Function IsLineDefInside

roomedit/source/objects.cpp:1008–1064

*/

BOOL IsLineDefInside (SHORT ldnum, SHORT x0, SHORT y0, SHORT x1, SHORT y1)
{
	LineDef *pLD = &LineDefs[ldnum];
	SHORT start = pLD->start;
	SHORT end   = pLD->end;

	Vertex *pVStart = &Vertexes[start];
	Vertex *pVEnd   = &Vertexes[end];
	SHORT lx0 = pVStart->x;
	SHORT ly0 = pVStart->y;
	SHORT lx1 = pVEnd->x;
	SHORT ly1 = pVEnd->y;
	SHORT i;

	// The LineDef start is entirely inside the square ?
	if (lx0 >= x0 && lx0 <= x1 && ly0 >= y0 && ly0 <= y1)
		return TRUE;

	// The LineDef end is entirely inside the square ?
	if (lx1 >= x0 && lx1 <= x1 && ly1 >= y0 && ly1 <= y1)
		return TRUE;


	// The LineDef crosses the y0 side (left) ?
	if ((ly0 > y0) != (ly1 > y0))
	{
		i = lx0 + (SHORT) ( (long) (y0 - ly0) * (long) (lx1 - lx0) / (long) (ly1 - ly0));
		if (i >= x0 && i <= x1)
			return TRUE;
	}

	// The LineDef crosses the y1 side (right) ?
	if ((ly0 > y1) != (ly1 > y1))
	{
		i = lx0 + (SHORT) ( (long) (y1 - ly0) * (long) (lx1 - lx0) / (long) (ly1 - ly0));
		if (i >= x0 && i <= x1)
			return TRUE;
	}

	// The LineDef crosses the x0 side (down) ?
	if ((lx0 > x0) != (lx1 > x0))
	{
		i = ly0 + (SHORT) ( (long) (x0 - lx0) * (long) (ly1 - ly0) / (long) (lx1 - lx0));
		if (i >= y0 && i <= y1)
			return TRUE;
	}

	// The LineDef crosses the x1 side (up) ?
	if ((lx0 > x1) != (lx1 > x1))
	{
		i = ly0 + (SHORT) ( (long) (x1 - lx0) * (long) (ly1 - ly0) / (long) (lx1 - lx0));
		if (i >= y0 && i <= y1)
			return TRUE;
	}

	return FALSE;
}