August 1997

Using OWL classes in C++Builder

When I first delved into C++Builder, as an OWL programmer I was a little dismayed to find I had to learn a new class library. Still, enough similarity existed between OWL and VCL that I could find my way around.

I noticed right away that VCL, like OWL, has classes called TRect, TPoint, and TSize. "Well, I know what to do with those!" I thought. But it didn't take long to realize that the VCL classes were like the OWL classes in name only--they were just wrappers around the Windows RECT, POINT, and SIZE structures, respectively. Bummer! I like those OWL classes!

Take TRect, for instance. It includes lots of overloaded constructors to let you easily create a TRect object. In addition, the overloaded operators and functions make manipulating rectangles easy with the OWL version of TRect. If only I could use the OWL TRect and other great OWL helper classes in my VCL applications.

In this article, we'll show how to incorporate some of the OWL helper classes in your C++Builder applications. In order to use the classes discussed in this article, you'll need Borland C++ 5.02. While you might be able to use classes from other versions of OWL, this article assumes that you have the C++ 5.02 update. We'll also discuss a couple of OWL classes that you probably don't know exist. Let's begin by looking at some specific classes you might want to use.

Winsys, here we come!

Several other classes in the Classlib/Winsys family may be of use--TProfile (an INI file-manipulation class), TRegistry, TString, and others. However, VCL provides good classes for these needs, so you don't have to bother with the Winsys classes that deal with INI files, the registry, string manipulation, and so on.

Putting Winsys classes to work

Assuming you want to use some of the Winsys classes in your C++Builder applications, how do you go about it? There are several ways:

	Add the appropriate Winsys source files directly to your application.
	Link the classes statically using BIDSF.LIB.
	Link the classes dynamically using BIDSF.DLL and the BIDSFI.LIB import library.

The method you use depends largely on your needs, although in most cases, I think you'll prefer the first method. Let's take a look at each of these options and how to implement them in a C++Builder application.

Adding Winsys source files to your project

Next, choose Project... from the C++Builder Options menu. In the resulting Project Options dialog box, click on the Directories/Conditionals tab. At the end of the Include Path field, add the path to the INCLUDE directory in which you've installed Borland C++ 5.02. In our case, we added the text

;c:\bc5\include

As long as you're in the Project Options dialog box, let's take care of step 4 in this process by adding a symbol to the Conditional Defines field. Type the following in that field:

BI_NAMESPACE

For the final step (besides writing code), you need to include the headers for the files. For example, the include directive for the GEOMETRY header looks like this:

#include <winsys\geometry.h>

As a result, you can modify an example shown in "The Magic of Namespaces" and use code like this:

using ::TRect;
TRect rect;

When you use the Winsys TRect with API functions rather than the VCL TRect, the fourth parameter of the DrawText() function requires a Windows RECT structure pointer. For reasons that are beyond my understanding, the VCL TRect class doesn't have an operator to convert a TRect pointer to a RECT pointer. However, the Winsys version of TRect does have such a conversion operator. If you used a VCL TRect, then the DrawText() function would require a cast, and you'd have to write it like this:

DrawText(Canvas->Handle, "HelloThere!", -1, (RECT*)&rect, DT_SINGLELINE);

Because the Winsys TRect class has a RECT* conversion operator, you can write the DrawText() function without a cast, like so:

DrawText(Canvas->Handle, "Hello There!", -1, &rect, DT_SINGLELINE);

Listing AMAINFORM.CPP

//---------------------------------------------------
#include <winsys\geometry.h>
#include <winsys\uimetric.h>
#include <winsys\system.h>
#include <vcl.h>
#pragma hdrstop
#include "MainForm.h"

//---------------------------------------------------
#pragma resource "*.dfm"
TForm1 *Form1;

//---------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)
{
}

//---------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
  // Create a string.
  String s = "Operating System: ";

  // If we're running Win95 append "Win95" to the end
  // of the string.

  if (TSystem::IsWin95()) 
    s += "Win95";

  // Otherwise must be NT so add "Windows NT" to
  //  the end of the string. Also add the NT version
  // number and the build number to the string.

  else {
    s += "Windows NT ";
    s += String((int)TSystem::GetMajorVersion());
    s += ", Build No. " +
    String((int)TSystem::GetBuildNumber());
  }

  // Display the string in the label.
  Label1->Caption = s;
}

//---------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
  // Tell the compiler we want the global version
  // of TRect and not the VCL version.
  using ClassLib::TRect;

  // Create a TRect object.
  TRect wndRect;

  // Get the window rect using API GetWindowRect.
  GetWindowRect(Handle, &wndRect);

  // Inflate the rect by 100 pixels all around.
  wndRect.Inflate(100, 100);

  // Move the window to the new size and location.
  MoveWindow(Handle, wndRect.Top(), wndRect.Left(),
    wndRect.Width(), wndRect.Height(), true);

  // Make x the height of a menu.
  int x = TUIMetric::CyMenu;

  // Make y the width of a vertical scrollbar.
  int y = TUIMetric::CxVScroll;  

  // Create a TRect object using x and y as the top
  // and left coordinates.
  TRect rect(x, y, 200, 40);  

  // Use it in the API DrawText call.
  DrawText(Canvas->Handle, "Hello There!", -1, &rect, DT_SINGLELINE);
}
//---------------------------------------------------