Asynchronously determines a proxy URI to use for @msg and calls @callback.
the #SoupURI you want a proxy for
the #GMainContext to invoke @callback in
a #GCancellable, or %NULL
callback to invoke with the proxy address
data for @callback
Deprecated: #SoupProxyURIResolver is deprecated in favor of #GProxyResolver
2.26.3
See Implementation
Asynchronously determines a proxy URI to use for @msg and calls @callback.