new_contents: # doc-export: CodeEditor
  """
  This example demonstrates a code editor widget based on CodeMirror.
  """
  
  # todo: Maybe this should be a widget in the library (flexx.ui.CodeMirror) ?
  
  from flexx import ui, app, event
  from flexx.pyscript.stubs import window
  
  
  # Associate CodeMirror's assets with this module so that Flexx will load
  # them when (things from) this module is used.
  base_url = 'https://cdnjs.cloudflare.com/ajax/libs/codemirror/'
  app.assets.associate_asset(__name__, base_url + '5.21.0/codemirror.min.css')
  app.assets.associate_asset(__name__, base_url + '5.21.0/codemirror.min.js')
  
  
  class CodeEditor(ui.Widget):
      """ A CodeEditor widget based on CodeMirror.
      """
      
      CSS = """
      .flx-CodeEditor > .CodeMirror {
          width: 100%;
          height: 100%;
      }
      """
      
      class JS:
          
          def init(self):
              # https://codemirror.net/doc/manual.html
              options = dict(value='type code here ...',
                             mode='python',
                             theme='default',
                             indentUnit=4,
                             smartIndent=True,
                             lineWrapping=True,
                             lineNumbers=True,
                             firstLineNumber=1,
                             readOnly=False,
                             )
              self.cm = window.CodeMirror(self.node, options)
          
          @event.connect('size')
          def __on_size(self, *events):
              self.cm.refresh()
  
  
  if __name__ == '__main__':
      app.launch(CodeEditor, 'xul')
      app.run()
  
subject: Add example for code editor widget based on codemirror