Experimented with a PathFollower Game Object Component.

src/gameobjects/components/Path.js

@@ -0,0 +1,418 @@
+/**
+ * @author       Richard Davey <rich@photonstorm.com>
+ * @copyright    2018 Photon Storm Ltd.
+ * @license      {@link https://github.com/photonstorm/phaser/blob/master/license.txt|MIT License}
+ */
+
+var DegToRad = require('../../math/DegToRad');
+var GetBoolean = require('../../tweens/builders/GetBoolean');
+var GetValue = require('../../utils/object/GetValue');
+var TWEEN_CONST = require('../../tweens/tween/const');
+var Vector2 = require('../../math/Vector2');
+
+/**
+ * Settings for a PathFollower.
+ *
+ * @typedef {object} PathConfig
+ *
+ * @property {number} duration - The duration of the path follow.
+ * @property {number} from - The start position of the path follow, between 0 and 1.
+ * @property {number} to - The end position of the path follow, between 0 and 1.
+ * @property {boolean} [positionOnPath=false] - Whether to position the PathFollower on the Path using its path offset.
+ * @property {boolean} [rotateToPath=false] - Should the PathFollower automatically rotate to point in the direction of the Path?
+ * @property {number} [rotationOffset=0] - If the PathFollower is rotating to match the Path, this value is added to the rotation value. This allows you to rotate objects to a path but control the angle of the rotation as well.
+ * @property {boolean} [verticalAdjust=false] - [description]
+ */
+
+/**
+ * Provides properties and methods used to allow a Game Object to follow a Path automatically.
+ *
+ * @name Phaser.GameObjects.Components.Transform
+ * @since 3.12.0
+ */
+var Path = {
+
+    /**
+     * The Path this PathFollower is following. It can only follow one Path at a time.
+     *
+     * @name Phaser.GameObjects.Components.Path#path
+     * @type {Phaser.Curves.Path}
+     * @since 3.12.0
+     */
+    path: null,
+
+    /**
+     * Should the PathFollower automatically rotate to point in the direction of the Path?
+     *
+     * @name Phaser.GameObjects.Components.Path#rotateToPath
+     * @type {boolean}
+     * @default false
+     * @since 3.12.0
+     */
+    rotateToPath: false,
+
+    /**
+     * [description]
+     *
+     * @name Phaser.GameObjects.Components.Path#pathRotationVerticalAdjust
+     * @type {boolean}
+     * @default false
+     * @since 3.12.0
+     */
+    pathRotationVerticalAdjust: false,
+
+    /**
+     * If the PathFollower is rotating to match the Path (@see Phaser.GameObjects.Components.Path#rotateToPath)
+     * this value is added to the rotation value. This allows you to rotate objects to a path but control
+     * the angle of the rotation as well.
+     *
+     * @name Phaser.GameObjects.Components.Path#pathRotationOffset
+     * @type {number}
+     * @default 0
+     * @since 3.12.0
+     */
+    pathRotationOffset: 0,
+
+    /**
+     * An additional vector to add to the PathFollowers position, allowing you to offset it from the
+     * Path coordinates.
+     *
+     * @name Phaser.GameObjects.Components.Path#pathOffset
+     * @type {Phaser.Math.Vector2}
+     * @since 3.12.0
+     */
+    pathOffset: {
+
+        factory: function ()
+        {
+            return new Vector2();
+        }
+
+    },
+
+    /**
+     * [description]
+     *
+     * @name Phaser.GameObjects.Components.Path#pathVector
+     * @type {Phaser.Math.Vector2}
+     * @since 3.12.0
+     */
+    pathVector: {
+
+        factory: function ()
+        {
+            return new Vector2();
+        }
+
+    },
+
+    /**
+     * The Tween used for following the Path.
+     *
+     * @name Phaser.GameObjects.Components.Path#pathTween
+     * @type {Phaser.Tweens.Tween}
+     * @since 3.12.0
+     */
+    pathTween: null,
+
+    /**
+     * Settings for the PathFollower.
+     *
+     * @name Phaser.GameObjects.Components.Path#pathConfig
+     * @type {?PathConfig}
+     * @default null
+     * @since 3.12.0
+     */
+    pathConfig: null,
+
+    /**
+     * Records the direction of the follower so it can change direction.
+     *
+     * @name Phaser.GameObjects.Components.Path#_prevDirection
