[Glade-users] Threading with GTK/Glade

[james cameron compaq com (James Cameron)]

Johnathan,

I understand the need to keep the design of the interaction with the
external device in one piece of code ... I've done lots of state
critical code; microcontrollers, digital RF base stations, and computer
to computer communication.

Having thought again about the physical configuration you describe, I
would recommend a per serial port process instead of one for all ports.

Under Linux or another UNIX based operating system, you might then have
the following processes;

- gui
  - port 1
  - port 2
  - port 3
  etc

This will allow you to write the port processes without any threading;
instead using the operating system for process context switching.  No
efficiency change; your time is more expensive anyway.  An advantage of
using processes is that each process is isolated from the others, so a
fault (never! ;-)) in one process will not propogate and take down the
system as a whole.

Your description of operations suggests an event sequence to me; which
would represent the communication between the GUI process and the port
processes.

port -> gui : "i'm port 4; i'm started"
port -> gui : "i'm port 4; gizmo detected, serial number x, programming"
port -> gui : "i'm port 4; programming complete, success|fail"

I note there doesn't appear to be any communication in the other
direction.  If that is so, a simple shared pipe would be sufficient. 
I'd recommend a text protocol for ease of testing; you can use echo to
write messages into the pipe.  Here is how I see the GUI operating;

a) the GUI creates the pipe,
b) the GUI fork()'s and exec()'s the port processes attached to pipe,
c) the GUI tells GTK+ that the pipe is an input source,
   (using gtk_input_add_full)
d) the GUI returns to the GTK+ main loop,
e) GTK+ calls the GUI handler when a message arrives in the pipe,
f) the handler figures out what to update on screen and returns.

Have a look at my gtsl program on http://quozl.netrek.org/ts/ for an
example of connecting a Glade application to an external event source;
in this case a serial port.

-- 
James Cameron                                 (james cameron compaq com)

http://quozl.linux.org.au/         (or)         http://quozl.netrek.org/