Look before and after empty lines for max indent level

Previously the indentation guide level for empty lines was
derived by only looking after the empty line which caused gaps
in certain cases.

Now the indentation for an empty line is the higher value of the
previous non-empty line indentation and the following non-empty
line indentation.

Closes #588

spec/app/editor-spec.coffee

@@ -1565,6 +1565,20 @@ describe "Editor", ->
           expect(editor.renderedLines.find('.line:eq(10) .indent-guide').length).toBe 2
           expect(editor.renderedLines.find('.line:eq(10) .indent-guide').text()).toBe '    '
 
+      describe "when the indentation level on a line after an empty line is changed", ->
+        it "updates the indent guide on the empty line", ->
+          editor.attachToDom()
+          config.set("editor.showIndentGuide", true)
+
+          expect(editor.renderedLines.find('.line:eq(10) .indent-guide').length).toBe 1
+          expect(editor.renderedLines.find('.line:eq(10) .indent-guide').text()).toBe '  '
+
+          editor.setCursorBufferPosition([11])
+          editor.indentSelectedRows()
+
+          expect(editor.renderedLines.find('.line:eq(10) .indent-guide').length).toBe 2
+          expect(editor.renderedLines.find('.line:eq(10) .indent-guide').text()).toBe '    '
+
       describe "when a line contains only whitespace", ->
         it "displays an indent guide on the line", ->
           editor.attachToDom()
@@ -1577,6 +1591,16 @@ describe "Editor", ->
           expect(editor.renderedLines.find('.line:eq(10) .indent-guide').length).toBe 2
           expect(editor.renderedLines.find('.line:eq(10) .indent-guide').text()).toBe '    '
 
+        it "uses the highest indent guide level from the next or previous non-empty line", ->
+          editor.attachToDom()
+          config.set("editor.showIndentGuide", true)
+
+          editor.setCursorBufferPosition([1, Infinity])
+          editor.insertNewline()
+          expect(editor.getCursorBufferPosition()).toEqual [2, 0]
+          expect(editor.renderedLines.find('.line:eq(2) .indent-guide').length).toBe 2
+          expect(editor.renderedLines.find('.line:eq(2) .indent-guide').text()).toBe '    '
+
       describe "when the line has leading and trailing whitespace", ->
         it "does not display the indent guide in the trailing whitespace", ->
           editor.attachToDom()
@@ -1587,7 +1611,7 @@ describe "Editor", ->
           expect(editor.renderedLines.find('.line:eq(1) .indent-guide')).toHaveClass('leading-whitespace')
 
       describe "when the line is empty and end of show invisibles are enabled", ->
-        it "renders the indent guides interleaved the end of line invisibles", ->
+        it "renders the indent guides interleaved with the end of line invisibles", ->
           editor.attachToDom()
           config.set("editor.showIndentGuide", true)
           config.set("editor.showInvisibles", true)

src/app/editor.coffee

@@ -1185,21 +1185,34 @@ class Editor extends View
     @updateLayerDimensions()
     @updatePaddingOfRenderedLines()
 
+  computeSurroundingEmptyLineChanges: (change) ->
+    emptyLineChanges = []
+
+    if change.bufferDelta?
+      afterStart = change.end + change.bufferDelta + 1
+      if @lineForBufferRow(afterStart) is ''
+        afterEnd = afterStart
+        afterEnd++ while @lineForBufferRow(afterEnd + 1) is ''
+        emptyLineChanges.push({start: afterStart, end: afterEnd, screenDelta: 0})
+
+      beforeEnd = change.start - 1
+      if @lineForBufferRow(beforeEnd) is ''
+        beforeStart = beforeEnd
+        beforeStart-- while @lineForBufferRow(beforeStart - 1) is ''
+        emptyLineChanges.push({start: beforeStart, end: beforeEnd, screenDelta: 0})
+
+    emptyLineChanges
+
   computeIntactRanges: ->
     return [] if !@firstRenderedScreenRow? and !@lastRenderedScreenRow?
 
     intactRanges = [{start: @firstRenderedScreenRow, end: @lastRenderedScreenRow, domStart: 0}]
 
     if not @mini and @showIndentGuide
-      trailingEmptyLineChanges = []
+      emptyLineChanges = []
       for change in @pendingChanges
-        continue unless change.bufferDelta?
-        start = change.end + change.bufferDelta + 1
-        continue unless @lineForBufferRow(start) is ''
-        end = start
-        end++ while @lineForBufferRow(end + 1) is ''
-        trailingEmptyLineChanges.push({start, end, screenDelta: 0})
-        @pendingChanges.push(trailingEmptyLineChanges...)
+        emptyLineChanges.push(@computeSurroundingEmptyLineChanges(change)...)
+      @pendingChanges.push(emptyLineChanges...)
 
     for change in @pendingChanges
       newIntactRanges = []
@@ -1355,15 +1368,31 @@ class Editor extends View
     Editor.buildLineHtml({tokens, text, lineEnding, fold, isSoftWrapped, invisibles, eolInvisibles, htmlEolInvisibles, attributes, @showIndentGuide, indentation, @activeEditSession, @mini})
 
   @buildIndentation: (screenRow, activeEditSession) ->
-    indentation = 0
-    while --screenRow >= 0
-      bufferRow = activeEditSession.bufferPositionForScreenPosition([screenRow]).row
-      bufferLine = activeEditSession.lineForBufferRow(bufferRow)
-      unless bufferLine is ''
-        indentation = Math.ceil(activeEditSession.indentLevelForLine(bufferLine))
-        break
+    bufferRow = activeEditSession.bufferPositionForScreenPosition([screenRow]).row
+    bufferLine = activeEditSession.lineForBufferRow(bufferRow)
+    if bufferLine is ''
+      indentation = 0
+      nextRow = screenRow + 1
+      while nextRow < activeEditSession.getBuffer().getLineCount()
+        bufferRow = activeEditSession.bufferPositionForScreenPosition([nextRow]).row
+        bufferLine = activeEditSession.lineForBufferRow(bufferRow)
+        if bufferLine isnt ''
+          indentation = Math.ceil(activeEditSession.indentLevelForLine(bufferLine))
+          break
+        nextRow++
 
-    indentation
+      previousRow = screenRow - 1
+      while previousRow >= 0
+        bufferRow = activeEditSession.bufferPositionForScreenPosition([previousRow]).row
+        bufferLine = activeEditSession.lineForBufferRow(bufferRow)
+        if bufferLine isnt ''
+          indentation = Math.max(indentation, Math.ceil(activeEditSession.indentLevelForLine(bufferLine)))
+          break
+        previousRow--
+
+      indentation
+    else
+      Math.ceil(activeEditSession.indentLevelForLine(bufferLine))
 
   buildHtmlEndOfLineInvisibles: (screenLine) ->
     invisibles = []
@@ -1571,9 +1600,8 @@ class Editor extends View
 
         return indentGuideHtml.join('')
 
-    invisibles = htmlEolInvisibles
-    if invisibles.length > 0
-      invisibles
+    if htmlEolInvisibles.length > 0
+      htmlEolInvisibles
     else
       '&nbsp;'