How bad if I don't offer a surface when creating a device?

[psionic12]

Hi,
For some reason, I want to create a device before any window exists. In order to do this, I have to write like this:

        let adapter = instance.request_adapter(
            &wgpu::RequestAdapterOptions {
                power_preference: wgpu::PowerPreference::HighPerformance,
                compatible_surface: None,
            },

It works just fine on my machine, windows created later do rendering images, though I didn't test the code thoroughly. I wondered how bad is that to set compatible_surface: None?

And if it is bad, is it a good idea to create a window that doing nothing (even not showing), just for creating a device?

[kvark]

The surface provided there isn't required by the adapter/device. The relationship is separate: if you have a surface that you want to present on, you'd specify it here in order to guarantee that you can present on this surface. Without it provided at adapter creation, there is easily a situation where the surface can't be presented on some of the machines.

[psionic12]

Sound harmless to me since I'm creating a queue just for transferring, right?
I did this in vulkan, except that I will explicitly finding a transfer queue family, while I didn't find the related API in wgpu.

[cwfitzgerald]

Correct, if you're not rendering to a surface, you don't need to worry about that.

As for multiple queue, we don't currently support it, so you can use the primary queue for everything.

[psionic12]

That would be nice if multiple queues feature is support. It would improve the performance of wgpu on some high-end graphic cards.

[cwfitzgerald]

It's definitely on our radar (there's an issue open for it) but it's going to require a massive amount of work to get right.