scrollbar(n) Tk Built-In Commands scrollbar(n)
scrollbar - Create and manipulate scrollbar widgets
scrollbar pathName ?options?
-activebackground -highlightcolor -repeatdelay
-background -highlightthickness -repeatinterval
-borderwidth -jump -takefocus
-cursor -orient -troughcolor
See the options manual entry for details on the standard options.
[-activerelief 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. [-command command] Specifies the prefix of a Tcl 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 Tcl command is invoked. The actual command con-
sists 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
additional arguments appended by the scrollbar as described in SCROLLING COMMANDS below.
[-elementborderwidth 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. [-width width] Specifies the desired nar-
row 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.
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 or in the option database to configure aspects of the scrollbar such as its
colors, 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, but path-
Name'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 vis-
ible 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 asso-
ciated 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 the BINDINGS section below for details.
A scrollbar displays five elements, which are referred to in the widget commands for the
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.
The scrollbar command creates a new Tcl command whose name is pathName. This command may
be used to invoke various operations on the widget. It has the following general form:
pathName option ?arg arg ...?
Option and the args determine the exact behavior 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 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.
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 widget. If no option is speci-
fied, returns a list describing all of the available options for pathName (see
Tk_ConfigureInfo for information on the format of this list). If option is speci-
fied with no value, then the command returns a list describing the one named option
(this list will be identical to the corresponding sublist of the value returned if
no option is specified). If one or more option-value pairs are specified, then the
command modifies 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 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.
Returns the scrollbar settings in the form of a list whose elements are the argu-
ments 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 scrollbar widget.
pathName 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
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 Tcl command generated from the scrollbar's -command
option. The command may take any of the following forms. In each case, prefix is the
contents 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 fraction 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
prefix scroll number units
The widget should adjust its view by number units. The units are defined in what-
ever 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
prefix scroll number pages
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 com-
mand syntax, the set widget command has the following form:
pathName 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 widget command returns a list of four integers, consisting of
the totalUnits, windowUnits, firstUnit, and lastUnit values from the last set widget com-
The commands generated by scrollbars also have a different form when the old syntax is
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 widget command.
The most recent set widget command 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.
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.
 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.
 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.
 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.
 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.
 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.
 If button 2 is pressed over the trough or the slider, it sets the view to corre-
spond 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.
 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 docu-
ment; if the mouse is anywhere else then the button press has no effect.
 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
 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.
 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.
 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.
 The Prior and Next keys have the same behavior as mouse clicks over trough1 and
 The Home key adjusts the view to the top (left edge) of the document.
 The End key adjusts the view to the bottom (right edge) of the document.
Tk 4.1 scrollbar(n)