Also the get_screen_title() function would need to call evaluate_echo__until_stalled() on the header/global/footer output because it would have stalled on the missing $HEADER_TEXT before outputting anything at all really (well it should stall -- we'd need to make the code smart enough to recognise if the data the $HEADER_TEXT symbol needs is actually missing at that point).

One issue that would come up is errors. If we get a fatal error but have already started, we're in trouble. I propose we detect this in our error API and have a mechanism to insert a meta-refresh header, that takes the user to a new error screen -- that is arguably valid XHTML5, as we are allowed in-stream metas now, and if we don't finish the XHTML stream, it doesn't matter, we're dumping it and we have done a valid parse to the point of it being dumped.

Moving this stuff elsewhere.