Fix critical degradation #785

Author: t9md

lib/motions/general-motions.coffee

@@ -166,18 +166,22 @@ class MoveUpDown extends Motion
   direction: null
 
   getScreenRowCount: (cursor) ->
-    unless (@isLinewise() and @editor.isSoftWrapped())
-      return 1
-    else
-      cursorBufferRow = cursor.getBufferRow()
-      cursorLineBufferRange = [[cursorBufferRow, 0], [cursorBufferRow, Infinity]]
-      cursorLineScreenRange = @editor.screenRangeForBufferRange(cursorLineBufferRange)
-      cursorLineScreenRange.getRowCount()
+    return 1 unless (@isLinewise() and @editor.isSoftWrapped())
+
+    cursorBufferRow = cursor.getBufferRow()
+    cursorLineBufferRange = [[cursorBufferRow, 0], [cursorBufferRow, Infinity]]
+    cursorLineScreenRange = @editor.screenRangeForBufferRange(cursorLineBufferRange)
+    cursorLineScreenRange.getRowCount()
 
   moveCursor: (cursor, count=1) ->
     _.times count, =>
-      unless cursor.getScreenRow() is 0
-        cursor["move#{@direction}"](@getScreenRowCount(cursor))
+      screenRowCount = @getScreenRowCount(cursor)
+      
+      if (@direction is 'Up') and not (cursor.getScreenRow() is 0)
+        cursor.moveUp(screenRowCount)
+        @ensureCursorIsWithinLine(cursor)
+      else if (@direction is 'Down') and not (cursor.getScreenRow() is @editor.getLastScreenRow())
+        cursor.moveDown(screenRowCount)
         @ensureCursorIsWithinLine(cursor)
 
 class MoveUp extends MoveUpDown