This isn't any better.

src/atom/browser.coffee

@@ -4,7 +4,10 @@ Document = require 'document'
 
 module.exports =
 class Browser extends Document
-  @register (path) -> /^https?:/.test path
+  Document.handlers.push this
+
+  @canOpen: (path) ->
+    /^https?:/.test path
 
   path: null
   html: $ "<div id='browser'></div>"
@@ -12,7 +15,7 @@ class Browser extends Document
     $ "<iframe src='#{@path}' style='width:100%;height:100%'></iframe>"
 
   open: ->
-    return false if not super
+    return false if not super path
 
     @html.html @iframe().bind 'load', (e) =>
       window.setTitle e.target.contentWindow.document.title

src/atom/document.coffee

@@ -5,30 +5,23 @@ Pane = require 'pane'
 # constructor.
 module.exports =
 class Document extends Pane
+  @handlers: []
+
+  @canOpen: () ->
+    throw "#{@name}: Must implement a 'canOpen' class method."
+
+  @forURL: (url) ->
+    handler = _.find @handlers, (handler) -> handler.canOpen url
+    throw "I DON'T KNOW ABOUT #{window.url}" if not handler
+    new handler
+
   position: "main"
-
   path: null
 
-  @handlers: {}
-
-  @handler: (path) ->
-    for name, {test, handler} of Document.handlers
-      return handler if test path
-    null
-
-  @register: (test) ->
-    Document.handlers[@name] = {test, handler: this}
-
-  @forURL: ->
-    if handler = @handler window.url
-      new handler
-    else
-      throw "I DON'T KNOW ABOUT #{window.url}"
-
   constructor: ->
 
   open: (path) ->
-    (@constructor is Document.handler path) and not @path
+    not @path and @constructor.canOpen path
 
   close: ->
     window.close()

src/atom/editor.coffee

@@ -9,13 +9,15 @@ ace = require 'ace/ace'
 
 module.exports =
 class Editor extends Document
-  @register (path) ->
-    not path or fs.isFile path
+  Document.handlers.push this
 
   dirty: false
   path: null
   html: $ "<div id='ace-editor'></div>"
 
+  @canOpen: (path) ->
+    not path or fs.isFile path
+
   constructor: ->
     @show()
 
@@ -74,7 +76,7 @@ class Editor extends Document
     if @path then _.last @path.split '/' else 'untitled'
 
   open: (path) ->
-    return false if not super
+    return false if not super path
 
     @path = path
     @dirty = false

src/atom/project.coffee

@@ -5,12 +5,15 @@ Document = require 'document'
 
 module.exports =
 class Project extends Document
-  @register (path) -> fs.isDirectory path
+  Document.handlers.push this
+
+  @canOpen: (path) ->
+    fs.isDirectory path
 
   html:
     $ '<img src="http://fc01.deviantart.net/fs70/f/2010/184/4/9/Neru_Troll_Face_by_nerutrollfaceplz.jpg">'
 
   open: (path) ->
-    return false if not super
+    return false if not super path
     @path = path
     @show()

src/atom/window.coffee

@@ -24,7 +24,7 @@ windowAdditions =
     url = atom.native.openPanel() unless url
     (atom.document.open url) or atom.app.open url
 
-  close: (url) ->
+  close: (path) ->
     @shutdown()
     $atomController.close