1     /**
2         A manager for all the objects in the game
3         @author <a href="mailto:matthewcasperson@gmail.com">Matthew Casperson</a>
4         @class
5     */
6     function GameObjectManager()
7 {
8 /** An array of game objects 9 @type Arary 10 */ 11 this.gameObjects = new Array();
12 /** The time that the last frame was rendered 13 @type Date 14 */ 15 this.lastFrame = new Date().getTime();
16 /** The global scrolling value of the x axis 17 @type Number 18 */ 19 this.xScroll = 0;
20 /** The global scrolling value of the y axis 21 @type Number 22 */ 23 this.yScroll = 0;
24 /** A reference to the ApplicationManager instance 25 @type ApplicationManager 26 */ 27 this.applicationManager = null;
28 /** A reference to the canvas element 29 @type HTMLCanvasElement 30 */ 31 this.canvas = null;
32 /** A reference to the 2D context of the canvas element 33 @type CanvasRenderingContext2D 34 */ 35 this.context2D = null;
36 /** A reference to the in-memory canvas used as a back buffer 37 @type HTMLCanvasElement 38 */ 39 this.backBuffer = null;
40 /** A reference to the backbuffer 2D context 41 @type CanvasRenderingContext2D 42 */ 43 this.backBufferContext2D = null;
44 45 /** 46 Initialises this object 47 @return A reference to the initialised object 48 */ 49 this.startupGameObjectManager = function()
50 {
51 // set the global pointer to reference this object 52 g_GameObjectManager = this;
53 54 // get references to the canvas elements and their 2D contexts 55 this.canvas = document.getElementById('canvas');
56 this.context2D = this.canvas.getContext('2d');
57 this.backBuffer = document.createElement('canvas');
58 this.backBuffer.width = this.canvas.width;
59 this.backBuffer.height = this.canvas.height;
60 this.backBufferContext2D = this.backBuffer.getContext('2d');
61 62 // create a new ApplicationManager 63 this.applicationManager = new ApplicationManager().startupApplicationManager();
64 65 // use setInterval to call the draw function 66 setInterval(function(){g_GameObjectManager.draw();}, SECONDS_BETWEEN_FRAMES);
67 68 return this;
69 }
70 71 /** 72 The render loop 73 */ 74 this.draw = function ()
75 {
76 // calculate the time since the last frame 77 var thisFrame = new Date().getTime();
78 var dt = (thisFrame - this.lastFrame)/1000;
79 this.lastFrame = thisFrame;
80 81 // clear the drawing contexts 82 this.backBufferContext2D.clearRect(0, 0, this.backBuffer.width, this.backBuffer.height);
83 this.context2D.clearRect(0, 0, this.canvas.width, this.canvas.height);
84 85 // first update all the game objects 86 for (x in this.gameObjects)
87 {
88 if (this.gameObjects[x].update)
89 {
90 this.gameObjects[x].update(dt, this.backBufferContext2D, this.xScroll, this.yScroll);
91 }
92 }
93 94 // then draw the game objects 95 for (x in this.gameObjects)
96 {
97 if (this.gameObjects[x].draw)
98 {
99 this.gameObjects[x].draw(dt, this.backBufferContext2D, this.xScroll, this.yScroll);
100 }
101 }
102 103 // copy the back buffer to the displayed canvas 104 this.context2D.drawImage(this.backBuffer, 0, 0);
105 };
106 107 /** 108 Adds a new GameObject to the gameObjects collection 109 @param gameObject The object to add 110 */ 111 this.addGameObject = function(gameObject)
112 {
113 this.gameObjects.push(gameObject);
114 this.gameObjects.sort(function(a,b){return a.zOrder - b.zOrder;})
115 };
116 117 /** 118 Removes a GameObject from the gameObjects collection 119 @param gameObject The object to remove 120 */ 121 this.removeGameObject = function(gameObject)
122 {
123 this.gameObjects.removeObject(gameObject);
124 }
125 }
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