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.TH SCROLLBAR 9
.SH NAME
scrollbar \- Create and manipulate scrollbar widgets
.SH SYNOPSIS
\f5scrollbar\fI pathName \fR?\fIoptions\fR?
.SH STANDARD OPTIONS
.EX
-activebackground -borderwidth      -orient
-background       -jump             -relief
.EE
.SH "WIDGET-SPECIFIC OPTIONS"
.TP
.B -activerelief \fIrelief\fP
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.
.TP
.B -command \fIcommand\fP
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 \f5.t xview\fR or \f5.t yview\fR, consisting of the
name of a widget and either \f5xview\fR (if the scrollbar is for
horizontal scrolling) or \f5yview\fR (for vertical scrolling).
All scrollable widgets have \f5xview\fR and \f5yview\fR commands
that take exactly the additional arguments appended by the scrollbar
as described in SCROLLING COMMANDS below.
.TP
.B -height \fIdist\fP
Specifies a desired height for the scrollbar.
If this option isn't specified, a suitable default height is chosen.
.TP
.B -width \fIdist\fP
Specifies a desired width for the scrollbar.
If this option isn't specified, a suitable default width is chosen.
.SH DESCRIPTION
The \f5scrollbar\fR command creates a new window (given by the
\fIpathName\fR 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 \f5scrollbar\fR command returns its \fIpathName\fR argument.
At the time this command is invoked, there must not exist a window
named \fIpathName\fR.
.PP
A scrollbar is a widget that displays two arrows, one at each end of
the scrollbar, and a \fIslider\fR in the middle portion of the
scrollbar.
It provides information about what is visible in an \fIassociated window\fR
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 document.
.PP
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.

.SH ELEMENTS
A scrollbar displays five elements, which are referred to in the
widget commands for the scrollbar:
.TP 12
\f5arrow1\fR
The top or left arrow in the scrollbar.
.TP 12
\f5trough1\fR
The region between the slider and \f5arrow1\fR.
.TP 12
\f5slider\fR
The rectangle that indicates what is visible in the associated widget.
.TP 12
\f5trough2\fR
The region between the slider and \f5arrow2\fR.
.TP 12
\f5arrow2\fR
The bottom or right arrow in the scrollbar.

.SH "WIDGET COMMAND"
The \f5scrollbar\fR command creates a new Tk command whose
name is \fIpathName\fR.  This
command may be used to invoke various
operations on the widget.  It has the following general form:
.RS
.EX
\fIpathName option \fR?\fIarg arg ...\fR?
.EE
.RE
\fIOption\fR and the \fIarg\fRs
determine the exact behaviour of the command.  The following
commands are possible for scrollbar widgets:
.TP
\fIpathName \f5activate \fR?\fIelement\fR?
Marks the element indicated by \fIelement\fR as active, which
causes it to be displayed as specified by the \f5activebackground\fR option.
The only element values understood by this command are \f5arrow1\fR,
\f5slider\fR, or \f5arrow2\fR.
If any other value is specified then no element of the scrollbar
will be active.
If \fIelement\fR is not specified, the command returns
the name of the element that is currently active, or an empty string
if no element is active.
.TP
\fIpathName \f5cget\fR \fIoption\fR
Returns the current value of the configuration option given
by \fIoption\fR.
\fIOption\fR may have any of the values accepted by the \f5scrollbar\fR
command.
.TP
\fIpathName \f5configure\fR ?\fIoption\fR? ?\fIvalue option value ...\fR?
Query or modify the configuration options of the widget.
If no \fIoption\fR is specified, returns a list of all of
the available options for \fIpathName\fR.  If
one or more \fIoption-value\fR 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.
\fIOption\fR may have any of the values accepted by the \f5scrollbar\fR
command.
.TP
\fIpathName \f5delta \fIdeltaX deltaY\fR
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 \fIdeltaX\fR pixels to the right (\fIdeltaY\fR is
ignored in this case).
If the scrollbar is vertical, the result indicates how much the
scrollbar setting must change to move the slider \fIdeltaY\fR pixels
down.  The arguments and the result may be zero or negative.
.TP
\fIpathName \f5fraction \fIx y\fR
Returns a real number between 0 and 1 indicating where the point
given by \fIx\fR and \fIy\fR 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.
\fIX\fR and \fIy\fR must be pixel coordinates relative to the scrollbar
widget.
If \fIx\fR and \fIy\fR refer to a point outside the trough, the closest
point in the trough is used.
.TP
\fIpathName \f5get\fR
Returns the scrollbar settings in the form of a list whose
elements are the arguments to the most recent \f5set\fR widget command.
.TP
\fIpathName \f5identify\fR \fIx y\fR
Returns the name of the element under the point given by \fIx\fR and
\fIy\fR (such as \f5arrow1\fR), or an empty string if the point does
not lie in any element of the scrollbar.
\fIX\fR and \fIy\fR must be pixel coordinates relative to the scrollbar
widget.
.TP
\fIpathName \f5set\fR \fIfirst last\fR
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 \fIfirst\fR is 0.2 and \fIlast\fR 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.

.SH "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 \f5-command\fR option.
The command may take any of the following forms.
In each case, \fIprefix\fR is the contents of the
\f5-command\fR option, which usually has a form like \f5.t yview\fR
.TP
\fIprefix \f5moveto \fIfraction\fR
\fIFraction\fR is a real number between 0 and 1.
The widget should adjust its view so that the point given
by \fIfraction\fR appears at the beginning of the widget.
If \fIfraction\fR 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.
.TP
\fIprefix \f5scroll \fInumber \f5unit\fR
The widget should adjust its view by \fInumber\fR units.
The units are defined in whatever way makes sense for the widget,
such as characters or lines in a text widget.
\fINumber\fR 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.
.TP
\fIprefix \f5scroll \fInumber \f5page\fR
The widget should adjust its view by \fInumber\fR 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.
\fINumber\fR is either 1, which means the next page should
become visible, or -1, which means that the previous page should
become visible.

.SH 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 horizontal behaviour is described in parentheses.

.IP [1]
Pressing button 1 over \f5arrow1\fR 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.
.IP [2]
Pressing button 1 over \f5trough1\fR 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.
.IP [3]
Pressing button 1 over the slider and dragging causes the view
to drag with the slider.
If the \f5jump\fR option is true, then the view doesn't drag along
with the slider;  it changes only when the mouse button is released.
.IP [4]
Pressing button 1 over \f5trough2\fR 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.
.IP [5]
Pressing button 1 over \f5arrow2\fR 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.
.IP [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.
.SH SEE ALSO
.IR options (9),
.IR types (9)