From 7e03880bd09b86eb139d66dd83323b3ac5fa0fd7 Mon Sep 17 00:00:00 2001
From: Corey Johnson & Nathan Sobo <cj+nathan@github.com>
Date: Mon, 11 Mar 2013 17:31:17 -0600
Subject: [PATCH] Add $.fn.scrollUp and .scrollDown

These scroll the element by a small amount up or down.
---
 spec/stdlib/jquery-extensions-spec.coffee | 30 +++++++++++++++++++++++
 src/stdlib/jquery-extensions.coffee       |  6 +++++
 2 files changed, 36 insertions(+)

diff --git a/spec/stdlib/jquery-extensions-spec.coffee b/spec/stdlib/jquery-extensions-spec.coffee
index 6b781370b..4bdd8fd11 100644
--- a/spec/stdlib/jquery-extensions-spec.coffee
+++ b/spec/stdlib/jquery-extensions-spec.coffee
@@ -1,4 +1,5 @@
 $ = require 'jquery'
+_ = require 'underscore'
 {View, $$} = require 'space-pen'
 
 describe 'jQuery extensions', ->
@@ -76,6 +77,35 @@ describe 'jQuery extensions', ->
         'a1': "A1: Waste perfectly-good steak"
         'a2': null
 
+  describe "$.fn.scrollUp/Down/ToTop/ToBottom", ->
+    it "scrolls the element in the specified way if possible", ->
+      view = $$ -> @div => _.times 20, => @div('A')
+      view.css(height: 100, width: 100, overflow: 'scroll')
+      view.attachToDom()
+
+      view.scrollUp()
+      expect(view.scrollTop()).toBe 0
+
+      view.scrollDown()
+      expect(view.scrollTop()).toBeGreaterThan 0
+      previousScrollTop = view.scrollTop()
+      view.scrollDown()
+      expect(view.scrollTop()).toBeGreaterThan previousScrollTop
+
+      view.scrollToBottom()
+      expect(view.scrollTop()).toBe view.prop('scrollHeight') - 100
+      previousScrollTop = view.scrollTop()
+      view.scrollDown()
+      expect(view.scrollTop()).toBe previousScrollTop
+      view.scrollUp()
+      expect(view.scrollTop()).toBeLessThan previousScrollTop
+      previousScrollTop = view.scrollTop()
+      view.scrollUp()
+      expect(view.scrollTop()).toBeLessThan previousScrollTop
+
+      view.scrollToTop()
+      expect(view.scrollTop()).toBe 0
+
   describe "Event.prototype", ->
     class GrandchildView extends View
       @content: -> @div class: 'grandchild'
diff --git a/src/stdlib/jquery-extensions.coffee b/src/stdlib/jquery-extensions.coffee
index 089363577..fe403c2a9 100644
--- a/src/stdlib/jquery-extensions.coffee
+++ b/src/stdlib/jquery-extensions.coffee
@@ -7,6 +7,12 @@ $.fn.scrollBottom = (newValue) ->
   else
     @scrollTop() + @height()
 
+$.fn.scrollDown = ->
+  @scrollTop(@scrollTop() + $(window).height() / 20)
+
+$.fn.scrollUp = ->
+  @scrollTop(@scrollTop() - $(window).height() / 20)
+
 $.fn.scrollToTop = ->
   @scrollTop(0)