[PATCH wayland v4] doc: start documenting Xwayland
ppaalanen at gmail.com
Mon Dec 18 10:45:48 UTC 2017
On Mon, 18 Dec 2017 11:17:22 +0100
Olivier Fourdan <fourdan at gmail.com> wrote:
> Hi Pekka,
> Sorry in advance for my (too) late comment... Just one thing I would have
> mentioned (see below).
> On 18 August 2017 at 15:29, Pekka Paalanen <ppaalanen at gmail.com> wrote:
> > From: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> > This is a rough intro to what Xwayland is and does, with just one
> > implementation detail so far (Window identification).
> > I paid no attention to formatting details, those can be polished in
> > follow-ups. I just want the prose out.
> > I also just quickly whacked up the diagram, would be happy to see
> > someone replace it with a nicer one. I just didn't have time to learn
> > dot for now.
> > v2:
> > - typo fix
> > - rephrase "talking to hardware" as "driving the displays"
> > - mention circular dependency in intro
> > - add section to explain rootless and rootful modes
> > - remove paragraph about Xwayland protocol usage
> > - move TBD part to the end under a new section header
> > v3:
> > - use "advantage" and "disadvantage" instead of "pro" and "con"
> > - slight rewording on rootful mode and rootless mode paragraphs
> > - removed the paragraph about the lack of shell and special Wayland
> > protocol extensions
> > - removed the commented out list of ideas to write
> > v4:
> > - typo fixes pointed out by Yong
> > Cc: Olivier Fourdan <ofourdan at redhat.com>
> > Cc: Jonas Ådahl <jadahl at gmail.com>
> > Cc: Daniel Stone <daniel at fooishbar.org>
> > Signed-off-by: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
> > ---
> > doc/publican/Makefile.am | 5 +-
> > doc/publican/sources/Wayland.xml | 1 +
> > doc/publican/sources/Xwayland.xml | 170
> > +++++++++++++++++++++
> > .../sources/images/xwayland-architecture.png | Bin 0 -> 7611 bytes
> > 4 files changed, 175 insertions(+), 1 deletion(-)
> > create mode 100644 doc/publican/sources/Xwayland.xml
> > create mode 100644 doc/publican/sources/images/xwayland-architecture.png
> > + <section id="sect-X11-Application-Support-xwm">
> > + <title>X Window Manager (XWM)</title>
> > + <para>
> > + From the X11 point of view, the X window manager (XWM) living
> > inside a
> > + Wayland compositor is just like any other window manager. The
> > difference
> > + is mostly in which process it resides in, and the few extra
> > conventions
> > + in the X11 protocol to support Wayland window management (WWM)
> > + specifically.
> > + </para>
> > + <para>
> > + There are two separate asynchronous communication channels between
> > + Xwayland and a Wayland compositor: one uses the Wayland protocol,
> > and the
> > + other one, solely for XWM, uses X11 protocol. This setting demands
> > great
> > + care from the XWM implementation to avoid (random) deadlocks with
> > + Xwayland. It is often nearly impossible to prove that synchronous or
> > + blocking X11 calls from XWM cannot cause a deadlock, and therefore
> > it is
> > + strongly recommended to make all X11 communications asynchronous.
> > All
> That is not possible using Xlib which waits for a reply (_XReply) for many
> things, so maybe it would be worth mentioning that xcb is better suited for
> (for example mutter is using Xlib and seems a lot more sensitive to such
> dead locks than weston which uses xcb)
sure, a patch is welcome. :-)
> + Wayland communications are already asynchonous by design.
> > + </para>
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