[Kde-bindings] Using threads with QtRuby

[Richard Dale]

On Sunday 07 February 2010 05:16:24 pm Uriel wrote:
> I've done some debuging on QtRuby and GtkRuby and it seems that I've
> found the problem and the trick GtkRuby uses.
> I absolutely don't know how does glib works and why does the following
> solution work but all the magic is in custom poll function.
> GtkRuby's poll function interacts directly with Ruby's threads mechanism
> and doing something with blocking regions.
> 
> So here is the result of my "research". I've compiled the following code
> as a shared library:
> 
> #include <glib.h>
> #include <ruby.h>
> 
> static GPollFunc default_poll_func;
> 
> typedef struct _PollInfo
> {
>      GPollFD *ufds;
>      guint nfsd;
>      gint timeout;
>      gint result;
> } PollInfo;
> 
> static VALUE
> rg_poll_in_blocking(void *data)
> {
>      PollInfo *info = data;
> 
>      info->result = default_poll_func(info->ufds, info->nfsd,
> info->timeout);
> 
>      return Qnil;
> }
> 
> static gint
> rg_poll(GPollFD *ufds, guint nfsd, gint timeout)
> {
>      PollInfo info;
> 
>      info.ufds = ufds;
>      info.nfsd = nfsd;
>      info.timeout = timeout;
>      info.result = 0;
> 
>      rb_thread_blocking_region(rg_poll_in_blocking, &info, RUBY_UBF_IO,
> NULL);
> 
>      return info.result;
> }
> 
> void foo() {
>    default_poll_func = g_main_context_get_poll_func(NULL);
>    g_main_context_set_poll_func(NULL, rg_poll);
> }
> 
> And then, in ruby program, called this function like this:
> 
> require 'dl/func'
> 
> lib = DL.dlopen './foo.so'
> cfunc = DL::CFunc.new lib['foo'], DL::TYPE_VOID
> func = DL::Function.new cfunc, []
> 
> func.call
> 
> After this call threads began to work. And by the way, when I was using
> the workaround from the previous message my test thread finished in 17
> seconds time. But with custom poll function it finish just in 2-3 seconds.
> 
> That's just the simple illustration of an idea. Full GtkRuby's file
> contains some preprocessor conditions for Ruby 1.8 and Ruby 1.9 and you
> can be interested in looking at it. This file can be found at
> `http://downloads.sourceforge.net/ruby-gnome2/ruby-gtk2-0.19.3.tar.gz`
> and it's called `glib/src/rbglib_maincontext.c`.
That's interesting - it looks like we could steal this code then. I'm 
surprised there in nothing about locks/semaphores in there. Maybe that is 
somewhere else in the gtk ruby code. Although it takes longer in terms of 
elapsed time, another interesting measurement would be how much cpu time each 
solution used.

-- Richard