Highlighter emits change events.

Changes to the buffer may cause lines beyond the scope of the textual
change to be re-highlighted. If so so, this is reflected in the
pre/post range of Highlighter's change events.

spec/atom/highlighter-spec.coffee

@@ -15,9 +15,16 @@ describe "Highlighter", ->
       expect(highlighter.tokensForRow(11)[1]).toEqual(type: 'keyword', value: 'return')
 
   describe "when the buffer changes", ->
+    changeHandler = null
+
+    beforeEach ->
+      changeHandler = jasmine.createSpy('changeHandler')
+      highlighter.on "change", changeHandler
+
     describe "when lines are updated, but none are added or removed", ->
       it "updates tokens for each of the changed lines", ->
-        buffer.change(new Range([0, 0], [2, 0]), "foo()\nbar()\n")
+        range = new Range([0, 0], [2, 0])
+        buffer.change(range, "foo()\nbar()\n")
 
         expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'identifier', value: 'foo')
         expect(highlighter.tokensForRow(1)[0]).toEqual(type: 'identifier', value: 'bar')
@@ -25,16 +32,30 @@ describe "Highlighter", ->
         # line 2 is unchanged
         expect(highlighter.tokensForRow(2)[1]).toEqual(type: 'keyword', value: 'if')
 
+        expect(changeHandler).toHaveBeenCalled()
+        [event] = changeHandler.argsForCall[0]
+
+        expect(event.preRange).toEqual range
+        expect(event.postRange).toEqual new Range([0, 0], [2,0])
+
       it "updates tokens for lines beyond the changed lines if needed", ->
         buffer.insert([5, 30], '/* */')
+        changeHandler.reset()
+
         buffer.insert([2, 0], '/*')
         expect(highlighter.tokensForRow(3)[0].type).toBe 'comment'
         expect(highlighter.tokensForRow(4)[0].type).toBe 'comment'
         expect(highlighter.tokensForRow(5)[0].type).toBe 'comment'
 
+        expect(changeHandler).toHaveBeenCalled()
+        [event] = changeHandler.argsForCall[0]
+        expect(event.preRange).toEqual new Range([2, 0], [6, buffer.getLine(6).length])
+        expect(event.postRange).toEqual new Range([2, 0], [6, buffer.getLine(6).length])
+
     describe "when lines are both updated and removed", ->
       it "updates tokens to reflect the removed lines", ->
-        buffer.change(new Range([1, 0], [3, 0]), "foo()")
+        range = new Range([1, 0], [3, 0])
+        buffer.change(range, "foo()")
 
         # previous line 0 remains
         expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'keyword.definition', value: 'var')
@@ -48,9 +69,29 @@ describe "Highlighter", ->
         expect(highlighter.tokensForRow(3)[1]).toEqual(type: 'identifier', value: 'current')
         expect(highlighter.tokensForRow(4)[3]).toEqual(type: 'keyword.operator', value: '<')
 
+        expect(changeHandler).toHaveBeenCalled()
+        [event] = changeHandler.argsForCall[0]
+        expect(event.preRange).toEqual range
+        expect(event.postRange).toEqual new Range([1, 0], [1, 5])
+
+      it "updates tokens for lines beyond the changed lines if needed", ->
+        buffer.insert([5, 30], '/* */')
+        changeHandler.reset()
+
+        buffer.change(new Range([2, 0], [3, 0]), '/*')
+        expect(highlighter.tokensForRow(2)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(3)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(4)[0].type).toBe 'comment'
+
+        expect(changeHandler).toHaveBeenCalled()
+        [event] = changeHandler.argsForCall[0]
+        expect(event.preRange).toEqual new Range([2, 0], [6, buffer.getLine(5).length])
+        expect(event.postRange).toEqual new Range([2, 0], [5, buffer.getLine(5).length])
+
     describe "when lines are both updated and inserted", ->
       it "updates tokens to reflect the inserted lines", ->
-        buffer.change(new Range([1, 0], [2, 0]), "foo()\nbar()\nbaz()\nquux()")
+        range = new Range([1, 0], [2, 0])
+        buffer.change(range, "foo()\nbar()\nbaz()\nquux()")
 
         # previous line 0 remains
         expect(highlighter.tokensForRow(0)[0]).toEqual(type: 'keyword.definition', value: 'var')
@@ -67,3 +108,25 @@ describe "Highlighter", ->
         # previous line 3 is pushed down to become line 5
         expect(highlighter.tokensForRow(5)[3]).toEqual(type: 'identifier', value: 'pivot')
 
+        expect(changeHandler).toHaveBeenCalled()
+        [event] = changeHandler.argsForCall[0]
+        expect(event.preRange).toEqual range
+        expect(event.postRange).toEqual new Range([1, 0], [4, 6])
+
+      it "updates tokens for lines beyond the changed lines if needed", ->
+        buffer.insert([5, 30], '/* */')
+        changeHandler.reset()
+
+        buffer.insert([2, 0], '/*\nabcde\nabcder')
+        expect(highlighter.tokensForRow(2)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(3)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(4)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(5)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(6)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(7)[0].type).toBe 'comment'
+        expect(highlighter.tokensForRow(8)[0].type).not.toBe 'comment'
+
+        expect(changeHandler).toHaveBeenCalled()
+        [event] = changeHandler.argsForCall[0]
+        expect(event.preRange).toEqual new Range([2, 0], [6, buffer.getLine(8).length])
+        expect(event.postRange).toEqual new Range([2, 0], [8, buffer.getLine(8).length])

src/atom/highlighter.coffee

@@ -16,7 +16,8 @@ class Highlighter
     @tokenizer = (new Mode).getTokenizer()
 
   handleBufferChange: (e) ->
-    { preRange, postRange } = e
+    preRange = e.preRange.copy()
+    postRange = e.postRange.copy()
 
     previousState = @lines[preRange.end.row].state
     newLines = @tokenizeRows('start', postRange.start.row, postRange.end.row)
@@ -28,6 +29,13 @@ class Highlighter
       previousState = @lines[nextRow].state
       @lines[nextRow] = @tokenizeRow(@lines[row].state, nextRow)
 
+      preRange.end.row++
+      preRange.end.column = @buffer.getLine(nextRow).length
+      postRange.end.row++
+      postRange.end.column = @buffer.getLine(nextRow).length
+
+    @trigger("change", {preRange, postRange})
+
   tokenizeRows: (startState, startRow, endRow) ->
     state = startState
     for row in [startRow..endRow]
@@ -41,3 +49,10 @@ class Highlighter
   tokensForRow: (row) ->
     @lines[row].tokens
 
+  on: (eventName, handler) ->
+    @eventHandlers ?= {}
+    @eventHandlers[eventName] ?= []
+    @eventHandlers[eventName].push(handler)
+
+  trigger: (eventName, event) ->
+    @eventHandlers?[eventName]?.forEach (handler) -> handler(event)