scrollbar(n) Tk Built-In Commands scrollbar(n)_________________________________________________________________NAMEscrollbar - Create and manipulate scrollbar widgets
SYNOPSISscrollbar 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
Tk 4.1 1
scrollbar(n) Tk Built-In Commands scrollbar(n)
less than 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.
_________________________________________________________________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 por-
tion of the scrollbar. It provides information about what
is visible in an associated window that displays an docu-
ment of some sort (such as a file being edited or a draw-
ing). The position and size of the slider indicate which
portion of the document is visible in the associated win-
dow. 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 associ-
ated 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.
Tk 4.1 2
scrollbar(n) Tk Built-In Commands scrollbar(n)
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 scroll-
bar 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 path-
Name (see Tk_ConfigureInfo for information on the
format of this list). If option is specified with
no value, then the command returns a list describ-
ing the one named option (this list will be identi-
cal 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
Tk 4.1 3
scrollbar(n) Tk Built-In Commands scrollbar(n)
ignored in this case). If the scrollbar is verti-
cal, the result indicates how much the scrollbar
setting must change to move the slider deltaY pix-
els 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 corre-
sponds to the bottom or right, 0.5 corresponds to
the middle, and so on. X and y must be pixel coor-
dinates 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 associ-
ated widget to tell the scrollbar about the current
view in the widget. The command takes two argu-
ments, 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 docu-
ment, 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 like .t yview
Tk 4.1 4
scrollbar(n) Tk Built-In Commands scrollbar(n)
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 begin-
ning 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 win-
dow, 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.
OLD COMMAND SYNTAX
In versions of Tk before 4.0, the set and get widget com-
mands 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 follow-
ing 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 corre-
spond to lines of text. WindowUnits indicates the
total number of units that can fit in the associ-
ated window at one time. FirstUnit and lastUnit
give the indices of the first and last units cur-
rently visible in the associated window (zero cor-
responds 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, windowU-
nits, firstUnit, and lastUnit values from the last set
widget command.
Tk 4.1 5
scrollbar(n) Tk Built-In Commands scrollbar(n)
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 wid-
get'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 argu-
ments 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 scroll-
bars, 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 that the document appears to move up (left)
one unit. If the button is held down, the action
auto-repeats.
Tk 4.1 6
scrollbar(n) Tk Built-In Commands scrollbar(n)
[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 docu-
ment; if the mouse is over arrow2 or trough2 the
view changes to the very bottom (right) of the doc-
ument; if the mouse is anywhere else then the but-
ton 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 scroll-
bars 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, respec-
tively.
[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
Tk 4.1 7