There are three types of combo boxes: simple, drop down, and drop down
Varieties of combo
list. All combo boxes show their edit area at all times, but some can show
boxes
and hide their list box areas. The following table summarizes the properties
of each type of combo box.
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Table 10. 11
Style Can hide list? T xt must match list?e
Summary of combo
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box styles
Simple No No
Drop down Y s Noe
Drop down list Y s Y se e
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From a user’ perspective, these are the distinctions between the differents
styles of combo boxes:
■ A simple combo box cannot hide its list box area. Its edit area behaves
just like an edit control; the user can enter and edit text, and the text
doesn’t need to match one of the items in the list. If the text does match,
the corresponding list item is selected.
■ A drop down combo box behaves like a simple combo box, with one
exception. In its initial state, its list area isn’t displayed. It appears when
the user clicks on the icon to the right of the edit area. When drop down
combo boxes aren’t being used, they take up less space than a simple
combo box or a list box.
■ The list area of a drop down list combo box behaves like the list area of a
drop down combo box—it appears only when needed. The two combo
box types differ in the behavior of their edit areas. Whereas drop down
edit areas behave like regular edit controls, drop down list edit areas are
limited to displaying only the text from one of their list items. When the
edit text matches the item text, no more characters can be entered.
Drop down list combo boxes are useful in cases where no other selection is
Choosing combo
acceptable besides those listed in the list area. For example, when choosing
box types
a printer you can only choose a printer accessible from your system.,
On the other hand, drop down combo boxes can accept entries other than
those found in the list. A typical use of drop down combo boxes is selecting
disk files for opening or saving. The user can either search through
directories to find the appropriate file in the list, or type the full path name
and file name in the edit area, regardless of whether the file name appears
in the list area.
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OWL P ogrammer’ Guider s
