Servers could send arbitrary metadata with each frame

[rsodre]

Information could be shared between applications thru the stablished Syphon connection.
Using a NSDictionary would leave the server and client open to share anything.
As an example, render time, document name, color correction, name of a complementary Syphon texture.

[bangnoise]

We have thought about this.

The main obstacle is that (by design) there is no concept of frames as individual entities, just a single surface with changing content. There is no way to tie metadata to a single frame because the content can change at any time. This might still be useful for less transient information.

[maybites]

to continue the discussion from #82:

This is what spout says about its own implementation: frameBufferSharing

But I understand now it might be tricky to implement it in a water thight manner.

[bangnoise]

@maybites we specifically don't want to block server and client processes in the way Spout does.

[vade]

To chime in, I think this can be revisited if we decide to tackle internally pooling IOSurfaces, which would allow us to vend unique surfaces per frame (though they would have re-used addresses), and potentially associate user low cost user data dictionary along with it. I dont want to promise anything we can't deliver, but its worth mentioning.

[vade]

for reference :

/* These calls let you attach property list types to a IOSurface buffer.  These calls are 
   expensive (they essentially must serialize the data into the kernel) and thus should be avoided whenever
   possible.   Note:  These functions can not be used to change the underlying surface properties. */
- (void)setAttachment:(id)anObject forKey:(NSString *)key;
- (nullable id)attachmentForKey:(NSString *)key;
- (void)removeAttachmentForKey:(NSString *)key;
- (void)setAllAttachments:(NSDictionary<NSString *, id> *)dict;
- (nullable NSDictionary<NSString *, id> *)allAttachments;
- (void)removeAllAttachments;

[maybites]

@bangnoise

we specifically don't want to block server and client processes in the way Spout does.

Oh, I get that. I wouldn't advocate it, I just added that link for reference.

But I am glad to hear you considering this feature seriously and see the potential benefit of it. A low cost user data dictionary would be the way to go. Thats what I am doing with spout, serialized to and from a byte buffer.