Mastering Perl/Tk

Defining Scrollbar Parts

Figure 6-1 shows all the different parts of a Scrollbar and their names.

Figure 6-1. Different parts of a Scrollbar

The trough is the sunken part between the two arrows. It is divided into two parts, trough1 and trough2, by the slider. The slider is the rectangle that indicates how much of the window is available for scrolling. If you were in the middle of the list, you would see the slider rectangle in the center of the trough with space on either side of it. The arrows on either end are called arrow1 and arrow2. If the Scrollbar were vertical (rotated 90 degrees clockwise), arrow1 would be the top arrow.

Clicking on either arrow will move the information in the associated widget one unit at a time. What the unit is depends on the type of widget with which the Scrollbar is associated. With an Entry widget, the units are characters. With a Listbox widget and a vertical Scrollbar, the units are lines. Clicking in the trough on either side of the slider will page the information in the widget in that direction. You can also click directly on the slider and, holding the mouse button down, move it directly.

Scrollbars can be horizontal or vertical. They typically reside on the bottom and/or to the right of the widget they are scrolling, but not always.

Not just any widget can have scrollbars attached to it. Generally speaking, for a widget to be ...