From ab02d5f25fa18168ea5e6cde07441be64de9bfd9 Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@github.com>
Date: Wed, 2 Apr 2014 18:55:38 -0600
Subject: [PATCH] Update the vertical scroll bar when scrollTop changes in the
 model

---
 spec/editor-component-spec.coffee | 10 ++++++++++
 src/editor-component.coffee       |  4 ++++
 2 files changed, 14 insertions(+)

diff --git a/spec/editor-component-spec.coffee b/spec/editor-component-spec.coffee
index 51afa07bf..0d37088e9 100644
--- a/spec/editor-component-spec.coffee
+++ b/spec/editor-component-spec.coffee
@@ -82,6 +82,16 @@ describe "EditorComponent", ->
     expect(cursorNodes[0].offsetTop).toBe 6 * lineHeightInPixels
     expect(cursorNodes[0].offsetLeft).toBe 11 * charWidth
 
+  it "updates the scroll bar when the scrollTop is changed in the model", ->
+    node.style.height = 4.5 * lineHeightInPixels + 'px'
+    component.updateAllDimensions()
+
+    scrollbarNode = node.querySelector('.vertical-scrollbar')
+    expect(scrollbarNode.scrollTop).toBe 0
+
+    editor.setScrollTop(10)
+    expect(scrollbarNode.scrollTop).toBe 10
+
   it "accounts for character widths when positioning cursors", ->
     atom.config.set('editor.fontFamily', 'sans-serif')
     editor.setCursorScreenPosition([0, 16])
diff --git a/src/editor-component.coffee b/src/editor-component.coffee
index d15b68eaf..9d67c646a 100644
--- a/src/editor-component.coffee
+++ b/src/editor-component.coffee
@@ -78,6 +78,10 @@ EditorCompont = React.createClass
     @getDOMNode().removeEventListener 'mousewheel', @onMousewheel
 
   componentDidUpdate: ->
+    # React offers a scrollTop property on element descriptors but it doesn't
+    # seem to work when reloading the editor while already scrolled down.
+    # Perhaps it's trying to assign it before the element inside is tall enough?
+    @refs.verticalScrollbar.getDOMNode().scrollTop = @props.editor.getScrollTop()
     @measureNewLines()
 
   observeEditor: ->