Migration guide?

[Kristian Høgsberg]

On Sun, May 6, 2012 at 4:30 PM, Gregory Merchan
<gregory.merchan at gmail.com> wrote:
> Hi,
>
> I looking for a migration guide from X11 to Wayland. Most of my Google
> search results are real estate listings for properties with windows in
> Wayland, MA.
>
> I have just a few things I hope someone will help me with:
>
> 1. The X property mechanism was generic, so we could have ICCCM, MWM,
> EWMH, etc. properties without changing the X server. Will Wayland also
> have such a generic mechanism?

No, the generic mechanism was there to let the X server act as a
middle man between  applications and window managers.  In wayland the
server is the window manager and has to understand all requests
instead of just passing them through.  So anything that ICCCM, EWMH
would standardize through properties and selections, we'll just define
wayland interfaces for.  I cases where one client really wants to talk
to another client, the server has to mediate.  For example, copy and
paste or drag and drag are at the core client-to-client communication,
and in these cases work by the source client telling the server what
it offers, and then server then announcing that to potential target
clients.

> 2. Was the work requested in this message ever done?
> http://lists.freedesktop.org/archives/wayland-devel/2010-November/000270.html
> . (I could work on this maybe later this month, if it's not done.)

A lot of that is done, copy and paste, drag and drop and most of the
window types.  One missing piece for desktop type environments is a
mechanism to let toolkits position popup menus intelligently, without
knowing their absolute position.

> 3. X11 famously abided by the rule of determining "mechanism, not
> policy". Is there a similar rule for Wayland?

To some extent. There's the core part of the protocol that concerns
surfaces and their content, input events and the outputs.  That's all
fairly generic and the more policy-like functionality is in wl_shell,
which is "EWMH for Wayland".  That said, X was policy free largely
because it had to be.  There were no shared libraries or loadable
modules to allow for easily reusing the core parts of X or loading a
WM module into it.  There was only one X server, policy had to be
out-of-process and the protocol grew a lot of ugly corner cases and
special purpose requests to support this.  Is there a particular
reason you're asking?

> 4. I'm concerned about the implications of this message:
> http://lists.freedesktop.org/archives/wayland-devel/2012-January/001845.html
> . It looks like policy was being written into Wayland, but maybe that
> discussion was about Weston?

Click to focus is just a weston thing if that's what you're concerned
about.  The policy/mechanism line isn't as black and white as it
sounds - what specifically are you thinking of?

Kristian