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Windows Programming

Notes 3.3 Creating the Programs Window

There are two chief things you must perform in order to generate even the simplest window:
you must create the middle point of the program, and you must tell the operating system how
to react when the user does what.
Just like a C++ program always contains a main() function, a Win32 program requires a central
function call WinMain. The syntax of that function is:
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow );
Dissimilar to the C++ main() function, the arguments of the WinMain() function are not optional.
Your program will require them to converse with the operating system.

The first argument, hInstance, is a handle to the instance of the program you are writing.
The second argument, hPrevInstance, is used if your program had any earlier instance. If not, this
argument can be unnoticed, which will always be the case.

The third argument, lpCmdLine, is a string that displays all items used on the command line to
compile the application.
The last argument, nCmdShow, handles how the window you are building will be displayed.

An object that represents on your screen is known as a window. Since there can be different types
of windows in your programs, your first accountability is to manage them, know where they
are, what they are doing, why and when. The first control you must exercise on these dissimilar
windows is to host them so that all windows of your program belong to an entity known as the
main window. This main window is created by means of an object that can be called a class
(strictly, a structure).
The Win32 library offers two classes for generating the main window and you can use any one
of them. They are WNDCLASS and WNDCLASSEX. The second adds only a slight trait to the
first. Thus, we will mostly use the WNDCLASSEX structure.

The WNDCLASS and the WNDCLASSEX classes are defined as below:
typedef struct _WNDCLASS { typedef struct _WNDCLASSEX {
UINT style; UINT cbSize;
WNDPROC lpfnWndProc; UINT style;
int cbClsExtra; WNDPROC lpfnWndProc;
int cbWndExtra; int cbClsExtra;
HINSTANCE hInstance; int cbWndExtra;
HICON hIcon; HINSTANCE hInstance;
HCURSOR hCursor; HICON hIcon;
HBRUSH hbrBackground; HCURSOR hCursor;
LPCTSTR lpszMenuName; HBRUSH hbrBackground;
LPCTSTR lpszClassName; LPCTSTR lpszMenuName;
} WNDCLASS, *PW LPCTSTR lpszClassName;
HICON hIconSm;
} WNDCLASSEX, *PWNDCLASSEX;

!
Caution To create a window, you must “fill out” this class, which means you must supply
a value for each of its members so the operating system would identify what your program
is anticipated to do.

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