Ubuntu Manpage: Tk::Scrollbar - Create and manipulate Scrollbar widgets

Provided by: perl-tk_804.031-1build1_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.

KEYWORDS

       scrollbar, widget