Teach Yourself Borland C++ in 14 Days - portal

C++ Class Frameworks and the Visual Component Model
■ Double-clicking the event handler’s name in the Object Inspector will display the
Code Editor and take you to the section of code containing the event handler.
■ Each event handler contains the function parameters needed to properly
handle that event.
C++Builder and VCL
As I have said, VCL is a library written in Object Pascal. VCL is written in Object Pascal
because it was written for Delphi. It made perfect sense for the people at Borland to take an
already-existing class library and adapt it for use in C++Builder. There was no point in
starting from scratch to build C++Builder when they could hit the ground running by
implementing Delphi’s VCL. An added benefit is that users of Delphi can easily move to
C++Builder, and vice versa. Because both are using the same VCL, you don’t have to learn
a new framework when moving around in the Delphi/C++Builder family.
C++Builder is a C++ compiler, and VCL is an Object Pascal library. How does that work,
exactly? Truthfully, you shouldn’t be concerned about how it works at the compiler level, but
rather how it affects the way you program in C++Builder. The bottom line is that VCL is
Object Pascal and is nearly invisible. Take the following code snippet, for instance:
int screenW = GetSystemMetrics(SM_CXSCREEN);
int screenH = GetSystemMetrics(SM_CYSCREEN);
int h = MainForm->Height;
int w = MainForm->Width;
MainForm->Top = (screenH / 2) - (h / 2);
MainForm->Left = (screenW / 2) - (w / 2);
TPoint cPt;
GetCursorPos(cPt);
h -= 150;
w -= 150;
MainForm->Height = h;
MainForm->Width = w;
for (int i=0;iHeight = h + i;
MainForm->Width = w + i;
SetCursorPos(
MainForm->Left + MainForm->Width,
MainForm->Top + MainForm->Height);
}
SetCursorPos(cPt.x, cPt.y);
Now, in this code, which is Object Pascal and which is C++? As far as you are concerned, it’s
all C++. VCL and C++ work together seamlessly to give you rapid application development
using C++. VCL gives you RAD through components, and the rest of your code can be
written in C++.
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