fix(widgets) events in react reverse controlled env

[chrisgervang]

Closes #8877

Background

Exploring a way to exclude widgets from the deck event manager and push it above maplibre. Currently mouse event on a widget performs deck picking, which is an unwanted interaction.

propagation_short.mov

Rearranging the DOM so that the deck picker and widgets are peer elements fix the deck picking issue. Also, by nesting the deck children, such as react-map-gl in reversed controlled configuration, the deck widgets events aren't blocked by maplibre.

<!-- react-map-gl reverse controlled DOM -->
<div id="react-deckgl-wrapper">
  <div class="event-manager-root">
    <canvas class="deck-overlay" />
    <div class="react-deck-view">
      <div class="react-map-gl-root" />
      <div class="some-other-child-component" />
    </div>
  </div>
  <div class="deck-widgets-container">
    <div class="deck-view-widgets">
      <div class="fill"/>
      <div class="top-left"/>
    </div>
  </div>
</div>

react-widget-dom.mov

---

Flavors to test:

• no basemap
• React reverse controlled
• MapboxOverlay overlaid
• MapboxOverlay interleaved
• Script tag
• Python/Jupyter notebook
• GoogleMapsOverlay

Change List

• Core
  • If present as a child of parent, selects an .event-manager-root element for EventManager to use for picking.
  • If present as a child of parent, selects an .deck-widgets-container element for WidgetManager to add widgets to.
• React
  • Nests deck overlay and <DeckGL/> children under .event-manager-root
  • Nests deck widgets under .deck-widgets-container

---

Note

Medium Risk
Changes the DOM structure and event-root selection for React rendering, which can affect pointer/gesture handling and widget placement across integrations, though it preserves fallbacks for non-React/legacy setups.

Overview
Fixes widget interaction issues in React reverse-controlled basemap setups by splitting the DOM roots for input events vs. widgets.

React DeckGL now renders a .deck-events-root wrapper containing the canvas + children, and a sibling .deck-widgets-root container for widgets. Core Deck initialization is updated to attach EventManager to .deck-events-root (when present) and WidgetManager to .deck-widgets-root (falling back to the prior parents when absent).

The arc website example is updated to include @deck.gl/widgets (Zoom/Compass/Fullscreen) and its stylesheet to exercise the new behavior.

^{Written by Cursor Bugbot for commit 103fd90. This will update automatically on new commits. Configure here.}

[coveralls]

coverage: 91.082% (+0.003%) from 91.079%
when pulling 8ebe54f on chr/rearrange-widget-dom
into 51dc2a3 on master.

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

[felixpalmer]

@chrisgervang adding this broke the website build with the latest loaders, any idea why? f939449

[chrisgervang]

What's the error? How confident are we it has to do with loaders, or could it also be broken on master?

[felixpalmer]

Module not found: Error: Can't resolve '@deck.gl/widgets/stylesheet.css' in '/home/runner/work/deck.gl/deck.gl/examples/website/arc'

see: https://github.com/visgl/deck.gl/actions/runs/22398533353/job/64838419323

It doesn't seem broken on master, so it's a bit of a mystery to me