SCROLLBAR(9) Kernel Developer's Manual SCROLLBAR(9)

scrollbar - Create and manipulate scrollbar widgets

scrollbar pathName ?options?

-activebackground -borderwidth      -orient
-background       -jump             -relief

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 Tk 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 Tk 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.
Specifies a desired height for the scrollbar. If this option isn't specified, a suitable default height is chosen.
Specifies a desired width for the scrollbar. If this option isn't specified, a suitable default width is chosen.

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 to configure aspects of the scrollbar such as its colours, 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.

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 Tk 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 behaviour of the command. The following commands are possible for scrollbar widgets:
Marks the element indicated by element as active, which causes it to be displayed as specified by the activebackground option. 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.
Returns the current value of the configuration option given by option. Option may have any of the values accepted by the scrollbar command.
Query or modify the configuration options of the widget. If no option is specified, returns a list of all of the available options for pathName. 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.
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.
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.
Returns the scrollbar settings in the form of a list whose elements are the arguments to the most recent set widget command.
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.
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 Tk 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

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.
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.
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.

Tk automatically creates bindings for scrollbars that give them the following default behaviour. If the behaviour is different for vertical and horizontal scrollbars, the horizontal behaviour 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.
[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.
[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 behaviour as pressing button 1.

options (9), types (9)