/// <summary>
/// Returns first element of list (O(1))
/// </summary>
public T front()
{
return(_head.elem());
}
/** Used in polygon composition to composit polygons into scan lines
* Combining polya and polyb into one super-polygon stored in polya.
**/
private static void combLeft(ref GeomPoly polya, ref GeomPoly polyb)
{
var ap = polya.points;
var bp = polyb.points;
var ai = ap.begin();
var bi = bp.begin();
var b = bi.elem();
CxFastListNode <Vector2> prea = null;
while (ai != ap.end())
{
var a = ai.elem();
if (vec_dsq(a, b) < float.Epsilon)
{
//ignore shared vertex if parallel
if (prea != null)
{
var a0 = prea.elem();
b = bi.next().elem();
Vector2 u = a - a0;
//vec_new(u); vec_sub(a.p.p, a0.p.p, u);
Vector2 v = b - a;
//vec_new(v); vec_sub(b.p.p, a.p.p, v);
var dot = vec_cross(u, v);
if (dot * dot < float.Epsilon)
{
ap.erase(prea, ai);
polya.length--;
ai = prea;
}
}
//insert polyb into polya
var fst = true;
CxFastListNode <Vector2> preb = null;
while (!bp.empty())
{
var bb = bp.front();
bp.pop();
if (!fst && !bp.empty())
{
ai = ap.insert(ai, bb);
polya.length++;
preb = ai;
}
fst = false;
}
//ignore shared vertex if parallel
ai = ai.next();
var a1 = ai.elem();
ai = ai.next(); if (ai == ap.end())
{
ai = ap.begin();
}
var a2 = ai.elem();
var a00 = preb.elem();
Vector2 uu = a1 - a00;
//vec_new(u); vec_sub(a1.p, a0.p, u);
Vector2 vv = a2 - a1;
//vec_new(v); vec_sub(a2.p, a1.p, v);
var dot1 = vec_cross(uu, vv);
if (dot1 * dot1 < float.Epsilon)
{
ap.erase(preb, preb.next());
polya.length--;
}
return;
}
prea = ai;
ai = ai.next();
}
}
