code: def make_slider_range(self, cursor_pos):
          
          # The slider range indicator position follows the mouse vertical
          # position while its height corresponds to the part of the file that
          # is currently visible on screen.
  
          vsb = self.editor.verticalScrollBar()
          groove_height = self.get_scrollbar_position_height()
          slider_height = self.value_to_position(vsb.pageStep())-self.offset
  
          # Calcul the minimum and maximum y-value to constraint the slider
          # range indicator position to the height span of the scrollbar area
          # where the slider may move.
          min_ypos = self.offset
          max_ypos = groove_height + self.offset - slider_height
  
          # Determine the bounded y-position of the slider rect.
          slider_y = max(min_ypos, min(max_ypos, cursor_pos.y()-slider_height/2))
  
          return QRect(1, slider_y, self.WIDTH-2, slider_height)
docs: Make slider range QRect