SCROLLBAR(9) SCROLLBAR(9)
NAME
scrollbar - Create and manipulate scrollbar widgets
SYNOPSIS
scrollbar pathName ?options?
STANDARD OPTIONS
-activebackground -borderwidth -orient
-background -jump -relief
WIDGET-SPECIFIC OPTIONS
-activerelief relief
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.
-command command
Specifies the prefix of a Tk command to invoke to
change the view in the widget associated with the
scrollbar. When a user requests a view change by
manipulating the scrollbar, a Tk command is invoked.
The actual command consists of this option followed by
additional information as described later. This option
almost always has a value such as .t xview or .t yview,
consisting of the name of a widget and either xview (if
the scrollbar is for horizontal scrolling) or yview
(for vertical scrolling). All scrollable widgets have
xview and yview commands that take exactly the addi-
tional arguments appended by the scrollbar as described
in SCROLLING COMMANDS below.
-height dist
Specifies a desired height for the scrollbar. If this
option isn't specified, a suitable default height is
chosen.
-width dist
Specifies a desired width for the scrollbar. If this
option isn't specified, a suitable default width is
chosen.
DESCRIPTION
The scrollbar command creates a new window (given by the
pathName argument) and makes it into a scrollbar widget.
Additional options, described above, may be specified on the
command line to configure aspects of the scrollbar such as
its colours, orientation, and relief. The scrollbar command
returns its pathName argument. At the time this command is
invoked, there must not exist a window named pathName.
Page 1 Plan 9 (printed 12/22/24)
SCROLLBAR(9) SCROLLBAR(9)
A scrollbar is a widget that displays two arrows, one at
each end of the scrollbar, and a slider in the middle por-
tion of the scrollbar. It provides information about what
is visible in an associated window that displays a 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 docu-
ment.
Scrollbars can be used to adjust the view in the associated
window by clicking or dragging with the mouse. See the
BINDINGS section below for details.
ELEMENTS
A scrollbar displays five elements, which are referred to in
the widget commands 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 COMMAND
The scrollbar command creates a new Tk command whose name is
pathName. This command may be used to invoke various opera-
tions on the widget. It has the following general form:
pathName option ?arg arg ...?
Option and the args determine the exact behaviour of the
command. The following commands are possible for scrollbar
widgets:
pathName activate ?element?
Marks the element indicated by element as active, which
causes it to be displayed as specified by the active-
background option. The only element values understood
by this command are arrow1, slider, or arrow2. If any
other value is specified then no element of the scroll-
bar will be active. If element is not specified, the
command returns the name of the element that is cur-
rently active, or an empty string if no element is
active.
Page 2 Plan 9 (printed 12/22/24)
SCROLLBAR(9) SCROLLBAR(9)
pathName cget option
Returns the current value of the configuration option
given by option. Option may have any of the values
accepted by the scrollbar command.
pathName configure ?option? ?value option value ...?
Query or modify the configuration options of the wid-
get. If no option is specified, returns a list of all
of the available options for pathName. If one or more
option-value pairs are specified, then the command mod-
ifies 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 scrollbar command.
pathName 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 scroll-
bar 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.
pathName 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 bot-
tom 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.
pathName get
Returns the scrollbar settings in the form of a list
whose elements are the arguments to the most recent set
widget command.
pathName 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 scroll-
bar widget.
pathName set first last
This command is invoked by the scrollbar's associated
widget to tell the scrollbar about the current view in
Page 3 Plan 9 (printed 12/22/24)
SCROLLBAR(9) SCROLLBAR(9)
the widget. The command takes two arguments, each of
which is a real fraction between 0 and 1. The frac-
tions describe the range of the document that is visi-
ble 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 Tk command generated from
the scrollbar's -command option. The command may take any
of the following forms. In each case, prefix is the con-
tents of the -command option, which usually has a form like
.t yview
prefix moveto fraction
Fraction is a real number between 0 and 1. The widget
should adjust its view so that the point given by frac-
tion appears at the beginning of the widget. If frac-
tion 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.
prefix scroll number unit
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.
prefix 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.
BINDINGS
Tk automatically creates bindings for scrollbars that give
them the following default behaviour. If the behaviour is
different for vertical and horizontal scrollbars, the
Page 4 Plan 9 (printed 12/22/24)
SCROLLBAR(9) SCROLLBAR(9)
horizontal behaviour 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.
[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 screen-
ful so that the document appears to move up (left) one
screenful.
[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 behaviour as
pressing button 1.
SEE ALSO
options(9), types(9)
Page 5 Plan 9 (printed 12/22/24)