Xwayland on demand (Re: [PATCH xwayland 3/3] xwayland: Handle the case of windows being realized before redirection)

[Pekka Paalanen]

On Wed, 16 Jan 2019 14:05:01 -0500
Adam Jackson <ajax at nwnk.net> wrote:

> On Wed, 2019-01-16 at 11:52 +0200, Pekka Paalanen wrote:
> 
> > What I think we would need is a way to launch Xwayland, but ensure it
> > does not process the real X11 apps until all the preparations (xrdb,
> > XWM init, etc.) have finished. What the preparations are exactly, only
> > the Wayland compositor (the desktop) will know.  
> 
> Who's launching this first X11 app, and why are they unable to defer
> launching it until the Xwayland is prepared? There's quite a few ways
> we could add this kind of interlock to setup, I just want to clarify
> which problem we're solving first.

Hi Adam,

any user action could be starting the very first real X11 app:
- user clicking a launcher icon on the desktop, e.g. for a game
- user issuing a command in a shell in a terminal window
- a Wayland app launching another app that just happens to be an X11 app

In the current setup of on-demand Xwayland, the Wayland compositor will
be listening on the X11 DISPLAY socket. When the Wayland compositor
sees the first X11 client attempting to connect, it will launch
Xwayland process and passes the listening socket to it.

IOW, the real X11 apps exists and attempts to connect first, which then
leads to spawning the Xwayland server. That can of course be changed if
there are better ideas. The main point of on-demand launching is that
Xwayland doesn't get started at the same time with the rest of the
desktop environment, unless there really is a X11 app to be ran.


Thanks,
pq
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