Fix gutter rendering when there are folds

Fixes #1059

spec/editor-spec.coffee

@@ -1766,6 +1766,14 @@ describe "Editor", ->
         expect(editor.gutter.find('.line-number:first').intValue()).toBe 2
         expect(editor.gutter.find('.line-number:last').intValue()).toBe 11
 
+      it "re-renders the correct line number range when there are folds", ->
+        editor.activeEditSession.foldBufferRow(1)
+        expect(editor.gutter.find('.line-number-1')).toHaveClass 'fold'
+
+        buffer.insert([0, 0], '\n')
+
+        expect(editor.gutter.find('.line-number-2')).toHaveClass 'fold'
+
     describe "when wrapping is on", ->
       it "renders a • instead of line number for wrapped portions of lines", ->
         editSession.setSoftWrap(true)

src/gutter.coffee

@@ -141,12 +141,23 @@ class Gutter extends View
     updateAllLines = not (startScreenRow? and endScreenRow?)
     updateAllLines |= endScreenRow <= @firstScreenRow or startScreenRow >= @lastScreenRow
 
-    for change in changes
-      # When there is a change to the bufferRow -> screenRow map (i.e. a fold),
-      # then rerender everything.
-      if (change.screenDelta or change.bufferDelta) and change.screenDelta != change.bufferDelta
-        updateAllLines = true
-        break
+    unless updateAllLines
+      minChangeStartScreenRow = null
+      for change in changes
+        # When there is a change to the bufferRow -> screenRow map (i.e. a fold),
+        # then rerender everything.
+        if (change.screenDelta or change.bufferDelta) and change.screenDelta != change.bufferDelta
+          updateAllLines = true
+          break
+        else if change.screenDelta or change.bufferDelta
+          minChangeStartScreenRow = Math.min(change.start, minChangeStartScreenRow)
+
+      if minChangeStartScreenRow? and not updateAllLines
+        # Need to rerender when changes are before a fold
+        for screenRow in [minChangeStartScreenRow...endScreenRow]
+          if @getEditor().isFoldedAtScreenRow(screenRow)
+            updateAllLines = true
+            break
 
     if updateAllLines
       @lineNumbers[0].innerHTML = @buildLineElementsHtml(startScreenRow, endScreenRow)