Re: SYNC_INPUT and 23.1.

[Jason Rumney]

Jan Djärv wrote:
> Jason Rumney skrev:
> > Jan Djärv wrote:
> > > Stefan Monnier skrev:
> > > > > Are there any plans to make SYNC_INPUT the default for 23.1?
> > > >
> > > > That's a good idea.  Any objection?
> > >
> > > Sinc there has been no objections, I enabled this by default.  You 
> > > can pass --disable-sync-input to configure if there is problems.  
> > > But I guess we soon will start take advantage of sync input so the 
> > > disabled case will become obsolete.  When we feel confident that 
> > > sync input works, I'll remove the non-sync-input code.
> >
> > Is this just an X thing, or does it affect common code as well? Are 
> > there changes we should be making on other platforms to support 
> > SYNC_INPUT?
>
> I think Stefan can answer that best, AFAIK, he did the implementation.
> I assumed it was an X thing.  Does other platforms use signals for the 
> GUI
> loop?

Windows uses window messages for input, which arrive to Emacs on a 
separate thread for each frame. They are then pushed into the Lisp input 
queue. The process differs slightly from signal handlers in that no 
interrupt occurs when input arrives, we have to poll the frame's message 
queue periodically, but because this is performed by a separate thread, 
it is asynchronous from the point of view of the main Lisp thread. But I 
recall there are some problems caused by the fact that unlike signal 
handlers, the message handling thread does not interrupt the main Lisp 
thread, which have already been worked around on Windows, so the 
SYNC_INPUT changes may or may not be relevant.