FW: xrandr and xwayland

[Daniel Stone]

Hi David,

On Thu, 5 Aug 2021 at 22:17, David Deyo <ddeyo at tireprofiles.com> wrote:
> > Sounds like you're missing wl_display_flush() in your client code, so the requests don't make it to the socket buffer until they're forced to because it's filled up.
>
> That did it.  You guys are awesome.  I don’t suppose there’s a Weston doc somewhere that would have told me that, had I looked.

It's a little bit buried, but this is the best explanation of how to
integrate Wayland into an event loop, as you would with a toolkit:
  https://wayland.freedesktop.org/docs/html/apb.html#Client-classwl__display_1a40039c1169b153269a3dc0796a54ddb0

If you scroll up to the main wl_display section, it explains how event
queues are used as well.

Broadly speaking, the advice is to:
- when active, process your events and send any requests
- immediately before you go into a passive state (waiting for events,
sleeping, etc), flush the display so your requests get delivered
- run the prepare_read_queue() / dispatch_queue_pending() loop
immediately before sleeping, in order to make sure you get all events
queued for you, then flush again in case you've queued any requests
from your event handlers
- poll on the Wayland display FD as well as any other activity sources
(other event queues, timers, etc)
- when you wake up, dispatch your Wayland event queue as well as other
relevant event sources

> > Also, my taskbar is the wrong length and my background is black.  Other than that, pretty cool.
>
> Yep, desktop-shell isn't designed to handle runtime rotation. It could be made to pretty easily by working on the client code. For your case though I'd assume something like kiosk-shell would be a much better bet.

kiosk-shell is something we have in newer versions of Weston which
sounds like it would work well for your usecases - it's designed to
just run a single application fullscreen. You might want to check out
what we have in git, which will be released as 10.0 in a few weeks'
time.

The rotation patches never got merged because we had some issues with
the IIO integration in particular, but having runtime rotation tests
sure would be nice, and kiosk-shell should at least be a lot easier to
fix than desktop-shell, if it does even need any fixes.

Cheers,
Daniel