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scrollbar(n) Tk Built-In Commands scrollbar(n)
NAME
scrollbar - Create and manipulate scrollbar widgets
SYNOPSIS
scrollbar pathName ?options? -activebackground -highlight-
color -repeatdelay -background -highlightthickness -repeatinter-
val -borderwidth -jump -takefocus -cursor -orient -trough-
color -highlightbackground -relief
WIDGET-SPECIFIC OPTIONS
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. 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 com-
mand 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 argu-
ments appended by the scrollbar as described in SCROLLING COMMANDS
below. Specifies the width of borders drawn around the internal ele-
ments 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. 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 command creates a new window (given by the pathName argu-
ment) 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, ori-
entation, and relief. The scrollbar command returns its pathName argu-
ment. At the time this command is invoked, there must not exist a win-
dow 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 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.
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 associ-
ated 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 ele-
ment 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 avail-
able 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 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 ele-
ments 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 coordi-
nates 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 docu-
ment 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 com-
mand 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 fraction is 0 it refers to the
beginning of the document. 1.0 refers to the end of the docu-
ment, 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 compatibil-
ity, 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 wid-
get; for example, in a text editor widget units might corre-
spond 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 corre-
sponds 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 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 wid-
get 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 ver-
tical 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 docu-
ment 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 behav-
ior 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, respec-
tively. 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 doc-
ument.
[14] The End key adjusts the view to the bottom (right edge) of the
document.
EXAMPLE
Create a window with a scrollable text widget: toplevel .tl text .tl.t
-yscrollcommand {.tl.s set} scrollbar .tl.s -command {.tl.t yview} grid
.tl.t .tl.s -sticky nsew grid columnconfigure .tl 0 -weight 1 grid row-
configure .tl 0 -weight 1
KEYWORDS
scrollbar, widget
Tk 4.1 scrollbar(n)
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