// JS-DASH2.TXT (c) J R Stockton www.merlyn.demon.co.uk >= 2009-12-31

// From sitedata.htm 2009-12-29, adjusted :

function dashTo(X2, Y2, Ptrn) { // segment of dasked line set
  // X2 Y2 : X & Y to go TO ; internal X1 Y1 to go FROM
  // Ptrn as [6,4, 1,4] // mark-space pairs indexed by Seg
  // supply Ptrn only for the first point of a dashed line set
  if (Ptrn) {
    this.Obj = {Patn:Ptrn, Seg:0, Phs:0, X1:X2, Y1:Y2} ; return }
  var XDis, YDis, Dist, X, More, T, Ob = this.Obj
  XDis = X2 - Ob.X1				// DeltaX
  YDis = Y2 - Ob.Y1				// DeltaY
  Dist = Math.sqrt(XDis*XDis + YDis*YDis)	// length
  this.save()
  this.translate(Ob.X1, Ob.Y1)
  this.rotate(Math.atan2(YDis, XDis))
  this.moveTo(0, 0) ; X = 0 // Now dash pattern from 0,0 to Dist,0
  do {
    T = Ob.Patn[Ob.Seg]	// Full segment
    X += T - Ob.Phs	// Move by unused seg
    More = X < Dist	// Not too far?
    if (!More) { Ob.Phs = T - (X - Dist) ; X = Dist } // adjust
    Ob.Seg%2 ? this.moveTo(X, 0) : this.lineTo(X, 0)
    if (More) { Ob.Phs = 0 ; Ob.Seg = ++Ob.Seg % Ob.Patn.length }
    } while (More)
  Ob.X1 = X2 ; Ob.Y1 = Y2
  this.restore() }

if (CX) CanvasRenderingContext2D.prototype.dashTo = dashTo

// End.