Simplify DisplayBuffer's change event handling

spec/app/display-buffer-spec.coffee

@@ -65,7 +65,6 @@ describe "DisplayBuffer", ->
             [[event]]= changeHandler.argsForCall
             expect(event.oldRange).toEqual([[7, 0], [8, 20]])
             expect(event.newRange).toEqual([[7, 0], [7, 47]])
-            expect(event.lineNumbersChanged).toBeTruthy()
 
         describe "when the update causes a line to softwrap an additional time", ->
           it "rewraps the line and emits a change event", ->
@@ -79,7 +78,6 @@ describe "DisplayBuffer", ->
             [[event]] = changeHandler.argsForCall
             expect(event.oldRange).toEqual([[7, 0], [8, 20]])
             expect(event.newRange).toEqual([[7, 0], [9, 20]])
-            expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when buffer lines are inserted", ->
         it "inserts / updates wrapped lines and emits a change event", ->
@@ -93,7 +91,6 @@ describe "DisplayBuffer", ->
           [event] = changeHandler.argsForCall[0]
           expect(event.oldRange).toEqual([[7, 0], [8, 20]])
           expect(event.newRange).toEqual([[7, 0], [10, 20]])
-          expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when buffer lines are removed", ->
         it "removes lines and emits a change event", ->
@@ -107,7 +104,6 @@ describe "DisplayBuffer", ->
           [event] = changeHandler.argsForCall[0]
           expect(event.oldRange).toEqual([[3, 0], [9, 5]])
           expect(event.newRange).toEqual([[3, 0], [3, 22]])
-          expect(event.lineNumbersChanged).toBeTruthy()
 
     describe "position translation", ->
       it "translates positions accounting for wrapped lines", ->
@@ -142,7 +138,6 @@ describe "DisplayBuffer", ->
         [event] = changeHandler.argsForCall[0]
         expect(event.oldRange).toEqual([[0, 0], [15, 2]])
         expect(event.newRange).toEqual([[0, 0], [18, 2]])
-        expect(event.lineNumbersChanged).toBeTruthy()
 
   describe "structural folding", ->
     describe ".unfoldAll()", ->
@@ -237,7 +232,6 @@ describe "DisplayBuffer", ->
           [event] = changeHandler.argsForCall[0]
           expect(event.oldRange).toEqual [[4, 0], [7, 1]]
           expect(event.newRange).toEqual [[4, 0], [4, 101]]
-          expect(event.lineNumbersChanged).toBeTruthy()
           changeHandler.reset()
 
           fold.destroy()
@@ -251,7 +245,6 @@ describe "DisplayBuffer", ->
           [[event]] = changeHandler.argsForCall
           expect(event.oldRange).toEqual [[4, 0], [4, 101]]
           expect(event.newRange).toEqual [[4, 0], [7, 1]]
-          expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when a fold spans a single line", ->
         it "renders a fold placeholder for the folded line but does not skip any lines", ->
@@ -270,7 +263,6 @@ describe "DisplayBuffer", ->
 
           # Line numbers don't actually change, but it's not worth the complexity to have this
           # be false for single line folds since they are so rare
-          expect(event.lineNumbersChanged).toBeTruthy()
           changeHandler.reset()
 
           fold.destroy()
@@ -285,7 +277,6 @@ describe "DisplayBuffer", ->
           [[event]] = changeHandler.argsForCall
           expect(event.oldRange).toEqual [[4, 0], [4, 101]]
           expect(event.newRange).toEqual [[4, 0], [4, 101]]
-          expect(event.lineNumbersChanged).toBeTruthy()
           changeHandler.reset()
 
       describe "when a fold is nested within another fold", ->
@@ -368,7 +359,6 @@ describe "DisplayBuffer", ->
           [[event]] = changeHandler.argsForCall
           expect(event.oldRange).toEqual [[1, 0], [3, 1]]
           expect(event.newRange).toEqual [[1, 0], [1, 6]]
-          expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when the old range surrounds two nested folds", ->
         it "removes both folds and replaces the selection with the new text", ->
@@ -385,7 +375,6 @@ describe "DisplayBuffer", ->
           [[event]] = changeHandler.argsForCall
           expect(event.oldRange).toEqual [[1, 0], [3, 2]]
           expect(event.newRange).toEqual [[1, 0], [1, 9]]
-          expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when multiple changes happen above the fold", ->
         it "repositions folds correctly", ->
@@ -410,7 +399,6 @@ describe "DisplayBuffer", ->
             [[event]] = changeHandler.argsForCall
             expect(event.oldRange).toEqual [[0, 0], [1, 1]]
             expect(event.newRange).toEqual [[0, 0], [0, 3]]
-            expect(event.lineNumbersChanged).toBeTruthy()
             changeHandler.reset()
 
