{ Turbo List }
{ Copyright (c) 1989 by Borland Interational, Inc. }

program ListDemo;
{ From P-57 of the Object-Oriented Programming Guide.
  Dynamic objects & destructors.
}

uses Graph, Figures;

type
  ArcPtr = ^Arc;
  Arc = object(Circle)
    StartAngle, EndAngle : Integer;
    constructor Init(InitX, InitY : Integer;
                     InitRadius : Integer;
                     InitStartAngle, InitEndAngle : Integer);
    procedure Show; virtual;
    procedure Hide; virtual;
  end;

  NodePtr = ^Node;
  Node = record
    Item : PointPtr;
    Next : NodePtr;
  end;

  ListPtr = ^List;
  List = object
    Nodes: NodePtr;
    constructor Init;
    destructor Done; virtual;
    procedure Add(Item : PointPtr);
    procedure Report;
  end;

var
  GraphDriver : Integer;
  GraphMode : Integer;
  Temp : String;
  AList : List;
  PArc : ArcPtr;
  PCircle : CirclePtr;
  RootNode : NodePtr;


{--------------------------------------------------------}
{ Procedures that are not methods:                       }
{--------------------------------------------------------}

procedure OutTextLn(TheText : String);
begin
  OutText(TheText);
  MoveTo(0, GetY+12);
end;


procedure HeapStatus(StatusMessage : String);
begin
  Str(MemAvail : 6, Temp);
  OutTextLn(StatusMessage+Temp);
end;


{--------------------------------------------------------}
{ Arc's method implementations:                          }
{--------------------------------------------------------}

constructor Arc.Init(InitX, InitY : Integer;
                     InitRadius : Integer;
                     InitStartAngle, InitEndAngle : Integer);

begin
  Circle.Init(InitX, InitY, InitRadius);
  StartAngle := InitStartAngle;
  EndAngle := InitEndAngle;
end;

procedure Arc.Show;
begin
  Visible := True;
  Graph.Arc(X, Y, StartAngle, EndAngle, Radius);
end;

procedure Arc.Hide;
var
  TempColor : Word;
begin
  TempColor := Graph.GetColor;
  Graph.SetColor(GetBkColor);
  Visible := False;
  Graph.Arc(X, Y, StartAngle, EndAngle, Radius);
  SetColor(TempColor);
end;


{--------------------------------------------------------}
{ List's method implementations:                         }
{--------------------------------------------------------}

constructor List.Init;
begin
  Nodes := nil;
end;

destructor List.Done;
var
  N : NodePtr;
begin
  while Nodes <> nil do
  begin
    N := Nodes;
    Nodes := N^.Next;
    Dispose(N^.Item, Done);
    Dispose(N);
  end;
end;


procedure List.Add(Item : PointPtr);
var
  N : NodePtr;
begin
  New(N);
  N^.Item := Item;
  N^.Next := Nodes;
  Nodes := N;
end;

procedure List.Report;
var
  Current : NodePtr;
begin
  Current := Nodes;
  while Current <> nil do
    begin
      Str(Current^.Item^.GetX : 3, Temp);
      OutTextLn('X = '+Temp);
      Str(Current^.Item^.GetY : 3, Temp);
      OutTextLn('Y = '+Temp);
      Current := Current^.Next;
    end;
end;


{--------------------------------------------------------}
{ Main program:                                          }
{--------------------------------------------------------}

begin
  { Let the BGI determine what board you're using: }
  DetectGraph(GraphDriver, GraphMode);
  InitGraph(GraphDriver, GraphMode,'');
  if GraphResult <> GrOK then
    begin
      WriteLn('>>Halted on graphics error: ',
              GraphErrorMsg(GraphDriver));
      Halt(1);
    end;

  HeapStatus('Heap space before list is allocated: ');

  { Create a list }
  AList.Init;

  { Now create and add several figures to it in one operation }
  AList.Add(New(ArcPtr, Init(151, 82, 25, 200, 330)));
  AList.Add(New(CirclePtr, Init(400, 100, 40)));
  AList.Add(New(CirclePtr, Init(305, 136, 5)));

  { Traverse the list and display X,Y of the list's figures }
  AList.Report;

  HeapStatus('Heap space after list is allocated ');

  { Deallocate the whole list with one destructor call }
  AList.Done;

  HeapStatus('Heap space after list is cleaned up: ');

  OutText('Press Enter to end program: ');
  Readln;

  CloseGraph;
end.