Re: [Xen-devel] [PATCH] Paravirt framebuffer backend tools [2/5]

[Steven Smith <sos22-xen@xxxxxxxxxxxxx>]

> The backend gets keys in an encoding that depends on the software used
> to access the keyboard:
...
> The frontend needs to stuff Linux keycodes into the input layer.
> 
> Our job is to translate from frontend keysyms to Linux keycodes, and
> the question is to find out how and where.
I think you mean backend keysyms, but, yes, that's the basic issue.

> Translating SDL_keysym.scancode into Linux keycode should be
> straightforward, but translating X11 keysyms isn't.  Steven mentioned
> code in rdesktop that does that, and Anthony pointed to QEMU.
> 
> It would be nice to encapsulate all knowledge about frontend keysyms
> in the frontends, i.e. to translate to a common wire encoding there.
> Any reason why that's not the way to go?  Any reason why the wire
> encoding can't (or shouldn't) be simply Linux keycodes?
The main objection to sending Linux keycodes over the wire is that
their meaning depends on the keymap currently loaded.  This could
cause some problems if the machine running VNC viewer is using a
different keymap to the one loaded in the frontend.  However, every
other solution that's been suggested has lead to some keys being
unrepresentable, which is even worse.

Steven.

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