I borrowed a patch from TigerVNC that should fix this. Please re-test with the 2.2.x pre-release build:
https://turbovnc.org/DeveloperInfo/PreReleases DRC On 1/10/20 10:01 AM, Marc Legendre wrote: > Hi there, > > I am struggling with an issue where a modifier key can become stuck in > a "pressed" state in the server, and be hard to un-stuck. This can > happen for > example if a VNC client fails to send some key up events (e.g. if it loses > focus), or if multiple users try to interact with the same session. > > I managed to isolate a case with a specific key combination involving > **shift**. > > Precisely, the following sequence of input events will put the server into > a state where the alt modifier is active (not sure if I'm phrasing this > correctly), and simply pressing an alt key (client-side) won't help: > > * 65505 down -- ShiftLeft > * 65513 down -- AltLeft > * 65505 up -- ShiftLeft > * 65513 down -- AltLeft > * 65513 up -- AltLeft > > > Furthermore, I noticed that: > > * if a VNC client sends only a "65505 down" event, the server reacts > by generating a "key 50 pressed" event > * if a VNC client sends only a "65513 down" event, the server reacts > by generating a "key 64 pressed" event > * if a VNC client sends a "65505 down" event, then a "65513 down" > event, the server reacts by generating a "key 50 pressed" event, then > a "key **125** pressed" event > > Which I believe is consistent with this bit of configuration described > by xmodmap: > > ``` > $ xmodmap -pke | grep Alt_L > keycode 64 = Alt_L Meta_L Alt_L Meta_L > keycode 125 = NoSymbol Alt_L NoSymbol Alt_L > ``` > > Upon further inspection with xev and XQueryKeymap(), here are some > more details of what happens when the sequence described aboved is sent : > > | VNC event | X event (xev) | resulting modifier state (xev) | keys > pressed, according to XQueryKeymap() | > | ---------- | ------------- | ------------------------------ | > ----------- | > | 65505 down | key 50 down | 0x1 | > 50 | > | 65513 down | key 125 down | 0x9 | 50, > 125 | > | 65505 up | key 50 up | 0x8 | > 125 | > | 65513 down | key 64 down | 0x8 | 64, > 125 | > | 65513 up | key 64 up | 0x8 | > 125 | > | 65513 up | nothing | 0x8 | > 125 | > > From there, key 125 is still pressed, and thus alt is stuck enabled. > (It can be unblocked with "shift+alt", but of course this is not > intuitive). > > * What would be the proper way to fix/avoid this ? Could it be just a > configuration fix? Any hint? > * Also, is there a trick I could use or abuse to workaround this kind > of issue? (Like, a trick to "up" all the keys?) > * Am I completely off track? > > Any help/hint will be appreciated, I am discovering quite a lot of > things here. > > -- > Marc Legendre > AnatoScope > > -- > You received this message because you are subscribed to the Google > Groups "TurboVNC User Discussion/Support" group. > To unsubscribe from this group and stop receiving emails from it, send > an email to [email protected] > <mailto:[email protected]>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/turbovnc-users/3161d02e-d10c-443d-a1e7-e9206349c5b8%40googlegroups.com > <https://groups.google.com/d/msgid/turbovnc-users/3161d02e-d10c-443d-a1e7-e9206349c5b8%40googlegroups.com?utm_medium=email&utm_source=footer>. -- You received this message because you are subscribed to the Google Groups "TurboVNC User Discussion/Support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/turbovnc-users/ea0ae933-5911-ab67-fd04-52b692736ead%40virtualgl.org.
