diff --git a/src/lines-tile-component.coffee b/src/lines-tile-component.coffee
deleted file mode 100644
index c1cb2ba64..000000000
--- a/src/lines-tile-component.coffee
+++ /dev/null
@@ -1,288 +0,0 @@
-HighlightsComponent = require './highlights-component'
-ZERO_WIDTH_NBSP = '\ufeff'
-
-cloneObject = (object) ->
-  clone = {}
-  clone[key] = value for key, value of object
-  clone
-
-module.exports =
-class LinesTileComponent
-  constructor: ({@presenter, @id, @domElementPool, @assert}) ->
-    @measuredLines = new Set
-    @lineNodesByLineId = {}
-    @screenRowsByLineId = {}
-    @lineIdsByScreenRow = {}
-    @textNodesByLineId = {}
-    @insertionPointsBeforeLineById = {}
-    @insertionPointsAfterLineById = {}
-    @domNode = @domElementPool.buildElement("div")
-    @domNode.style.position = "absolute"
-    @domNode.style.display = "block"
-
-    @highlightsComponent = new HighlightsComponent(@domElementPool)
-    @domNode.appendChild(@highlightsComponent.getDomNode())
-
-  destroy: ->
-    @domElementPool.freeElementAndDescendants(@domNode)
-
-  getDomNode: ->
-    @domNode
-
-  updateSync: (state) ->
-    @newState = state
-    unless @oldState
-      @oldState = {tiles: {}}
-      @oldState.tiles[@id] = {lines: {}}
-
-    @newTileState = @newState.tiles[@id]
-    @oldTileState = @oldState.tiles[@id]
-
-    if @newState.backgroundColor isnt @oldState.backgroundColor
-      @domNode.style.backgroundColor = @newState.backgroundColor
-      @oldState.backgroundColor = @newState.backgroundColor
-
-    if @newTileState.zIndex isnt @oldTileState.zIndex
-      @domNode.style.zIndex = @newTileState.zIndex
-      @oldTileState.zIndex = @newTileState.zIndex
-
-    if @newTileState.display isnt @oldTileState.display
-      @domNode.style.display = @newTileState.display
-      @oldTileState.display = @newTileState.display
-
-    if @newTileState.height isnt @oldTileState.height
-      @domNode.style.height = @newTileState.height + 'px'
-      @oldTileState.height = @newTileState.height
-
-    if @newState.width isnt @oldState.width
-      @domNode.style.width = @newState.width + 'px'
-      @oldTileState.width = @newTileState.width
-
-    if @newTileState.top isnt @oldTileState.top or @newTileState.left isnt @oldTileState.left
-      @domNode.style['-webkit-transform'] = "translate3d(#{@newTileState.left}px, #{@newTileState.top}px, 0px)"
-      @oldTileState.top = @newTileState.top
-      @oldTileState.left = @newTileState.left
-
-    @updateLineNodes()
-
-    @highlightsComponent.updateSync(@newTileState)
-
-  removeLineNodes: ->
-    @removeLineNode(id) for id of @oldTileState.lines
-    return
-
-  removeLineNode: (id) ->
-    @domElementPool.freeElementAndDescendants(@lineNodesByLineId[id])
-    @removeBlockDecorationInsertionPointBeforeLine(id)
-    @removeBlockDecorationInsertionPointAfterLine(id)
-
-    delete @lineNodesByLineId[id]
-    delete @textNodesByLineId[id]
-    delete @lineIdsByScreenRow[@screenRowsByLineId[id]]
-    delete @screenRowsByLineId[id]
-    delete @oldTileState.lines[id]
-
-  updateLineNodes: ->
-    for id of @oldTileState.lines
-      unless @newTileState.lines.hasOwnProperty(id)
-        @removeLineNode(id)
-
-    newLineIds = null
-    newLineNodes = null
-
-    for id, lineState of @newTileState.lines
-      if @oldTileState.lines.hasOwnProperty(id)
-        @updateLineNode(id)
-      else
-        newLineIds ?= []
-        newLineNodes ?= []
-        newLineIds.push(id)
-        newLineNodes.push(@buildLineNode(id))
-        @screenRowsByLineId[id] = lineState.screenRow
-        @lineIdsByScreenRow[lineState.screenRow] = id
-        @oldTileState.lines[id] = cloneObject(lineState)
-
-    return unless newLineIds?
