At Wed, 10 Jan 2018 11:17:14 -0800 (PST), Mark Wunsch wrote: > The main question I have is: How does racket/gui set up and interact with > the NSApplication's main thread? > [...] > My sense of this crash is that there's something inside the racket/gui > internals [....] > that works around a "typical" NSApplication start-up sequence that makes > the osxvideosink code believe that it's running outside of the main NSApp > thread. "Typical" is in quotes because I honestly have no idea what I'm > talking about.
It's true that `racket/gui` avoids the usual run loop, so I expect that "osxvideosink.m" will think that it needs its own. Specifically, `[[NSRunLoop mainRunLoop] currentMode]` will return nil. And if `gst_osx_videosink_check_main_run_loop` runs in the main OS thread via a foreign call, then no events will be dispatched while it waits to check in teh backup way, because the Racket-level thread that pulses the main run loop will be blocked until the foreign call returns. Finally, if "osxvideosink.m" sets up its own run loop and hacks `isThread`, that would interact badly with `racket/gui` and could explain the crash. Does it help to wrap the `broadcast` call with (call-atomically-in-run-loop (lambda () ....)) using the implementation of `call-atomically-in-run-loop` below? ---------------------------------------- #lang racket/base (require racket/gui/base ffi/unsafe ffi/unsafe/objc ffi/unsafe/nsalloc) (provide call-atomically-in-run-loop) (import-class NSObject NSArray NSRunLoop) (define NSDefaultRunLoopMode (get-ffi-obj 'NSDefaultRunLoopMode #f _id)) (define-objc-class CallerContainer NSObject [proc] (-a _void (call) (proc))) (define (call-atomically-in-run-loop proc) (define result #f) (define s (make-semaphore)) (call-with-autorelease (lambda () (define obj (tell CallerContainer alloc)) (set-ivar! obj proc (lambda () (set! result (proc)) (semaphore-post s))) (tellv (tell NSRunLoop mainRunLoop) performSelector: #:type _SEL (selector call) target: obj argument: #f order: #:type _uint 0 modes: (tell (tell NSArray alloc) initWithObject: NSDefaultRunLoopMode)))) (yield s) result) ;; Example, gets a non-#f result: #; (call-atomically-in-run-loop (lambda () (tell (tell NSRunLoop mainRunLoop) currentMode))) -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.