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Unit 3: Windows Programming
The first thing you must do so as to create an application is to state a variable of either WNDCLASS Notes
or WNDCLASSEX type.
Example: Here is an example of a WNDCLASSEX variable:
INT WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
LPSTR lpCmdLine, int nCmdShow)
{
WNDCLASSEX WndClsEx;
return 0;
}
Self Assessment
Fill in the blanks:
5. The argument, ......................... , is used if your program had any earlier instance.
6. The argument, ......................... , handles how the window you are building will be displayed.
3.4 Messages and Adding a Message Loop
Message loop is utilized to catch messages and pass them onto our WndProc function.
First we are required to state a MSG variable. This is used to hold the message that has been
caught by the window.
MSG msg;
To discover out what the last message obtained was, we can use the GetMessage function. The
parameters for the function are specified below.
LPMSG lpMsg - After the function call, the parameter passed onto here will enclose the message
that was obtained.
HWND hwnd - This is used to state what window the message must be recovered for. If a NULL
is passed, a message for any window will be retrieved.
UINT wMsgFilterMin & UINT wMsgFilterMax - This declares the range of messages to obtain.
Each message has an integer value so you can identify exactly what messages you want to
receive. If you pass 0 for both parameters, all messages are obtained.
Notes The return value is 0 if a WM_QUIT message has been obtained. If the return value
is less than 0, some error has appeared. We only want to carry on if there was no error and
if there is no quit message. Keep in mind that we caused a quit message to be sent if the
window was closed.
When the GetMessage function is called, the function halts until a message is obtained. If you do
not want this, you can make use of the PeekMessage function which doesn’t stop, even if there
was no message. This is typically used if you are busy computing something else. If you go in
the course of the OpenGL or DirectX , you will use this.
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