Add LineWrapper.displayPositionFromBufferPosition

spec/atom/editor-spec.coffee

@@ -50,7 +50,7 @@ describe "Editor", ->
         buffer.insert([1,0], "/*")
         expect(editor.lines.find('.line:eq(2) span:eq(0)')).toMatchSelector '.comment'
 
-    fdescribe "when soft-wrap is enabled", ->
+    describe "when soft-wrap is enabled", ->
       beforeEach ->
         editor.attachToDom()
         editor.width(editor.charWidth * 50)

spec/atom/line-wrapper-spec.coffee

@@ -47,17 +47,35 @@ fdescribe "LineWrapper", ->
         expect(segments[2].lastIndex).toBe 65
         expect(_.pluck(segments[2], 'value').join('')).toBe 'right.push(current);'
 
+  xdescribe ".tokensForDisplayRow(row)", ->
+    it "returns tokens for the line fragment corresponding to the given display row", ->
+      expect(buffer.tokensForDisplayRow(3)).toEqual(wrapper.segmentsForRow(3)[0])
+      expect(buffer.tokensForDisplayRow(4)).toEqual(wrapper.segmentsForRow(3)[1])
+      expect(buffer.tokensForDisplayRow(5)).toEqual(wrapper.segmentsForRow(4)[0])
+
   describe ".displayPositionFromBufferPosition(point)", ->
-    it "returns the position of the indicated row and column on screen, accounting for wrapped lines", ->
-      # no wrap
+    it "translates the given buffer position to a display position, accounting for wrapped lines", ->
+      # before any wrapped lines
       expect(wrapper.displayPositionFromBufferPosition(row: 0, column: 5)).toEqual(row: 0, column: 5)
 
-      # wrap once
+      # on a wrapped line
       expect(wrapper.displayPositionFromBufferPosition(row: 3, column: 5)).toEqual(row: 3, column: 5)
       expect(wrapper.displayPositionFromBufferPosition(row: 3, column: 50)).toEqual(row: 3, column: 50)
       expect(wrapper.displayPositionFromBufferPosition(row: 3, column: 51)).toEqual(row: 4, column: 0)
 
-      # following a wrap
+      # following a wrapped line
       expect(wrapper.displayPositionFromBufferPosition(row: 4, column: 5)).toEqual(row: 5, column: 5)
 
+  describe ".bufferPositionFromDisplayPosition(point)", ->
+    it "translates the given display position to a buffer position, account for wrapped lines", ->
+      # before any wrapped lines
+      expect(wrapper.bufferPositionFromDisplayPosition(row: 0, column: 5)).toEqual(row: 0, column: 5)
+
+      # on a wrapped line
+      expect(wrapper.bufferPositionFromDisplayPosition(row: 3, column: 5)).toEqual(row: 3, column: 5)
+      expect(wrapper.bufferPositionFromDisplayPosition(row: 4, column: 0)).toEqual(row: 3, column: 51)
+      expect(wrapper.bufferPositionFromDisplayPosition(row: 4, column: 5)).toEqual(row: 3, column: 56)
+
+      # following a wrapped line
+      expect(wrapper.bufferPositionFromDisplayPosition(row: 5, column: 5)).toEqual(row: 4, column: 5)
 

src/atom/line-wrapper.coffee

@@ -34,6 +34,7 @@ class LineWrapper
         lastBreakIndex = startIndex
 
     currentSegment = []
+    currentSegment.startColumn = 0
     currentSegment.lastIndex = 0
     currentSegment.textLength = 0
     segments = [currentSegment]
@@ -42,6 +43,7 @@ class LineWrapper
       if currentSegment.lastIndex >= nextBreak
         nextBreak = breakIndices.shift()
         newSegment = []
+        newSegment.startColumn = currentSegment.lastIndex
         newSegment.lastIndex = currentSegment.lastIndex
         newSegment.textLength = 0
         segments.push(newSegment)
@@ -65,3 +67,13 @@ class LineWrapper
 
     { row, column }
 
+
+  bufferPositionFromDisplayPosition: (displayPosition) ->
+    bufferRow = 0
+    currentScreenRow = 0
+    for screenLines in @lines
+      for screenLine in screenLines
+        if currentScreenRow == displayPosition.row
+          return { row: bufferRow, column: screenLine.startColumn + displayPosition.column }
+        currentScreenRow++
+      bufferRow++