Question

im trying to create ball animation using gdi but i can’t get it working.
i created a ball using this

   Graphics graphics(hdc);

Pen pen(Color(255, 0, 0, 255));
graphics.DrawEllipse(&pen, sf , 0, 10, 10);
i have while loop that loops and adds 1 to sf value basicly like this sf++;
than i try to repaint the window(it doesn’t work) so ill end up with more than one circle ;/
here is the loop( the loop is int WM_PAINT)

while(sd==1)//sd equals 1
    {
        sf++;
        onPaint(hdc);
        InvalidateRect (hWnd, NULL, TRUE);// this should repaint the window but it doesn't
        UpdateWindow(hWnd);
    }

thanks in advance
Rami

Answer 1

In order to achieve animation I would suggest you use a timer. For example:

int OnCreate(HWND window, WPARAM wParam, LPARAM lParam)
{
   SetTimer(window, TIMER_ID, 1000, 0);
   return 0;
}

now window will receive WM_TIMER messages every second (1000ms). You should handle them:

int OnTimer(HWND window, WPARAM wParam, LPARAM lParam)
{
   if(TIMER_ID == wParam)
   {
      /*do stuff*/
      InvalidateRect(window, NULL, TRUE);//force window to repaint
   }
   return 0;
}

then you need to handle WM_PAINT message to do the drawing

int OnPaint(HWND window, WPARAM wParam, LPARAM lParam)
{
   PAINTSTRUCT ps;
   HDC dc = BeginPaint(&ps);
   Graphics graphics(hdc);
   graphics.Draw...
   EndPaint(&ps);
   return 0;
}