<!DOCTYPE html> <body> <script> // This document will contain an iframe which will either host echo-policy.py, // or will host another copy of this document, with the nesting level reduced // by one. This way, an arbitrary nesting depth can be achieved, with the // final inner-most frame reporting back the advertised required policy. // The 'id' URL parameter will be passed to the nested document. // The 'level' URL paramater will be reduced by 1 and passed to the nested // document if it was at least 1. (If it was 0, then echo-policy.py will be // nested instead, and the level parameter will not be passed.) // This document is served with a Document Policy header that should satisfy // any requests that include a required policy for the // 'lossless-images-max-bpp' feature. const params = new URLSearchParams(window.location.search); const id = params.get('id'); const level = params.get('level'); const iframe = document.createElement('iframe'); var hostname; if (level >= 1) { params.set('level',level-1); hostname = document.location.pathname + "?" + params.toString(); } else { params.delete('level'); hostname = "/document-policy/echo-policy.py?" + params.toString(); } iframe.src = hostname; document.body.appendChild(iframe); </script>