Enhance pane split methods. Spec them in pane-spec.

When a pane is split, it attempts to make a copy of its current item
if no items are passed to the split method. When splitting, multiple
items can also be passed to the constructor of the new pane.

spec/app/pane-spec.coffee

@@ -3,14 +3,16 @@ Pane = require 'pane'
 {$$} = require 'space-pen'
 
 describe "Pane", ->
-  [view1, view2, editSession1, editSession2, pane] = []
+  [container, view1, view2, editSession1, editSession2, pane] = []
 
   beforeEach ->
+    container = $$ -> @div id: 'panes'
     view1 = $$ -> @div id: 'view-1', 'View 1'
     view2 = $$ -> @div id: 'view-2', 'View 2'
     editSession1 = project.buildEditSession('sample.js')
     editSession2 = project.buildEditSession('sample.txt')
     pane = new Pane(view1, editSession1, view2, editSession2)
+    container.append(pane)
 
   describe ".initialize(items...)", ->
     it "displays the first item in the pane", ->
@@ -109,6 +111,61 @@ describe "Pane", ->
       pane.focus()
       expect(focusHandler).toHaveBeenCalled()
 
+  describe "split methods", ->
+    [view3, view4] = []
+    beforeEach ->
+      pane.showItem(editSession1)
+      view3 = $$ -> @div id: 'view-3', 'View 3'
+      view4 = $$ -> @div id: 'view-4', 'View 4'
+
+    describe "splitRight(items...)", ->
+      it "builds a row if needed, then appends a new pane after itself", ->
+        # creates the new pane with a copy of the current item if none are given
+        pane2 = pane.splitRight()
+        expect(container.find('.row .pane').toArray()).toEqual [pane[0], pane2[0]]
+        expect(pane2.items).toEqual [editSession1]
+        expect(pane2.currentItem).not.toBe editSession1 # it's a copy
+
+        pane3 = pane2.splitRight(view3, view4)
+        expect(pane3.getItems()).toEqual [view3, view4]
+        expect(container.find('.row .pane').toArray()).toEqual [pane[0], pane2[0], pane3[0]]
+
+    describe "splitRight(items...)", ->
+      it "builds a row if needed, then appends a new pane before itself", ->
+        # creates the new pane with a copy of the current item if none are given
+        pane2 = pane.splitLeft()
+        expect(container.find('.row .pane').toArray()).toEqual [pane2[0], pane[0]]
+        expect(pane2.items).toEqual [editSession1]
+        expect(pane2.currentItem).not.toBe editSession1 # it's a copy
+
+        pane3 = pane2.splitLeft(view3, view4)
+        expect(pane3.getItems()).toEqual [view3, view4]
+        expect(container.find('.row .pane').toArray()).toEqual [pane3[0], pane2[0], pane[0]]
+
+    describe "splitDown(items...)", ->
+      it "builds a column if needed, then appends a new pane after itself", ->
+        # creates the new pane with a copy of the current item if none are given
+        pane2 = pane.splitDown()
+        expect(container.find('.column .pane').toArray()).toEqual [pane[0], pane2[0]]
+        expect(pane2.items).toEqual [editSession1]
+        expect(pane2.currentItem).not.toBe editSession1 # it's a copy
+
+        pane3 = pane2.splitDown(view3, view4)
+        expect(pane3.getItems()).toEqual [view3, view4]
+        expect(container.find('.column .pane').toArray()).toEqual [pane[0], pane2[0], pane3[0]]
+
+    describe "splitUp(items...)", ->
+      it "builds a column if needed, then appends a new pane before itself", ->
+        # creates the new pane with a copy of the current item if none are given
+        pane2 = pane.splitUp()
+        expect(container.find('.column .pane').toArray()).toEqual [pane2[0], pane[0]]
+        expect(pane2.items).toEqual [editSession1]
+        expect(pane2.currentItem).not.toBe editSession1 # it's a copy
+
+        pane3 = pane2.splitUp(view3, view4)
+        expect(pane3.getItems()).toEqual [view3, view4]
+        expect(container.find('.column .pane').toArray()).toEqual [pane3[0], pane2[0], pane[0]]
+
   describe ".itemForPath(path)", ->
     it "returns the item for which a call to .getPath() returns the given path", ->
       expect(pane.itemForPath(editSession1.getPath())).toBe editSession1

src/app/pane.coffee

@@ -104,30 +104,34 @@ class Pane extends View
 
   verticalGridUnits: -> 1
 
-  splitUp: (view) ->
-    @split(view, 'column', 'before')
+  splitUp: (items...) ->
+    @split(items, 'column', 'before')
 
-  splitDown: (view) ->
-    @split(view, 'column', 'after')
+  splitDown: (items...) ->
+    @split(items, 'column', 'after')
 
-  splitLeft: (view) ->
-    @split(view, 'row', 'before')
+  splitLeft: (items...) ->
+    @split(items, 'row', 'before')
 
-  splitRight: (view) ->
-    @split(view, 'row', 'after')
+  splitRight: (items...) ->
+    @split(items, 'row', 'after')
 
-  split: (view, axis, side) ->
+  split: (items, axis, side) ->
     unless @parent().hasClass(axis)
       @buildPaneAxis(axis)
         .insertBefore(this)
         .append(@detach())
 
-    pane = new Pane(view)
+    items = [@copyCurrentItem()] unless items.length
+    pane = new Pane(items...)
     this[side](pane)
     rootView?.adjustPaneDimensions()
     pane.focus()
     pane
 
+  copyCurrentItem: ->
+    deserialize(@currentItem.serialize())
+
   remove: (selector, keepData) ->
     return super if keepData
     # find parent elements before removing from dom