Re: Real Time Drawing

[Athanasios Anastasiou <thanos atmail com>]

Thanks for your email and the helpful information John.

After some directions from Liam (see yesterdays mailing archive) i 
passed my app through valgrind and found out that there are too many 
errors happening in the GTK / X level. I suppose that it has something 
to do with the way i am using the thread library in combination with GTK.

I refrained from using the callback mechanism ( as you suggest) because 
whatever code is executed within there should execute in a time shorter 
than the "packet length".

I am dealing with a system which can not afford droping packets. So, one 
thread of execution reads and decodes from the serial port no matter 
what the rest of the app is doing, and a second thread is doing the 
processing. Probably a third thread will be handling display at a later 
stage. The threads communicate through a double linked list with mutex 
protection so that it is guaranteed that writting and reading is 
occuring at different memory addresses.

You are talking about a GAsyncQueue, now thats something i havent looked 
at. Another thing i havent looked at is threads in glib....I suspect 
that a lot of bad things occur when my "processing" thread tries to draw 
the signal on the widget because at some point i discovered that the 
thread lags and blocks (mind you there is nothing else in the processing 
thread except the plot code)

I see the point in the structure you suggest. I also tried that 
yesterday (Not exactly as you describe it but the idea is the same). The 
ReadAndDecode thread does its stuff and the processing thread 
invalidates the widget where the samples are to be drawn, the expose 
event handler handles the rest...... (And the question now arrises, what 
happens if an expose event from the app collides with an expose event 
that had to be sent because the user minimized and maximized the 
application???)

I also used pipes before i start coding for the main application to 
check that i had the decoding of the data frame correct. The decoded 
data was plotted through a pipe to gnuplot!!!

Still there are the same problems and i am suspecting that its in the 
developers responsibility to take care of thread safety in GTK, is that 
true? (i will also be reading on that, but any suggestions / ideas  are 
wellcome)

Thanks for the suggestion of the books also, they look good.

All the best.
thanOS