Locking graphics system - GUI/octave synchronization

[John W. Eaton]

On 14-Jul-2008, Michael Goffioul wrote:

| I know this has been discussed before, but would anyone see a major problem
| or showstopper in adding a mutex-based locking system that would allow
| to globally lock the graphics system? (through the use of specific methods
| in gh_manager, like lock() and unlock()).
| 
| I'm currently investigating the implementation of an event-queue in octave,
| which would allow a backend to post a callback from any thread, such that
| the callback is executed in the octave thread. During this posting, I need
| to check various things, like whether another callback is executing, whether
| it's interruptible, whether busyaction tells me to queue or discard the
| event... During these operations, I don't want the graphics system to change
| state, so a global locking scheme would really help.
| 
| If anybody objects, then I'll integrate this in the graphics mq. This will be
| based on the proposal I made a few months ago and on the more recent
| proposal from Maciek.

I don't have a problem with this change.  Would you like for me to go
ahead and apply the octave_mutext patch from the graphics mq to my
archive?

jwe