Selection and Cursor use Anchor to hold their buffer and screen positions

src/atom/anchor.coffee

@@ -0,0 +1,47 @@
+Point = require 'point'
+
+module.exports =
+class Anchor
+  editor: null
+  bufferPosition: null
+  screenPosition: null
+
+  constructor: (editor) ->
+    @editor = editor
+    @bufferPosition = new Point(0, 0)
+    @screenPosition = new Point(0, 0)
+
+  handleBufferChange: (e) ->
+    { oldRange, newRange } = e
+    position = @getBufferPosition()
+    return if position.isLessThan(oldRange.end)
+
+    newRow = newRange.end.row
+    newColumn = newRange.end.column
+    if position.row == oldRange.end.row
+      newColumn += position.column - oldRange.end.column
+    else
+      newColumn = position.column
+      newRow += position.row - oldRange.end.row
+
+    @setBufferPosition [newRow, newColumn]
+
+  getBufferPosition: ->
+    @bufferPosition
+
+  setBufferPosition: (position) ->
+    screenPosition = @editor.screenPositionForBufferPosition(position)
+    @setScreenPosition(screenPosition, clip: false)
+
+  getScreenPosition: ->
+    @screenPosition
+
+  setScreenPosition: (position, options={}) ->
+    position = Point.fromObject(position)
+    clip = options.clip ? true
+
+    @screenPosition = if clip then @editor.clipScreenPosition(position) else position
+    @bufferPosition = @editor.bufferPositionForScreenPosition(position)
+
+    Object.freeze @screenPosition
+    Object.freeze @bufferPosition

src/atom/composite-cursor.coffee

@@ -45,8 +45,8 @@ class CompositeCursor
   setBufferPosition: (bufferPosition) ->
     @moveCursors (cursor) -> cursor.setBufferPosition(bufferPosition)
 
-  refreshScreenPosition: ->
-    @moveCursors (cursor) -> cursor.refreshScreenPosition()
+  updateBufferPosition: ->
+    @moveCursors (cursor) -> cursor.setBufferPosition(cursor.getBufferPosition())
 
   moveLeft: ->
     @moveCursors (cursor) -> cursor.moveLeft()

src/atom/cursor.coffee

@@ -1,4 +1,5 @@
 {View} = require 'space-pen'
+Anchor = require 'anchor'
 Point = require 'point'
 _ = require 'underscore'
 
@@ -7,45 +8,38 @@ class Cursor extends View
   @content: ->
     @pre class: 'cursor idle', => @raw ' '
 
+  anchor: null
   editor: null
-  screenPosition: null
-  bufferPosition: null
   wordRegex: /(\w+)|([^\w\s]+)/g
 
   initialize: (@editor) ->
-    @screenPosition = new Point(0, 0)
+    @anchor = new Anchor(@editor)
     @one 'attach', => @updateAppearance()
 
   handleBufferChange: (e) ->
-    { newRange, oldRange } = e
-    position = @getBufferPosition()
-    return if position.isLessThan(oldRange.end)
-
-    newRow = newRange.end.row
-    newColumn = newRange.end.column
-    if position.row == oldRange.end.row
-      newColumn += position.column - oldRange.end.column
-    else
-      newColumn = position.column
-      newRow += position.row - oldRange.end.row
-
-    @setBufferPosition([newRow, newColumn])
+    @anchor.handleBufferChange(e)
+    @refreshScreenPosition()
 
   remove: ->
     @editor.compositeCursor.removeCursor(this)
     @editor.compositeSelection.removeSelectionForCursor(this)
     super
 
+  getBufferPosition: ->
+    @anchor.getBufferPosition()
+
+  setBufferPosition: (bufferPosition) ->
+    @anchor.setBufferPosition(bufferPosition)
+    @refreshScreenPosition()
+
+  getScreenPosition: ->
+    @anchor.getScreenPosition()
+
   setScreenPosition: (position, options={}) ->
-    position = Point.fromObject(position)
-    clip = options.clip ? true
-
-    @screenPosition = if clip then @editor.clipScreenPosition(position) else position
-    @bufferPosition = @editor.bufferPositionForScreenPosition(position)
-
-    Object.freeze @screenPosition
-    Object.freeze @bufferPosition
+    @anchor.setScreenPosition(position, options)
+    @refreshScreenPosition(position, options)
 
+  refreshScreenPosition: ->
     @goalColumn = null
     @updateAppearance()
     @trigger 'cursor:position-changed'
@@ -54,18 +48,6 @@ class Cursor extends View
     window.clearTimeout(@idleTimeout) if @idleTimeout
     @idleTimeout = window.setTimeout (=> @addClass 'idle'), 200
 
