Renderer indicates when a screen line starts a foldable region

src/app/ace-fold-adaptor.coffee

@@ -0,0 +1,6 @@
+module.exports =
+class AceFoldAdaptor
+  constructor: (@buffer) ->
+
+  getLine: (bufferRow) ->
+    @buffer.lineForRow(bufferRow)

src/app/fold-suggester.coffee

@@ -0,0 +1,10 @@
+AceFoldAdaptor = require 'ace-fold-adaptor'
+
+module.exports =
+class FoldSuggester
+  constructor: (@buffer) ->
+    @aceFoldMode = @buffer.getMode().foldingRules
+    @aceFoldAdaptor = new AceFoldAdaptor(@buffer)
+
+  isBufferRowFoldable: (bufferRow) ->
+    @aceFoldMode.getFoldWidget(@aceFoldAdaptor, null, bufferRow) == "start"

src/app/renderer.coffee

@@ -1,5 +1,6 @@
 _ = require 'underscore'
 Highlighter = require 'highlighter'
+FoldSuggester = require 'fold-suggester'
 LineMap = require 'line-map'
 Point = require 'point'
 EventEmitter = require 'event-emitter'
@@ -22,6 +23,7 @@ class Renderer
   constructor: (@buffer, options={}) ->
     @id = @constructor.idCounter++
     @highlighter = new Highlighter(@buffer, options.tabText ? '  ')
+    @foldSuggester = new FoldSuggester(@buffer)
     @maxLineLength = options.maxLineLength ? Infinity
     @activeFolds = {}
     @foldsById = {}
@@ -161,6 +163,7 @@ class Renderer
     startBufferColumn = 0
     while currentBufferRow <= endBufferRow
       screenLine = @highlighter.lineForRow(currentBufferRow)
+      screenLine.foldable = @foldSuggester.isBufferRowFoldable(currentBufferRow)
 
       if fold = @largestFoldForBufferRow(currentBufferRow)
         screenLine = screenLine.copy()

src/app/screen-line-fragment.coffee

@@ -8,6 +8,7 @@ class ScreenLineFragment
   tokens: null
   screenDelta: null
   bufferDelta: null
+  foldable: null
 
   constructor: (@tokens, @text, screenDelta, bufferDelta, extraFields) ->
     @screenDelta = Point.fromObject(screenDelta)
@@ -15,7 +16,7 @@ class ScreenLineFragment
     _.extend(this, extraFields)
 
   copy: ->
-    new ScreenLineFragment(@tokens, @text, @screenDelta, @bufferDelta, { @state })
+    new ScreenLineFragment(@tokens, @text, @screenDelta, @bufferDelta, { @state, @foldable })
 
   splitAt: (column) ->
     return [new ScreenLineFragment([], '', [0, 0], [0, 0]), this] if column == 0
@@ -36,7 +37,7 @@ class ScreenLineFragment
     [leftScreenDelta, rightScreenDelta] = @screenDelta.splitAt(column)
     [leftBufferDelta, rightBufferDelta] = @bufferDelta.splitAt(column)
 
-    leftFragment = new ScreenLineFragment(leftTokens, leftText, leftScreenDelta, leftBufferDelta, {@state})
+    leftFragment = new ScreenLineFragment(leftTokens, leftText, leftScreenDelta, leftBufferDelta, {@state, @foldable})
     rightFragment = new ScreenLineFragment(rightTokens, rightText, rightScreenDelta, rightBufferDelta, {@state})
     [leftFragment, rightFragment]