unsure how to use UI::queue_main with multiple threads

[Treeki]

Hey there,

I'm experimenting with iui as a new Rust programmer and I'm unsure whether I've hit upon a design issue with UI::queue_main, or if there's a solution I've just missed, as this method isn't used in any of the examples.

According to the iui documentation, UI::queue_main will queue a function to execute on the GUI thread - I assume this is the thread that called UI::init().

libui explicitly states you can call uiQueueMain from any thread, but I can't figure out how to do this with iui; it requires a UI instance which I cannot obtain in non-GUI threads as UI is neither Send nor Sync.

Is there a way to do this, or is this a bug/design flaw? Any advice would be appreciated!

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For reference - I'm trying to offload ongoing USB device I/O using hidapi-rs onto a background thread and have it notify the GUI thread when data comes in or when the device is connected/disconnected.

The only method I can figure out for doing this is to have the GUI create a channel where the Sender is moved into the background thread and Reciever::try_recv is called regularly on a timer, but this feels inelegant to me and I'd much rather be able to have the background thread notify the GUI through libui's queuing mechanism so that it can update immediately.

[NoraCodes]

libui explicitly states you can call uiQueueMain from any thread

This is problem on our side, then, for sure. I think an API whereby we hand out a queuing token which is Send from UI and then provide queue_main on that token is the way to go here.

[quickdudley]

queue_main doesn't actually use the self argument.

[quickdudley]

I have a branch at https://github.com/quickdudley/libui-rs/tree/55-async-queue-main which might address this; but I'm still figuring out how to test it. Will submit a pull request if I can do so.