[PATCH] mi: ensure chained button mappings from SD -> MD (#19282)

[Thomas Jaeger]

Alexia: What is the point of remapping buttons willy-nilly before
posting an event anyway?  The comment suggests it just servers as a
reminder of how remapping works.  It's problematic in that proper
DeviceMappingNotify events aren't send and I don't want to think about
what could potentially happen if some client calls XTestFakeButtonEvent
(let alone XTestFakeDeviceButtonEvent) at the right moment.  The problem
in bug #19282 was fixed in ubuntu by simply skipping the remapping step,
and I'm not aware of any issues that this may have caused.

Peter Hutterer wrote:
> After copying the master event, flip the detail field to the mapped button of
> the SD, not the physical button. This way if the SD has a mapping 1:3 and the
> MD has a mapping of 3:4, a press on button 1 on the SD results in a core event
> on button 4.
> 
> X.Org Bug 19282 <http://bugs.freedesktop.org/show_bug.cgi?id=19282>
> 
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> ---
>  mi/mieq.c       |   26 ++++++++++++++++++++++++--
>  xkb/ddxDevBtn.c |    2 +-
>  2 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/mi/mieq.c b/mi/mieq.c
> index 82bbb2c..e1f647d 100644
> --- a/mi/mieq.c
> +++ b/mi/mieq.c
> @@ -277,15 +277,32 @@ ChangeDeviceID(DeviceIntPtr dev, xEvent* event)
>          DebugF("[mi] Unknown event type (%d), cannot change id.\n", type);
>  }
>  
> +static void
> +FixUpEventForMaster(DeviceIntPtr mdev, DeviceIntPtr sdev, xEvent* original,
> +                    EventListPtr master, int count)
> +{
> +    /* Ensure chained button mappings, i.e. that the detail field is the
> +     * value of the mapped button on the SD, not the physical button */
> +    if (original->u.u.type == DeviceButtonPress || original->u.u.type == DeviceButtonRelease)
> +    {
> +        int btn = original->u.u.detail;
> +        if (!sdev->button)
> +            return; /* Should never happen */
> +
> +        master->event->u.u.detail = sdev->button->map[btn];

Shouldn't this be master->event[count].u.u.detail... ?