From: Per-erik Martin <lists@...>
Date: 2013-05-04T01:32:36+09:00
Subject: Re: ruby 2.0 with tk 8.5 on Raspberry Pi

I finally managed to find a way to work around this problem. I hesitate
to call is a "solution", since I still don't know exactly why it behaves
this way, or why the workaround works...

It's clear that there was something fishy going on with the thread
scheduling, so I've done lots of testing with threads in ruby on the
RPi, but couldn't find anything strange there. It seems the issue,
whatever it is, is at least partly in the tk library, or tk binding in
ruby.

Reading tk.rb finally made me suspect the RUN_EVENTLOOP_ON_MAIN_THREAD
setting which seems to be set differently depending on platform.

And lo and behold, changing line 1239 in tk.rb:

RUN_EVENTLOOP_ON_MAIN_THREAD = false

into

RUN_EVENTLOOP_ON_MAIN_THREAD = true

made it work! I know this isn't the the correct fix, but will do for me
now; this has been a major show-stopper for me. (It really should detect
the Raspberry Pi platform and set it for this only, but I'm not going to
bother about that now.)

One question remains: Why does this has to be different on Raspberry Pi
running wheezy? It's not needed on Ubuntu or Mac OS X (unless you're
running and older tk version. Is it something with the tk build on RPi?
Or the pthread libraries on RPi? Or is it something about the arm
architecture?

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