Make it possible to build examples with just X11 / just Wayland

[madsmtm]

No description provided.

[madsmtm]

Winit is a dev-dependency, so even though we add it to top-level features table here, it will be ignored in downstream applications.

[MarijnS95]

A more informative description PR description at all would have been nice. We already "supported" building with just the X11/Wayland features, but that (for examples / dev-dependencies) accidentally used to pull in the entire dependency stack via winit which you now tidied up. Did that cause any compile-time issues? Or just runtime issues when winit defaults to a Wayland connection while softbuffer only had the X11 backend enabled and "vice-versa"?

[madsmtm]

A more informative description PR description at all would have been nice.

Sorry, I thought the title was descriptive enough (and that it was a mostly inconsequential change anyhow).

We already "supported" building with just the X11/Wayland features, but that (for examples / dev-dependencies) accidentally used to pull in the entire dependency stack via winit which you now tidied up. Did that cause any compile-time issues? Or just runtime issues when winit defaults to a Wayland connection while softbuffer only had the X11 backend enabled and "vice-versa"?

With default features enabled for Winit, it defaults to Wayland, which means it provides a WaylandDisplayHandle/WaylandWindowHandle to Softbuffer, which, when Softbuffer is compiled without support for Wayland, panics.

I know that you can use WAYLAND_DISPLAY or DISPLAY or smth to make Winit use the X11 backend in that case, but it was sometimes a bit annoying for my setup (and I also haven't read up on what I actually need to set those values to to force X11).

[MarijnS95]

With default features enabled for Winit, it defaults to Wayland, which means it provides a WaylandDisplayHandle/WaylandWindowHandle to Softbuffer, which, when Softbuffer is compiled without support for Wayland, panics.

Yeah, exactly. That's the context I guessed from the changes, but this situation didn't immediately become clear from the title and missing description.

Indeed I meant that building softbuffer with a specific backend (before this fix) also had to be started/controlled with those environment variables to ensure winit uses a matching backend too.