added deltaX, deltaY in processPicking

gui/src/2D/controls/button.ts

@@ -89,7 +89,7 @@ export class Button extends Rectangle {
 
     // While being a container, the button behaves like a control.
     /** @hidden */
-    public _processPicking(x: number, y: number, type: number, pointerId: number, buttonIndex: number): boolean {
+    public _processPicking(x: number, y: number, type: number, pointerId: number, buttonIndex: number, deltaX?: number, deltaY?: number): boolean {
         if (!this._isEnabled || !this.isHitTestVisible || !this.isVisible || this.notRenderable) {
             return false;
         }
@@ -113,7 +113,7 @@ export class Button extends Rectangle {
             }
         }
 
-        this._processObservables(type, x, y, pointerId, buttonIndex);
+        this._processObservables(type, x, y, pointerId, buttonIndex, deltaX, deltaY);
 
         return true;
     }