Added render queue

lib/epubjs/queue.js

@@ -0,0 +1,94 @@
+EPUBJS.Queue = function(_context){
+  this._q = [];
+  this.context = _context;
+  this.tick = EPUBJS.core.requestAnimationFrame;
+  this.running = false;
+};
+
+// Add an item to the queue
+EPUBJS.Queue.prototype.enqueue = function(task, args, context) {
+  // Handle single args without context
+  if(args && !args.length) {
+    args = [args];
+  }
+
+  this._q.push({
+    "task" : task,
+    "args"     : args,
+    "context"  : context
+  });
+  return this._q;
+};
+
+// Run one item
+EPUBJS.Queue.prototype.dequeue = function(){
+  var inwait, task;
+
+  if(this._q.length) {
+    inwait = this._q.shift();
+    task = inwait.task;
+
+    if(typeof task === "function"){
+      // Task is a function that returns a promise
+      return task.apply(inwait.context || this.context, inwait.args);
+    } else {
+      // Task is a promise
+      return task;
+    }
+
+  } else {
+    return null;
+  }
+};
+
+// Run All Immediately
+EPUBJS.Queue.prototype.flush = function(){
+  while(this._q.length) {
+    this.dequeue();
+  }
+};
+
+// Run all sequentially, at convince
+EPUBJS.Queue.prototype.run = function(){
+  if(!this.running && this._q.length) {
+    this.running = true;
+    this.dequeue().then(function(){
+      this.running = false;
+    }.bind(this));
+  }
+  
+  this.tick.call(window, this.run.bind(this));
+};
+
+// Clear all items in wait
+EPUBJS.Queue.prototype.clear = function(){
+  this._q = [];
+};
+
+EPUBJS.Queue.prototype.length = function(){
+  return this._q.length;
+};
+
+// Create a new tast from a callback
+EPUBJS.Task = function(task, args, context){
+  var toApply = args || [];
+  var scope = context || this.context;
+
+  return function(){
+
+    return new RSVP.Promise(function(resolve, reject) {
+
+      var callback = function(value){
+        resolve(value);
+      };
+      // Add the callback to the arguments list
+      toApply.push(callback);
+
+      // Apply all arguments to the functions
+      task.apply(scope, toApply);
+    
+    });
+
+  };
+
+};