Add DisplayBuffer.copy

spec/app/display-buffer-spec.coffee

@@ -16,6 +16,28 @@ describe "DisplayBuffer", ->
     displayBuffer.destroy()
     buffer.release()
 
+  describe ".copy()", ->
+    it "creates a new DisplayBuffer with the same initial state", ->
+      marker1 = displayBuffer.markBufferRange([[1, 2], [3, 4]], id: 1)
+      marker2 = displayBuffer.markBufferRange([[2, 3], [4, 5]], isReversed: true, id: 2)
+      marker3 = displayBuffer.markBufferPosition([5, 6], id: 3)
+      displayBuffer.createFold(3, 5)
+
+      displayBuffer2 = displayBuffer.copy()
+      expect(displayBuffer2.id).not.toBe displayBuffer.id
+      expect(displayBuffer2.buffer).toBe displayBuffer.buffer
+      expect(displayBuffer2.getTabLength()).toBe displayBuffer.getTabLength()
+
+      expect(displayBuffer2.getMarkerCount()).toEqual displayBuffer.getMarkerCount()
+      expect(displayBuffer2.findMarker(id: 1)).toEqual marker1
+      expect(displayBuffer2.findMarker(id: 2)).toEqual marker2
+      expect(displayBuffer2.findMarker(id: 3)).toEqual marker3
+      expect(displayBuffer2.isFoldedAtBufferRow(3)).toBeTruthy()
+
+      # can diverge from origin
+      displayBuffer2.destroyFoldsContainingBufferRow(3)
+      expect(displayBuffer2.isFoldedAtBufferRow(3)).not.toBe displayBuffer.isFoldedAtBufferRow(3)
+
   describe "when the buffer changes", ->
     it "renders line numbers correctly", ->
       originalLineCount = displayBuffer.getLineCount()

src/app/display-buffer-marker.coffee

@@ -154,10 +154,7 @@ class DisplayBufferMarker
 
   isEqual: (other) ->
     return false unless other instanceof @constructor
-    @getBufferRange().isEqual(other.getBufferRange()) and
-      @isReversed() is other.isReversed() and
-      @hasTail() is other.hasTail() and
-      _.isEqual(@getAttributes(), other.getAttributes())
+    @bufferMarker.isEqual(other.bufferMarker)
 
   # Returns a {String} representation of the marker
   inspect: ->

src/app/display-buffer.coffee

@@ -1,8 +1,9 @@
 _ = require 'underscore'
+guid = require 'guid'
+{Point, Range} = require 'telepath'
 TokenizedBuffer = require 'tokenized-buffer'
 RowMap = require 'row-map'
 EventEmitter = require 'event-emitter'
-{Point, Range} = require 'telepath'
 Fold = require 'fold'
 Token = require 'token'
 DisplayBufferMarker = require 'display-buffer-marker'
@@ -20,7 +21,7 @@ class DisplayBuffer
   ### Internal ###
 
   constructor: (@buffer, options={}) ->
-    @id = @constructor.idCounter++
+    @id = guid.create().toString()
     @tokenizedBuffer = new TokenizedBuffer(@buffer, options)
     @softWrapColumn = options.softWrapColumn ? Infinity
     @markers = {}
@@ -32,6 +33,11 @@ class DisplayBuffer
     @subscribe @buffer, 'markers-updated', @handleMarkersUpdated
     @subscribe @buffer, 'marker-created', @handleMarkerCreated
 
+  copy: ->
+    newDisplayBuffer = new DisplayBuffer(@buffer, tabLength: @getTabLength())
+    @findMarkers(displayBufferId: @id).map (marker) -> marker.copy(displayBufferId: newDisplayBuffer.id)
+    newDisplayBuffer
+
   updateAllScreenLines: ->
     @maxLineLength = 0
     @screenLines = []
@@ -109,6 +115,12 @@ class DisplayBuffer
         @buffer.markRange([[startRow, 0], [endRow, Infinity]], @foldMarkerAttributes())
     @foldForMarker(foldMarker)
 
+  isFoldedAtBufferRow: (bufferRow) ->
+    @largestFoldContainingBufferRow(bufferRow)?
+
+  isFoldedAtScreenRow: (screenRow) ->
+    @largestFoldContainingBufferRow(@bufferRowForScreenRow(screenRow))?
+
   # Destroys the fold with the given id
   destroyFoldWithId: (id) ->
     @foldsByMarkerId[id]?.destroy()
@@ -405,6 +417,9 @@ class DisplayBuffer
   getMarkers: ->
     @buffer.getMarkers().map ({id}) => @getMarker(id)
 
+  getMarkerCount: ->
+    @buffer.getMarkerCount()
+
   # Constructs a new marker at the given screen range.
   #
   # range - The marker {Range} (representing the distance between the head and tail)