eframe has features for selecting between x11 and wayland. eframe does
not forward the features to glutin. This makes glutin always compile
with both backends enabled. This change forwards the feature. This
allows users of egui to compile less dependencies when they only need
one of x11, wayland.
To understand this change, read the glutin Cargo.toml [1] and the glutin
build.rs [2]. You always have to enable glutin's glx feature with the
x11 feature. The other default features (egl, wgl) stay enabled. This is
intentional so that everything continues to work as before. We could
further minimize when egl and wgl are enabled, but that is not part of
this change. There is little reason to do so because those feature
already only add dependencies when you compile glutin for the right
platform (for example wgl on windows).
[1]
https://github.com/rust-windowing/glutin/blob/v0.32.1/glutin/Cargo.toml
[2]
https://github.com/rust-windowing/glutin/blob/v0.32.1/glutin/build.rs
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