             fold1.destroy()
@@ -425,7 +413,6 @@ describe "DisplayBuffer", ->
             [[event]] = changeHandler.argsForCall
             expect(event.oldRange).toEqual [[1, 0], [1, 1]]
             expect(event.newRange).toEqual [[1, 0], [3, 101]]
-            expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when the old range straddles the beginning of a fold", ->
         it "replaces lines in the portion of the range that precedes the fold and adjusts the end of the fold to encompass additional lines", ->
@@ -452,7 +439,6 @@ describe "DisplayBuffer", ->
           [[event]] = changeHandler.argsForCall
           expect(event.oldRange).toEqual [[6, 0], [7, 2]] # Expands ranges to encompes entire line
           expect(event.newRange).toEqual [[6, 0], [6, 5]]
-          expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when the old range is inside a fold", ->
         describe "when the end of the new range precedes the end of the fold", ->
@@ -473,7 +459,6 @@ describe "DisplayBuffer", ->
             [[event]] = changeHandler.argsForCall
             expect(event.oldRange).toEqual [[2, 0], [2, 1]]
             expect(event.newRange).toEqual [[2, 0], [2, 1]]
-            expect(event.lineNumbersChanged).toBeTruthy()
 
         describe "when the end of the new range exceeds the end of the fold", ->
           it "expands the fold to contain all the inserted lines", ->
@@ -493,7 +478,6 @@ describe "DisplayBuffer", ->
             [[event]] = changeHandler.argsForCall
             expect(event.oldRange).toEqual [[2, 0], [2, 1]]
             expect(event.newRange).toEqual [[2, 0], [2, 1]]
-            expect(event.lineNumbersChanged).toBeTruthy()
 
       describe "when the old range straddles the end of the fold", ->
         describe "when the end of the new range precedes the end of the fold", ->
@@ -519,7 +503,6 @@ describe "DisplayBuffer", ->
           [[event]] = changeHandler.argsForCall
           expect(event.oldRange).toEqual [[3, 0], [3, 1]]
           expect(event.newRange).toEqual [[3, 0], [4, 1]]
-          expect(event.lineNumbersChanged).toBeTruthy()
 
     describe "position translation", ->
       it "translates positions to account for folded lines and characters and the placeholder", ->

src/app/display-buffer.coffee

@@ -35,7 +35,7 @@ class DisplayBuffer
     oldRange = @rangeForAllLines()
     @buildLineMap()
     newRange = @rangeForAllLines()
-    @trigger 'change', { oldRange, newRange, lineNumbersChanged: true }
+    @trigger 'change', { oldRange, newRange }
 
   lineForRow: (row) ->
     @lineMap.lineForScreenRow(row)
@@ -87,7 +87,7 @@ class DisplayBuffer
       @lineMap.replaceScreenRows(oldScreenRange.start.row, oldScreenRange.end.row, lines)
       newScreenRange = @screenLineRangeForBufferRange(bufferRange)
 
-      @trigger 'change', oldRange: oldScreenRange, newRange: newScreenRange, lineNumbersChanged: true
+      @trigger 'change', oldRange: oldScreenRange, newRange: newScreenRange
 
     fold
 
@@ -111,7 +111,7 @@ class DisplayBuffer
       @lineMap.replaceScreenRows(oldScreenRange.start.row, oldScreenRange.end.row, lines)
       newScreenRange = @screenLineRangeForBufferRange(bufferRange)
 
-      @trigger 'change', oldRange: oldScreenRange, newRange: newScreenRange, lineNumbersChanged: true
+      @trigger 'change', oldRange: oldScreenRange, newRange: newScreenRange
 
   destroyFoldsContainingBufferRow: (bufferRow) ->
     for row, folds of @activeFolds
@@ -195,10 +195,15 @@ class DisplayBuffer
   handleTokenizedBufferChange: (e) ->
     @handleBufferChange(e.bufferChange) if e.bufferChange
 
-    newRange = e.newRange.copy()
-    newRange.start.row = @bufferRowForScreenRow(@screenRowForBufferRow(newRange.start.row))
+    { oldRange, newRange } = e
+    oldRange = oldRange.copy()
+    newRange = newRange.copy()
 
-    oldScreenRange = @screenLineRangeForBufferRange(e.oldRange)
+    foldAdjustedStartRow = @bufferRowForScreenRow(@screenRowForBufferRow(newRange.start.row))
+    oldRange.start.row = foldAdjustedStartRow
+    newRange.start.row = foldAdjustedStartRow
+
+    oldScreenRange = @screenLineRangeForBufferRange(oldRange)
 
     newScreenLines = @buildLinesForBufferRows(newRange.start.row, newRange.end.row)
     @lineMap.replaceScreenRows oldScreenRange.start.row, oldScreenRange.end.row, newScreenLines
@@ -208,7 +213,6 @@ class DisplayBuffer
       oldRange: oldScreenRange
       newRange: newScreenRange
       bufferChange: e.bufferChange
-      lineNumbersChanged: !e.oldRange.coversSameRows(newRange) or !oldScreenRange.coversSameRows(newScreenRange)
 
   buildLineForBufferRow: (bufferRow) ->
     @buildLinesForBufferRows(bufferRow, bufferRow)