+public-webapps, -www-tag in replies to avoid cross-posting


Domenic wrote, to www-tag:

> [C]an shadow DOM be used to explain existing elements, like <video> or
> <input type="range">, in terms of a lower-level primitive?
> As of now, it seems like it cannot, for two reasons:
> 1. Native elements have extra capabilities which are not granted by
> shadow DOM, or by custom elements. For example, they can participate
> in form submission.

Authors need to be able to participate in form submission, but this is
independent of Custom Elements.

Web applications often maintain state in JS objects that have no direct
DOM representation. Such applications may want such state to be

Existing form elements map one field name to many values. People often
build custom controls precisely because those controls hold more
complex values that would be better represented as many names to many
values. Subclassing existing form elements don't get you this.

And inheriting from HTMLInputElement is insane (not because inheriting
is insane, but because HTMLInputElement is insane), so that's not really
how we want author-defined objects to become submittable.

Given the above I don't think we should try to solve the "how authors
can participate in form submission" problem by enabling the subclassing
of existing form elements. Instead, we should define a protocol
implementable by any JS object, which allows that JS object to expose
names and values to the form validation and submission processes.

Something like this:

  function Point(x, y) {
    this.x = x;
    this.y = y;
  Point.prototype.formData = function() {
    return {
      "x": this.x,
      "y": this.y

  var theForm = document.querySelector("#my-form");

  var p = new Point(4,2);


This is obviously a super hand-wavy strawman and would need to be
fleshed out. Thoughts?


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