On Wed, 14 Mar 2018 06:41:53 -0400
Simon Ser <cont...@emersion.fr> wrote:

> On March 14, 2018 10:22 AM, Peter Hutterer <peter.hutte...@who-t.net> wrote:
> > sorry about the delay, but better late than too late ;)  
> 
> No problem, thanks for your review!
> 
> > On Sun, Mar 11, 2018 at 05:53:42PM -0400, Simon Ser wrote:  
> > > This adds a new protocol to negotiate server- and client-side rendering of
> > > window decorations for xdg-toplevels. This allows compositors that want
> > > to draw decorations themselves to send their preference to clients, and
> > > clients that prefer server-side decorations to request them.
> > > 
> > > This is inspired by a protocol from KDE [1] which has been implemented in
> > > KDE and Sway and was submitted for consideration in 2017 [2]. This patch
> > > provides an updated protocol with those concerns taken into account.
> > > 
> > > Signed-off-by: Simon Ser <cont...@emersion.fr>
> > > Reviewed-by: Drew DeVault <s...@cmpwn.com>
> > > Reviewed-by: David Edmundson <da...@davidedmundson.co.uk>
> > > Reviewed-by: Alan Griffiths <alan.griffi...@canonical.com>
> > > Reviewed-by: Tony Crisci <t...@dubstepdish.com>
> > > 
> > > [1] 
> > > https://github.com/KDE/kwayland/blob/master/src/client/protocols/server-decoration.xml
> > > [2] 
> > > https://lists.freedesktop.org/archives/wayland-devel/2017-October/035564.html
> > > ---
> > > 
> > > This was iterated on privately between representatives of Sway and wlroots
> > > (Simon Ser, Drew DeVault and Tony Crisci), KDE and Qt (David Edmundson),
> > > and Mir (Alan Griffiths).
> > > 
> > > A proof-of-concept of a client and server implementation is available at 
> > > [1].
> > > 
> > > Changes from v2 to v3: fix typos, clarify xdg_toplevel_decoration.destroy
> > > semantics, clarify that clients always need to support CSD and can receive
> > > configure events at any time.
> > > 
> > > [1] https://github.com/swaywm/wlroots/pull/638
> > > 
> > >  Makefile.am                                        |   1 +
> > >  unstable/xdg-toplevel-decoration/README            |   4 +
> > >  .../xdg-toplevel-decoration-unstable-v1.xml        | 132 
> > > +++++++++++++++++++++
> > >  3 files changed, 137 insertions(+)
> > >  create mode 100644 unstable/xdg-toplevel-decoration/README
> > >  create mode 100644 
> > > unstable/xdg-toplevel-decoration/xdg-toplevel-decoration-unstable-v1.xml
> > > 
> > > diff --git a/Makefile.am b/Makefile.am
> > > index 4b9a901..07744e9 100644
> > > --- a/Makefile.am
> > > +++ b/Makefile.am
> > > @@ -17,6 +17,7 @@ unstable_protocols =                                    
> > >                         \
> > >   
> > > unstable/keyboard-shortcuts-inhibit/keyboard-shortcuts-inhibit-unstable-v1.xml
> > >  \
> > >   unstable/xdg-output/xdg-output-unstable-v1.xml                          
> > > \
> > >   unstable/input-timestamps/input-timestamps-unstable-v1.xml      \
> > > + 
> > > unstable/xdg-toplevel-decoration/xdg-toplevel-decoration-unstable-v1.xml  
> > >       \
> > >   $(NULL)
> > >  
> > >  stable_protocols =                                                       
> > >         \
> > > diff --git a/unstable/xdg-toplevel-decoration/README 
> > > b/unstable/xdg-toplevel-decoration/README
> > > new file mode 100644
> > > index 0000000..e927110
> > > --- /dev/null
> > > +++ b/unstable/xdg-toplevel-decoration/README
> > > @@ -0,0 +1,4 @@
> > > +xdg_toplevel_decoration protocol
> > > +
> > > +Maintainers:
> > > +Simon Ser <cont...@emersion.fr>
> > > diff --git 
> > > a/unstable/xdg-toplevel-decoration/xdg-toplevel-decoration-unstable-v1.xml
> > >  
> > > b/unstable/xdg-toplevel-decoration/xdg-toplevel-decoration-unstable-v1.xml
> > > new file mode 100644
> > > index 0000000..a34cb73
> > > --- /dev/null
> > > +++ 
> > > b/unstable/xdg-toplevel-decoration/xdg-toplevel-decoration-unstable-v1.xml
> > > @@ -0,0 +1,132 @@
> > > +<?xml version="1.0" encoding="UTF-8"?>
> > > +<protocol name="xdg_toplevel_decoration_unstable_v1">
> > > +  <copyright>
> > > +    Copyright © 2018 Simon Ser
> > > +
> > > +    Permission is hereby granted, free of charge, to any person 
> > > obtaining a
> > > +    copy of this software and associated documentation files (the 
> > > "Software"),
> > > +    to deal in the Software without restriction, including without 
> > > limitation
> > > +    the rights to use, copy, modify, merge, publish, distribute, 
> > > sublicense,
> > > +    and/or sell copies of the Software, and to permit persons to whom the
> > > +    Software is furnished to do so, subject to the following conditions:
