Allow listening to frames.

[akorchev]

Extracted two methods from setup and teardown that will allow me to attach the backend to an iframe. I need a DropTarget to live inside an iframe. Here is how I would do it

class Frame extends React.Component {
  static contextTypes = {
    dragDropManager: PropTypes.object.isRequired
  }
  render() {
     return <iframe></iframe>
  }
  componentDidMount() {
      const { contentDocument } = findDOMNode(this)
      this.context.dragDropManager.backend.addEventListeners(contentDocument.defaultView)
  }
  componentWillUnmount() {
      const { contentDocument } = findDOMNode(this)
      this.context.dragDropManager.backend.removeEventListeners(contentDocument.defaultView)
  }
}

[nelix]

That is much simpler than I was expecting.
Do you think you could add some tests and maybe an example?

[akorchev]

I can definitely create an example. Not sure how to create tests though. This is only half of the solution - the other half is to get the dragDropManager to the iframe which I will show in the example.

[akorchev]

Here is the example: https://github.com/akorchev/react-dnd-cross-frame

[gaearon]

Thanks. I don't promise to support or test this in the future but I see no harm in adding it.
👍

[gaearon]

Note that I still reference window in a couple of places so this won't cover all cases. There's a couple of places where I add a mousemove listener on window, and it's important to do this lazily for better perf. I'm open to merging more PRs handling this but I won't work on it myself.