The source code is as follows:
#include <windows.h>
#define ID_TIMER 1 LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
VOID CALLBACK TimerProc(HWND, UINT, UINT, DWORD);
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PSTR szCmdLine, int iCmdShow)
{
static char szAppName[] = TEXT("Beeper2");
HWND hwnd;
WNDCLASS wndclass;
MSG msg;
wndclass.style = CS_HREDRAW | CS_VREDRAW;
wndclass.lpfnWndProc = WndProc;
wndclass.cbClsExtra = 0;
wndclass.cbWndExtra = 0;
wndclass.hInstance = hInstance;
wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;
if(!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT ("Program requires Windows NT!"), szAppName, MB_ICONERROR);
return 0;
}
hwnd = CreateWindow(szAppName, TEXT("Beeper2 Timer Demo"),
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, CW_USEDEFAULT,
CW_USEDEFAULT, CW_USEDEFAULT,
NULL, NULL, hInstance, NULL);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);
while(GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch(message)
{
case WM_CREATE:
SetTimer(hwnd, ID_TIMER, 1000, TimerProc);
return 0;
case WM_DESTROY:
KillTimer(hwnd, ID_TIMER);
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
VOID CALLBACK TimerProc(HWND hwnd, UINT message, UINT iTimerID, DWORD dwTime)
{
static BOOL fFlipFlop = FALSE;
HBRUSH hBrush;
HDC hdc;
RECT rect;
MessageBeep(-1);
fFlipFlop = !fFlipFlop;
GetClientRect(hwnd, &rect);
hdc = GetDC(hwnd);
hBrush = CreateSolidBrush(fFlipFlop ? RGB(255, 0, 0) : RGB(0, 0, 255));
FillRect(hdc, &rect, hBrush);
ReleaseDC(hwnd, hdc);
DeleteObject(hBrush);
}The result is the same as BEEPER1.
The difference between BEEPER1 and BEEPER2: Windows sends timer messages to TimerProc instead of WndProc.