-
-    for id, i in newLineIds
-      lineNode = newLineNodes[i]
-      @lineNodesByLineId[id] = lineNode
-      if nextNode = @findNodeNextTo(lineNode)
-        @domNode.insertBefore(lineNode, nextNode)
-      else
-        @domNode.appendChild(lineNode)
-
-      @insertBlockDecorationInsertionPointBeforeLine(id)
-      @insertBlockDecorationInsertionPointAfterLine(id)
-
-  removeBlockDecorationInsertionPointBeforeLine: (id) ->
-    if insertionPoint = @insertionPointsBeforeLineById[id]
-      @domElementPool.freeElementAndDescendants(insertionPoint)
-      delete @insertionPointsBeforeLineById[id]
-
-  insertBlockDecorationInsertionPointBeforeLine: (id) ->
-    {hasPrecedingBlockDecorations, screenRow} = @newTileState.lines[id]
-
-    if hasPrecedingBlockDecorations
-      lineNode = @lineNodesByLineId[id]
-      insertionPoint = @domElementPool.buildElement("content")
-      @domNode.insertBefore(insertionPoint, lineNode)
-      @insertionPointsBeforeLineById[id] = insertionPoint
-      insertionPoint.dataset.screenRow = screenRow
-      @updateBlockDecorationInsertionPointBeforeLine(id)
-
-  updateBlockDecorationInsertionPointBeforeLine: (id) ->
-    oldLineState = @oldTileState.lines[id]
-    newLineState = @newTileState.lines[id]
-    insertionPoint = @insertionPointsBeforeLineById[id]
-    return unless insertionPoint?
-
-    if newLineState.screenRow isnt oldLineState.screenRow
-      insertionPoint.dataset.screenRow = newLineState.screenRow
-
-    precedingBlockDecorationsSelector = newLineState.precedingBlockDecorations.map((d) -> ".atom--block-decoration-#{d.id}").join(',')
-
-    if precedingBlockDecorationsSelector isnt oldLineState.precedingBlockDecorationsSelector
-      insertionPoint.setAttribute("select", precedingBlockDecorationsSelector)
-      oldLineState.precedingBlockDecorationsSelector = precedingBlockDecorationsSelector
-
-  removeBlockDecorationInsertionPointAfterLine: (id) ->
-    if insertionPoint = @insertionPointsAfterLineById[id]
-      @domElementPool.freeElementAndDescendants(insertionPoint)
-      delete @insertionPointsAfterLineById[id]
-
-  insertBlockDecorationInsertionPointAfterLine: (id) ->
-    {hasFollowingBlockDecorations, screenRow} = @newTileState.lines[id]
-
-    if hasFollowingBlockDecorations
-      lineNode = @lineNodesByLineId[id]
-      insertionPoint = @domElementPool.buildElement("content")
-      @domNode.insertBefore(insertionPoint, lineNode.nextSibling)
-      @insertionPointsAfterLineById[id] = insertionPoint
-      insertionPoint.dataset.screenRow = screenRow
-      @updateBlockDecorationInsertionPointAfterLine(id)
-
-  updateBlockDecorationInsertionPointAfterLine: (id) ->
-    oldLineState = @oldTileState.lines[id]
-    newLineState = @newTileState.lines[id]
-    insertionPoint = @insertionPointsAfterLineById[id]
-    return unless insertionPoint?
