title: My kivy Scrollview behaves differently in touch event and mouse scroll event
body: <p>I made a windows application using Kivy(v.1.10.1) and Python(v.3.6.6) under VS code. I want to use ScrollView below BoxLayout. However, it does not work well. In other words, it scrolls two times(attached image) when using mouse scroll but scrolls only one time when using touch screen. My goal is single scrolling using mouse wheel. What should I do? Please help me!</p>
  
  <p>my kivy code</p>
  
  <pre><code>    #:kivy 1.10.1
  &lt;Test&gt;:    
      BoxLayout:
          orientation:'vertical'
          size:root.size
          AnchorLayout:
              id:upper_bar
              anchor_x:'left'
              anchor_y:'top'
              ActionBar:
                  size_hint_y:None
                  size_hint_x:1
                  height:30
                  ActionView:
                      ActionPrevious:
                          with_previous: False
                          title:''
                          app_icon:''
                      ActionGroup:
                          text:'File'
                          mode:'spinner'
                          ActionButton:
                              text:'Open'
                          ActionButton:
                              text:'Add New Obj'
  
          AnchorLayout:
              id:main_field
              anchor_x:'center'
              anchor_y:'center'
              size_hint_y:None
              size_hint_x:1
              height:root.height - upper_bar.height - lower_bar.height
              ScrollView:
                  id:main_field
                  do_scroll_y:True
                  pos_hint: {'top': 1}
                  ScatterLayout:
                      size_hint:[None,None]
                      size:1000,1000
                      canvas:
                          Rectangle: 
                              pos:10,10
                              size:100,200
                          Rectangle: 
                              pos:300,150
                              size:100,200
  
          AnchorLayout:
              id:lower_bar
              size_hint_y:None
              size_hint_x:1
              height:30
              anchor_x:'left'
              anchor_y:'bottom'
              Button:
                  text:'lower bar'
  </code></pre>
  
  <p>my python code</p>
  
  <pre><code>    #:Python 3.6.6
  from kivy.app import App
  from kivy.uix.widget import Widget
  from kivy.lang import Builder
  Builder.load_file('Test.kv')
  class UpperBar(Widget):
      pass
  
  class MainField(Widget):
      pass
  
  class LowerBar(Widget):
      pass
  
  class Test(Widget):
      pass
  
  class TestApp(App):
      def build(self):
          return Test()
      pass
  
  if __name__ == '__main__':
      TestApp().run()
  </code></pre>
  
  <p>my result of upper code 
  <a href="https://i.stack.imgur.com/OenJV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/OenJV.png" alt="my result of upper code"></a></p>
  
  <p><a href="https://i.stack.imgur.com/cvOux.png" rel="nofollow noreferrer">result of ikolim's suggestion</a></p>