[Gutter] Create Gutter and GutterContainer w/ API to hide/show

src/gutter-container.coffee

@@ -0,0 +1,78 @@
+{Emitter} = require 'event-kit'
+{Subscriber} = require 'emissary'
+Gutter = require './gutter'
+
+# This class encapsulates the logic for adding and modifying a set of gutters.
+
+module.exports =
+class GutterContainer
+  Subscriber.includeInto(this)
+  constructor: ->
+    @gutters = []
+    @emitter = new Emitter
+
+  destroy: ->
+    @gutters = null
+    @emitter.dispose()
+    @unsubscribe()
+
+  # Creates and returns a {Gutter}.
+  # * `options` An {Object} with the following fields:
+  #   * `name` (required) A unique {String} to identify this gutter.
+  #   * `priority` (optional) A {Number} that determines stacking order between
+  #       gutters. Lower priority items are forced closer to the edges of the
+  #       window. (default: -100)
+  #   * `visible` (optional) {Boolean} specifying whether the gutter is visible
+  #       initially after being created. (default: true)
+  addGutter: (options) ->
+    options = options ? {}
+    gutterName = options.name
+    if gutterName == null
+      throw new Error 'A name is required to create a gutter.'
+    if @gutterWithName gutterName
+      throw new Error 'Tried to create a gutter with a name that is already in use.'
+    newGutter = new Gutter this, options
+
+    inserted = false
+    # Insert the gutter into the gutters array, sorted in ascending order by 'priority'.
+    # This could be optimized, but there are unlikely to be many gutters.
+    for i in [0...@gutters.length]
+      if @gutters[i].priority >= newGutter.priority
+        @gutters.splice(i, 0, newGutter)
+        inserted = true
+        break
+    if !inserted
+      @gutters.push newGutter
+    return newGutter
+
+  getGutters: ->
+    @gutters.slice()
+
+  gutterWithName: (name) ->
+    for gutter in @gutters
+      if gutter.name == name then return gutter
+    null
+
+  ###
+  Section: Event Subscription
+  ###
+
+  # @param callback: function( nameOfRemovedGutter )
+  onDidRemoveGutter: (callback) ->
+    @emitter.on 'did-remove-gutter', callback
+
+  ###
+  Section: Private Methods
+  ###
+
+  # Processes the destruction of the gutter. Throws an error if this gutter is
+  # not within this gutterContainer.
+  removeGutter: (gutter) ->
+    index = @gutters.indexOf gutter
+    if index > -1
+      @gutters.splice(index, 1)
+      @unsubscribe gutter
+      @emitter.emit 'did-remove-gutter', gutter.name
+    else
+      throw new Error 'The given gutter cannot be removed because it is not ' +
+          'within this GutterContainer.'

src/gutter.coffee

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+{Emitter} = require 'event-kit'
+
+# Public: This class represents a gutter within a TextEditor.
+
+DefaultPriority = -100
+
+module.exports =
+class Gutter
+  # * `gutterContainer` The {GutterContainer} object to which this gutter belongs.
+  # * `options` An {Object} with the following fields:
+  #   * `name` (required) A unique {String} to identify this gutter.
+  #   * `priority` (optional) A {Number} that determines stacking order between
+  #       gutters. Lower priority items are forced closer to the edges of the
+  #       window. (default: -100)
+  #   * `visible` (optional) {Boolean} specifying whether the gutter is visible
+  #       initially after being created. (default: true)
+  constructor: (gutterContainer, options) ->
+    @gutterContainer = gutterContainer
+    @name = options?.name
+    @priority = options?.priority ? DefaultPriority
+    @visible = options?.visible ? true
+
+    @emitter = new Emitter
+
+  destroy: ->
+    @gutterContainer.removeGutter(this)
+    @emitter.emit 'did-destroy'
+    @emitter.dispose()
+
+  hide: ->
+    if @visible
+      @visible = false
+      @emitter.emit 'did-change-visible', this
+
+  show: ->
+    if not @visible
+      @visible = true
+      @emitter.emit 'did-change-visible', this
+
+  isVisible: ->
+    @visible
+
+  # Calls your `callback` when the {Gutter}'s' visibility changes.
+  #
+  # * `callback` {Function}
+  #  * `gutter` The {Gutter} whose visibility changed.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidChangeVisible: (callback) ->
+    @emitter.on 'did-change-visible', callback
+
+  # Calls your `callback` when the {Gutter} is destroyed
+  #
+  # * `callback` {Function}
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to unsubscribe.
+  onDidDestroy: (callback) ->
+    @emitter.on 'did-destroy', callback