Re: Displaying live video -- how to notify main loop from another thread?

[Marek Peca]

Hello,

> For playing video, Eric wrote a simple view a while ago that used an 
> NSOpenGLView, so bypassed the entire GNUstep drawing stack and gave good 
> performance, so you might consider this approach.  This also has the 
> advantage that the image stays in VRAM as a texture once the camera has 
> captured it, so redraws are very cheap.

thanks for the info, I'll look at it. However, I would like to not include 
a dependence on OpenGL, while all the application is strictly 2D... (yes, 
I know, that accelerated 2D video is often done these days using OpenGL, 
but I am unsure, whether this is the right way).

> You can receive notification of data available on a file descriptor by 
> wrapping it in an NSFileHandle and then calling a method like 
> -waitForDataInBackgroundAndNotify.  This will post a notification when 
> there is data available for drawing.

Great, so this is something like that XtAppAddInput, right?

> -setNeedsDisplay: also ought to work.  I think this is a bug in GNUstep
> - this ought to wake up the main thread if it is sleeping and trigger a 
> redraw.

It seemed to me, because there is a statement, that this message is 
thread-safe in contrast to lots of other GNUstep GUI calls. Is the bug 
tracked somewhere? Can I help?

>  If it doesn't, you can poke the main thread with 
> -performSelectorInMainThread:

As Tom did said, thanks for the confirmation. I wonder, whether it is OK 
to work with pthreads, or if it may break the things.


Best regards,
Marek