On Mon, 23 Jan 2017 22:18:19 +0000 Emmanuele Bassi <eba...@gmail.com> wrote: > Hi; > > On 23 January 2017 at 22:09, rbd <r...@soest.hawaii.edu> wrote: > > >> It is not quite that bad. The documentation for > >> g_source_add_unix_fd() is inadequate, but although not immediately > >> obvious the prepare, check and finalize handlers can in fact > >> usually just be set to NULL (provided you have set the 'events' > >> argument for g_source_add_unix_fd() correctly) so you only need to > >> provide the dispatch handler, which executes your callback when an > >> event occurs. > >> > >> The poor quality of the documentation is the real problem here. I > >> would give it a try and see how you get on with it. > > > > > > Nothing about the g_source_* functions is obvious from the official > > docs, either immediately or otherwise! ;-> Seriously, one of the > > least illuminated points there actually has to do with timeouts, > > exactly where in the check->prepare->dispatch sequence the poll() > > gets done, etc. > > Of course, patches and bugs for the documentation are welcome. > > A good set of articles on GSource and the main context API in GLib is > on Philip Withnall's blog; Philip actually contributed back that > documentation in the API reference, but this kind of discussions on > how the implementation works is ill-suited for an API documentation. > > See: > > - https://tecnocode.co.uk/2014/03/27/what-is-gmaincontext/ > - https://tecnocode.co.uk/2015/05/05/a-detailed-look-at-gsource/ > - > https://tecnocode.co.uk/2014/04/19/ensuring-functions-are-called-in-the-right-context/ > > The second article also covers your use case pretty accurately.
I don't want to appear argumentative, but the second article is not of great assistance with respect to the OP's usage of a wrapper for poll() which executes a callback in the glib main loop when a file descriptor becomes available for reading - as the OP put it, a replacement for XtAppAddInput(). For that (if not using GIOChannel) he needs g_source_add_unix_fd(), NULL for the prepare, check and finalize handlers and a dispatch handler which executes the callback and a type derived from GSource which interfaces with that. As far as I can see there is little in the second article which explains that. (And I have not seen any other article which does that either.) The second article is concerned with a more complex implementation of a non-file descriptor based event source. For a file descriptor based event source these days you just use g_source_add_unix_fd(), which does most of the boiler plate for you, were one to know it. Let me stress I am not being negative here. I very much appreciate the efforts of the glib developers. But I have stubbed my toe on exactly the same issue myself: having said that, setting up a few test cases and reading the source code made it apparent fairly quickly how g_source_add_unix_fd() actually works, and from there it was pretty straightforward. Chris _______________________________________________ gtk-app-devel-list mailing list gtk-app-devel-list@gnome.org https://mail.gnome.org/mailman/listinfo/gtk-app-devel-list
