2+ modals on same page make an issue

[rowdyroad]

Summary:

I what to use < body > class 'ReactModal__Body--open' to freeze background page (overflow:hidden).
But there is some issue if we have 2+ on same page (component)

Steps to reproduce:

1. Create component
2. Add 2+ < ReactModal > components on page
3. Set for some of them isOpen attribute to true

Expected behavior:

There is class name of < body > as 'ReactModal__Body--open' if some of ReactModal component isOpen.

Additional notes:

In 1.6.5 version we have this code:
if (props.isOpen) { elementClass(document.body).add('ReactModal__Body--open'); } else { elementClass(document.body).remove('ReactModal__Body--open'); }

So, one of < ReactModal > is open and add class to body, some is close and remove it. In Google Dev Console we can see, what react changes body tag constantly (CPU for tab is about 50% for i7).

It can be resolved(workaround) by JSX-condition wrapping and set permanently isOpen={true}

[MarkMurphy]

I think one potential solution here would be to implement a ModalManager that keeps track of open modals. Each modal instance would have the responsibility of registering itself and its state with the ModalManager.

Here's a quick and dirty example:

const registry = new Set()

class Modal extends Component {
  renderPortal(props) {
    const prevRegistrySize = registry.size

    if (props.isOpen) {
      registry.add(this)
    } else {
      registry.delete(this)
    }

    if (registry.size && prevRegistrySize === 0) {
      elementClass(document.body).add('ReactModal__Body--open')
    }
    else if (registry.size === 0 && prevRegistrySize !== 0) {
      elementClass(document.body).remove('ReactModal__Body--open')
    }

    // ...
  }
}

[diasbruno]

Marked as duplicated. #231
See PR #326.