Huge Aether performance fix; spells now scroll while debugging.

app/views/play/level/tome/spell.coffee

@@ -56,7 +56,7 @@ module.exports = class Spell
 
   createAether: (thang) ->
     aetherOptions =
-      thisValue: thang.createUserContext()
+      #thisValue: thang.createUserContext()   # slooow, and not useful I guess?
       problems:
         jshint_W040: {level: "ignore"}
         aether_MissingThis: {level: (if thang.requiresThis then 'error' else 'warning')}

app/views/play/level/tome/spell_toolbar_view.coffee

@@ -63,6 +63,7 @@ module.exports = class SpellToolbarView extends View
     @setStatementRatio e.offsetX / @$el.find('.progress').width()
     @updateTime()
     @maintainIndexHover = true
+    @updateScroll()
 
   onProgressMouseOut: (e) ->
     @maintainIndexHover = false
@@ -73,6 +74,7 @@ module.exports = class SpellToolbarView extends View
     lastTime = @statementTime
     @setStatementIndex @statementIndex + delta
     @updateTime() if @statementIndex isnt lastTime
+    @updateScroll()
 
   updateTime: ->
     @maintainIndexScrub = true
@@ -80,6 +82,12 @@ module.exports = class SpellToolbarView extends View
     @maintainIndexScrubTimeout = _.delay (=> @maintainIndexScrub = false), 500
     Backbone.Mediator.publish 'level-set-time', time: @statementTime, scrubDuration: 500
 
+  updateScroll: ->
+    return unless statementStart = @callState?.statements?[@statementIndex]?.range[0]
+    text = @ace.getValue()
+    currentLine = text.substr(0, statementStart).split('\n').length - 1
+    @ace.scrollToLine currentLine, true, true
+
   setCallState: (callState, statementIndex, @callIndex, @metrics) ->
     return if callState is @callState and statementIndex is @statementIndex
     return unless @callState = callState

app/views/play/level/tome/spell_view.coffee

@@ -69,6 +69,7 @@ module.exports = class SpellView extends View
     @ace.setShowPrintMargin false
     @ace.setShowInvisibles false
     @ace.setBehavioursEnabled false
+    @ace.setAnimatedScroll true
     @toggleControls null, @writable
     @aceSession.selection.on 'changeCursor', @onCursorActivity
     $(@ace.container).find('.ace_gutter').on 'click', '.ace_error, .ace_warning, .ace_info', @onAnnotationClick
@@ -461,6 +462,7 @@ module.exports = class SpellView extends View
       markerRange.id = @aceSession.addMarker markerRange, clazz, "text"
       @markerRanges.push markerRange
       @aceSession.addGutterDecoration start.row, clazz if clazz is 'executing'
+    null
 
   onAnnotationClick: ->
     alertBox = $("<div class='alert alert-info fade in'>#{msg}</div>")