Recursively invoke forceUpdate() on a tree of components. Demo: https://jsfiddle.net/developit/642ctu04/

preact-deep-force-update.js

/** Invoke `.forceUpdate()` on a component and all descendants. */
export default function deepForceUpdate(component) {
  component.forceUpdate();

  // high-order child recursion
  if (component._component) {
    deepForceUpdate(component._component);
  }
  else if (component.base) {
    updateComponentsFromDom(component.base);
  }
}

function updateComponentsFromDom(node, fn) {
  let children = node.childNodes;
  for (let i=children && children.length; i--; ) {
    let child = children[i];
    if (child._component) {
      deepForceUpdate(child._component);
    }
    else {
      updateComponentsFromDom(child, fn);
    }
  }
}