AddNullXY for the TFastLineSeries

Problem:

Solution:

Function TChartSeries.AddNull(Const ALabel:String):Longint;
begin
  result:=Add( 0, ALabel, clNone );
end; 

Function TChartSeries.AddNullXY(Const X,Y:Double; Const 
ALabel:String):Longint;
begin
  result:=AddXY(X,Y,ALabel,clNone );
end; 

The TFastLineSeries.DrawValue method draws all point with the same color and therefore all points are drawn in SeriesColor. The solution is (again) to override DrawValue method and differentiate between "normal" (ValueColor<>clNone) and "null" (ValueColor:=clNone) points.

procedure TMyFastLineSeries.DrawValue(ValueIndex:LongInt);
Var X : Longint;
Y : Longint;
tmpX : Longint;
tmpY : Longint;
tmp3D : Boolean;
tmpC : TColor;
Begin
  X:=CalcXPos(ValueIndex);
  Y:=CalcYPos(ValueIndex);
  tmpColor:=ValueColor[ValueIndex];
  tmp3D:=ParentChart.View3D; 

// the whole trick of null value is it's Color=clNone
  if (OldColor=clNone) or (tmpColor=clNone) then
  begin
   OldX:=X;
   OldY:=Y;
  end; 

With ParentChart.Canvas do
begin
  if ValueIndex=FirstValueIndex then
   if (ValueIndex>0) then
   begin
    tmpX:=CalcXPos(ValueIndex-1);
    tmpY:=CalcYPos(ValueIndex-1);
    tmpC:=ValueColor[ValueIndex-1];
    if (tmpColor=clNone) or (tmpC=clNone) then
     if tmp3D then MoveTo3D(X,Y,MiddleZ) else MoveTo(X,Y)
     else
     if tmp3D then LineWithZ(tmpX,tmpY,X,Y,MiddleZ)
    else Line(tmpX,tmpY,X,Y)
   end
   else
   if tmp3D then MoveTo3D(X,Y,MiddleZ) else MoveTo(X,Y)
    else
     if (X<>OldX) or (Y<>OldY) then
      if tmp3D then LineTo3D(X,Y,MiddleZ) else LineTo(X,Y)
     else
     begin
      MoveTo(X,Y);
      OldColor:=tmpColor;
      Exit;
     end
   end;
   OldX:=X;
   OldY:=Y;
   OldColor:=tmpColor;
End;