Make escape item a property instead of setter

docs/api/touch-bar.md

@@ -14,16 +14,15 @@ Creates a new touch bar with the specified items. Use
 **Note:** The TouchBar API is currently experimental and may change or be
 removed in future Electron releases.
 
-### Instance Methods
+### Instance Properties
 
-The following methods are available on instances of `TouchBar`:
+The following properties are available on instances of `TouchBar`:
 
-#### `touchBar.setEscapeItem([touchBarItem])`
+#### `touchBar.escapeItem`
 
-* `touchBarItem` (TouchBarButton | TouchBarColorPicker | TouchBarGroup | TouchBarLabel | TouchBarPopover | TouchBarScrubber | TouchBarSegmentedControl | TouchBarSlider | TouchBarSpacer) - (Optional) The touch bar item to replace the escape button with
-
-Replaces the "esc" button on the touchbar with the given TouchBarItem, if `touchBarItem` is not provided or is falsey the button is reset
-to the "esc" button automatically.
+The `TouchBarItem` that will replace the "esc" button on the touch bar when set.
+Setting to `null` restores the default "esc" button. Changing this value
+immediately updates the escape item in the touch bar.
 
 ## Examples
 

lib/browser/api/touch-bar.js

@@ -2,8 +2,6 @@ const {EventEmitter} = require('events')
 
 let nextItemID = 1
 
-const DEFAULT_ESCAPE_ITEM = new EventEmitter()
-
 class TouchBar extends EventEmitter {
   // Bind a touch bar to a window
   static _setOnWindow (touchBar, window) {
@@ -32,7 +30,7 @@ class TouchBar extends EventEmitter {
     this.windowListeners = {}
     this.items = {}
     this.ordereredItems = []
-    this.escapeItem = DEFAULT_ESCAPE_ITEM
+    this.escapeItem = null
     this.changeListener = (item) => {
       this.emit('change', item.id, item.type)
     }
@@ -53,19 +51,24 @@ class TouchBar extends EventEmitter {
     })
   }
 
-  setEscapeItem (item) {
+  set escapeItem (item) {
     if (item != null && !(item instanceof TouchBarItem)) {
       throw new Error('Escape item must be an instance of TouchBarItem')
     }
-    if (item == null) {
-      item = DEFAULT_ESCAPE_ITEM
+    if (this.escapeItem != null) {
+      this.escapeItem.removeListener('change', this.changeListener)
+    }
+    this._escapeItem = item
+    if (this.escapeItem != null) {
+      this.escapeItem.on('change', this.changeListener)
     }
-    this.escapeItem.removeListener('change', this.changeListener)
-    this.escapeItem = item
-    this.escapeItem.on('change', this.changeListener)
     this.emit('escape-item-change', item)
   }
 
+  get escapeItem () {
+    return this._escapeItem
+  }
+
   _addToWindow (window) {
     const {id} = window
 
@@ -80,7 +83,7 @@ class TouchBar extends EventEmitter {
     this.on('change', changeListener)
 
     const escapeItemListener = (item) => {
-      window._setEscapeTouchBarItem(item)
+      window._setEscapeTouchBarItem(item != null ? item : {})
     }
     this.on('escape-item-change', escapeItemListener)
 
@@ -107,7 +110,7 @@ class TouchBar extends EventEmitter {
     this.windowListeners[id] = removeListeners
 
     window._setTouchBarItems(this.ordereredItems)
-    window._setEscapeTouchBarItem(this.escapeItem)
+    escapeItemListener(this.escapeItem)
   }
 
   _removeFromWindow (window) {

spec/api-touch-bar-spec.js

@@ -23,7 +23,7 @@ describe('TouchBar module', function () {
   it('throws an error when an invalid escape item is set', function () {
     assert.throws(() => {
       const touchBar = new TouchBar([])
-      touchBar.setEscapeItem('esc')
+      touchBar.escapeItem = 'esc'
     }, /Escape item must be an instance of TouchBarItem/)
   })
 
@@ -66,12 +66,12 @@ describe('TouchBar module', function () {
         label: 'foo'
       })
       window.setTouchBar(touchBar)
-      touchBar.setEscapeItem(escapeButton)
+      touchBar.escapeItem = escapeButton
       label.label = 'baz'
       escapeButton.label = 'hello'
       window.setTouchBar()
       window.setTouchBar(new TouchBar([new TouchBarLabel({label: 'two'})]))
-      touchBar.setEscapeItem()
+      touchBar.escapeItem = null
     })
   })
 })