这段代码什么意思

lqhde158

    static int yPosToucan;
    static int yAdd;
    GUI_RECT   Rect = {0, 0, 0, 0};
    yPosToucan = 20;
    yAdd       = 1;

    yPosToucan += yAdd;
    if (yPosToucan >= 100) {
      yAdd = -yAdd;
      yPosToucan = 100;
    } else if (yPosToucan <= 20) {
      yAdd = -yAdd;
      yPosToucan = 20;
    }
    Rect.x0 = 146;
    Rect.y0 = yPosToucan - 5;
    Rect.x1 = Rect.x0 + _bmToucan.XSize - 1;
    Rect.y1 = Rect.y0 + _bmToucan.YSize - 1 + 5;
    WM_InvalidateRect(pMsg->hWin, &Rect);