Disable auto-scroll and make overflow-x hidden when soft-wrap is enabled

spec/atom/editor-spec.coffee

@@ -353,6 +353,60 @@ describe "Editor", ->
           editor.setCursorScreenPosition([2, 3])
           expect(editor.lines.scrollLeft()).toBe(0)
 
+        describe "when soft-wrap is on", ->
+          beforeEach ->
+            editor.setSoftWrap(true)
+
+          it "does not scroll the buffer", ->
+            editor.width(charWidth * 30)
+
+            # moving right
+            editor.setCursorScreenPosition([2, 24])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 25])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 28])
+            expect(editor.scrollLeft()).toBe 0
+
+            # moving left
+            editor.setCursorScreenPosition([2, 9])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 8])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 5])
+            expect(editor.scrollLeft()).toBe 0
+
+        describe "when soft-wrap is on", ->
+          beforeEach ->
+            editor.setSoftWrap(true)
+
+          it "does not scroll the buffer", ->
+            editor.width(charWidth * 30)
+
+            # moving right
+            editor.setCursorScreenPosition([2, 24])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 25])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 28])
+            expect(editor.scrollLeft()).toBe 0
+
+            # moving left
+            editor.setCursorScreenPosition([2, 9])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 8])
+            expect(editor.scrollLeft()).toBe 0
+
+            editor.setCursorScreenPosition([2, 5])
+            expect(editor.scrollLeft()).toBe 0
+
       describe "when left is pressed on the first column", ->
         describe "when there is a previous line", ->
           it "wraps to the end of the previous line", ->

src/atom/cursor.coffee

@@ -128,7 +128,9 @@ class Cursor extends View
       @editor.scrollTop(desiredTop)
 
   autoScrollHorizontally: (position) ->
-    charsInView = @editor.lines.width() / @width()
+    return if @editor.softWrap
+
+    charsInView = @editor.width() / @width()
     maxScrollMargin = Math.floor((charsInView - 1) / 2)
     scrollMargin = Math.min(@editor.hScrollMargin, maxScrollMargin)
     margin = scrollMargin * @width()

src/atom/editor.coffee

@@ -230,10 +230,13 @@ class Editor extends View
   setSoftWrap: (@softWrap) ->
     @setMaxLineLength()
     if @softWrap
+      @addClass 'soft-wrap'
       @_setMaxLineLength = => @setMaxLineLength()
       $(window).on 'resize', @_setMaxLineLength
     else
       $(window).off 'resize', @_setMaxLineLength
+      @removeClass 'soft-wrap'
+
 
   clipScreenPosition: (screenPosition, options={}) ->
     @renderer.clipScreenPosition(screenPosition, options)

static/editor.css

@@ -12,6 +12,10 @@
   -webkit-user-select: none;
 }
 
+.editor.soft-wrap {
+  overflow-x: hidden;
+}
+
 .editor .content {
   display: -webkit-flexbox;
 }
@@ -24,7 +28,7 @@
 }
 
 .editor .gutter.drop-shadow {
-  -webkit-box-shadow: -2px 0px 10px 2px #222;  
+  -webkit-box-shadow: -2px 0px 10px 2px #222;
 }
 
 .editor .lines {