From 579c6ba6074d6b275c26749f4d54b1e073d2c33c Mon Sep 17 00:00:00 2001
From: Richard Davey <rdavey@gmail.com>
Date: Sun, 3 Jun 2018 17:08:08 +0100
Subject: [PATCH] Body.useDamping is a new boolean property that allows you to
 use a damping effect for drag, rather than the default linear deceleration.

---
 src/physics/arcade/Body.js            | 21 ++++++++++++++++++++-
 src/physics/arcade/components/Drag.js | 17 +++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/src/physics/arcade/Body.js b/src/physics/arcade/Body.js
index 774feaa60..acc516e57 100644
--- a/src/physics/arcade/Body.js
+++ b/src/physics/arcade/Body.js
@@ -411,7 +411,8 @@ var Body = new Class({
         this.onOverlap = false;
 
         /**
-         * The Body's absolute maximum velocity, in pixels per second.
+         * The Body's absolute maximum velocity.
+         * 
          * This limits the Body's rate of movement but not its `velocity` values (which can still exceed `maxVelocity`).
          *
          * @name Phaser.Physics.Arcade.Body#maxVelocity
@@ -430,6 +431,24 @@ var Body = new Class({
          */
         this.friction = new Vector2(1, 0);
 
+        /**
+         * If this Body is using `drag` for deceleration this property controls how the drag is applied.
+         * If set to `true` drag will use a damping effect rather than a linear approach. If you are
+         * creating a game where the Body moves freely at any angle (i.e. like the way the ship moves in
+         * the game Asteroids) then you will get a far smoother and more visually correct deceleration
+         * by using damping, avoiding the axis-drift that is prone with linear deceleration.
+         *
+         * If you enable this property then you should use far smaller `drag` values with linear, as
+         * they are used as a multiplier on the velocity. Values such as 0.95 will give a nice slow
+         * deceleration, where-as smaller values, such as 0.5 will stop an object almost immediately.
+         *
+         * @name Phaser.Physics.Arcade.Body#useDamping
+         * @type {boolean}
+         * @default false
+         * @since 3.10.0
+         */
+        this.useDamping = false;
+
         /**
          * The rate of change of this Body's rotation, in degrees per second.
          *
diff --git a/src/physics/arcade/components/Drag.js b/src/physics/arcade/components/Drag.js
index 2bda340e8..2e527cfe2 100644
--- a/src/physics/arcade/components/Drag.js
+++ b/src/physics/arcade/components/Drag.js
@@ -61,6 +61,23 @@ var Drag = {
     {
         this.body.drag.y = value;
 
+        return this;
+    },
+
+    /**
+     * [description]
+     *
+     * @method Phaser.Physics.Arcade.Components.Drag#setDamping
+     * @since 3.10.0
+     *
+     * @param {boolean} value - `true` to use damping for deceleration, or `false` to use linear deceleration.
+     *
+     * @return {this} This Game Object.
+     */
+    setDamping: function (value)
+    {
+        this.body.useDamping = value;
+
         return this;
     }