// gives the intersection-point between two lines, returns true, if any
// computes the crossing point between the (infinite) lines
// defined by the endpoints of the DLines, then checks if it
// lies within the two rectangles defined by the DLines endpoints
bool DLine::intersection(
const DLine &line,
DPoint &inter,
bool endpoints) const
{
double ix, iy;
//do not return true if parallel edges are encountered
if (slope() == line.slope()) return false;
//two possible checks:
// only check for overlap on endpoints if option parameter set,
// compute crossing otherwise
// or skip computation if endpoints overlap (can't have "real" crossing)
// (currently implemented)
//if (endpoints) {
if (m_start == line.m_start || m_start == line.m_end) {
inter = m_start;
if (endpoints) return true;
else return false;
}
if (m_end == line.m_start || m_end == line.m_end) {
inter = m_end;
if (endpoints) return true;
else return false;
}
//}//if endpoints
//if the edge is vertical, we cannot compute the slope
if (isVertical())
ix = m_start.m_x;
else
if (line.isVertical())
ix = line.m_start.m_x;
else
ix = (line.yAbs() - yAbs())/(slope() - line.slope());
//set iy to the value of the infinite line at xvalue ix
//use a non-vertical line (can't be both, otherwise they're parallel)
if (isVertical())
iy = line.slope() * ix + line.yAbs();
else
iy = slope() * ix + yAbs();
inter = DPoint(ix, iy); //the (infinite) lines cross point
DRect tRect(line);
DRect mRect(*this);
return (tRect.contains(inter) && mRect.contains(inter));
}
