Arcade Physics Body deltaX and deltaY methods will now return the previous steps delta values, rather than zero. Fix phaserjs#3987

Author: photonstorm

CHANGELOG.md

@@ -252,6 +252,7 @@ Setting the `resolution` property in the Game Config to a value other than 1 wou
 * Calling Arcade Physics `collide` during an `update` method wouldn't inject the results back into the Body parent, causing the bodies to carry on moving. Using Colliders worked, but manually checking did not. Now, both methods work. Fix #3777 (thanks @samme)
 * The `setTintFill` method would ignore the `alpha` value of the Game Object in the shader. The alpha value is now blended with the tint fill, allowing you to properly alpha out tint-filled Game Objects. Fix #3992 (thanks @trl-bsd)
 * Arcade Physics World `collideSpriteVsTilemapLayer` now syncs the collision results back to the body, allowing you to call `collide` from within an update loop once again. Fix #3999 (thanks @nkholski @mikewesthad)
+* Arcade Physics Body `deltaX` and `deltaY` methods will now return the previous steps delta values, rather than zero. Fix #3987 (thanks @HaoboZ)
 
 ### Examples, Documentation and TypeScript
 

src/physics/arcade/Body.js

@@ -920,8 +920,8 @@ var Body = new Class({
             }
         }
 
-        this._dx = this.deltaX();
-        this._dy = this.deltaY();
+        this._dx = this.position.x - this.prev.x;
+        this._dy = this.position.y - this.prev.y;
     },
 
     /**
@@ -934,8 +934,8 @@ var Body = new Class({
      */
     postUpdate: function ()
     {
-        this._dx = this.deltaX();
-        this._dy = this.deltaY();
+        this._dx = this.position.x - this.prev.x;
+        this._dy = this.position.y - this.prev.y;
 
         if (this.moves)
         {
@@ -1327,7 +1327,7 @@ var Body = new Class({
      */
     deltaX: function ()
     {
-        return this.position.x - this.prev.x;
+        return this._dx;
     },
 
     /**
@@ -1341,7 +1341,7 @@ var Body = new Class({
      */
     deltaY: function ()
     {
-        return this.position.y - this.prev.y;
+        return this._dy;
     },
 
     /**

src/physics/arcade/World.js

@@ -1665,6 +1665,10 @@ var World = new Class({
             this.emit('collide', body1.gameObject, body2.gameObject, body1, body2);
         }
 
+        //  sync changes back to the bodies
+        body1.postUpdate();
+        body2.postUpdate();
+
         return true;
     },