Emanuele Feronato

var game;
var speedMult = 0.7;
// this is the friction which will slow down the map. Must be less than 1
var friction = 0.99;
window.onload = function() {	
	game = new Phaser.Game(480, 480, Phaser.AUTO, "");
 game.state.add("PlayGame", playGame);
 game.state.start("PlayGame");
}
var playGame = function(game){};
playGame.prototype = {
 preload: function(){
 game.load.image("map", "map.png");
 },
 create: function(){ 
 // the big map to scroll
 this.scrollingMap = game.add.image(0, 0, "map");
 // map will accept inputs
 this.scrollingMap.inputEnabled = true;
 // map can be dragged
 this.scrollingMap.input.enableDrag(false);
 // custom property: we save map position
 this.scrollingMap.savedPosition = new Phaser.Point(this.scrollingMap.x, this.scrollingMap.y);
 // custom property: the map is not being dragged at the moment
 this.scrollingMap.isBeingDragged = false; 
 // custom property: map is not moving (or is moving at no speed)
 this.scrollingMap.movingSpeed = 0; 
 // map can be dragged only if it entirely remains into this rectangle
 this.scrollingMap.input.boundsRect = new Phaser.Rectangle(game.width - this.scrollingMap.width, game.height - this.scrollingMap.height, this.scrollingMap.width * 2 - game.width, this.scrollingMap.height * 2 - game.height);
 // when the player starts dragging...
 this.scrollingMap.events.onDragStart.add(function(){
 // set isBeingDragged property to true
 this.scrollingMap.isBeingDragged = true;
 // set movingSpeed property to zero. This will stop moving the map
 // if the player wants to drag when it's already moving
 this.scrollingMap.movingSpeed = 0;
 }, this);
 // when the player stops dragging...
 this.scrollingMap.events.onDragStop.add(function(){
 // set isBeingDragged property to false
 this.scrollingMap.isBeingDragged = false;
 }, this);
 },
 update:function(){
 // if the map is being dragged...
 if(this.scrollingMap.isBeingDragged){
 // save current map position
 this.scrollingMap.savedPosition = new Phaser.Point(this.scrollingMap.x, this.scrollingMap.y);
 }
 // if the map is NOT being dragged...
 else{
 // if the moving speed is greater than 1...
 if(this.scrollingMap.movingSpeed > 1){
 // adjusting map x position according to moving speed and angle using trigonometry
 this.scrollingMap.x += this.scrollingMap.movingSpeed * Math.cos(this.scrollingMap.movingangle);
 // adjusting map y position according to moving speed and angle using trigonometry
 this.scrollingMap.y += this.scrollingMap.movingSpeed * Math.sin(this.scrollingMap.movingangle);
 // keep map within boundaries
 if(this.scrollingMap.x < game.width - this.scrollingMap.width){
 this.scrollingMap.x = game.width - this.scrollingMap.width;
 }
 // keep map within boundaries
 if(this.scrollingMap.x > 0){
 this.scrollingMap.x = 0;
 }
 // keep map within boundaries
 if(this.scrollingMap.y < game.height - this.scrollingMap.height){
 this.scrollingMap.y = game.height - this.scrollingMap.height;
 }
 // keep map within boundaries
 if(this.scrollingMap.y > 0){
 this.scrollingMap.y = 0;
 }
 // applying friction to moving speed
 this.scrollingMap.movingSpeed *= friction;
 // save current map position
 this.scrollingMap.savedPosition = new Phaser.Point(this.scrollingMap.x, this.scrollingMap.y);
 }
 // if the moving speed is less than 1...
 else{
 // checking distance between current map position and last saved position
 // which is the position in the previous frame
 var distance = this.scrollingMap.savedPosition.distance(this.scrollingMap.position);
 // same thing with the angle
 var angle = this.scrollingMap.savedPosition.angle(this.scrollingMap.position);
 // if the distance is at least 4 pixels (an arbitrary value to see I am swiping)
 if(distance > 4){
 // set moving speed value
 this.scrollingMap.movingSpeed = distance * speedMult;
 // set moving angle value
 this.scrollingMap.movingangle = angle;
 }
 }
 }
 }
}

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