From 314e082f1db2867ced4ac114327ebd0a850177c8 Mon Sep 17 00:00:00 2001
From: Nathan Sobo <nathan@github.com>
Date: Thu, 27 Aug 2015 17:40:01 -0600
Subject: [PATCH] Clean up max scroll margin code
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Previously we were attempting the same computation twice, once
incorrectly when returning the scroll margins as integers and then doing
the same thing in terms of pixels. This just cleans up the original
calculation. It’s *slightly* different because it takes the floor to
continue returning integers, but the behavior is extremely close.
---
 spec/text-editor-presenter-spec.coffee |  6 +++---
 src/display-buffer.coffee              | 17 +++++++----------
 2 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/spec/text-editor-presenter-spec.coffee b/spec/text-editor-presenter-spec.coffee
index f859a37a0..44b1035fc 100644
--- a/spec/text-editor-presenter-spec.coffee
+++ b/spec/text-editor-presenter-spec.coffee
@@ -1214,7 +1214,7 @@ describe "TextEditorPresenter", ->
 
           # showing
           expectStateUpdate presenter, -> editor.getSelections()[1].clear()
-          expect(stateForCursor(presenter, 1)).toEqual {top: 5, left: 5 * 10, width: 10, height: 10}
+          expect(stateForCursor(presenter, 1)).toEqual {top: 0, left: 5 * 10, width: 10, height: 10}
 
           # hiding
           expectStateUpdate presenter, -> editor.getSelections()[1].setBufferRange([[3, 4], [3, 5]])
@@ -1226,11 +1226,11 @@ describe "TextEditorPresenter", ->
 
           # adding
           expectStateUpdate presenter, -> editor.addCursorAtBufferPosition([4, 4])
-          expect(stateForCursor(presenter, 2)).toEqual {top: 5, left: 4 * 10, width: 10, height: 10}
+          expect(stateForCursor(presenter, 2)).toEqual {top: 0, left: 4 * 10, width: 10, height: 10}
 
           # moving added cursor
           expectStateUpdate presenter, -> editor.getCursors()[2].setBufferPosition([4, 6])
-          expect(stateForCursor(presenter, 2)).toEqual {top: 5, left: 6 * 10, width: 10, height: 10}
+          expect(stateForCursor(presenter, 2)).toEqual {top: 0, left: 6 * 10, width: 10, height: 10}
 
           # destroying
           destroyedCursor = editor.getCursors()[2]
diff --git a/src/display-buffer.coffee b/src/display-buffer.coffee
index c1e80c576..5d5628689 100644
--- a/src/display-buffer.coffee
+++ b/src/display-buffer.coffee
@@ -177,21 +177,18 @@ class DisplayBuffer extends Model
   # visible - A {Boolean} indicating of the tokenized buffer is shown
   setVisible: (visible) -> @tokenizedBuffer.setVisible(visible)
 
-  getVerticalScrollMargin: -> Math.min(@verticalScrollMargin, (@getHeight() - @getLineHeightInPixels()) / 2)
+  getVerticalScrollMargin: ->
+    maxScrollMargin = Math.floor(((@getHeight() / @getLineHeightInPixels()) - 1) / 2)
+    Math.min(@verticalScrollMargin, maxScrollMargin)
+
   setVerticalScrollMargin: (@verticalScrollMargin) -> @verticalScrollMargin
 
-  getVerticalScrollMarginInPixels: ->
-    scrollMarginInPixels = @getVerticalScrollMargin() * @getLineHeightInPixels()
-    maxScrollMarginInPixels = (@getHeight() - @getLineHeightInPixels()) / 2
-    Math.min(scrollMarginInPixels, maxScrollMarginInPixels)
+  getVerticalScrollMarginInPixels: -> @getVerticalScrollMargin() * @getLineHeightInPixels()
 
-  getHorizontalScrollMargin: -> Math.min(@horizontalScrollMargin, (@getWidth() - @getDefaultCharWidth()) / 2)
+  getHorizontalScrollMargin: -> Math.min(@horizontalScrollMargin, Math.floor(((@getWidth() / @getDefaultCharWidth()) - 1) / 2))
   setHorizontalScrollMargin: (@horizontalScrollMargin) -> @horizontalScrollMargin
 
-  getHorizontalScrollMarginInPixels: ->
-    scrollMarginInPixels = @getHorizontalScrollMargin() * @getDefaultCharWidth()
-    maxScrollMarginInPixels = (@getWidth() - @getDefaultCharWidth()) / 2
-    Math.min(scrollMarginInPixels, maxScrollMarginInPixels)
+  getHorizontalScrollMarginInPixels: -> scrollMarginInPixels = @getHorizontalScrollMargin() * @getDefaultCharWidth()
 
   getHorizontalScrollbarHeight: -> @horizontalScrollbarHeight
   setHorizontalScrollbarHeight: (@horizontalScrollbarHeight) -> @horizontalScrollbarHeight