scrollbar(n) Tk (4.1) scrollbar(n)
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NAME
scrollbar - Create and manipulate scrollbar widgets
SYNOPSIS
scrollbar pathName ?options?
STANDARD OPTIONS
-activebackground-highlightbackground-orient-takefocus
-background-highlightcolor-relief-troughcolor
-borderwidth-highlightthickness-repeatdelay
-cursor-jump-repeatinterval
See the options manual entry for details on the standard
options.
WIDGET-SPECIFIC OPTIONS
Command-Line Name:-activerelief
Database Name: activeRelief
Database Class: 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-Line Name:-command
Database Name: command
Database Class: 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 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
additional arguments appended by the scrollbar as
described in SCROLLING COMMANDS below.
Command-Line Name:-elementborderwidth
Database Name: elementBorderWidth
Database Class: BorderWidth
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
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scrollbar(n) Tk (4.1) scrollbar(n)
zero, the value of the borderWidth option is used in
its place.
Command-Line Name:-width
Database Name: width
Database Class: 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.
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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 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 pathName'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 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
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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 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 specified, 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 specified 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
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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.
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.
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
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 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 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
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scrollbar(n) Tk (4.1) scrollbar(n)
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
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.
prefix 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.
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 command 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,
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scrollbar(n) Tk (4.1) scrollbar(n)
firstUnit, and lastUnit values from the last set widget
command.
The commands generated by scrollbars also have a different
form when the old syntax is being used:
prefix 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 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.
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
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scrollbar(n) Tk (4.1) scrollbar(n)
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
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