+     * @type {integer}
+     * @private
+     * @since 3.12.0
+     */
+    _prevDirection: TWEEN_CONST.PLAYING_FORWARD,
+
+    /**
+     * Set the Path that this PathFollower should follow.
+     *
+     * Optionally accepts {@link PathConfig} settings.
+     *
+     * @method Phaser.GameObjects.Components.Path#setPath
+     * @since 3.12.0
+     *
+     * @param {Phaser.Curves.Path} path - The Path this PathFollower is following. It can only follow one Path at a time.
+     * @param {PathConfig} [config] - Settings for the PathFollower.
+     *
+     * @return {this} This Game Object.
+     */
+    setPath: function (path, config)
+    {
+        if (config === undefined) { config = this.pathConfig; }
+
+        var tween = this.pathTween;
+
+        if (tween && tween.isPlaying())
+        {
+            tween.stop();
+        }
+
+        this.path = path;
+
+        if (config)
+        {
+            this.startFollow(config);
+        }
+
+        return this;
+    },
+
+    /**
+     * Set whether the PathFollower should automatically rotate to point in the direction of the Path.
+     *
+     * @method Phaser.GameObjects.Components.Path#setRotateToPath
+     * @since 3.12.0
+     *
+     * @param {boolean} value - Whether the PathFollower should automatically rotate to point in the direction of the Path.
+     * @param {number} [offset=0] - Rotation offset in degrees.
+     * @param {boolean} [verticalAdjust=false] - [description]
+     *
+     * @return {this} This Game Object.
+     */
+    setRotateToPath: function (value, offset, verticalAdjust)
+    {
+        if (offset === undefined) { offset = 0; }
+        if (verticalAdjust === undefined) { verticalAdjust = false; }
+
+        this.rotateToPath = value;
+
+        this.pathRotationOffset = offset;
+        this.pathRotationVerticalAdjust = verticalAdjust;
+
+        return this;
+    },
+
+    /**
+     * Is this PathFollower actively following a Path or not?
+     *
+     * To be considered as `isFollowing` it must be currently moving on a Path, and not paused.
+     *
+     * @method Phaser.GameObjects.Components.Path#isFollowing
+     * @since 3.12.0
+     *
+     * @return {boolean} `true` is this PathFollower is actively following a Path, otherwise `false`.
+     */
+    isFollowing: function ()
+    {
+        var tween = this.pathTween;
+
+        return (tween && tween.isPlaying());
+    },
+
+    /**
+     * Starts this PathFollower following its given Path.
+     *
+     * @method Phaser.GameObjects.Components.Path#startFollow
+     * @since 3.12.0
+     *
+     * @param {(number|PathConfig)} [config={}] - The duration of the follow, or a PathFollower config object.
+     * @param {number} [startAt=0] - Optional start position of the follow, between 0 and 1.
+     *
+     * @return {this} This Game Object.
+     */
+    startFollow: function (config, startAt)
+    {
+        if (config === undefined) { config = {}; }
+        if (startAt === undefined) { startAt = 0; }
+
+        var tween = this.pathTween;
+
+        if (tween && tween.isPlaying())
+        {
+            tween.stop();
+        }
+
+        if (typeof config === 'number')
+        {
+            config = { duration: config };
+        }
+
+        //  Override in case they've been specified in the config
+        config.from = 0;
+        config.to = 1;
+
+        //  Can also read extra values out of the config:
+
+        var positionOnPath = GetBoolean(config, 'positionOnPath', false);
+
+        this.rotateToPath = GetBoolean(config, 'rotateToPath', false);
+        this.pathRotationOffset = GetValue(config, 'rotationOffset', 0);
+        this.pathRotationVerticalAdjust = GetBoolean(config, 'verticalAdjust', false);
+
+        this.pathTween = this.scene.sys.tweens.addCounter(config);
+
+        //  The starting point of the path, relative to this follower
+        this.path.getStartPoint(this.pathOffset);
+
+        if (positionOnPath)
+        {
+            this.x = this.pathOffset.x;
+            this.y = this.pathOffset.y;
+        }
+
+        this.pathOffset.x = this.x - this.pathOffset.x;
