Add method for updating the buffer only

[christoph-heiss]

Hi,
I basically needed a way to update the framebuffer independently of input due to blocking and expense of updating the input state.

I had this branch laying around for some time now, I rebased & updated the changes so the branch can be merged, before it completely code-rots. Although very specialized, I'd like to get this upstream.

Tested only on Linux/X11, but all the code is basically a copy of update_with_buffer_stride with any input updates ripped out.

I'm open for suggestions and be willing to further work on this if needed in order to get this merged.

[nyovaya]

@christoph-heiss I think it might be senseful then to remove the update_buffer_with_stride function. So that we only have a function which updates input and one which updates the framebuffer(in the public API).

[emoon]

I agree with @nifker here. That would make it a bit cleaner

[christoph-heiss]

As suggested, I've removed the .update_buffer_with_stride() completely.
I then also renamed the remaining method to simply .update_buffer() to better represent the new API.

The second commit just adapts all examples to the new Window API.

As always, only tested on Linux/X11 and RFC'ing on this.

[nyovaya]

@christoph-heiss Seems fine to me. But Wayland is struggling a bit here - Ill take a look at it.

[nyovaya]

@christoph-heiss Ok we are using single files on Wayland for a framebuffer so it would be nice if you include a note for Wayland that "when the buffer is too often updated without using update() the application will crash because too many files have been opened".
I currently think of returning an error if there were more than 10 continuous buffer updates without any update() call.

[nyovaya]

I think there is no compositor which holds 20 framebuffers at the same time.
I would add this in line '1104' in 'wayland.rs':
"assert!(self.display.buf_pool.pool.len() < 20, "Leaking file descriptors");"

[christoph-heiss]

@nifker TBH, that sounds kind of like a hack to me. I'd be willing to work on a proper solution for this and can set me up a wayland-environment for this, I guess.

This sounds like the compositor needs to explicitly "consume" the frames in-flight we write out to the fd (don't really know the proper wayland-way words, never worked with it before), and this behaviour must be kind of hidden(?) somewhere in .update().

I'll see what I can do when I get around that, so the PR can stay open as-is for now.

[nyovaya]

Not sure if I can figure something better out, as calling update() will be mandatory anyway, so the developer just needs to make sure to call it once in a while.

[emoon]

Closing due to no progress, if this is still of interest we can re-open