title: How to clear wxpython frame content when dragging a panel?
body: <p>I have 3 panels and I want to make drags on them.
  The problem is that when I do a drag on one this happens:
  <a href="http://img41.yfrog.com/img41/9043/soundlog.png" rel="nofollow noreferrer">http://img41.yfrog.com/img41/9043/soundlog.png http://img41.yfrog.com/img41/9043/soundlog.png</a></p>
  
  <p>How can I refresh the frame to happear its color when the panel is no longer there?</p>
  
  <p>This is the code that I have to make the drag:</p>
  
  <pre><code>def onMouseMove(self, event):
      (self.pointWidth, self.pointHeight) = event.GetPosition()
      (self.width, self.height) = self.GetSizeTuple()
      if (self.pointWidth&gt;100 and self.pointWidth&lt;(self.width-100) and self.pointHeight &lt; 15) or self.parent.dragging:
          self.SetCursor(wx.StockCursor(wx.CURSOR_SIZING))
  
          """implement dragging"""
          if not event.Dragging():
              self.w = 0
              self.h = 0
              return
          self.CaptureMouse()
          if self.w == 0 and self.h == 0:
              (self.w, self.h) = event.GetPosition()
          else:
              (posw, posh) = event.GetPosition()
              displacement = self.h - posh
              self.SetPosition( self.GetPosition() - (0, displacement))
      else:
          self.SetCursor(wx.StockCursor(wx.CURSOR_ARROW))
  
  def onDraggingDown(self, event):
      if self.pointWidth&gt;100 and self.pointWidth&lt;(self.width-100) and self.pointHeight &lt; 15:
          self.parent.dragging = 1
          self.SetCursor(wx.StockCursor(wx.CURSOR_ARROW))
          self.SetBackgroundColour('BLUE')
          self.parent.SetTransparent(220)
          self.Refresh()
  
  def onDraggingUp(self, event):
      self.parent.dragging = 0
      self.parent.SetTransparent(255)
      self.SetCursor(wx.StockCursor(wx.CURSOR_ARROW))
  </code></pre>
  
  <p>and this are the binds for this events:</p>
  
  <pre><code>self.Bind(wx.EVT_MOTION, self.onMouseMove)
  self.Bind(wx.EVT_LEFT_DOWN, self.onDraggingDown)
  self.Bind(wx.EVT_LEFT_UP, self.onDraggingUp)
  </code></pre>
  
  <p>With this, if I click on the top of the panel, and move down or up, the panel position changes (I drag the panel) to the position of the mouse.</p>