feat: existent::transition

packages/entity/traits/existent.trait.js

@@ -1,4 +1,5 @@
-import {compose} from '@avocado/core';
+import {compose, TickingPromise} from '@avocado/core';
+import {TransitionResult} from '@avocado/mixins';
 
 import {StateProperty, Trait} from '../trait';
 
@@ -29,6 +30,22 @@ class ExistentBase extends Trait {
         this.entity.emit('destroyed');
       },
 
+      transition: (props, duration, easing) => {
+        const result = new TransitionResult(
+          this.entity,
+          props,
+          duration,
+          easing
+        );
+        const promise = new TickingPromise((resolve) => {
+          resolve(result.promise);
+        });
+        promise.ticker = (elapsed) => {
+          result.tick(elapsed);
+        }
+        return promise;
+      },
+
     };
   }
 

packages/mixins/index.js

@@ -1,4 +1,4 @@
 export {EventEmitterMixin as EventEmitter} from './event-emitter';
 export {LfoMixin as Lfo} from './lfo';
 export {PropertyMixin as Property} from './property';
-export {TransitionMixin as Transition} from './transition';
+export {TransitionMixin as Transition, TransitionResult} from './transition';

packages/mixins/transition/index.js

@@ -28,6 +28,7 @@
 // compatible.
 
 import TransitionResult from './result';
+export {TransitionResult};
 
 export function TransitionMixin(Superclass) {
   return class Transition extends Superclass {