concerns over wayland and need for wayland app display to X Server

[David Jackson]

When I initially heard of Wayland, my reaction was of great concern, for I
was concerned that this could affect my network transparency use and my
desire to have multiple desktop sessions on the same computer with a mix of
local and remote apps displayed to them.

If wayland can provide assurance of two critical features, the ability to
on a runtime, per process basis select via a command line switch to display
a Wayland native application to a local or remote X server, and the already
planned feature to allow X applications to be displayed to Wayland, my
concerns will be alleviated and I will have no concern over Wayland. The
first feature of wayland app to X protocol may be able to be implemented by
some glue code from wayland client API to xlib to send graphical data from
the wayland native application onto an X server over X protocol.

This feature is vitally important to me.

Wayland should take it upon itself to gaurantee that this is possible and
provide a standard mechanism to make it possible, perhaps a set of Wayland
client side drivers can be made which would then send the graphics to a
regular X server, and the driver could be selected at runtime on a per
process basis. We should not count on widget or application developers to
have to explicitely implement this feature but should be gauranteed by
wayland itself, the reason is there are some shoddy developers who may not
expicitely include such a feature, but it is important to make sure that
all applications can be run on one computer and displayed to another,
displayed to an X server, or that an application can be displayed to one of
many local display server sessions, including local X servers such as
Xvnc.  This should not be a problem as the driver for either display to X
or display to wayland target could be linked at runtime perhaps (dynamic
link).

With the likelyhood that there could be many wayland apps which are native
eventually and to avoid having to have two copies of each application
installed, the above is a sensible and reasonable idea that would actually
greatly assure the flexibility of wayland since dynamic linking or some
other type of runtime client output driver loading would assure that the
wayland system is flexible and that other kinds of output drivers could
also be developed and added to a system without having to recompile any
applications. This gives the system flexibility and modularity that can
give it much more power.

We have many computers which are legacy and have only X servers and it
would be greatly beneficial that there will be a guarantee that future
Native wayland apps can be displayed to it on a per app basis, such as
through this idea that there could be a client side wayland driver that
will send the graphics onto an X server over X protocol and that this
driver can be selected at run time with a simple command line argument.

The driver would probably be glue code between the wayland client API and
the xlib API. This would allow a feature that would be critical to us to
allow a single wayland app to be displayed to a X server, this would also
give us network transparency as well as full backwards and forwards
compatibility.

The fact we have a network transparent desktop environment where apps are
not tied to a single display and one can run multiple instance of an app on
the same computer displaying to multiple display servers running on local
machine and on remote machines has been one of the great strengths of
Linux. The ability as well to create many headless X sessions which can
then be accessed as needed by VNC clients (Xvnc. Xnest, Xvfb+x11vnc) is
also of great value.

The ability to display a native wayland app to an X server would basically
assure these possibilities are available and that I will be able to
continue to route my applications as needed to remote displays on other
machines, would assure backward and forward compatibility, and give us full
network transparency on the per application level, and allow for multiple
local X desktop sessions to be able to remain a possibility whilst using
native wayland applications displaying to the X servers.
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