Localize grammar reloading / setting to LanguageMode

Previously, logic associated with swapping grammars was a bit
scattered. Now grammar reloading / assignment methods delegate to
LanguageMode directly, and it emits a 'grammar-changed' event when
the grammar changes. Now EditSession and TokenizedBuffer listen for
this event and perform necessary actions for grammar change.

src/app/edit-session.coffee

@@ -57,7 +57,7 @@ class EditSession
     @subscribe @displayBuffer, "changed", (e) =>
       @trigger 'screen-lines-changed', e
 
-    @subscribe syntax, 'grammars-loaded', => @reloadGrammar()
+    @languageMode.on 'grammar-changed', => @handleGrammarChange()
 
   getViewClass: ->
     require 'editor'
@@ -846,17 +846,14 @@ class EditSession
   getGrammar: -> @languageMode.grammar
 
   setGrammar: (grammar) ->
-    @languageMode.grammar = grammar
-    @handleGrammarChange()
+    @languageMode.setGrammar(grammar)
 
   reloadGrammar: ->
-    @handleGrammarChange() if @languageMode.reloadGrammar()
+    @languageMode.reloadGrammar()
 
   handleGrammarChange: ->
     @unfoldAll()
-    @displayBuffer.tokenizedBuffer.resetScreenLines()
     @trigger 'grammar-changed'
-    true
 
   getDebugSnapshot: ->
     [

src/app/editor.coffee

@@ -1147,16 +1147,9 @@ class Editor extends View
   setGrammar: (grammar) ->
     throw new Error("Only mini-editors can explicity set their grammar") unless @mini
     @activeEditSession.setGrammar(grammar)
-    @handleGrammarChange()
 
   reloadGrammar: ->
-    grammarChanged = @activeEditSession.reloadGrammar()
-    @handleGrammarChange() if grammarChanged
-    grammarChanged
-
-  handleGrammarChange: ->
-    @clearRenderedLines()
-    @updateDisplay()
+    @activeEditSession.reloadGrammar()
 
   bindToKeyedEvent: (key, event, callback) ->
     binding = {}

src/app/language-mode.coffee

@@ -2,6 +2,7 @@ Range = require 'range'
 _ = require 'underscore'
 require 'underscore-extensions'
 {OnigRegExp} = require 'oniguruma'
+EventEmitter = require 'event-emitter'
 
 module.exports =
 class LanguageMode
@@ -12,14 +13,18 @@ class LanguageMode
   constructor: (@editSession) ->
     @buffer = @editSession.buffer
     @reloadGrammar()
+    syntax.on 'grammars-loaded', => @reloadGrammar()
+
+  setGrammar: (grammar) ->
+    return if grammar is @grammar
+    @grammar = grammar
+    @trigger 'grammar-changed', grammar
 
   reloadGrammar: ->
-    path = @buffer.getPath()
-    pathContents = @buffer.cachedDiskContents
-    previousGrammar = @grammar
-    @grammar = syntax.selectGrammar(path, pathContents)
-    throw new Error("No grammar found for path: #{path}") unless @grammar
-    previousGrammar isnt @grammar
+    if grammar = syntax.selectGrammar(@buffer.getPath(), @buffer.getText())
+      @setGrammar(grammar)
+    else
+      throw new Error("No grammar found for path: #{path}")
 
   toggleLineCommentsForBufferRows: (start, end) ->
     scopes = @editSession.scopesForBufferPosition([start, 0])
@@ -158,3 +163,5 @@ class LanguageMode
   foldEndRegexForScopes: (scopes) ->
     if foldEndPattern = syntax.getProperty(scopes, 'editor.foldEndPattern')
       new OnigRegExp(foldEndPattern)
+
+_.extend LanguageMode.prototype, EventEmitter

src/app/tokenized-buffer.coffee

@@ -23,6 +23,7 @@ class TokenizedBuffer
     @id = @constructor.idCounter++
     @resetScreenLines()
     @buffer.on "changed.tokenized-buffer#{@id}", (e) => @handleBufferChange(e)
+    @languageMode.on 'grammar-changed', => @resetScreenLines()
 
   resetScreenLines: ->
     @screenLines = @buildPlaceholderScreenLinesForRows(0, @buffer.getLastRow())