Use model scroll api in scroll commands

lib/scroll.coffee

@@ -11,33 +11,38 @@ class Scroll
 
 class ScrollDown extends Scroll
   execute: (count=1) ->
-    @keepCursorOnScreen(count)
-    @scrollUp(count)
+    oldFirstRow = @editor.getFirstVisibleScreenRow()
+    @editor.setFirstVisibleScreenRow(oldFirstRow + count)
+    newFirstRow = @editor.getFirstVisibleScreenRow()
 
-  keepCursorOnScreen: (count) ->
-    {row, column} = @editor.getCursorScreenPosition()
-    firstScreenRow = @rows.first + @scrolloff + 1
-    if row - count <= firstScreenRow
-      @editor.setCursorScreenPosition([firstScreenRow + count, column])
+    for cursor in @editor.getCursors()
+      position = cursor.getScreenPosition()
+      if position.row <= newFirstRow + @scrolloff
+        cursor.setScreenPosition([position.row + newFirstRow - oldFirstRow, position.column], autoscroll: false)
 
-  scrollUp: (count) ->
-    lastScreenRow = @rows.last - @scrolloff
-    @editor.scrollToScreenPosition([lastScreenRow + count, 0])
+    # TODO: remove
+    # This is a workaround for a bug fixed in atom/atom#10062
+    @editorElement.component.updateSync()
+
+    return
 
 class ScrollUp extends Scroll
   execute: (count=1) ->
-    @keepCursorOnScreen(count)
-    @scrollDown(count)
-
-  keepCursorOnScreen: (count) ->
-    {row, column} = @editor.getCursorScreenPosition()
-    lastScreenRow = @rows.last - @scrolloff - 1
-    if row + count >= lastScreenRow
-      @editor.setCursorScreenPosition([lastScreenRow - count, column])
-
-  scrollDown: (count) ->
-    firstScreenRow = @rows.first + @scrolloff
-    @editor.scrollToScreenPosition([firstScreenRow - count, 0])
+    oldFirstRow = @editor.getFirstVisibleScreenRow()
+    oldLastRow = @editor.getLastVisibleScreenRow()
+    @editor.setFirstVisibleScreenRow(oldFirstRow - count)
+    newLastRow = @editor.getLastVisibleScreenRow()
+
+    for cursor in @editor.getCursors()
+      position = cursor.getScreenPosition()
+      if position.row >= newLastRow - @scrolloff
+        cursor.setScreenPosition([position.row - (oldLastRow - newLastRow), position.column], autoscroll: false)
+
+    # TODO: remove
+    # This is a workaround for a bug fixed in atom/atom#10062
+    @editorElement.component.updateSync()
+
+    return
 
 class ScrollCursor extends Scroll
   constructor: (@editorElement, @opts={}) ->

spec/scroll-spec.coffee

@@ -21,30 +21,41 @@ describe "Scrolling", ->
 
   describe "scrolling keybindings", ->
     beforeEach ->
-      editor.setText("1\n2\n3\n4\n5\n6\n7\n8\n9\n10")
-      spyOn(editorElement, 'getFirstVisibleScreenRow').andReturn(2)
-      spyOn(editorElement, 'getLastVisibleScreenRow').andReturn(8)
-      spyOn(editor, 'scrollToScreenPosition')
-
-    describe "the ctrl-e keybinding", ->
-      beforeEach ->
-        spyOn(editor, 'getCursorScreenPosition').andReturn({row: 4, column: 0})
-        spyOn(editor, 'setCursorScreenPosition')
-
-      it "moves the screen down by one and keeps cursor onscreen", ->
+      editor.setText """
+        100
+        200
+        300
+        400
+        500
+        600
+        700
+        800
+        900
+        1000
+      """
+
+      editor.setCursorBufferPosition([1, 2])
+      editorElement.setHeight(editorElement.getHeight() * 4 / 10)
+      expect(editor.getVisibleRowRange()).toEqual [0, 4]
+
+    describe "the ctrl-e and ctrl-y keybindings", ->
+      it "moves the screen up and down by one and keeps cursor onscreen", ->
         keydown('e', ctrl: true)
-        expect(editor.scrollToScreenPosition).toHaveBeenCalledWith([7, 0])
-        expect(editor.setCursorScreenPosition).toHaveBeenCalledWith([6, 0])
+        expect(editor.getFirstVisibleScreenRow()).toBe 1
+        expect(editor.getLastVisibleScreenRow()).toBe 5
+        expect(editor.getCursorScreenPosition()).toEqual [2, 2]
 
-    describe "the ctrl-y keybinding", ->
-      beforeEach ->
-        spyOn(editor, 'getCursorScreenPosition').andReturn({row: 6, column: 0})
-        spyOn(editor, 'setCursorScreenPosition')
+        keydown('2')
+        keydown('e', ctrl: true)
+        expect(editor.getFirstVisibleScreenRow()).toBe 3
+        expect(editor.getLastVisibleScreenRow()).toBe 7
+        expect(editor.getCursorScreenPosition()).toEqual [4, 2]
 
-      it "moves the screen up by one and keeps the cursor onscreen", ->
+        keydown('2')
         keydown('y', ctrl: true)
-        expect(editor.scrollToScreenPosition).toHaveBeenCalledWith([3, 0])
-        expect(editor.setCursorScreenPosition).toHaveBeenCalledWith([4, 0])
+        expect(editor.getFirstVisibleScreenRow()).toBe 1
+        expect(editor.getLastVisibleScreenRow()).toBe 5
+        expect(editor.getCursorScreenPosition()).toEqual [2, 2]
 
   describe "scroll cursor keybindings", ->
     beforeEach ->