In order to enable this you need to define the `draggableNode` prop on
the `<WithDrag>` component. For example:

```
class DraggableItems extends React.Component {
  render() {
    return (
      <DraggableContext onDrag={ onItemMoved }>
        <ol>
          {
            items.map((item, index) => {
              return (
                <WithDrop key={ index } index={ index }>
                  <DraggableItem />
                </WithDrop>
              );
            });
          }
        </ol>
      </DraggableContext>
    );
  }
}

...

class DraggableItem extends React.Component {
  render() {
    return (
      <li ref={ (node) => { this._listItem = node; } } >
        <WithDrag draggableNode={ () => { return this._listItem; } }>
          <span>{ item.content }</span>
        </WithDrag>
      </li>
    );
  }
}
```

Note that the `draggableNode` is passed as a function because the ref
`_listItem` is undefined until the component is mounted.

In order to enable this you need to define the `draggableNode` prop on
the `<WithDrag>` component. For example:

```
class DraggableItems extends React.Component {
  render() {
    return (
      <DraggableContext onDrag={ onItemMoved }>
        <ol>
          {
            items.map((item, index) => {
              return (
                <WithDrop key={ index } index={ index }>
                  <DraggableItem />
                </WithDrop>
              );
            });
          }
        </ol>
      </DraggableContext>
    );
  }
}

...

class DraggableItem extends React.Component {
  render() {
    return (
      <li ref={ (node) => { this._listItem = node; } } >
        <WithDrag draggableNode={ () => { return this._listItem; } }>
          <span>{ item.content }</span>
        </WithDrag>
      </li>
    );
  }
}
```

Note that the `draggableNode` is passed as a function because the ref
`_listItem` is undefined until the component is mounted.

Use 'selectstart' event listener to call preventDefault if the user is
dragging a dom node or is already dragging.

Fix Safari cursor for drag and drop