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VCL Components
Important Common Properties
All components have certain properties in common. For instance, all visual components have
Left and Top properties that determine where the component is placed on the form.
Properties such as Left, Top, Height, and Width are self-explanatory, so I won’t go over them.
A few of the common properties, however, warrant a closer look.
The Align Property
On Day 7, “Working with the Form Designer and the Menu Designer,” I discussed the Align
and Alignment properties, so I won’t go over those again in detail. Refer to Day 7 for complete
information on Align. It should be noted here, however, that not all components expose the
Align property at design time. A single-line edit control, for instance, should occupy a
standard height, so the features of the Align property do not make sense for that type of
component. As you gain experience with C++Builder, and depending on the type of
applications you write, you will probably rely heavily on the Align property.
Color My World
NOTE
The Color property sets the background color for the component. (The text color is set
through the Font property.) Although the Color property is simple to use, there are a few
aspects of component colors that should be pointed out.
The way the Color property is handled in the Object Inspector is somewhat unique. If you
click on the Value column, you will see the drop-down arrow button indicating that you can
choose from a list of color values. That is certainly the case, but there’s more to it than that.
If you double-click on the Value column, the Color dialog box is displayed. This dialog box
allows you to choose a color from one of the predefined colors or to create your own colors
by clicking the Define Custom Colors button. Figure 8.1 shows the Color dialog box after
the Define Custom Colors button has been clicked.
This is the same Color dialog box that will be displayed if you implement
the ColorDialog component in your application.
If you choose a color from the Color dialog box, you will see that the value of the Color
property changes to a hexadecimal string. This string represents the red, green, and blue
(RGB) values that make up the color. If you know the exact RGB value of a color (not likely!),
you can type it in.
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