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

[Carlos Garnacho]

Hi Pekka,

On Thu, Jan 17, 2019 at 10:04 AM Pekka Paalanen <ppaalanen at gmail.com> wrote:
>
> On Thu, 17 Jan 2019 09:47:05 +0100
> Olivier Fourdan <ofourdan at redhat.com> wrote:
>
> > Hi,
> >
> > On Thu, Jan 17, 2019 at 9:23 AM Pekka Paalanen <ppaalanen at gmail.com> wrote:
> > >
> > For xrdb specifically, actually, the X11 resources are stored in a
> > couple of properties on the root window ("RESOURCE_MANAGER" and
> > "SCREEN_RESOURCES") so Xwayland /could/ set those on init, it's more
> > the whole logic of merging resources from different files, optionally
> > invoking a C preprocessor, etc. that would be painful in Xwayland
> > IMHO.
> >
> > So if there was a way to (re)use xrdb to send the resources string to
> > stdout instead of setting the property itself, Xwayland could possibly
> > get values to set the properties and do that on startup before any X11
> > client had a chance to connect.
> >
> > Maybe that would be simplereasier than having side-channels or
> > interlocking in place at startup?
>
> Hi Olivier,
>
> maybe, but that is again a solution to just one specific issue, while I
> believe there is a whole category of issues like this. The XWM init is
> another.
>
> If someone starts a X11 window manager as the very first X11 client,
> could that break the whole Wayland compositor's XWM thing completely?
> Do we want to protect against that?

In this concrete case, the compositor might also shot Xwayland down if
it fails to acquire the WM selection.

>
> Is it worth to solve the whole category at once? I don't know.

Maybe belonging in the category is Xsettings management, esp. those
that affect UI. It might be visually jarring if the client gets to
display with different theme/icons than the ones it'll eventually get.
Again not sure how much of a practical problem this is, accounting
that toolkits should be good about wayland support, and the outliers
are probably not concerned about Xsettings.

Anyhow, saying "what a compositor may want to run before launching a
x11 client is compositor-dependent" doesn't help give any shape to the
issue :).

Cheers,
  Carlos

>
>
> Thanks,
> pq