Re: Event loop and http::geturl

Jonathan Kelly <jonkelly@fastmail.fm> wrote:

So, it looks like ::http::geturl is operating asynchronously, despite my
program NOT using -command.

It does.  It is documented as such:

man n http:

  Note: The event queue is even used without the -command option.   As a
  side effect, arbitrary commands may be processed while http::geturl is
  running.


The code snippets below are from http-2.9.5.tm which was distributed
(at least) with 8.6.12:

Buried deep in http::geturl:

        # geturl does EVERYTHING asynchronously, so if the user
        # calls it synchronously, we just do a wait here.
        http::wait $token

And the implementation of http::wait is:

    proc http::wait {token} {
        variable $token
        upvar 0 $token state

        if {![info exists state(status)] || $state(status) eq ""} {
            # We must wait on the original variable name, not the upvar alias
            vwait ${token}(status)
        }

        return [status $token]
    }

And the 'vwait' there reenters the event loop and allows other events
to be processed.