Lifetime of `Context`

[daxpedda]

I know this is not released yet, but after #64 Context and Surface were split.

How long is Context supposed to be kept alive? Does it need to stay alive as long as Surface, or can it be safely dropped while Surface is kept around and used?

[ids1024]

Anything from the Context that's still needed is reference counted, so the Context struct can be dropped.

Though the underlying RawDisplayHandle and RawWindowHandle must remain valid for the lifetime of the Surface, or its undefined behavior.

[daxpedda]

Thanks!

[kpreid]

I'd like to propose reopening this issue, as this could be specified more clearly in the documentation for everyone to see. The current safety documentation for Surface::new says:

Ensure that the provided objects are valid to draw a 2D buffer to, and are valid for the lifetime of the Context

which could be interpreted as anything from @daxpedda's “stay alive as long as Surface” to the perverse “it doesn't matter if the handle stops being valid while you're still using the Surface, as long as you drop the Context first so its 'lifetime' has ended”. (And “the lifetime of” isn't probably what you mean either, since the lifetime of the &W reference will most likely end before the surface is done.)

(I also wish "the provided objects are valid to draw a 2D buffer to" was phrased as something that the author of a cross-platform program finds actionable — what documentation should they read to know what it means? But that's not this issue.)

This is a little nitpicky, but I think that it's important to help users writing unsafe code by making it easy to understand what requirements they must uphold — or many of them will just give up and proceed sloppily.

[notgull]

This is now fixed as of #132