add test: cursor position in bidirectional lines

spec/fixtures/sample-bidirectional.txt

@@ -0,0 +1 @@
+Persian, locally known as Parsi or Farsi (زبان فارسی), the predominant modern descendant of Old Persian.

spec/lines-yardstick-spec.coffee

@@ -202,3 +202,73 @@ describe "LinesYardstick", ->
       it "clips negative horizontal pixel positions", ->
         expect(linesYardstick.screenPositionForPixelPosition(top: 0, left: -10)).toEqual [0, 0]
         expect(linesYardstick.screenPositionForPixelPosition(top: 1 * 14, left: -10)).toEqual [1, 0]
+
+describe "In bidirectional lines", ->
+      [editor, linesYardstick, createdLineNodes, mockLineNodesProvider] = []
+      beforeEach ->
+          waitsForPromise ->
+              atom.workspace.open('sample-bidirectional.txt').then (o) -> editor = o
+
+          runs ->
+              createdLineNodes = []
+
+              buildLineNode = (screenRow) ->
+                  startIndex = 0
+                  scopes = []
+                  screenLine = editor.screenLineForScreenRow(screenRow)
+                  lineNode = document.createElement("div")
+                  lineNode.style.whiteSpace = "pre"
+                  for tagCode in screenLine.tagCodes when tagCode isnt 0
+                      if editor.displayLayer.isCloseTagCode(tagCode)
+                          scopes.pop()
+                      else if editor.displayLayer.isOpenTagCode(tagCode)
+                          scopes.push(editor.displayLayer.tagForCode(tagCode))
+                      else
+                          text = screenLine.lineText.substr(startIndex, tagCode)
+                          startIndex += tagCode
+
+                          span = document.createElement("span")
+                          span.className = scopes.join(' ').replace(/\.+/g, ' ')
+                          span.textContent = text
+                          lineNode.appendChild(span)
+                  jasmine.attachToDOM(lineNode)
+                  createdLineNodes.push(lineNode)
+                  lineNode
+
+              mockLineNodesProvider =
+                  lineNodesById: {}
+
+                  lineIdForScreenRow: (screenRow) ->
+                      editor.screenLineForScreenRow(screenRow)?.id
+
+                  lineNodeForScreenRow: (screenRow) ->
+                      if id = @lineIdForScreenRow(screenRow)
+                          @lineNodesById[id] ?= buildLineNode(screenRow)
+
+                  textNodesForScreenRow: (screenRow) ->
+                      lineNode = @lineNodeForScreenRow(screenRow)
+                      iterator = document.createNodeIterator(lineNode, NodeFilter.SHOW_TEXT)
+                      textNodes = []
+                      textNodes.push(textNode) while textNode = iterator.nextNode()
+                      textNodes
+
+              editor.setLineHeightInPixels(14)
+              lineTopIndex = new LineTopIndex({defaultLineHeight: editor.getLineHeightInPixels()})
+              linesYardstick = new LinesYardstick(editor, mockLineNodesProvider, lineTopIndex, atom.grammars)
+
+      afterEach ->
+          lineNode.remove() for lineNode in createdLineNodes
+          atom.themes.removeStylesheet('test')
+
+      describe "LinesYardstick::pixelPositionForScreenPosition(screenPosition)", ->
+          it "should converts screen positions to correct pixel positions", ->
+              atom.styles.addStyleSheet """
+              * {
+                  font-size: 14px;
+                  font-family: monospace;
+              }
+              """
+              expect(linesYardstick.pixelPositionForScreenPosition(Point(0, 15))).toEqual({left: 126, top: 0})
+              expect(linesYardstick.pixelPositionForScreenPosition(Point(0, 62))).toEqual({left: 521, top: 0})
+              expect(linesYardstick.pixelPositionForScreenPosition(Point(0, 58))).toEqual({left: 487, top: 0})
+              expect(linesYardstick.pixelPositionForScreenPosition(Point(0, Infinity))).toEqual({left: 873.703125, top: 0})