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 intial 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
scrollbar, widget