Another solution to this problem is the combo box, which we’ll talk about next.
Deletes (clears) the current selection, if any, in the edit control of the combo box.
It provides a standard format for Web pages to create a link, provide the refresh period for a page to change, embed audio files, embed Javascript, lay out the combo box, and form pages into different frames.
Text edit controls are often used either as data-entry fields in database applications (including Web sites connected to databases), as option entry fields in dialog boxes, or as the entry field in a combo box.
Figure 21-15 shows a bounded slider used by Microsoft in the Windows Display Settings dialog. It works like a slider or scrollbar, but has four discrete positions that represent distinct resolution settings. Microsoft could easily have used a noneditable combo box in its place, too.
If drag-and-drop is implemented in list controls, it should also be implemented in combo boxes.
After combo boxes were admitted onto the toolbar, the precedent was set, and all kinds of idioms appeared, as we have already discussed in Chapter 21. Some of these toolbar idioms are shown in Figure 23-1.
