scrollbar - Create and manipulate 'scrollbar' scrolling control
and indicator widgets
scrollbar pathName ?options?
-activebackground -highlightcolor -repeatdelay
-background -highlightthickness -repeatinterval
-borderwidth -jump -takefocus
-cursor -orient -troughcolor
-highlightbackground -relief
See the options manual entry for details on the standard
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 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.
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 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.
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.
- 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 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 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.
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 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.
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,
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.
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 does not
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.
- [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.
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 rowconfigure .tl 0 -weight 1