> > > +
> > > +    The above copyright notice and this permission notice (including the 
> > > next
> > > +    paragraph) shall be included in all copies or substantial portions 
> > > of the
> > > +    Software.
> > > +
> > > +    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
> > > EXPRESS OR
> > > +    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
> > > MERCHANTABILITY,
> > > +    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT 
> > > SHALL
> > > +    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 
> > > OTHER
> > > +    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 
> > > ARISING
> > > +    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
> > > +    DEALINGS IN THE SOFTWARE.
> > > +  </copyright>
> > > +
> > > +  <interface name="zxdg_toplevel_decoration_manager_v1" version="1">
> > > +    <description summary="window decoration manager">
> > > +      This interface permits choosing between client-side and server-side
> > > +      window decorations for a toplevel surface.
> > > +
> > > +      A window decoration is a user interface component used to move, 
> > > resize and
> > > +      change a window's state. It can be managed either by the client 
> > > (part of
> > > +      the surface) or by the server.
> > > +
> > > +      By advertising this interface the server announces support for 
> > > server-side
> > > +      window decorations. Note that even if the server supports 
> > > server-side
> > > +      window decorations, clients must still support client-side 
> > > decorations.
> > > +
> > > +      Warning! The protocol described in this file is experimental and
> > > +      backward incompatible changes may be made. Backward compatible 
> > > changes
> > > +      may be added together with the corresponding interface version 
> > > bump.
> > > +      Backward incompatible changes are done by bumping the version 
> > > number in
> > > +      the protocol and interface names and resetting the interface 
> > > version.
> > > +      Once the protocol is to be declared stable, the 'z' prefix and the
> > > +      version number in the protocol and interface names are removed and 
> > > the
> > > +      interface version number is reset.
> > > +    </description>
> > > +
> > > +    <enum name="error">
> > > +      <entry name="unconfigured_buffer" value="1"/>
> > > +      <entry name="already_constructed" value="2"/>
> > > +    </enum>
> > > +
> > > +    <request name="destroy" type="destructor">
> > > +      <description summary="destroy the decoration manager object">
> > > +        Destroy the decoration manager.
> > > +      </description>
> > > +    </request>
> > > +
> > > +    <request name="get_decoration">
> > > +      <description summary="create a new decoration object">
> > > +        Create a new decoration object associated with the given 
> > > toplevel.
> > > +
> > > +        Creating an xdg_toplevel_decoration from an xdg_toplevel which 
> > > has a
> > > +        buffer attached or committed is a client error, and any attempts 
> > > by a
> > > +        client to attach or manipulate a buffer prior to the first
> > > +        xdg_toplevel_decoration.configure call must also be treated as
> > > +        errors.  
> > 
> > I'm missing a comment that describes what happens if the xdg_toplevel is
> > destroyed. There is some object dependency here that needs to be stated. Do
> > we need an event here? Or are we assuming that clients are smart enough to
> > keep track of destroy events. Either way - needs to be explicitly stated.  
> 
> What about requiring clients to destroy the zxdg_toplevel_decoration_v1 before
> the xdg_toplevel?

Hi,

you can, but then you need an error code for clients that get it wrong.

A common convention is to instead say that zxdg_toplevel_decoration_v1
becomes "inert" when the associated xdg_toplevel is destroyed. It means
the object will not send any events, and all requests except destroy
will be ignored. This approach is often used with racy cases where
requiring a single order of actions is not possible, and it comes with
the disadvantage of needing to define what happens if you pass an inert
object of this type as an argument in some other interface, or if the
inert object had requests that create more objects.

Both ways are possible. You may want to check how xdg_toplevel deals
with xdg_surface destruction and how xdg_surface deals with wl_surface
destruction. Maybe consistency would be the best plan?


Thanks,
pq

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