[mcclim-devel] execute-frame-command

[Andy Hefner]

On 5/25/06, Christophe Rhodes <csr21 at cam.ac.uk> wrote:
> Hi,
>
> Is
>
>   (defun foo ()
>     (let ((frame (make-application-frame 'climacs)))
>       (clim-sys:make-process (lambda () (run-frame-top-level frame)))
>       (execute-frame-command frame `(com-find-file "/tmp/foo.txt"))))
>
> expected to be "safe"?  At present, this is subject to a race
> condition, because the frame need not have been adopted properly by
> the time the execute-frame-command runs, and so it need not have a
> top-level sheet.

I still think this is a bad idea - the application thread may be
running another command, or an event handler might be accessing the
stream state or output history, and the usual thread safety problems
can crop up. McCLIM could add a lock around command execution and
locks on stream panes that would protect you 99.9% of the time (but
still wouldn't solve your problem).

It might be a better idea to follow the suggestion made in the spec of
queuing command events that can be executed in the main thread at its
leisure (adding an enqueued-commands slot to the frame which the event
handler for command events fills, and perhaps have read-frame-command
first pull commands from that queue).