+        this.pathOffset.y = this.y - this.pathOffset.y;
+
+        this._prevDirection = TWEEN_CONST.PLAYING_FORWARD;
+
+        if (this.rotateToPath)
+        {
+            //  Set the rotation now (in case the tween has a delay on it, etc)
+            var nextPoint = this.path.getPoint(0.1);
+
+            this.rotation = Math.atan2(nextPoint.y - this.y, nextPoint.x - this.x) + DegToRad(this.pathRotationOffset);
+        }
+
+        this.pathConfig = config;
+
+        return this;
+    },
+
+    /**
+     * Pauses this PathFollower. It will still continue to render, but it will remain motionless at the
+     * point on the Path at which you paused it.
+     *
+     * @method Phaser.GameObjects.Components.Path#pauseFollow
+     * @since 3.12.0
+     *
+     * @return {this} This Game Object.
+     */
+    pauseFollow: function ()
+    {
+        var tween = this.pathTween;
+
+        if (tween && tween.isPlaying())
+        {
+            tween.pause();
+        }
+
+        return this;
+    },
+
+    /**
+     * Resumes a previously paused PathFollower.
+     *
+     * If the PathFollower was not paused this has no effect.
+     *
+     * @method Phaser.GameObjects.Components.Path#resumeFollow
+     * @since 3.12.0
+     *
+     * @return {this} This Game Object.
+     */
+    resumeFollow: function ()
+    {
+        var tween = this.pathTween;
+
+        if (tween && tween.isPaused())
+        {
+            tween.resume();
+        }
+
+        return this;
+    },
+
+    /**
+     * Stops this PathFollower from following the path any longer.
+     *
+     * This will invoke any 'stop' conditions that may exist on the Path, or for the follower.
+     *
+     * @method Phaser.GameObjects.Components.Path#stopFollow
+     * @since 3.12.0
+     *
+     * @return {this} This Game Object.
+     */
+    stopFollow: function ()
+    {
+        var tween = this.pathTween;
+
+        if (tween && tween.isPlaying())
+        {
+            tween.stop();
+        }
+
+        return this;
+    },
+
+    /**
+     * Internal update handler that advances this PathFollower along the path.
+     *
+     * Called automatically by the Scene step, should not typically be called directly.
+     *
+     * @method Phaser.GameObjects.Components.Path#preUpdate
+     * @protected
+     * @since 3.12.0
+     *
+     * @param {integer} time - The current timestamp as generated by the Request Animation Frame or SetTimeout.
+     * @param {number} delta - The delta time, in ms, elapsed since the last frame.
+     */
+    preUpdate: function (time, delta)
+    {
+        this.anims.update(time, delta);
+
+        var tween = this.pathTween;
+
+        if (tween)
+        {
+            var tweenData = tween.data[0];
+
+            if (tweenData.state !== TWEEN_CONST.PLAYING_FORWARD && tweenData.state !== TWEEN_CONST.PLAYING_BACKWARD)
+            {
+                //  If delayed, etc then bail out
+                return;
+            }
+
+            var pathVector = this.pathVector;
+
+            this.path.getPoint(tween.getValue(), pathVector);
+
+            pathVector.add(this.pathOffset);
+
+            var oldX = this.x;
+            var oldY = this.y;
+
+            this.setPosition(pathVector.x, pathVector.y);
+
+            var speedX = this.x - oldX;
+            var speedY = this.y - oldY;
+
+            if (speedX === 0 && speedY === 0)
+            {
+                //  Bail out early
+                return;
+            }
+
+            if (tweenData.state !== this._prevDirection)
+            {
+                //  We've changed direction, so don't do a rotate this frame
+                this._prevDirection = tweenData.state;
+
+                return;
+            }
+
+            if (this.rotateToPath)
+            {
+                this.rotation = Math.atan2(speedY, speedX) + DegToRad(this.pathRotationOffset);
+
+                if (this.pathRotationVerticalAdjust)
+                {
+                    this.flipY = (this.rotation !== 0 && tweenData.state === TWEEN_CONST.PLAYING_BACKWARD);
+                }
+            }
+        }
+    }
+
+};
+
+module.exports = Path;

