Render the longest screen row without painting it

spec/text-editor-component-spec.coffee

@@ -219,6 +219,54 @@ describe "TextEditorComponent", ->
       expectTileContainsRow(tilesNodes[2], 7, top: 1 * lineHeightInPixels)
       expectTileContainsRow(tilesNodes[2], 8, top: 2 * lineHeightInPixels)
 
+    fffit "renders the longest screen row even when it's not visible", ->
+      wrapperNode.style.height = 2 * lineHeightInPixels + 'px'
+      component.measureDimensions()
+      nextAnimationFrame()
+
+      tileNodes = component.tileNodesForLines()
+      expect(tileNodes.length).toBe(3)
+
+      expect(getComputedStyle(tileNodes[0]).visibility).toBe("visible")
+      expect(tileNodes[0].querySelectorAll(".line").length).toBe(3)
+
+      expect(getComputedStyle(tileNodes[1]).visibility).toBe("visible")
+      expect(tileNodes[1].querySelectorAll(".line").length).toBe(3)
+
+      # tile with the longest screen row
+      expect(getComputedStyle(tileNodes[2]).visibility).toBe("hidden")
+      expect(tileNodes[2].querySelectorAll(".line").length).toBe(1)
+
+      verticalScrollbarNode.scrollTop = 4 * lineHeightInPixels
+      verticalScrollbarNode.dispatchEvent(new UIEvent('scroll'))
+      nextAnimationFrame()
+
+      tileNodes = component.tileNodesForLines()
+      expect(tileNodes.length).toBe(2) # don't render an extra tile if the longest screen row is already visible
+
+      expect(getComputedStyle(tileNodes[0]).visibility).toBe("visible")
+      expect(tileNodes[0].querySelectorAll(".line").length).toBe(3)
+
+      expect(getComputedStyle(tileNodes[1]).visibility).toBe("visible")
+      expect(tileNodes[1].querySelectorAll(".line").length).toBe(3)
+
+      verticalScrollbarNode.scrollTop = 0 * lineHeightInPixels
+      verticalScrollbarNode.dispatchEvent(new UIEvent('scroll'))
+      nextAnimationFrame()
+
+      tileNodes = component.tileNodesForLines()
+      expect(tileNodes.length).toBe(3)
+
+      expect(getComputedStyle(tileNodes[0]).visibility).toBe("visible")
+      expect(tileNodes[0].querySelectorAll(".line").length).toBe(3)
+
+      expect(getComputedStyle(tileNodes[1]).visibility).toBe("visible")
+      expect(tileNodes[1].querySelectorAll(".line").length).toBe(3)
+
+      # tile with the longest screen row
+      expect(getComputedStyle(tileNodes[2]).visibility).toBe("hidden")
+      expect(tileNodes[2].querySelectorAll(".line").length).toBe(1)
+
     it "updates the lines when lines are inserted or removed above the rendered row range", ->
       wrapperNode.style.height = 4.5 * lineHeightInPixels + 'px'
       component.measureDimensions()
@@ -2986,7 +3034,7 @@ describe "TextEditorComponent", ->
 
       atom.views.performDocumentPoll()
       nextAnimationFrame()
-      expect(componentNode.querySelectorAll('.line')).toHaveLength(6)
+      expect(componentNode.querySelectorAll('.line')).toHaveLength(7) # visible rows + the longest screen row
 
       gutterWidth = componentNode.querySelector('.gutter').offsetWidth
       componentNode.style.width = gutterWidth + 14 * charWidth + editor.getVerticalScrollbarWidth() + 'px'

src/lines-tile-component.coffee

@@ -47,6 +47,10 @@ class LinesTileComponent
       @domNode.style.zIndex = @newTileState.zIndex
       @oldTileState.zIndex = @newTileState.zIndex
 
+    if @newTileState.visibility isnt @oldTileState.visibility
+      @domNode.style.visibility = @newTileState.visibility
+      @oldTileState.visibility = @newTileState.visibility
+
     if @newTileState.display isnt @oldTileState.display
       @domNode.style.display = @newTileState.display
       @oldTileState.display = @newTileState.display