change to gtk-1.2/threads.scm

[Jon Wilson]

Hi,
I was playing around with guile-gtk today.  It looks quite nice.  I'm 
trying to write a guile + gtk program that will give me both a useful 
window (to draw in), and a guile repl.  I'll have some procedures 
available to guile which emit signals to the drawing area in the window 
to cause drawing to happen in the callbacks.  So, given this, 
gtk-threads-ensure-handler seemed like the thing to use.  However, it 
also seemed to do some slightly screwy things.  One of them I think I 
have largely fixed.  That is, after starting the gtk-main loop in 
another thread (via ensure-handler of course), the main guile thread in 
which the repl was running would no longer respond.  I could type scheme 
expressions there and hit enter, and nothing would happen (well, as I 
typed, characters appeared, but it was plain that no evaluation was 
occuring), until I closed the gtk-window, at which time everything I had 
typed would be evaluated as normal.  This, I believe I have fixed.  If 
we change threads.scm to:

(define gtk-threads-handler? #f)
(define gtk-threads-ensure-handler #f)

(let ((handler-running? #f))
 (set! gtk-threads-handler?
       (lambda () handler-running?))
 (set! gtk-threads-ensure-handler
       (lambda ()
         (if (not handler-running?)
               (begin-thread
                 (dynamic-wind
                       (lambda ()
                         (gdk-threads-enter)
                         (set! handler-running? #t))
                       (lambda ()
                         (while #t
                                (if (gtk-events-pending)
                                  (gtk-main-iteration)
                                  (yield))))
                       (lambda ()
                         (set! handler-running? #f)
                         (gdk-threads-leave))))))))

This allows another thread to run unimpeded as long as there are not gtk 
events waiting.  Also, by putting the definitions of these two functions 
into a let, we can protect handler-running? from getting clobbered, as 
well as avoiding taking up an extra top-level binding.

So, the second problem that I have is that after ending a guile session 
in which I had run ensure-handler, the terminal is broken.  I type, but 
no text appears.  However, the terminal is clearly getting what I type.  
If I don't look at what I am typing everything is as normal.  Anybody 
know what might cause this?  I exit the gtk-main loop by closing the 
window (thus calling gtk-main-quit, I believe), and then exit guile by 
pressing C-d at the remaining guile prompt.  Is this the wrong thing?
Regards,
Jon