Add Pane::onDidActivate

spec/pane-spec.coffee

@@ -28,6 +28,29 @@ describe "Pane", ->
       expect(pane.getItems().length).toBe 2
       expect(pane.getActiveItem()).toBe pane.itemAtIndex(0)
 
+  describe "::activate()", ->
+    [container, pane1, pane2] = []
+
+    beforeEach ->
+      container = new PaneContainer(root: new Pane)
+      container.getRoot().splitRight()
+      [pane1, pane2] = container.getPanes()
+
+    it "changes the active pane on the container", ->
+      expect(container.getActivePane()).toBe pane2
+      pane1.activate()
+      expect(container.getActivePane()).toBe pane1
+      pane2.activate()
+      expect(container.getActivePane()).toBe pane2
+
+    it "invokes ::onDidActivate() observers", ->
+      eventCount = 0
+      pane1.onDidActivate -> eventCount++
+      pane1.activate()
+      pane1.activate()
+      pane2.activate()
+      expect(eventCount).toBe 2
+
   describe "::addItem(item, index)", ->
     it "adds the item at the given index", ->
       pane = new Pane(items: [new Item("A"), new Item("B")])

src/pane-container.coffee

@@ -36,6 +36,8 @@ class PaneContainer extends Model
     root: @root?.serialize()
     activePaneId: @activePane.id
 
+  getRoot: -> @root
+
   replaceChild: (oldChild, newChild) ->
     throw new Error("Replacing non-existent child") if oldChild isnt @root
     @root = newChild

src/pane.coffee

@@ -94,6 +94,9 @@ class Pane extends Model
   # Called by the view layer to construct a view for this model.
   getViewClass: -> PaneView ?= require './pane-view'
 
+  onDidActivate: (fn) ->
+    @emitter.on 'did-activate', fn
+
   onDidAddItem: (fn) ->
     @emitter.on 'did-add-item', fn
 
@@ -123,6 +126,7 @@ class Pane extends Model
   activate: ->
     @container?.activePane = this
     @emit 'activated'
+    @emitter.emit 'did-activate'
 
   getPanes: -> [this]