abtmtr-v4/views/scripts/interface.js

function propagateStyles(rootStyles, parent) {
  if (parent == null && window.frameElement == null) return;
  const wfParent = parent ?? window.frameElement.parentElement;
  wfParent.style.setProperty(
    "--background-color",
    rootStyles.getPropertyValue("--background-color")
  );
  wfParent.style.setProperty("--color", rootStyles.getPropertyValue("--color"));
  wfParent.style.setProperty(
    "--accent-color",
    rootStyles.getPropertyValue("--accent-color")
  );
  wfParent.style.setProperty(
    "--accent-color-fg",
    rootStyles.getPropertyValue("--accent-color-fg")
  );
  wfParent.style.setProperty("--border-style", "0.0625em solid var(--color)");
}

window.addEventListener("load", () => {
  propagateStyles(getComputedStyle(document.documentElement));
});