C++ WIN32: where to put code that executes as program is running

Question

This seems like a simple question but I don't know where to put Win32 code that executes whilst the program is running. As a simplified example, I provide an example that contains what I believe to be standard Win32 Window initialisation code, followed by a simple 'Beep' command. I have tried slotting the beep command in various different places, but the result is one of the following three:

1. The beep occurs and loops endlessly
2. No beep is heard at all
3. The beep only occurs as I close the program

The code I am using is shown below. This is simply an example I have lifted from an online resource, with my beep command added at the end. There are no compiler errors. In this example, the beep occurs as I close the program. As you might expect, this is my first Win32 app.

#include <windows.h>

    /*  Declare Windows procedure  */
    LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

    /*  Make the class name into a global variable  */
    char szClassName[ ] = "WindowsApp";

    int WINAPI WinMain (HINSTANCE hThisInstance,
                HINSTANCE hPrevInstance,
                LPSTR lpszArgument,
                int nFunsterStil)

{
                    HWND hwnd;               /* This is the handle for our window */
                    MSG messages;            /* Here messages to the application are saved */
                    WNDCLASSEX wincl;        /* Data structure for the windowclass */

       /* The Window structure */
       wincl.hInstance = hThisInstance;
       wincl.lpszClassName = szClassName;
       wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
       wincl.style = CS_DBLCLKS;                 /* Catch double-clicks */
       wincl.cbSize = sizeof (WNDCLASSEX);

       /* Use default icon and mouse-pointer */
       wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
       wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
       wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
       wincl.lpszMenuName = NULL;                 /* No menu */
       wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */
       wincl.cbWndExtra = 0;                      /* structure or the window instance */
       /* Use Windows's default color as the background of the window */
       wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

       /* Register the window class, and if it fails quit the program */
       if (!RegisterClassEx (&wincl))
               return 0;

       /* The class is registered, let's create the program*/
       hwnd = CreateWindowEx (
           0,                   /* Extended possibilites for variation */
           szClassName,         /* Classname */
           "Matt's Program That Beeps",       /* Title Text */
           WS_OVERLAPPEDWINDOW, /* default window */
           CW_USEDEFAULT,       /* Windows decides the position */
           CW_USEDEFAULT,       /* where the window ends up on the screen */
           544,                 /* The programs width */
           375,                 /* and height in pixels */
           HWND_DESKTOP,        /* The window is a child-window to desktop */
           NULL,                /* No menu */
           hThisInstance,       /* Program Instance handler */
           NULL                 /* No Window Creation data */
            );

       /* Make the window visible on the screen */
       ShowWindow (hwnd, nFunsterStil);

       /* Run the message loop. It will run until GetMessage() returns 0 */
       while (GetMessage (&messages, NULL, 0, 0))
       {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
       }

       /* The program return-value is 0 - The value that PostQuitMessage() gave */
       return messages.wParam;
}

/*  This function is called by the Windows function DispatchMessage()  */
LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 switch (message)                  /* handle the messages */
 {
    case WM_DESTROY:
        PostQuitMessage (0);       /* send a WM_QUIT to the message queue */
        break;
    default:                      /* for messages that we don't deal with */
        return DefWindowProc (hwnd, message, wParam, lParam);
}
    Beep( 750, 300 );              /* This is the beep command */
    return 0;
}

Answer 1

Putting it simply, if you want the code to run on every window message (you probably don't) then put the beep call at the top of your window proc. If you want it to occur only for certain messages, then add a case for those messages, and put it in that case.