-
-    if newLineState.screenRow isnt oldLineState.screenRow
-      insertionPoint.dataset.screenRow = newLineState.screenRow
-
-    followingBlockDecorationsSelector = newLineState.followingBlockDecorations.map((d) -> ".atom--block-decoration-#{d.id}").join(',')
-
-    if followingBlockDecorationsSelector isnt oldLineState.followingBlockDecorationsSelector
-      insertionPoint.setAttribute("select", followingBlockDecorationsSelector)
-      oldLineState.followingBlockDecorationsSelector = followingBlockDecorationsSelector
-
-  findNodeNextTo: (node) ->
-    for nextNode, index in @domNode.children
-      continue if index is 0 # skips highlights node
-      return nextNode if @screenRowForNode(node) < @screenRowForNode(nextNode)
-    return
-
-  screenRowForNode: (node) -> parseInt(node.dataset.screenRow)
-
-  buildLineNode: (id) ->
-    {lineText, tagCodes, screenRow, decorationClasses} = @newTileState.lines[id]
-
-    lineNode = @domElementPool.buildElement("div", "line")
-    lineNode.dataset.screenRow = screenRow
-
-    if decorationClasses?
-      for decorationClass in decorationClasses
-        lineNode.classList.add(decorationClass)
-
-    textNodes = []
-    startIndex = 0
-    openScopeNode = lineNode
-    for tagCode in tagCodes when tagCode isnt 0
-      if @presenter.isCloseTagCode(tagCode)
-        openScopeNode = openScopeNode.parentElement
-      else if @presenter.isOpenTagCode(tagCode)
-        scope = @presenter.tagForCode(tagCode)
-        newScopeNode = @domElementPool.buildElement("span", scope.replace(/\.+/g, ' '))
-        openScopeNode.appendChild(newScopeNode)
-        openScopeNode = newScopeNode
-      else
-        textNode = @domElementPool.buildText(lineText.substr(startIndex, tagCode))
-        startIndex += tagCode
-        openScopeNode.appendChild(textNode)
-        textNodes.push(textNode)
-
-    if startIndex is 0
-      textNode = @domElementPool.buildText(' ')
-      lineNode.appendChild(textNode)
-      textNodes.push(textNode)
-
-    if lineText.endsWith(@presenter.displayLayer.foldCharacter)
-      # Insert a zero-width non-breaking whitespace, so that
-      # LinesYardstick can take the fold-marker::after pseudo-element
-      # into account during measurements when such marker is the last
-      # character on the line.
-      textNode = @domElementPool.buildText(ZERO_WIDTH_NBSP)
-      lineNode.appendChild(textNode)
-      textNodes.push(textNode)
-
-    @textNodesByLineId[id] = textNodes
-    lineNode
-
-  updateLineNode: (id) ->
-    oldLineState = @oldTileState.lines[id]
-    newLineState = @newTileState.lines[id]
-
-    lineNode = @lineNodesByLineId[id]
-
-    newDecorationClasses = newLineState.decorationClasses
-    oldDecorationClasses = oldLineState.decorationClasses
-
-    if oldDecorationClasses?
-      for decorationClass in oldDecorationClasses
-        unless newDecorationClasses? and decorationClass in newDecorationClasses
-          lineNode.classList.remove(decorationClass)
-
-    if newDecorationClasses?
