Re: [gtk-vnc-devel] PATCH: sticky modifier keys

[Anthony Liguori <anthony codemonkey ws>]

Daniel P. Berrange wrote:
> On Mon, Jul 09, 2007 at 09:11:12AM -0500, Anthony Liguori wrote:
>   
> > Daniel P. Berrange wrote:
> >     
> > > Even with the use of a keyboard grab, there are certain key combinations
> > > that are completely ungrabbable using regular GTK / X libraries. The prime
> > > examples are  Ctrl-Alt-Backspace, and  Ctrl+Alt+Fn.  This isn't a problem
> > > for traditional VNC servers, but when talking to a virtualed guest OS, then
> > > you do need a way to send these combos to the guest OS.
> > >
> > > This patch adds the 'sticky modifiers' concept currently used in 
> > > virt-manager
> > > Basically, if a Ctrl or Alt key is pressed 3 times in a row, then it is
> > > treated as sticky until the next non-modifier key is released. This allows
> > > you to type  'Ctrl Ctrl Ctrl Alt+F1'  to send 'Ctrl+Alt+F1' to the guest.
> > > This is off by default.
> > >  
> > >       
> > Hrm, I don't like this very much.  I'd prefer a sendkey like abstraction 
> > and then virt-manager could implement "stick modifiers" if it was desired.
> >     
>
> How about a method taking
>
>     vnc_display_send_key(VncDisplay *vnc, int *keysyms);
>
> Where keysyms is a NULL terminated array of GTK keysym codes. Or could
> explicitly have a count
>
>     vnc_display_send_key(VncDisplay *vnc, int *keysyms, int nkeysyms);
>
> In either case, if there was > 1 keysym listed, it would send all the
> key down events, and then all the key up events. This would let you 
> send  Ctrl+Alt+Del in single call, rather than having have another
> up/down parameter to vnc_display_send_key method.
>
>
>  eg
>
>    int cad[] = { GDK_Control_L, GDK_Alt_L, GDK_Delete, 0 }
>    vnc_display_send_key(vnc, cad);
>
> Or
>
>    int cad[] = { GDK_Control_L, GDK_Alt_L, GDK_Delete }
>    vnc_display_send_key(vnc, cad, sizeof(cad)/sizeof(cad[0]));
>   

I prefer this syntax personally.  0 might be a valid key after all.

Regards,

Anthony Liguori

> > I think a much more common way of addressing this problem will be to 
> > have a menu entry allowing certain combinations to be sent.  The big 
> > usability problem with sticky modifiers is that if a user mistypes, 
> > something really bad could happen (like restarting X).
> >     
>
> I think ultimately, both a menu full of special keys & sticky keys
> are both ugly hacks. The ultimate is to be able to grab the keyboard
> and be able to enter all possible key strokes.
>
> One of the desktop / X guys  at Red Hat suggested I might want to also
> try out using  XKB apis which would let us block the special Ctrl-Alt+Fn
> and Ctrl-Alt-Backspace/Del  sequences from the local host too, while in
> a keygrab scenario. In the mean time, the send_key thing should be 
> sufficient. 
>
> Dan.
>