Update cursor view when selection screen position changes

src/selection-component.coffee

@@ -1,12 +1,19 @@
 {React, div} = require 'reactionary'
+SubscriberMixin = require './subscriber-mixin'
 CursorComponent = require './cursor-component'
 
 module.exports =
 SelectionComponent = React.createClass
-  render: ->
-    console.log "render selection component"
+  mixins: [SubscriberMixin]
 
+  render: ->
     {selection, lineHeight, charWidth} = @props
     {cursor} = selection
     div className: 'selection',
       CursorComponent({cursor, lineHeight, charWidth})
+
+  componentDidMount: ->
+    @subscribe @props.selection, 'screen-range-changed', => @forceUpdate()
+
+  componentWillUnmount: ->
+    @unsubscribe()