-      for decorationClass in newDecorationClasses
-        unless oldDecorationClasses? and decorationClass in oldDecorationClasses
-          lineNode.classList.add(decorationClass)
-
-    oldLineState.decorationClasses = newLineState.decorationClasses
-
-    if not oldLineState.hasPrecedingBlockDecorations and newLineState.hasPrecedingBlockDecorations
-      @insertBlockDecorationInsertionPointBeforeLine(id)
-    else if oldLineState.hasPrecedingBlockDecorations and not newLineState.hasPrecedingBlockDecorations
-      @removeBlockDecorationInsertionPointBeforeLine(id)
-
-    if not oldLineState.hasFollowingBlockDecorations and newLineState.hasFollowingBlockDecorations
-      @insertBlockDecorationInsertionPointAfterLine(id)
-    else if oldLineState.hasFollowingBlockDecorations and not newLineState.hasFollowingBlockDecorations
-      @removeBlockDecorationInsertionPointAfterLine(id)
-
-    if newLineState.screenRow isnt oldLineState.screenRow
-      lineNode.dataset.screenRow = newLineState.screenRow
-      @lineIdsByScreenRow[newLineState.screenRow] = id
-      @screenRowsByLineId[id] = newLineState.screenRow
-
-    @updateBlockDecorationInsertionPointBeforeLine(id)
-    @updateBlockDecorationInsertionPointAfterLine(id)
-
-    oldLineState.screenRow = newLineState.screenRow
-    oldLineState.hasPrecedingBlockDecorations = newLineState.hasPrecedingBlockDecorations
-    oldLineState.hasFollowingBlockDecorations = newLineState.hasFollowingBlockDecorations
-
-  lineNodeForScreenRow: (screenRow) ->
-    @lineNodesByLineId[@lineIdsByScreenRow[screenRow]]
-
-  lineNodeForLineId: (lineId) ->
-    @lineNodesByLineId[lineId]
-
-  textNodesForLineId: (lineId) ->
-    @textNodesByLineId[lineId].slice()
-
-  lineIdForScreenRow: (screenRow) ->
-    @lineIdsByScreenRow[screenRow]
-
-  textNodesForScreenRow: (screenRow) ->
-    @textNodesByLineId[@lineIdsByScreenRow[screenRow]]?.slice()
diff --git a/src/lines-tile-component.js b/src/lines-tile-component.js
new file mode 100644
index 000000000..0e98600ed
--- /dev/null
+++ b/src/lines-tile-component.js
@@ -0,0 +1,348 @@
+const HighlightsComponent = require('./highlights-component')
+const ZERO_WIDTH_NBSP = '\ufeff'
+
+module.exports = class LinesTileComponent {
+  constructor ({presenter, id, domElementPool, assert}) {
+    this.presenter = presenter
+    this.id = id
+    this.domElementPool = domElementPool
+    this.assert = assert
+    this.measuredLines = new Set()
+    this.lineNodesByLineId = {}
+    this.screenRowsByLineId = {}
+    this.lineIdsByScreenRow = {}
+    this.textNodesByLineId = {}
+    this.insertionPointsBeforeLineById = {}
+    this.insertionPointsAfterLineById = {}
+    this.domNode = this.domElementPool.buildElement('div')
+    this.domNode.style.position = 'absolute'
+    this.domNode.style.display = 'block'
+    this.highlightsComponent = new HighlightsComponent(this.domElementPool)
+    this.domNode.appendChild(this.highlightsComponent.getDomNode())
+  }
+
+  destroy () {
+    this.domElementPool.freeElementAndDescendants(this.domNode)
+  }
+
+  getDomNode () {
+    return this.domNode
+  }
+
+  updateSync (state) {
+    this.newState = state
+    if (this.oldState == null) {
+      this.oldState = {tiles: {}}
+      this.oldState.tiles[this.id] = {lines: {}}
+    }
+
+    this.newTileState = this.newState.tiles[this.id]
+    this.oldTileState = this.oldState.tiles[this.id]
+
+    if (this.newState.backgroundColor !== this.oldState.backgroundColor) {
+      this.domNode.style.backgroundColor = this.newState.backgroundColor
+      this.oldState.backgroundColor = this.newState.backgroundColor
+    }
+
+    if (this.newTileState.zIndex !== this.oldTileState.zIndex) {
+      this.domNode.style.zIndex = this.newTileState.zIndex
