docs: def buildcss(app, buildpath, imagefile):
      """Create CSS file."""
      # set default values
      div = 'body'
      repeat = 'repeat-y'
      position = 'center'
      attachment = 'scroll'
  
      if app.config.sphinxmark_div != 'default':
          div = app.config.sphinxmark_div
  
      if app.config.sphinxmark_repeat is False:
          repeat = 'no-repeat'
  
      if app.config.sphinxmark_fixed is True:
          attachment = 'fixed'
  
      border = app.config.sphinxmark_border
      if border == 'left' or border == 'right':
          css = template('border', div=div, image=imagefile, side=border)
      else:
          css = template('watermark', div=div, image=imagefile, repeat=repeat,
                         position=position, attachment=attachment)
      LOG.debug('[sphinxmark] Template: ' + css)
      cssname = 'sphinxmark.css'
      cssfile = os.path.join(buildpath, cssname)
  
      with open(cssfile, 'w') as f:
          f.write(css)
  
      return(cssname)