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Advanced Perl Programming

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Tk Widget Reference
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A.6 Scrollbars and Scrolling

Scrollbars support the methods and properties shown in Table A.11.


Table A.11: Scrollbar Properties and Methods (in addition to Table 8-1)

Properties

Description

command

Callback is typically used to change the view in the associated widget (that is, calls that widget's xview or yview ).

Methods

set (first, last)

This is typically invoked by the associated widget to tell it about the widget's current view. Both first and last are fractions between 0 and 1. Values of 0.2 and 0.6 tell the scrollbar that the widget is currently showing the area between 20% and 60% of the document, respectively.

get

Returns the scrollbar settings as a list (first, last).

All scrollable widget types that can be scrolled (listbox, text, canvas) support the methods in Table A.12 in addition to their own (and the generic ones listed in Table A.1).


Table A.12: Scrollable Widget Properties and Methods

Properties

Description

xscrollincrement,

yscrollincrement

If specified, scrolling can be done in units of these increments.

xscrollcommand,

yscrollcommand

Tell widget what to do when it repositions internally. Typically, this option looks like this:

$scrollbar->configure

Methods

yview (`moveto', fraction)

xview, yview come in two forms. If the first argument is "moveto," then the widget is instructed to change its view in a way that fraction represents the topmost (or leftmost, in the case of xview) line or pixel.

yview(`scroll', number, what)

(similarly for xview)

This instructs the widget to adjust the view in the window up or down according to number of increments. what specifies whether these increments are in units or pages. If what is units, then it is in terms of the increment properties shown above.


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