal scrollbars these keys have no effect.
[10]
In horizontal scrollbars the Up and Down keys have the same behavior as mouse clicks over arrow1 and
arrow2, respectively. In vertical scrollbars these keys have no effect.
[11]
In horizontal scrollbars Control-Up and Control-Down have the same behavior as mouse clicks over
trough1 and trough2, respectively. In vertical scrollbars these keys have no effect.
[12]
The Prior and Next keys have the same behavior as mouse clicks over trough1 and trough2,
respectively.
[13]
The Home key adjusts the view to the top (left edge) of the document.
[14]
The End key adjusts the view to the bottom (right edge) of the document.
SEE ALSO
Tk::callbacks Tk::Scrolled
KEYWORDS
scrollbar, widget