src/gameobjects/components/index.js

@@ -20,6 +20,7 @@ module.exports = {
     GetBounds: require('./GetBounds'),
     Mask: require('./Mask'),
     Origin: require('./Origin'),
+    Path: require('./Path'),
     Pipeline: require('./Pipeline'),
     ScaleMode: require('./ScaleMode'),
     ScrollFactor: require('./ScrollFactor'),

src/gameobjects/pathfollower/PathFollowerFactory.js

@@ -5,7 +5,23 @@
  */
 
 var GameObjectFactory = require('../GameObjectFactory');
-var PathFollower = require('./PathFollower');
+var Path = require('../components/Path');
+var Sprite = require('../sprite/Sprite');
+
+/**
+ * [description]
+ *
+ * @function hasGetterOrSetter
+ * @private
+ *
+ * @param {object} def - The object to check.
+ *
+ * @return {boolean} True if it has a getter or setter, otherwise false.
+ */
+function hasGetterOrSetter (def)
+{
+    return def && def.constructor === Object && ((!!def.get && typeof def.get === 'function') || (!!def.set && typeof def.set === 'function'));
+}
 
 /**
  * Creates a new PathFollower Game Object and adds it to the Scene.
@@ -16,21 +32,65 @@ var PathFollower = require('./PathFollower');
  * @since 3.0.0
  *
  * @param {Phaser.Curves.Path} path - The Path this PathFollower is connected to.
- * @param {number} x - The horizontal position of this Game Object in the world.
- * @param {number} y - The vertical position of this Game Object in the world.
- * @param {string} texture - The key of the Texture this Game Object will use to render with, as stored in the Texture Manager.
+ * @param {Phaser.GameObjects.GameObject|number} x - The GameObject to augment, or the horizontal position of this Game Object in the world.
+ * @param {number} [y] - The vertical position of this Game Object in the world.
+ * @param {string} [texture] - The key of the Texture this Game Object will use to render with, as stored in the Texture Manager.
  * @param {(string|integer)} [frame] - An optional frame from the Texture this Game Object is rendering with.
  *
  * @return {Phaser.GameObjects.PathFollower} The Game Object that was created.
  */
 GameObjectFactory.register('follower', function (path, x, y, key, frame)
 {
-    var sprite = new PathFollower(this.scene, path, x, y, key, frame);
+    var gameObject = x;
 
-    this.displayList.add(sprite);
-    this.updateList.add(sprite);
+    // Create a sprite if x is not an object
+    if (typeof x !== 'object')
+    {
+        gameObject = new Sprite(this.scene, x, y, key, frame);
+    }
 
-    return sprite;
+    // Mixin the Path component
+    var mixins = [
+        Path
+    ];
+
+    for (var i = 0; i < mixins.length; i++)
+    {
+        var mixin = mixins[i];
+
+        for (var m in mixin)
+        {
+            if (typeof mixin[m] === 'function')
+            {
+                Object.defineProperty(gameObject, m, {value: mixin[m]});
+            }
+            else if (mixin[m] && typeof mixin[m].factory === 'function')
+            {
+                gameObject[m] = mixin[m].factory();
+            }
+            else if (hasGetterOrSetter(mixin[m]))
+            {
+                Object.defineProperty(gameObject, key, {
+                    get: mixin[key].get,
+                    set: mixin[key].set
+                });
+            }
+            else
+            {
+                gameObject[m] = mixin[m];
+            }
+        }
+    }
+
+    // Set the given arguments as properties
+    gameObject.path = path;
+    gameObject.pathOffset.set(x, y);
+
+    // Add to the display list and update list
+    this.displayList.add(gameObject);
+    this.updateList.add(gameObject);
+
+    return gameObject;
 });
 
 //  When registering a factory function 'this' refers to the GameObjectFactory context.