Feature/more controls over custom trigger

[vtsybulin]

@gregnb @MatthewHerbst Hello! Faced kinda same need as per #219

However I need even more control then just binding to some single trigger ref, so I decided to go with context provider to expose the handleClick method directly to be used afterward. Sample:

import ReactToPrint, { PrintContext } from 'react-to-print';

...

<ReactToPrint content={() => this.componentRef}>
    <PrintContext.Consumer>
	{({ handlePrint }) => (
          <button onClick={handlePrint}>Print this out!</button>
	)}
     </PrintContext.Consumer>
</ReactToPrint>

Also wrapped ReactToPrint into [useReactToPrint] hook to be used with functional components. Sample:

import { useReactToPrint } from 'react-to-print';

...

const Example = () => {
  const componentRef = useRef();
  const handlePrint = useReactToPrint({
    content: () => componentRef.current,
  });
  
  return (
    <div>
      <ComponentToPrint ref={componentRef} />
      <button onClick={handlePrint}>Print this out!</button>
    </div>
  );
};

Let me know what you think! Thanks.

[MatthewHerbst]

This is fantastic, thank you!

My only concern is that it would be a breaking change since we currently support React 15. As mentioned in the review comments, I don't mind making that breaking change, but would want to add a few more breaking changes in at the same time which could delay this by a couple of days. Do you mind waiting until the weekend for this to be released? Happy to get it out sooner if you can make the code not break when using React 15.

[MatthewHerbst]

Suggested change

	In case you don't want to specify `trigger` directly within other props but you rather want to gain some extra control over it, you could make use of PrintContext. By using PrintContext you can get direct access to the `handlePrint` method which triggers printing action.
	If you need extra control over printing and don't want to specify `trigger` directly, `PrintContext` allows you to gain direct access to the `handlePrint` method which triggers the print action.

[MatthewHerbst]

Suggested change

	For the functional components, there is a useReactToPrint hook, which accepts an object with the same configuration props as `<ReactToPrint />` itself and returns a handlePrint function, by calling which you can trigger printing action.
	For functional components, use the `useReactToPrint` hook, which accepts an object with the same configuration props as `<ReactToPrint />` returns a `handlePrint` function which when called will trigger the print action.

[MatthewHerbst]

Suggested change

	### Calling from functional components with [useReactToPrint](https://reactjs.org/docs/hooks-intro.html)
	### Calling from functional components with `useReactToPrint` [hook](https://reactjs.org/docs/hooks-intro.html)

[MatthewHerbst]

Is there a way to make this conditional based on React.createContext existing? Right now we support React v15 which does not have createContext (introduced in React 16.3.0). I would actually be ok making a major version change to drop React 15, however, I'd want to get a few more breaking changes in I've been meaning to do, which would delay shipping this by a few days.

[MatthewHerbst]

Similar to the above comment, is there a way to make this a no-op (just export undefined or something) if the user is on React 15 (which doesn't have useMemo and useCallback?

[vtsybulin]

@MatthewHerbst Hi. Thanks for the feedback! Sounds cool. Sorry for the v15 thing missed that :/ Let me take a look tomorrow so I can update accordingly If you're ok with that?

[MatthewHerbst]

No problem. If you're not in a rush then I'm happy to move deploying this to the weekend so I can get a few other changes in, and then we can do a major version release and drop React 15 support (which we should do anyways for a variety of reasons).

[jtart]

hey @MatthewHerbst, are you close to releasing this at all?

[vtsybulin]

@MatthewHerbst Hey! Sorry, it's been a while, was a bit busy. I hope it's better now. Let me know if anything extra is required, thanks!

[vtsybulin]

@MatthewHerbst nice! thanks 👍

[MatthewHerbst]

@vtsybulin thank you! I'm working on a few small things, will have it in a new release in a couple of hours

[vtsybulin]

@MatthewHerbst Cool. Let me know if you have anything else in mind to assist with.

[MatthewHerbst]

This is published with the just released version 2.8.0-beta.1. I'll release 2.8.0 either later tonight or tomorrow once I have a chance to do more testing.

[MatthewHerbst]

Published as 2.8.0, thanks again!

[vtsybulin]

Great 👍