Add a way to retrieve the EGL display

[ceyusa]

to say EGLDisplay or XDisplay

[jdm]

@francesca64 Are you the right person to review these changes?

[jdm]

Note: this is addressing #1078.

[francesca64]

@jdm I'm the right person, but there are currently a few other things I need to review, so it can be hard to find time.

@ceyusa thanks for the PR!

Window::native_display follows the style of the platform_display and platform_window methods that were deprecated in glutin/winit a while ago, and were recently removed. The convention we've moved to is using WindowExt methods per-platform, each with their own documentation and descriptive name (native_display isn't really an acceptable name, simply because it's so similar to the name of a method that was recently removed).

I'm also not a fan of having external types exposed, since it means that dependency upgrades could be breaking changes. We use void pointers (*mut std::os::raw::c_void) to get around this issue (see #939 for discussion).

Having macOS and iOS return 0 isn't idiomatic, and is very surprising/dangerous. My recommendation is to just create WindowExt methods (probably get_egl_display) for the platforms that can have an EGLDisplay. You can use an Option, and document on Windows that None indicates WGL, and on X11 that None indicates GLX (in which case, the XDisplay can be retrieved via WindowExt::get_xlib_display; also including a note that Wayland always uses EGL).

[ceyusa]

Thanks a lot for the review! :)

My recommendation is to just create WindowExt methods (probably get_egl_display) for the platforms that can have an EGLDisplay.

If I understand correctly, this method should be in in winit, not int glutin. Do I understand correctly?

[ceyusa]

Do I understand correctly?

Nope. I did not :) there's no EGL code in winit...

[ceyusa]

Sorry, I'm lost. I'm staring at the code and the only way that I see is creating a GlContextExt trait with the get_egl_display() method, implemented by the platform's GlContext.

Otherwise, I should add the method in winit's trait and implement them in glutin, which looks odd to me.

[francesca64]

Right, sorry. I think GlContextExt makes sense for this.

[ceyusa]

\o/ all checks passed

@francesca64 whenever you can :)

[francesca64]

Sorry for the delay! This looks good to me, but it would be great if you could add a CHANGELOG entry. Then we'll be good to merge.

[ceyusa]

Sorry for the delay! This looks good to me, but it would be great if you could add a CHANGELOG entry. Then we'll be good to merge.

Done :)