Re: Trouble: GTK + Octave + PThreads

[John W. Eaton]

On  5-Nov-1998, Rafael Laboissiere <address@hidden> wrote:

| [gtk-list people: if this thread is becoming too Octave-specific, please
| tell me and I will remove the gtk-list address from the Cc: list.]

I removed gtk-list because I'm not a subscriber (and don't want to
become one) so I can't post there anyway.

| With GTK+ (as with other X-based GUI toolkits) it is necessary to launch
| a main loop (gtk_main, for instance) which will take care of the mouse
| events.  As my application will be launched from the Octave prompt, it
| gets blocked when gtk_main is called, unless I use threads.
| 
|     JWE> Can't you just use something like select() to decide where
|     JWE> input is coming from?
| 
| Yes, if my application would be taking care of the readline loop, which
| is not the case (Octave is doing it).
| 
|     JWE> With Tcl/Tk and some other X-based GUI toolkits, it is
|     JWE> relatively easy to continue to get input from the readline
|     JWE> prompt while also allowing the GUI objects to function.  
| 
| I am not sure, but I think that with Tcl/Tk, the function Tcl_Init
| spawns a whole new process, which communicate with the main program
| through Tcl_Eval.  This is not the case of the application I am planning
| to write, as the GUI interface will be able to alter directly the
| workspace data of Octave.

The example Tcl/Tk code that I posted does not start a Tcl interpreter
in a separate process.  It's been a while since I thought about this,
but I believe the way it works by registering a function with readline
that handles events (event_hook, which calls Tcl_DoOneEvent) and then
also by telling Tcl not to do anything with input on stdin, so that
readline will get that.

I believe the same approach works with other toolkits.  In Xt, I think
the function to call to register the input function for stdin is
XtAppAddInput.

|     JWE> What does -D_REENTRANT do for complinig Octave?
| 
| I compiled version 2.0.13.91 with -D_REENTRANT.  It works normally. 

That doesn't answer my question.  What is the purpose of -D_REENTRANT?
That symbol is not used in the Octave code.  Adding it to the compiler
flags might have some effect on the functions declared in system
header files, but I don't think it will make the Octave code
reentrant.

jwe