Scroll Bars

A window that displays text (like this one) can be thought of as a viewport on a document. The scroll bar is the control on the side of the page that moves this viewport up and down if the entire document doesn't fit inside the viewport.

From a programmer's point of view, a scroll bar is a control that allows the user to select a value from a range of discrete values. For example, in a text editing program, the program has to figure out how many lines of text there are in the document and how much text can fit within the viewport, and set the range and thumb size of the scroll bars to reflect these values, so when the user of the program changes the position of the scroll bar, the program will scroll the text in a predictable manner.

The scroll bar position can be changed in a number of ways.

I like scroll bars a lot, if you hadn't noticed from the bajillion scroll bars I have in the program. Most of these are part of other controls, like the list boxes, the algorithm control, and the LCD controls. They're used for scrolling on the list boxes, but for the other controls they're used for setting the value of the control.