Focus the Delete Button in a Confirm Dialog

To focus the delete button, instead of the cancel button, when opening the delete annotation dialog, register an annotations.willChange event listener:

instance.addEventListener("annotations.willChange", (event) => {
  const annotation = event.annotations.get(0);
  if (
    event.reason === PSPDFKit.AnnotationsWillChangeReason.DELETE_START
  ) {
    console.log("Will open deletion confirmation dialog");
    // We need to wrap the logic in a `setTimeOut()`, because the modal will be rendered on the next tick.
    setTimeout(function () {
      // The button is in the context of the PSPDFKit iframe.
      const button = instance.contentDocument.getElementsByClassName(
    }, 0);

This has been tested with PSPDFKit for Web 2020.6.1.