[RFC PATCH xserver] xwayland: avoid race condition on new keymap

[Peter Hutterer]

On Fri, Dec 15, 2017 at 04:43:47PM +0100, Olivier Fourdan wrote:
> When the Wayland compositor notifies of a new keymap, for the first X11
> client using the keyboard, the last slave keyboard used might still not
> be set (i.e. “lastSlave” is still NULL).
> 
> As a result, the new keymap is not applied, and the first X11 window
> will have the wrong keymap set initially.
> 
> Apply the new keymap to the master keyboard as long as there's one.
> 
> Bugzilla: https://bugzilla.gnome.org/show_bug.cgi?id=791383
> Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
> ---
>  Note: screencast of the problem here:
>     https://bugzilla.gnome.org/attachment.cgi?id=365231
> 
>  “RFC” because that fixes the issue but there might be better ways to
>  avoid the problem?

I don't think there is. The situation where no event has been sent by a
keyboard yet has always been hairy and I remember fixing the odd bug here
and there for this.

remote: I: patch #193509 updated using rev 170c95978530f6373bdf4488116902b273f3abf4.
remote: I: 1 patch(es) updated to state Accepted.
To git+ssh://git.freedesktop.org/git/xorg/xserver
   c72049530..170c95978  master -> master

Thanks!

Cheers,
   Peter
 
>  hw/xwayland/xwayland-input.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/hw/xwayland/xwayland-input.c b/hw/xwayland/xwayland-input.c
> index 439903032..c613690cd 100644
> --- a/hw/xwayland/xwayland-input.c
> +++ b/hw/xwayland/xwayland-input.c
> @@ -710,7 +710,7 @@ keyboard_handle_keymap(void *data, struct wl_keyboard *keyboard,
>      XkbDeviceApplyKeymap(xwl_seat->keyboard, xkb);
>  
>      master = GetMaster(xwl_seat->keyboard, MASTER_KEYBOARD);
> -    if (master && master->lastSlave == xwl_seat->keyboard)
> +    if (master)
>          XkbDeviceApplyKeymap(master, xkb);
>  
>      XkbFreeKeyboard(xkb, XkbAllComponentsMask, TRUE);
> -- 
> 2.14.3
> 
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