Function FDrawClip

xgeneral.cpp:843–882

// viewport or if entire line is outside of viewport and nothing at all drawn.

flag FDrawClip(int x1, int y1, int x2, int y2, int xl, int yl, int xh, int yh,
  int skip, int *x0, int *y0)
{
  if ((x1 < xl && x2 < xl) || (y1 < yl && y2 < yl) ||  // Skip if outside
    (x1 > xh && x2 > xh) || (y1 > yh && y2 > yh))      // bounding box.
    return fFalse;
  if (x1 < xl)
    ClipLesser (&y1, &x1, &y2, &x2, xl);    // Check left side of window.
  if (x2 < xl)
    ClipLesser (&y2, &x2, &y1, &x1, xl);
  if (y1 < yl)
    ClipLesser (&x1, &y1, &x2, &y2, yl);    // Check top side of window.
  if (y2 < yl)
    ClipLesser (&x2, &y2, &x1, &y1, yl);
  if (x1 > xh)
    ClipGreater(&y1, &x1, &y2, &x2, xh);    // Check right of window.
  if (x2 > xh)
    ClipGreater(&y2, &x2, &y1, &x1, xh);
  if (y1 > yh)
    ClipGreater(&x1, &y1, &x2, &y2, yh);    // Check bottom of window.
  if (y2 > yh)
    ClipGreater(&x2, &y2, &x1, &y1, yh);
  if (x1 < xl || x2 < xl || y1 < yl || y2 < yl ||  // Skip if not inside
    x1 > xh || x2 > xh || y1 > yh || y2 > yh)      // bounding box.
    return fFalse;
  DrawDash(x1, y1, x2, y2, skip);           // Go draw the line.

  // Return coordinates at which drawn line crosses bounding box.
  if (x0 != NULL) {
    if (x1 == xl || x1 == xh || y1 == yl || y1 == yh) {
      *x0 = x1; *y0 = y1;
      return fTrue;
    }
    if (x2 == xl || x2 == xh || y2 == yl || y2 == yh) {
      *x0 = x2; *y0 = y2;
      return fTrue;
    }
  }
  return fFalse;
}


// Fast version of rotating that assumes the slow trigonometry values have