cyclelistAndCanvasOfDart

cyclelistAndCanvasOfDart

import 'dart:html';


void main() {
  Vec2 p1=new Vec2(50,50);
  Vec2 p2=new Vec2(100,50);
  Vec2 p3=new Vec2(100,100);
  Vec2 p4=new Vec2(50,100); 

  HtmlCanvas canvas = new HtmlCanvas("#canvas")
  
  canvas.context.beginPath();
  canvas.context.moveTo(p1.x, p1.y);
  canvas.context.lineTo(p2.x, p2.y); 
  canvas.context.lineTo(p3.x, p3.y); 
  canvas.context.lineTo(p4.x, p4.y);
  canvas.context.lineWidth=4; 
  canvas.context.strokeStyle='red';
  canvas.context.closePath(); 
  canvas.context.stroke(); 
}

class HtmlCanvas{
  CanvasRenderingContext2D _context = null; 
  String _id;
  HtmlCanvas (String id) {
    _id = id; 
    _context = (querySelector(id) as CanvasElement).context2D;

  }
  CanvasRenderingContext2D  get context {
    return _context;
  }
  String toString(){
    return "HtmlCanas($_id)";
  }
}

class Vec2 {
  var vec=<num>[0,0];
  num get x {
    return vec[0];
  }
  set x(num value){
    vec[0]=value;
  }
  
  num get y {
    return vec[1];
  }
  set y(num value){
    vec[1] = value; 
  }
  
  Vec2 (num x, num y){
    vec[0]=x;
    vec[1]=y;
  }
  Vec2.fromList (List<num> a){
    assert(a.length == 2);
    vec[0] = a[0];
    vec[1] = a[1];
  }
  String toString(){
    return "(${vec[0]},${vec[1]})";
  }
}

class ListNode<T>{
  T value; 
  ListNode<T> prev=null; 
  ListNode<T> next=null;
  ListNode(T v,[ListNode<T> p,ListNode<T> n]){
    value = v;
    prev = p; 
    next = n; 
  }
  String toString(){
      return "Node($value)";
  }
}

class CycleList<T>{
  ListNode<T> head=null; 
  int _size = 0; 
  int get size {
    return _size; 
  }
  void append(T v){
    ListNode<T> node = new ListNode<T>(v);
    if(head == null){
      head = node;
      node.prev=head;
      node.next=head; 
    } else {
      node.prev = head.prev; 
      node.next = head; 
      head.prev = node; 
      node.prev.next = node; 
    }
    _size ++; 
  }
  void remove(ListNode<T> node){
    assert(head != null);
    assert(size > 0);
    if(size==1){
      head = null; 
    } else {
      node.prev.next = node.next;
      node.next.prev = node.prev;    
    }
    _size --; 
  }
  String toString(){
    StringBuffer sb=new StringBuffer();
    
    sb.write("[");
    var node = head;
    do {
      if(node ==null) break; 
      sb.write(node);
      node=node.next; 
    } while(node!=head);
    sb.write("]"); 
    return sb.toString();  
  }
}