+      this.oldTileState.zIndex = this.newTileState.zIndex
+    }
+
+    if (this.newTileState.display !== this.oldTileState.display) {
+      this.domNode.style.display = this.newTileState.display
+      this.oldTileState.display = this.newTileState.display
+    }
+
+    if (this.newTileState.height !== this.oldTileState.height) {
+      this.domNode.style.height = this.newTileState.height + 'px'
+      this.oldTileState.height = this.newTileState.height
+    }
+
+    if (this.newState.width !== this.oldState.width) {
+      this.domNode.style.width = this.newState.width + 'px'
+      this.oldTileState.width = this.newTileState.width
+    }
+
+    if (this.newTileState.top !== this.oldTileState.top || this.newTileState.left !== this.oldTileState.left) {
+      this.domNode.style.transform = `translate3d(${this.newTileState.left}px, ${this.newTileState.top}px, 0px)`
+      this.oldTileState.top = this.newTileState.top
+      this.oldTileState.left = this.newTileState.left
+    }
+
+    this.updateLineNodes()
+    this.highlightsComponent.updateSync(this.newTileState)
+  }
+
+  removeLineNodes () {
+    for (const id of Object.keys(this.oldTileState.lines)) {
+      this.removeLineNode(id)
+    }
+  }
+
+  removeLineNode (id) {
+    this.domElementPool.freeElementAndDescendants(this.lineNodesByLineId[id])
+    this.removeBlockDecorationInsertionPointBeforeLine(id)
+    this.removeBlockDecorationInsertionPointAfterLine(id)
+    delete this.lineNodesByLineId[id]
+    delete this.textNodesByLineId[id]
+    delete this.lineIdsByScreenRow[this.screenRowsByLineId[id]]
+    delete this.screenRowsByLineId[id]
+    delete this.oldTileState.lines[id]
+  }
+
+  updateLineNodes () {
+    for (const id of Object.keys(this.oldTileState.lines)) {
+      if (!this.newTileState.lines.hasOwnProperty(id)) {
+        this.removeLineNode(id)
+      }
+    }
+
+    const newLineIds = []
+    const newLineNodes = []
+    for (const id of Object.keys(this.newTileState.lines)) {
+      const lineState = this.newTileState.lines[id]
+      if (this.oldTileState.lines.hasOwnProperty(id)) {
+        this.updateLineNode(id)
+      } else {
+        newLineIds.push(id)
+        newLineNodes.push(this.buildLineNode(id))
+        this.screenRowsByLineId[id] = lineState.screenRow
+        this.lineIdsByScreenRow[lineState.screenRow] = id
+        this.oldTileState.lines[id] = Object.assign({}, lineState)
+      }
+    }
+
+    while (newLineIds.length > 0) {
+      const id = newLineIds.shift()
+      const lineNode = newLineNodes.shift()
+      this.lineNodesByLineId[id] = lineNode
+      const nextNode = this.findNodeNextTo(lineNode)
+      if (nextNode == null) {
+        this.domNode.appendChild(lineNode)
+      } else {
+        this.domNode.insertBefore(lineNode, nextNode)
+      }
+      this.insertBlockDecorationInsertionPointBeforeLine(id)
+      this.insertBlockDecorationInsertionPointAfterLine(id)
+    }
+  }
+
+  removeBlockDecorationInsertionPointBeforeLine (id) {
+    const insertionPoint = this.insertionPointsBeforeLineById[id]
+    if (insertionPoint != null) {
+      this.domElementPool.freeElementAndDescendants(insertionPoint)
+      delete this.insertionPointsBeforeLineById[id]
+    }
+  }
+
+  insertBlockDecorationInsertionPointBeforeLine (id) {
+    const {hasPrecedingBlockDecorations, screenRow} = this.newTileState.lines[id]
+    if (hasPrecedingBlockDecorations) {
+      const lineNode = this.lineNodesByLineId[id]
+      const insertionPoint = this.domElementPool.buildElement('content')
+      this.domNode.insertBefore(insertionPoint, lineNode)
+      this.insertionPointsBeforeLineById[id] = insertionPoint
+      insertionPoint.dataset.screenRow = screenRow
+      this.updateBlockDecorationInsertionPointBeforeLine(id)
