Replace RootView.proto.addPane with Pane.proto.split method

src/app/editor.coffee

@@ -66,6 +66,9 @@ class Editor extends View
     @saveCurrentEditSession()
     { viewClass: "Editor", @editSessions, @activeEditSessionIndex, @isFocused }
 
+  copy: ->
+    new Editor(@serialize())
+
   bindKeys: ->
     @on 'save', => @save()
     @on 'move-right', => @moveCursorRight()
@@ -491,21 +494,19 @@ class Editor extends View
     @setCursorBufferPosition(fold.start)
 
   splitLeft: ->
-    @split('row', 'before')
+    @pane().splitLeft(@copy())
 
   splitRight: ->
-    @split('row', 'after')
+    @pane().splitRight(@copy())
 
   splitUp: ->
-    @split('column', 'before')
+    @pane().splitUp(@copy())
 
   splitDown: ->
-    @split('column', 'after')
+    @pane().splitDown(@copy())
 
-  split: (axis, side) ->
-    return unless rootView = @rootView()
-    editor = new Editor(@serialize())
-    rootView.addPane(editor, this.parent(), axis, side)
+  pane: ->
+    @parent('.pane').view()
 
   remove: (selector, keepData) ->
     return super if keepData

src/app/pane.coffee

@@ -1,4 +1,6 @@
 {View} = require 'space-pen'
+PaneRow = require 'pane-row'
+PaneColumn = require 'pane-column'
 
 module.exports =
 class Pane extends View
@@ -13,7 +15,7 @@ class Pane extends View
     viewClass: "Pane"
     wrappedView: @wrappedView.serialize()
 
-  adjustDimensions: ->
+  adjustDimensions: -> # do nothing
 
   horizontalGridUnits: ->
     1
@@ -21,3 +23,33 @@ class Pane extends View
   verticalGridUnits: ->
     1
 
+  splitUp: (view) ->
+    @split(view, 'column', 'before')
+
+  splitDown: (view) ->
+    @split(view, 'column', 'after')
+
+  splitLeft: (view) ->
+    @split(view, 'row', 'before')
+
+  splitRight: (view) ->
+    @split(view, 'row', 'after')
+
+  split: (view, axis, side) ->
+    unless @parent().hasClass(axis)
+      @buildPaneAxis(axis)
+        .insertBefore(this)
+        .append(@detach())
+
+    pane = new Pane(view)
+    this[side](pane)
+    @rootView().adjustPaneDimensions()
+    view
+
+  buildPaneAxis: (axis) ->
+    switch axis
+      when 'row' then new PaneRow
+      when 'column' then new PaneColumn
+
+  rootView: ->
+    @parents('#root-view').view()

src/app/root-view.coffee

@@ -53,7 +53,7 @@ class RootView extends View
 
   deserializePanes: (panesViewState) ->
     @panes.append @deserializeView(panesViewState)
-    @adjustSplitPanes()
+    @adjustPaneDimensions()
 
   deserializeView: (viewState) ->
     switch viewState.viewClass
@@ -78,7 +78,7 @@ class RootView extends View
       @setTitle(editor.buffer.path)
 
   editorRemoved: (editor) ->
-    @adjustSplitPanes()
+    @adjustPaneDimensions()
     if @editors().length
       @editors()[0].focus()
     else
@@ -105,18 +105,9 @@ class RootView extends View
         editor.focus()
         editor
 
-  addPane: (view, sibling, axis, side) ->
-    unless sibling.parent().hasClass(axis)
-      container = if axis == 'column' then new PaneColumn else new PaneRow
-      container.insertBefore(sibling).append(sibling.detach())
-    pane = new Pane(view)
-    sibling[side](pane)
-    @adjustSplitPanes()
-    view
-
-  adjustSplitPanes: ->
-    view = @panes.children().first().view()
-    view.adjustDimensions() if view
+  adjustPaneDimensions: ->
+    rootPane = @panes.children().first().view()
+    rootPane?.adjustDimensions()
 
   toggleFileFinder: ->
     return unless @project