Teach Yourself Borland C++ in 14 Days - portal

C++ Class Frameworks and the Visual Component Model
In addition to the GDI classes listed here, there are others that either work as helper classes
or extend a base class to provide extra functionality. As you work with C++Builder you will
learn more about these classes and how to use them. Figure 5.6 shows the hierarchy of the
VCL classes that encapsulate GDI operations.
Figure 5.6.
VCL GDI class
hierarchy.
TPicture
TObject
TPersistent
TGraphic TCanvas
TGraphicsObject
TBitmap TIcon TMetaFile TMetaFileCanvas TControlCanvas TBrush TFont TPen
Utility Classes
So far I have discussed component classes. VCL also contains utility classes you can use in
your applications. A utility class simplifies some tasks in Windows programming. For
instance, the TIniFile class eases the use of writing and reading Windows configuration files
(.INI files). Conventional wisdom has it that the use of .INI files is out and the Registry is
in. To aid in Registry operations, VCL has the TRegistry and TRegkeyInfo classes.
The TRect and TPoint classes (which are really just structures) aid in using various VCL and
Windows functions requiring a point or rectangle parameter.
The TStrings class is used to manipulate strings, and the TStringList class allows for arrays
of strings. These classes are used by many of the component classes to store strings. For
instance, the TMemo class uses a TStringList object for its Lines property. TStringList has the
capability to save its list of strings to file or load strings from a file using the LoadFromFile()
and SaveToFile() methods.
And That’s Not All…
By no means did I cover all of the VCL classes here. I did, however, touch on the classes that
you are most likely to use in your applications.
Flip back a few pages and take another look at Listing 5.1 and the OWL example that
performs the equivalent code in Listing 5.2. If you recall, I said that placing a bitmap image
on a window is even easier in C++Builder. Let me show you what I mean. First, begin a new
application in C++Builder. You should be looking at a blank form. Perform the following
steps:
1. Change the Caption property of the form to Bitmap Test Program.
2. Click on the Additional tab on the Component Palette, choose the Image component,
and place the component on the form.
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