Buffer updates anchors when it changes instead of EditSession

spec/app/buffer-spec.coffee

@@ -533,3 +533,23 @@ describe 'Buffer', ->
       expect(buffer.positionForCharacterIndex(30)).toEqual [1, 0]
       expect(buffer.positionForCharacterIndex(61)).toEqual [2, 0]
       expect(buffer.positionForCharacterIndex(408)).toEqual [12, 2]
+
+  describe "anchors", ->
+    [anchor, destroyHandler] = []
+
+    beforeEach ->
+      destroyHandler = jasmine.createSpy("destroyHandler")
+      anchor = buffer.addAnchorAtPosition([4, 25])
+      anchor.on 'destroy', destroyHandler
+
+    describe "when a buffer change precedes an anchor", ->
+      it "moves the anchor in accordance with the change", ->
+        buffer.delete([[3, 0], [4, 10]])
+        expect(anchor.getBufferPosition()).toEqual [3, 15]
+        expect(destroyHandler).not.toHaveBeenCalled()
+
+    describe "when a buffer change surrounds an anchor", ->
+      it "destroys the anchor", ->
+        buffer.delete([[3, 0], [5, 0]])
+        expect(destroyHandler).toHaveBeenCalled()
+        expect(buffer.getAnchors().indexOf(anchor)).toBe -1

src/app/anchor.coffee

@@ -12,8 +12,6 @@ class Anchor
   strong: false
 
   constructor: (@buffer, options = {}) ->
-
-    throw new Error("no edit session!") unless options.editSession
     { @editSession, @ignoreEqual, @strong } = options
 
   handleBufferChange: (e) ->
@@ -48,7 +46,7 @@ class Anchor
   setBufferPosition: (position, options={}) ->
     @bufferPosition = Point.fromObject(position)
     clip = options.clip ? true
-    @bufferPosition = @editSession.clipBufferPosition(@bufferPosition) if clip
+    @bufferPosition = @buffer.clipPosition(@bufferPosition) if clip
     @refreshScreenPosition(options)
 
   getScreenPosition: ->
@@ -70,6 +68,7 @@ class Anchor
       @trigger 'change-screen-position', @screenPosition, bufferChange: options.bufferChange
 
   refreshScreenPosition: (options={}) ->
+    return unless @editSession
     screenPosition = @editSession.screenPositionForBufferPosition(@bufferPosition, options)
     @setScreenPosition(screenPosition, bufferChange: options.bufferChange, clip: false, assignBufferPosition: false)
 

src/app/buffer-change-operation.coffee

@@ -38,7 +38,10 @@ class BufferChangeOperation
       newTextLines[lastLineIndex] += suffix
 
     @buffer.replaceLines(oldRange.start.row, oldRange.end.row, newTextLines)
-    @buffer.trigger 'change', { oldRange, newRange, oldText, newText }
+
+    event = { oldRange, newRange, oldText, newText }
+    @buffer.trigger 'change', event
+    anchor.handleBufferChange(event) for anchor in @buffer.getAnchors()
     newRange
 
   calculateNewRange: (oldRange, newText) ->

src/app/buffer.coffee

@@ -140,6 +140,15 @@ class Buffer
     operation = new BufferChangeOperation({buffer: this, oldRange, newText})
     @pushOperation(operation)
 
+  clipPosition: (position) ->
+    { row, column } = Point.fromObject(position)
+    row = 0 if row < 0
+    column = 0 if column < 0
+    row = Math.min(@getLastRow(), row)
+    column = Math.min(@lineLengthForRow(row), column)
+
+    new Point(row, column)
+
   prefixAndSuffixForRange: (range) ->
     prefix: @lines[range.start.row][0...range.start.column]
     suffix: @lines[range.end.row][range.end.column..]
@@ -179,6 +188,8 @@ class Buffer
   isModified: ->
     @modified
 
+  getAnchors: -> new Array(@anchors...)
+
   addAnchor: (options) ->
     anchor = new Anchor(this, options)
     @anchors.push(anchor)

src/app/cursor.coffee

@@ -18,7 +18,7 @@ class Cursor
     @setBufferPosition(bufferPosition) if bufferPosition
 
   destroy: ->
-    @editSession.removeAnchor(@anchor)
+    @anchor.destroy()
     @editSession.removeCursor(this)
     @trigger 'destroy'
 

src/app/edit-session.coffee

@@ -45,9 +45,7 @@ class EditSession
     @buffer.on "path-change.edit-session-#{@id}", =>
       @trigger 'buffer-path-change'
 
-    @buffer.on "change.edit-session-#{@id}", (e) =>
-      anchor.handleBufferChange(e) for anchor in @getAnchors()
-      @mergeCursors()
+    @buffer.on "change.edit-session-#{@id}", (e) => @mergeCursors()
 
     @displayBuffer.on "change.edit-session-#{@id}", (e) =>
       @trigger 'screen-lines-change', e
@@ -89,14 +87,8 @@ class EditSession
   getSoftWrap: -> @softWrap
   setSoftWrap: (@softWrap) ->
 
-  clipBufferPosition: (bufferPosition, options) ->
-    { row, column } = Point.fromObject(bufferPosition)
-    row = 0 if row < 0
-    column = 0 if column < 0
-    row = Math.min(@buffer.getLastRow(), row)
-    column = Math.min(@buffer.lineLengthForRow(row), column)
-
-    new Point(row, column)
+  clipBufferPosition: (bufferPosition) ->
+    @buffer.clipPosition(bufferPosition)
 
   getFileExtension: -> @buffer.getExtension()
   getPath: -> @buffer.getPath()