-  setBufferPosition: (bufferPosition) ->
-    @setScreenPosition(@editor.screenPositionForBufferPosition(bufferPosition), clip: false)
-
-  refreshScreenPosition: ->
-    @setBufferPosition(@bufferPosition)
-
-  getBufferPosition: ->
-    @bufferPosition
-
-  getScreenPosition: ->
-    @screenPosition
-
   getCurrentBufferLine: ->
     @editor.lineForBufferRow(@getBufferPosition().row)
 

src/atom/editor.coffee

@@ -222,7 +222,7 @@ class Editor extends View
     unless newRange.isSingleLine() and newRange.coversSameRows(oldRange)
       @gutter.renderLineNumbers(@getScreenLines())
 
-    @compositeCursor.refreshScreenPosition() unless e.bufferChanged
+    @compositeCursor.updateBufferPosition() unless e.bufferChanged
 
     lineElements = @buildLineElements(newRange.start.row, newRange.end.row)
     @replaceLineElements(oldRange.start.row, oldRange.end.row, lineElements)

src/atom/selection.coffee

@@ -1,3 +1,4 @@
+Anchor = require 'anchor'
 Cursor = require 'cursor'
 AceOutdentAdaptor = require 'ace-outdent-adaptor'
 Point = require 'point'
@@ -22,33 +23,25 @@ class Selection extends View
         @clearSelection()
 
   handleBufferChange: (e) ->
-    return unless @anchorScreenPosition
+    return unless @anchor
+    @anchor.handleBufferChange(e)
 
-    { oldRange, newRange } = e
-    position = @anchorBufferPosition
-    return if position.isLessThan(oldRange.end)
-
-    newRow = newRange.end.row
-    newColumn = newRange.end.column
-    if position.row == oldRange.end.row
-      newColumn += position.column - oldRange.end.column
-    else
-      newColumn = position.column
-      newRow += position.row - oldRange.end.row
-
-    @setAnchorBufferPosition([newRow, newColumn])
+  placeAnchor: ->
+    return if @anchor
+    @anchor = new Anchor(@editor)
+    @anchor.setScreenPosition @cursor.getScreenPosition()
 
   isEmpty: ->
     @getBufferRange().isEmpty()
 
   isReversed: ->
-    not @isEmpty() and @cursor.getBufferPosition().isLessThan(@anchorBufferPosition)
+    not @isEmpty() and @cursor.getBufferPosition().isLessThan(@anchor.getBufferPosition())
 
   intersectsWith: (otherSelection) ->
     @getScreenRange().intersectsWith(otherSelection.getScreenRange())
 
   clearSelection: ->
-    @anchorScreenPosition = null
+    @anchor = null
     @updateAppearance()
 
   updateAppearance: ->
@@ -87,8 +80,8 @@ class Selection extends View
     @regions = []
 
   getScreenRange: ->
-    if @anchorScreenPosition
-      new Range(@anchorScreenPosition, @cursor.getScreenPosition())
+    if @anchor
+      new Range(@anchor.getScreenPosition(), @cursor.getScreenPosition())
     else
       new Range(@cursor.getScreenPosition(), @cursor.getScreenPosition())
 
@@ -168,24 +161,6 @@ class Selection extends View
     fn()
     @retainSelection = false
 
-  placeAnchor: ->
-    return if @anchorScreenPosition
-    @setAnchorScreenPosition(@cursor.getScreenPosition())
-
-  setAnchorScreenPosition: (screenPosition) ->
-    bufferPosition = Point.fromObject(screenPosition)
-    @anchorScreenPosition = screenPosition
-    @anchorBufferPosition = @editor.bufferPositionForScreenPosition(screenPosition)
-
-  setAnchorBufferPosition: (bufferPosition) ->
-    bufferPosition = Point.fromObject(bufferPosition)
-    @anchorBufferPosition = bufferPosition
-    @anchorScreenPosition = @editor.screenPositionForBufferPosition(bufferPosition)
-
-  selectToScreenPosition: (position) ->
-    @modifySelection =>
-      @cursor.setScreenPosition(position)
-
   selectWord: ->
     row = @cursor.getScreenPosition().row
     column = @cursor.getScreenPosition().column
@@ -207,6 +182,9 @@ class Selection extends View
     rowLength = @editor.buffer.lineForRow(row).length
     @setBufferRange new Range([row, 0], [row, rowLength])
 
+  selectToScreenPosition: (position) ->
+    @modifySelection => @cursor.setScreenPosition(position)
+
   selectRight: ->
     @modifySelection => @cursor.moveRight()