/* ScrollVars: scoped clocks. OPT-IN, not part of styles.css.
 *
 * --sv-t and --sv-view inherit, so every write re-resolves the whole subtree
 * of a tracked element. Registered non-inheriting, a write reaches one
 * element. The price: a clock reaches only the elements that declare
 * `inherit` for it, every element on the path down to a reader included,
 * and a `var(--sv-t, 1)` fallback is never taken again (declare that default
 * on the tracked element). The shipped presets are forwarded below; your own
 * reader needs one rule, its LAST compound inside :has():
 *
 *   .sv :has(.my-card):not(.sv, [data-sv]), .my-card:not(.sv, [data-sv]) { --sv-t: inherit; }
 *
 * Measured behind a rendered-output gate: -63% style recalculation at 50
 * descendants per reader, +13% where every descendant is a reader, -23% on
 * scrollvars.dev's home page. Numbers, rule and when it pays: the guide,
 * "Scoped clocks". CSS comments ship, so this one stays short. */

/* Registration only where the path forwarding below can exist: a browser
 * with @property but without :has() would register the clocks and then have
 * no way to carry them down to a preset reader that is not a direct child,
 * which is exactly what the home page's parallax layers are. Below this
 * floor the sheet is inert and the clocks keep inheriting. */
@supports selector(:has(a)) {
  @property --sv-t {
    syntax: '<number>';
    inherits: false;
    initial-value: 0;
  }

  @property --sv-view {
    syntax: '<number>';
    inherits: false;
    initial-value: 0;
  }

  /* Presets that read a clock from a descendant of the tracked element. The
   * forward covers the READER and every element on the path down to it,
   * because a non-inheriting property is the initial value on each step in
   * between and `inherit` on the reader alone would read that. Keep this list
   * in step with styles/*.css: a test fails when a preset reads a clock from a
   * selector whose subject is not .sv and has no forward here. */
  .sv :has(.sv-drift):not(.sv, [data-sv]), .sv .sv-drift:not(.sv, [data-sv]) { --sv-view: inherit; }
  .sv :has(.sv-range):not(.sv, [data-sv]), .sv .sv-range:not(.sv, [data-sv]) { --sv-t: inherit; }
}