Teach Yourself Borland C++ in 14 Days - portal

VCL Components
You can use owner-drawn list boxes if needed. Owner-drawn list boxes are fairly common,
although you may not realize it. On Day 6 I talked about customizing the C++Builder
speedbar. As part of that discussion, we looked at the C++Builder Speedbar Editor dialog box,
which was shown in Figure 6.2. Go back and take another look at that figure. The Speedbar
Editor dialog box contains two list boxes. The list box on the left is a regular list box. It lists
the possible button groups you can choose from. The list box on the right is an owner-drawn
list box. It shows the actual button as it will appear on the speedbar, as well as a textual
description of what function the button performs.
Combo boxes are specialized list boxes. Actually, a combo box is a combination of a list box
and an edit control. The user can choose from the list or type in a value in the edit portion.
When the user chooses an item from the list, that item is placed in the edit control. There
are three different types of combo boxes. Table 8.5 lists the types of combo boxes and gives
a description of each.
Table 8.5. Types of combo boxes.
Item Description
Simple The simple style of the combo box is nothing more than an edit
control placed on top of a list box. The user can choose from the
list or type text in the edit portion.
Drop-down Similar to the simple style, except the list box portion is not
initially displayed. A drop-down button is provided so that the
user can view the list and choose an item. The user can also type
text in the edit portion.
Drop-down list This is the most restrictive type of combo box. As with the dropdown
style, the list is not initially exposed. The user can click the
drop-down button to expose the list and choose an item from
the list, but cannot enter text in the edit portion. Use this style
when you want the user to select only from a predetermined set
of choices.
You can get a program called ComboBox Test from http://www.mcp.com/sams/codecenter.html
that illustrates the different types of combo boxes. Figure 8.4 shows the test program running.
Run the program and try out the combo boxes to get a feel for how each works.
Table 8.6 lists the properties common to list boxes and combo boxes.
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