+    }
+  }
+
+  updateBlockDecorationInsertionPointBeforeLine (id) {
+    const oldLineState = this.oldTileState.lines[id]
+    const newLineState = this.newTileState.lines[id]
+    const insertionPoint = this.insertionPointsBeforeLineById[id]
+    if (insertionPoint != null) {
+      if (newLineState.screenRow !== oldLineState.screenRow) {
+        insertionPoint.dataset.screenRow = newLineState.screenRow
+      }
+
+      const precedingBlockDecorationsSelector = newLineState.precedingBlockDecorations
+        .map((d) => `.atom--block-decoration-${d.id}`)
+        .join(',')
+      if (precedingBlockDecorationsSelector !== oldLineState.precedingBlockDecorationsSelector) {
+        insertionPoint.setAttribute('select', precedingBlockDecorationsSelector)
+        oldLineState.precedingBlockDecorationsSelector = precedingBlockDecorationsSelector
+      }
+    }
+  }
+
+  removeBlockDecorationInsertionPointAfterLine (id) {
+    const insertionPoint = this.insertionPointsAfterLineById[id]
+    if (insertionPoint != null) {
+      this.domElementPool.freeElementAndDescendants(insertionPoint)
+      delete this.insertionPointsAfterLineById[id]
+    }
+  }
+
+  insertBlockDecorationInsertionPointAfterLine (id) {
+    const {hasFollowingBlockDecorations, screenRow} = this.newTileState.lines[id]
+    if (hasFollowingBlockDecorations) {
+      const lineNode = this.lineNodesByLineId[id]
+      const insertionPoint = this.domElementPool.buildElement('content')
+      this.domNode.insertBefore(insertionPoint, lineNode.nextSibling)
+      this.insertionPointsAfterLineById[id] = insertionPoint
+      insertionPoint.dataset.screenRow = screenRow
+      this.updateBlockDecorationInsertionPointAfterLine(id)
+    }
+  }
+
+  updateBlockDecorationInsertionPointAfterLine (id) {
+    const oldLineState = this.oldTileState.lines[id]
+    const newLineState = this.newTileState.lines[id]
+    const insertionPoint = this.insertionPointsAfterLineById[id]
+
+    if (insertionPoint != null) {
+      if (newLineState.screenRow !== oldLineState.screenRow) {
+        insertionPoint.dataset.screenRow = newLineState.screenRow
+      }
+
+      const followingBlockDecorationsSelector = newLineState.followingBlockDecorations
+        .map((d) => `.atom--block-decoration-${d.id}`)
+        .join(',')
+      if (followingBlockDecorationsSelector !== oldLineState.followingBlockDecorationsSelector) {
+        insertionPoint.setAttribute('select', followingBlockDecorationsSelector)
+        oldLineState.followingBlockDecorationsSelector = followingBlockDecorationsSelector
+      }
+    }
+  }
+
+  findNodeNextTo (node) {
+    let i = 1 // skip highlights node
+    while (i < this.domNode.children.length) {
+      const nextNode = this.domNode.children[i]
+      if (this.screenRowForNode(node) < this.screenRowForNode(nextNode)) {
+        return nextNode
+      }
+      i++
+    }
+    return null
+  }
+
+  screenRowForNode (node) {
+    return parseInt(node.dataset.screenRow)
+  }
+
+  buildLineNode (id) {
+    const {lineText, tagCodes, screenRow, decorationClasses} = this.newTileState.lines[id]
+
+    const lineNode = this.domElementPool.buildElement('div', 'line')
+    lineNode.dataset.screenRow = screenRow
+    if (decorationClasses != null) {
+      for (const decorationClass of decorationClasses) {
+        lineNode.classList.add(decorationClass)
+      }
+    }
+
+    const textNodes = []
+    let startIndex = 0
+    let openScopeNode = lineNode
+    for (const tagCode of tagCodes) {
+      if (tagCode !== 0) {
+        if (this.presenter.isCloseTagCode(tagCode)) {
+          openScopeNode = openScopeNode.parentElement
+        } else if (this.presenter.isOpenTagCode(tagCode)) {
+          const scope = this.presenter.tagForCode(tagCode)
