A Track Bar, or "slider", is a visual control with a sliding marker and optional tick marks. It can be oriented either horizontally or vertically. It is useful when you wish the user of your application to select a discrete value from a range of values. The ticks marks can appear above or below the sliding marker for horizontally oriented track bars, to the left or right of the sliding marker for vertically oriented track bars, or can be omitted all together. You specify the minimum and maximum values for the track bar which define the range of values your user can select, and an increment, that is the granularity of movement of the marker. You can also specify the spacing of the tick marks. For example, a track bar with a minimim of 0, maximum of 10, and increment of 1 will permit the user to select integers between 0 and 10 inclusive. The same track bar with an increment of 2 will permit selection only of even integers. You obtain and set the value of the track bar through its value attribute.

We'll illustrate the use of a Track Bar part in the next section with an enhancement to our example part combining the use of a track bar and a progress bar.