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Mon, 11 May 2020 17:19:33 +0000 (UTC) Date: Mon, 11 May 2020 18:19:30 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: B3r3n Subject: Re: Qemu, VNC and non-US keymaps Message-ID: <20200511171930.GS1135885@redhat.com> References: <20200511151155.GO1135885@redhat.com> <20200511152957.6CFA8D1826@zmta04.collab.prod.int.phx2.redhat.com> MIME-Version: 1.0 In-Reply-To: <20200511152957.6CFA8D1826@zmta04.collab.prod.int.phx2.redhat.com> User-Agent: Mutt/1.13.4 (2020-02-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/11 03:10:56 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Spam_score_int: -10 X-Spam_score: -1.1 X-Spam_bar: - X-Spam_report: (-1.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FROM_EXCESS_BASE64=0.979, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-discuss@nongnu.org, Philippe =?utf-8?Q?Mathieu-Daud=C3=83=C2=A9?= , qemu-devel , Gerd Hoffmann Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, May 11, 2020 at 05:29:48PM +0200, B3r3n wrote: > Hello Daniel, > > > There is no mention here of what VNC client program is being used, which > > is quite important, as key handling is a big mess in VNC. > I tested with TightVNC & noVNC through Apache. Both behaves the same. I did > not tested Ultr@VNC. AFAIK, neithe TightVNC nor Ultra@VNC support the scancode extension. noVNC does, for most modern browsers, so it might work if you remove the -k arg from QEMU. > > The default VNC protocol passes X11 keysyms over the wire. > > > > The remote desktop gets hardware scancodes and turns them into keysyms, > > which the VNC client sees. The VNC client passes them to the VNC server > > in QEMU, which then has to turn them back into hardware scancodes. This > > reverse mapping relies on knowledge of the keyboard mapping, and is what > > the "-k fr" argument tells QEMU. > > > > For this to work at all, the keymap used by the remote desktop must > > match the keymap used by QEMU, which must match the keymap used by > > the guest OS. Even this is not sufficient though, because the act > > of translating hardware scancodes into keysyms is *lossy*. There is > > no way to reliably go back to hardware scancodes, which is precisely > > what QEMU tries to do - some reverse mappings will be ambiguous. > Yes, I saw that topic passing by. Looks messy with all these interferences... > > > Due to this mess, years ago (over a decade) QEMU introduced a VNC > > protocol extension that allows for passing hardware scancodes over > > the wire. > I guess I also crossed something about this on Internet. > Are you talking of the RFB protocol ? Yes, RFB protocol is the technical name for the VNC wire protocol. > > With this extension, the VNC client gets the hardware scancode > > from the remote desktop, and passes it straight to the VNC server, > > which passes it straight to the guest OS, which then applies the > > localized keyboard mapping. This is good because the localized > > keyboard mapping conversion is now only done once, in the guest > > OS. > > > > To make use of this protocol extension to VNC, you must *NOT* > > pass any "-k" arg to QEMU, and must use a VNC client that has > > support for this protocol extension. The GTK-VNC widget supports > > this and is used by virt-viewer, remote-viewer, virt-manager, > > GNOME Boxes, Vinagre client applications. The TigerVNC client > > also supports this extension. > So if I read you, if the client "enforce" this protocol (supposed RFB), Qemu > will automatically uses it as well ? The client should automatically activate the extension if QEMU advertizes it, and QEMU advertizes it if you remove the -k arg. > Removing -k option is great to me if it works, since user will have its own > mapping and these are international :-) > > To summarize, my recommendation is to remove the "-k" arg entirely, > > and pick a VNC client that supports the scancode extension. > For now I am using TightVNC & noVNC. noVNC is precious since it widens the > user world, removing any client software constraint. As above, noVNC ought to support the extension. > > > It is possible there might be a genuine bug in QEMU's 'fr' keymap > > that can be fixed to deal with AltGr problems. Personally though I > > don't spend time investigating these problems, as the broad reverse > > keymapping problem is unfixable. The only sensible option is to take > > the route of using the VNC hardware scancode extension. It is notable > > that SPICE learnt from VNC's mistake and used hardware scancodes from > > the very start. > > This was another path I intend to follow : using SPICE and a "noSPICE" > client if VNC was too painful. > If I understand you, using SPICE could also solve the issue ? > > Many thanks for your inputs... Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|