+          const newScopeNode = this.domElementPool.buildElement('span', scope.replace(/\.+/g, ' '))
+          openScopeNode.appendChild(newScopeNode)
+          openScopeNode = newScopeNode
+        } else {
+          const textNode = this.domElementPool.buildText(lineText.substr(startIndex, tagCode))
+          startIndex += tagCode
+          openScopeNode.appendChild(textNode)
+          textNodes.push(textNode)
+        }
+      }
+    }
+
+    if (startIndex === 0) {
+      const textNode = this.domElementPool.buildText(' ')
+      lineNode.appendChild(textNode)
+      textNodes.push(textNode)
+    }
+
+    if (lineText.endsWith(this.presenter.displayLayer.foldCharacter)) {
+      const textNode = this.domElementPool.buildText(ZERO_WIDTH_NBSP)
+      lineNode.appendChild(textNode)
+      textNodes.push(textNode)
+    }
+
+    this.textNodesByLineId[id] = textNodes
+    return lineNode
+  }
+
+  updateLineNode (id) {
+    const oldLineState = this.oldTileState.lines[id]
+    const newLineState = this.newTileState.lines[id]
+    const lineNode = this.lineNodesByLineId[id]
+    const newDecorationClasses = newLineState.decorationClasses
+    const oldDecorationClasses = oldLineState.decorationClasses
+
+    if (oldDecorationClasses != null) {
+      for (const decorationClass of oldDecorationClasses) {
+        if (newDecorationClasses == null || !newDecorationClasses.includes(decorationClass)) {
+          lineNode.classList.remove(decorationClass)
+        }
+      }
+    }
+
+    if (newDecorationClasses != null) {
+      for (const decorationClass of newDecorationClasses) {
+        if (oldDecorationClasses == null || !oldDecorationClasses.includes(decorationClass)) {
+          lineNode.classList.add(decorationClass)
+        }
+      }
+    }
+
+    oldLineState.decorationClasses = newLineState.decorationClasses
+
+    if (!oldLineState.hasPrecedingBlockDecorations && newLineState.hasPrecedingBlockDecorations) {
+      this.insertBlockDecorationInsertionPointBeforeLine(id)
+    } else if (oldLineState.hasPrecedingBlockDecorations && !newLineState.hasPrecedingBlockDecorations) {
+      this.removeBlockDecorationInsertionPointBeforeLine(id)
+    }
+
+    if (!oldLineState.hasFollowingBlockDecorations && newLineState.hasFollowingBlockDecorations) {
+      this.insertBlockDecorationInsertionPointAfterLine(id)
+    } else if (oldLineState.hasFollowingBlockDecorations && !newLineState.hasFollowingBlockDecorations) {
+      this.removeBlockDecorationInsertionPointAfterLine(id)
+    }
+
+    if (newLineState.screenRow !== oldLineState.screenRow) {
+      lineNode.dataset.screenRow = newLineState.screenRow
+      this.lineIdsByScreenRow[newLineState.screenRow] = id
+      this.screenRowsByLineId[id] = newLineState.screenRow
+    }
+
+    this.updateBlockDecorationInsertionPointBeforeLine(id)
+    this.updateBlockDecorationInsertionPointAfterLine(id)
+    oldLineState.screenRow = newLineState.screenRow
+    oldLineState.hasPrecedingBlockDecorations = newLineState.hasPrecedingBlockDecorations
+    oldLineState.hasFollowingBlockDecorations = newLineState.hasFollowingBlockDecorations
+  }
+
+  lineNodeForScreenRow (screenRow) {
+    return this.lineNodesByLineId[this.lineIdsByScreenRow[screenRow]]
+  }
+
+  lineNodeForLineId (lineId) {
+    return this.lineNodesByLineId[lineId]
+  }
+
+  textNodesForLineId (lineId) {
+    return this.textNodesByLineId[lineId].slice()
+  }
+
+  lineIdForScreenRow (screenRow) {
+    return this.lineIdsByScreenRow[screenRow]
+  }
+
+  textNodesForScreenRow (screenRow) {
+    const textNodes = this.textNodesByLineId[this.lineIdsByScreenRow[screenRow]]
+    if (textNodes == null) {
+      return null
+    } else {
+      return textNodes.slice()
+    }
+  }
+}