Tk::Scrollbar - Create and manipulate Scrollbar widgets
$scrollbar =
$parent->Scrollbar(?options?);
-activebackground -highlightbackground -orient -takefocus
-background -highlightcolor -relief -troughcolor
-borderwidth -highlightthickness -repeatdelay
-cursor -jump -repeatinterval
See Tk::options for details of the standard options.
- Name: activeRelief
- Class: ActiveRelief
- Switch: -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.
- Name: command
- Class: Command
- Switch: -command
- Specifies a callback to invoke to change the view in the widget associated
with the scrollbar. When a user requests a view change by manipulating the
scrollbar, the callback is invoked. The callback is passed additional
arguments as described later. This option almost always has a value such
as [xview => $widget] or
[yview => $widget],
consisting of the a widget object and either xview (if the
scrollbar is for horizontal scrolling) or yview (for vertical
scrolling). All scrollable widgets have xview and yview
methods that take exactly the additional arguments appended by the
scrollbar as described in "SCROLLING COMMANDS" below.
- Name: elementBorderWidth
- Class: BorderWidth
- Switch: -elementborderwidth
- 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.
- Name: width
- Class: Width
- Switch: -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 method creates a new window (given by the
$widget 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 $widget argument. At the time this command is
invoked, there must not exist a window named
$widget, but $widget'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 "BINDINGS" below for
details.
A scrollbar displays five elements, which are referred to in the
methods 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 method creates a widget object. This object
supports the configure and cget methods described in
Tk::options which can be used to enquire and modify the options described
above. The widget also inherits all the methods provided by the generic
Tk::Widget class.
The following additional methods are available for scrollbar
widgets:
- $scrollbar->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.
- $scrollbar->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.
- $scrollbar->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.
- $scrollbar->get
- Returns the scrollbar settings in the form of a list whose elements are
the arguments to the most recent set method.
- $scrollbar->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.
- $scrollbar->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
callback specified as the scrollbar's -command option. The callback
may take several forms. In each case, the initial arguments passed are those
specified in the -command callback itself, which usually has a form
like [yview =>
$widget]. (Which will invoke
$widget->yview(...)
where the ... part is as below. See Tk::callbacks for details.) The callback
is passed additional arguments as follows:
- 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.
- 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.
- 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.
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 method has the following form:
- $scrollbar->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 method returns a list of four
integers, consisting of the totalUnits, windowUnits,
firstUnit, and lastUnit values from the last set
method.
The callbacks generated by scrollbars also have a different form
when the old syntax is being used, the callback is passed a single
argument:
- 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
method.
The most recent set method 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 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.
- [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.
Tk::callbacks Tk::Scrolled