Add PaneContainer::observePanes and ::onDidAddPane

spec/pane-container-spec.coffee

@@ -88,3 +88,17 @@ describe "PaneContainer", ->
       pane1.activate()
       pane2.activate()
       expect(observed).toEqual [pane1.itemAtIndex(0), pane2.itemAtIndex(0)]
+
+  describe "::observePanes()", ->
+    it "invokes with subscribers with all current and future panes", ->
+      container = new PaneContainer
+      container.getRoot().splitRight()
+      [pane1, pane2] = container.getPanes()
+
+      observed = []
+      container.observePanes (pane) -> observed.push(pane)
+
+      pane3 = pane2.splitDown()
+      pane4 = pane2.splitRight()
+
+      expect(observed).toEqual [pane1, pane2, pane3, pane4]

src/pane-axis.coffee

@@ -11,6 +11,10 @@ class PaneAxis extends Model
   atom.deserializers.add(this)
   Serializable.includeInto(this)
 
+  parent: null
+  container: null
+  orientation: null
+
   constructor: ({@container, @orientation, children}) ->
     @emitter = new Emitter
     @subscriptionsByChild = new WeakMap
@@ -28,6 +32,14 @@ class PaneAxis extends Model
     children: @children.map (child) -> child.serialize()
     orientation: @orientation
 
+  getParent: -> @parent
+
+  setParent: (@parent) -> @parent
+
+  getContainer: -> @container
+
+  setContainer: (@container) -> @container
+
   getViewClass: ->
     if @orientation is 'vertical'
       PaneColumnView ?= require './pane-column-view'
@@ -52,8 +64,8 @@ class PaneAxis extends Model
     @emitter.on 'did-destroy', fn
 
   addChild: (child, index=@children.length) ->
-    child.parent = this
-    child.container = @container
+    child.setParent(this)
+    child.setContainer(@container)
 
     @subscribeToChild(child)
 
@@ -74,8 +86,8 @@ class PaneAxis extends Model
     @unsubscribeFromChild(oldChild)
     @subscribeToChild(newChild)
 
-    newChild.parent = this
-    newChild.container = @container
+    newChild.setParent(this)
+    newChild.setContainer(@container)
 
     index = @children.indexOf(oldChild)
     @children.splice(index, 1, newChild)

src/pane-container.coffee

@@ -49,6 +49,13 @@ class PaneContainer extends Model
     fn(@getRoot())
     @onDidChangeRoot(fn)
 
+  onDidAddPane: (fn) ->
+    @emitter.on 'did-add-pane', fn
+
+  observePanes: (fn) ->
+    fn(pane) for pane in @getPanes()
+    @onDidAddPane ({pane}) -> fn(pane)
+
   onDidChangeActivePane: (fn) ->
     @emitter.on 'did-change-active-pane', fn
 
@@ -69,8 +76,8 @@ class PaneContainer extends Model
   getRoot: -> @root
 
   setRoot: (@root) ->
-    @root.parent = this
-    @root.container = this
+    @root.setParent(this)
+    @root.setContainer(this)
     @emitter.emit 'did-change-root', @root
     if not @getActivePane()? and @root instanceof Pane
       @setActivePane(@root)
@@ -127,6 +134,9 @@ class PaneContainer extends Model
   paneItemDestroyed: (item) ->
     @emitter.emit 'did-destroy-pane-item', item
 
+  didAddPane: (pane) ->
+    @emitter.emit 'did-add-pane', pane
+
   # Called by Model superclass when destroyed
   destroyed: ->
     pane.destroy() for pane in @getPanes()

src/pane.coffee

@@ -55,6 +55,16 @@ class Pane extends Model
   # Called by the view layer to construct a view for this model.
   getViewClass: -> PaneView ?= require './pane-view'
 
+  getParent: -> @parent
+
+  setParent: (@parent) -> @parent
+
+  getContainer: -> @container
+
+  setContainer: (container) ->
+    container.didAddPane({pane: this}) unless container is @container
+    @container = container
+
   ###
   Section: Event Subscription
   ###