On Mon, 18 Dec 2017 11:17:22 +0100 Olivier Fourdan <four...@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 <ppaala...@gmail.com> wrote: > > > From: Pekka Paalanen <pekka.paala...@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 <ofour...@redhat.com> > > Cc: Jonas Ådahl <jad...@gmail.com> > > Cc: Daniel Stone <dan...@fooishbar.org> > > Signed-off-by: Pekka Paalanen <pekka.paala...@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 > this? > > (for example mutter is using Xlib and seems a lot more sensitive to such > dead locks than weston which uses xcb) Hi Olivier, sure, a patch is welcome. :-) > + Wayland communications are already asynchonous by design. > > + </para> Thanks, pq
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