[Spice-devel] [PATCH linux/vd-agent 10/11] clipboard: only send release when no immediate grab

[Frediano Ziglio]

> 
> Hi
> 
> On Thu, Mar 28, 2019 at 5:30 PM Frediano Ziglio <fziglio at redhat.com> wrote:
> >
> > >
> > > From: Marc-André Lureau <marcandre.lureau at redhat.com>
> > >
> > > Do not send a release event between two grabs, this helps with window
> > > manager interaction issues on peer side.
> > >
> >
> > I would explain which kind of issue this is supposed to fix.
> 
> They react to clipboard events in different ways. The point is to
> minimize the amount of events to avoid extra unnecessary interactions.
> 
> In particular, on release event, some clipboard managers take the
> grab. This creates a race with Spice which does a release between
> grabs currently.
> 

As clipboard managers are not using SPICE I suppose here you
are talking about desktop clipboard release, not agent RELEASE
message. But on the previous sentence we were speaking about
agent RELEASE.

> >
> > > Advertise this behaviour via a capability introduced in spice-protocol
> > > 0.12.16, so the client doesn't need to do some time-based filtering.
> > >
> > > (the capability shouldn't need to be negotiated, a client shouldn't
> > > expect a release between two grabs)
> > >
> > > Signed-off-by: Marc-André Lureau <marcandre.lureau at redhat.com>
> >
> > I suppose Jakub/Victor could do a much better review/test than me.
> >
> > > ---
> > >  src/vdagent/clipboard.c | 12 ++++++------
> > >  src/vdagent/x11.c       |  7 +++----
> > >  src/vdagentd/vdagentd.c |  1 +
> > >  3 files changed, 10 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/src/vdagent/clipboard.c b/src/vdagent/clipboard.c
> > > index 9fb87e3..097c6ee 100644
> > > --- a/src/vdagent/clipboard.c
> > > +++ b/src/vdagent/clipboard.c
> > > @@ -242,13 +242,13 @@ static void clipboard_owner_change_cb(GtkClipboard
> > > *clipboard,
> > >          return;
> > >      }
> > >
> > > -    if (sel->owner == OWNER_GUEST) {
> > > -        clipboard_new_owner(c, sel_id, OWNER_NONE);
> > > -        udscs_write(c->conn, VDAGENTD_CLIPBOARD_RELEASE, sel_id, 0,
> > > NULL,
> > > 0);
> > > -    }
> > > -
> > > -    if (event->reason != GDK_OWNER_CHANGE_NEW_OWNER)
> > > +    if (event->reason != GDK_OWNER_CHANGE_NEW_OWNER) {
> > > +        if (sel->owner == OWNER_GUEST) {
> > > +            clipboard_new_owner(c, sel_id, OWNER_NONE);
> > > +            udscs_write(c->conn, VDAGENTD_CLIPBOARD_RELEASE, sel_id, 0,
> > > NULL, 0);
> > > +        }
> > >          return;
> > > +    }
> > >
> > >      /* if there's a pending request for clipboard targets, cancel it */
> > >      if (sel->last_targets_req)
> > > diff --git a/src/vdagent/x11.c b/src/vdagent/x11.c
> > > index c2515a8..9409b53 100644
> > > --- a/src/vdagent/x11.c
> > > +++ b/src/vdagent/x11.c
> > > @@ -530,11 +530,10 @@ static void vdagent_x11_handle_event(struct
> > > vdagent_x11
> > > *x11, XEvent event)
> > >          if (ev.xfev.owner == x11->selection_window)
> > >              return;
> > >
> > > -        /* If the clipboard owner is changed we no longer own it */
> >
> > Why not keeping this comment?
> 
> The comment is no longer valid with this change: if the clipboard
> owner is changed, the agent may still own the grab (at the protocol
> level).
> 

Yes, this prove what I was saying in the previous e-mail, you are
mixing desktop ownership and SPICE grab, if you consider from
desktop prospective (which is using owner definition like in
"ev.xfev.owner") the comment is still valid, but you are reading
it with different definitions so it became invalid.

> As you can see with the following line being removed:
> >
> > > -        vdagent_x11_set_clipboard_owner(x11, selection, owner_none);
> > > -
> > > -        if (ev.xfev.owner == None)
> > > +        if (ev.xfev.owner == None) {
> > > +            vdagent_x11_set_clipboard_owner(x11, selection, owner_none);
> > >              return;
> > > +        }
> > >
> > >          /* Request the supported targets from the new owner */
> > >          XConvertSelection(x11->display, ev.xfev.selection,
> > >          x11->targets_atom,
> > > diff --git a/src/vdagentd/vdagentd.c b/src/vdagentd/vdagentd.c
> > > index 72a3e13..683e5d3 100644
> > > --- a/src/vdagentd/vdagentd.c
> > > +++ b/src/vdagentd/vdagentd.c
> > > @@ -133,6 +133,7 @@ static void send_capabilities(struct
> > > vdagent_virtio_port
> > > *vport,
> > >      VD_AGENT_SET_CAPABILITY(caps->caps, VD_AGENT_CAP_MAX_CLIPBOARD);
> > >      VD_AGENT_SET_CAPABILITY(caps->caps, VD_AGENT_CAP_AUDIO_VOLUME_SYNC);
> > >      VD_AGENT_SET_CAPABILITY(caps->caps,
> > >      VD_AGENT_CAP_GRAPHICS_DEVICE_INFO);
> > > +    VD_AGENT_SET_CAPABILITY(caps->caps,
> > > VD_AGENT_CAP_CLIPBOARD_NO_RELEASE_ON_REGRAB);
> > >      virtio_msg_uint32_to_le((uint8_t *)caps, size, 0);
> > >
> > >      vdagent_virtio_port_write(vport, VDP_CLIENT_PORT,
> >