Problem with timeGetTime()
Dear all,
I am working on a long Windows program. I included all of the code so that I don’t miss anything.
Code:
/* Inverted Pendulum Project */
#include <windows.h>
#include <string.h>
#include <stdio.h>
#include "Clock2.h"
#define SamplingTime 3000 //in milliseconds
LRESULT CALLBACK WindowFunc(HWND, UINT, WPARAM, LPARAM); //Callback function prototype
//Variables used:
char szWinName[] = "MyWin"; /* name of window class */
char str[255] = ""; /* holds output string */
char *clr = " ";
BOOL greenlight = false;
UINT xref, x;
Clock timer;
//Main program:
int WINAPI WinMain(HINSTANCE hThisInst, HINSTANCE hPrevInst,
LPSTR lpszArgs, int nWinMode)
{
HWND hwnd;
MSG msg;
WNDCLASSEX wcl;
/* Define a window class. */
wcl.cbSize = sizeof(WNDCLASSEX);
wcl.hInstance = hThisInst; /* handle to this instance */
wcl.lpszClassName = szWinName; /* window class name */
wcl.lpfnWndProc = WindowFunc; /* window function */
wcl.style = 0; /* default style */
wcl.hIcon = LoadIcon(NULL, IDI_APPLICATION); /* standard icon */
wcl.hIconSm = LoadIcon(NULL, IDI_WINLOGO); /* small icon */
wcl.hCursor = LoadCursor(NULL, IDC_ARROW); /* cursor style */
wcl.lpszMenuName = NULL; /* no main menu */
wcl.cbClsExtra = 0; /* no extra */
wcl.cbWndExtra = 0; /* information needed */
/* Make the window white. */
wcl.hbrBackground = (HBRUSH) GetStockObject(WHITE_BRUSH);
/* Register the window class. */
if(!RegisterClassEx(&wcl)) return 0;
/* Now that a window class has been registered, a window
can be created. */
hwnd = CreateWindow(
szWinName, /* name of window class */
"Processing Mouse Messages", /* title */
WS_OVERLAPPEDWINDOW, /* window style - normal */
CW_USEDEFAULT, /* X coordinate - let Windows decide */
CW_USEDEFAULT, /* Y coordinate - let Windows decide */
CW_USEDEFAULT, /* width - let Windows decide */
CW_USEDEFAULT, /* height - let Windows decide */
HWND_DESKTOP, /* no parent window */
NULL, /* no menu */
hThisInst, /* handle of this instance of the program */
NULL /* no additional arguments */
);
/* Display the window. */
ShowWindow(hwnd, nWinMode);
UpdateWindow(hwnd);
/* Create the message loop. */
while(GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg); /* translate keyboard messages */
DispatchMessage(&msg); /* return control to Windows 98 */
}
return msg.wParam;
}
/* This function is called by Windows 98 and is passed
messages from the message queue.
*/
LRESULT CALLBACK WindowFunc(HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)
{
HDC hdc;
switch(message) {
case WM_CHAR:
hdc = GetDC(hwnd);
switch(wParam)
{
case 'r': case 'R': //Pressing 'r' or 'R' sets reference point, resets timer
greenlight = true;
timer.reset();
xref=x;
TextOut(hdc, 10, 400, clr, strlen(clr));
sprintf(str, "xref = %d", xref);
TextOut(hdc, 10, 400, str, strlen(str));
break;
case 's': case 'S': //Pressing 's' or 'S' halts all operations
greenlight = false;
break;
default:
greenlight = greenlight;
}
ReleaseDC(hwnd, hdc);
break;
case WM_RBUTTONDOWN: // Clicking right mouse button clears "YES!" message
hdc = GetDC(hwnd);
TextOut(hdc, 100, 400, clr, strlen(clr));
ReleaseDC(hwnd, hdc);
break;
case WM_LBUTTONDOWN: // Clicking left mouse button closes the window (terminates operations)
hdc = GetDC(hwnd);
PostQuitMessage(0);
ReleaseDC(hwnd, hdc);
break;
case WM_MOUSEMOVE: // Processing pointer motion
hdc = GetDC(hwnd);
if (greenlight == 1)
{
TextOut(hdc, 10, 50, clr, strlen(clr));
sprintf(str, "Time passed is %f seconds", (float)timer.time()/1000);
TextOut(hdc, 10, 50, str, strlen(str));
TextOut(hdc, 10, 10, clr, strlen(clr));
sprintf(str, "Mouse coordinates are at (%d, %d)", LOWORD(lParam), HIWORD(lParam));
TextOut(hdc, 10, 10, str, strlen(str));
if (timer.sample(SamplingTime))
{
TextOut(hdc, 100, 400, clr, strlen(clr));
sprintf(str, "YES!");
TextOut(hdc, 100, 400, str, strlen(str));
}
}
x=LOWORD(lParam); //Set x-coordinate
ReleaseDC(hwnd,hdc);
break;
case WM_DESTROY: // Terminate the program
PostQuitMessage(0);
break;
default:
/* Let Windows 98 process any messages not specified in
the preceding switch statement. */
return DefWindowProc(hwnd, message, wParam, lParam);
}
return 0;
}
Here is the Clock2.h header file:
Code:
MMRESULT begin = timeBeginPeriod(1);
MMRESULT end = timeEndPeriod(2);
class Clock
{
private:
DWORD timestarted; //time started (in seconds)
//DWORD sampler;
public:
Clock();
BOOL sample(const int&);
VOID reset();
VOID wait(const int&); //wait a certain number of seconds
long time(); //return the time in seconds since last reset
};
Clock::Clock()
{
//timestarted=(float)timeGetTime()/1000;
(*this).reset();
}
VOID Clock::reset()
{
timestarted = timeGetTime();
//sampler = timeGetTime();
return;
}
long Clock::time()
{
return timeGetTime()-timestarted; //return time elapsed in seconds
}
VOID wait(const int &tsec)
{
DWORD beginning = timeGetTime();
while(beginning + tsec > timeGetTime())
{ /* wait */}
return;
}
BOOL Clock::sample(const int &msec)
{
int center=time()%msec;
if(center >= 0 && center <= 4)
return true;
else
return false;
}
The problem is the following: I want to get the mouse coordinates every, say, 3 seconds. That is the point of the “sample” member function in the Clock2.h header file. Just to test the response of the computer, I ordered a “YES!” message to be displayed every time the sampling period elapses (so, in this example, every 3 seconds). This is not working unless I have an error range allowing at least 4 milliseconds to pass. Is there no way to do this with zero error (accumulation of error will render my program useless after a few seconds, because the actual time is less than 3 seconds). Thank you oh so dearly.