Update window via listener when escape item changes

lib/browser/api/touch-bar.js

@@ -28,9 +28,9 @@ class TouchBar extends EventEmitter {
     }
 
     this.windowListeners = {}
-    this.windows = {}
     this.items = {}
     this.ordereredItems = []
+    this.escapeItem = {}
 
     const registerItem = (item) => {
       this.items[item.id] = item
@@ -51,12 +51,12 @@ class TouchBar extends EventEmitter {
   }
 
   setEscapeItem (item) {
-    if (!item) item = {}
-    Object.keys(this.windows).forEach((windowID) => {
-      const window = this.windows[windowID]
-      window._setEscapeTouchBarItem(item)
-    })
-    this._escape = item
+    if (item != null && !(item instanceof TouchBarItem)) {
+      throw new Error('Escape item must be an instance of TouchBarItem')
+    }
+    if (item == null) item = {}
+    this.escapeItem = item
+    this.emit('escape-item-change', item)
   }
 
   _addToWindow (window) {
@@ -72,6 +72,11 @@ class TouchBar extends EventEmitter {
     }
     this.on('change', changeListener)
 
+    const escapeItemListener = (item) => {
+      window._setEscapeTouchBarItem(item)
+    }
+    this.on('escape-item-change', escapeItemListener)
+
     const interactionListener = (event, itemID, details) => {
       const item = this.items[itemID]
       if (item != null && item.onInteraction != null) {
@@ -82,19 +87,17 @@ class TouchBar extends EventEmitter {
 
     const removeListeners = () => {
       this.removeListener('change', changeListener)
+      this.removeListener('escape-item-change', escapeItemListener)
       window.removeListener('-touch-bar-interaction', interactionListener)
       window.removeListener('closed', removeListeners)
       window._touchBar = null
       delete this.windowListeners[id]
-      delete this.windows[id]
     }
     window.once('closed', removeListeners)
     this.windowListeners[id] = removeListeners
-    this.windows[id] = window
 
     window._setTouchBarItems(this.ordereredItems)
-
-    if (this._escape) window._setEscapeTouchBarItem(this._escape)
+    window._setEscapeTouchBarItem(this.escapeItem)
   }
 
   _removeFromWindow (window) {

spec/api-touch-bar-spec.js

@@ -20,6 +20,13 @@ describe('TouchBar module', function () {
     }, /Each item must be an instance of TouchBarItem/)
   })
 
+  it('throws an error when an invalid escape item is set', function () {
+    assert.throws(() => {
+      const touchBar = new TouchBar([])
+      touchBar.setEscapeItem('esc')
+    }, /Escape item must be an instance of TouchBarItem/)
+  })
+
   describe('BrowserWindow behavior', function () {
     let window