Introduce EditSession class, which replaces edit session hashes

src/app/edit-session.coffee

@@ -0,0 +1,38 @@
+Point = require 'point'
+Buffer = require 'buffer'
+
+module.exports =
+class EditSession
+  @deserialize: (state, rootView) ->
+    buffer = Buffer.deserialize(state.buffer, rootView.project)
+    session = new EditSession(buffer)
+    session.setScrollTop(state.scrollTop)
+    session.setScrollLeft(state.scrollLeft)
+    session.setCursorScreenPosition(state.cursorScreenPosition)
+    session
+
+  scrollTop: 0
+  scrollLeft: 0
+  cursorScreenPosition: null
+
+  constructor: (@buffer) ->
+    @setCursorScreenPosition([0, 0])
+
+  serialize: ->
+    buffer: @buffer.serialize()
+    scrollTop: @getScrollTop()
+    scrollLeft: @getScrollLeft()
+    cursorScreenPosition: @getCursorScreenPosition().serialize()
+
+  setScrollTop: (@scrollTop) ->
+  getScrollTop: -> @scrollTop
+
+  setScrollLeft: (@scrollLeft) ->
+  getScrollLeft: -> @scrollLeft
+
+  setCursorScreenPosition: (position) ->
+    @cursorScreenPosition = Point.fromObject(position)
+
+  getCursorScreenPosition: ->
+    @cursorScreenPosition
+

src/app/editor.coffee

@@ -6,6 +6,7 @@ Gutter = require 'gutter'
 Renderer = require 'renderer'
 Point = require 'point'
 Range = require 'range'
+EditSession = require 'edit-session'
 
 $ = require 'jquery'
 _ = require 'underscore'
@@ -50,11 +51,7 @@ class Editor extends View
 
   @deserialize: (viewState, rootView) ->
     viewState = _.clone(viewState)
-    viewState.editSessions = viewState.editSessions.map (editSession) ->
-      editSession = _.clone(editSession)
-      editSession.buffer = Buffer.deserialize(editSession.buffer, rootView.project)
-      editSession
-
+    viewState.editSessions = viewState.editSessions.map (state) -> EditSession.deserialize(state, rootView)
     new Editor(viewState)
 
   initialize: ({editSessions, activeEditSessionIndex, buffer, isFocused, @mini} = {}) ->
@@ -83,10 +80,7 @@ class Editor extends View
     { viewClass: "Editor", editSessions: @serializeEditSessions(), @activeEditSessionIndex, @isFocused }
 
   serializeEditSessions: ->
-    @editSessions.map (session) ->
-      session = _.clone(session)
-      session.buffer = session.buffer.serialize()
-      session
+    @editSessions.map (session) -> session.serialize()
 
   copy: ->
     Editor.deserialize(@serialize(), @rootView())
@@ -351,7 +345,7 @@ class Editor extends View
     if editSession
       @activeEditSessionIndex = index
     else
-      @editSessions.push({ buffer })
+      @editSessions.push(new EditSession(buffer))
       @activeEditSessionIndex = @editSessions.length - 1
     @loadEditSession()
 
@@ -381,11 +375,10 @@ class Editor extends View
     @scrollView.scrollLeft(editSession.scrollLeft ? 0)
 
   saveCurrentEditSession: ->
-    @editSessions[@activeEditSessionIndex] =
-      buffer: @buffer
-      cursorScreenPosition: @getCursorScreenPosition()
-      scrollTop: @scrollTop()
-      scrollLeft: @scrollView.scrollLeft()
+    session = @getActiveEditSession()
+    session.setCursorScreenPosition(@getCursorScreenPosition())
+    session.setScrollTop(@scrollTop())
+    session.setScrollLeft(@scrollView.scrollLeft())
 
   renderLines: ->
     @clearRenderedLines()

src/app/point.coffee

@@ -79,3 +79,6 @@ class Point
 
   toArray: ->
     [@row, @column]
+
+  serialize: ->
+    @toArray()