[Spice-devel] Adding support for mouse buttons SIDE and EXTRA (often scroll wheel push left or right)

[james harvey]

I have a Logitech G600 mouse.  The scroll wheel can be pushed left or right.

On Arch Linux host, evtest shows these as event codes 275 (BTN_SIDE)
and 276 (BTN_EXTRA.)  On host, they work as expected, by default as
back and forward in supported programs such as web browsers.

There are so many mice which generate these events, going all the way
back to the IntelliMouse Explorer in 1999.

QEMU supports these buttons.  For default PS/2 mouse emulation
support, see https://github.com/qemu/qemu/blob/master/hw/input/ps2.c
:700-701.  For "-device virtio-mouse-pci" support, see
https://github.com/qemu/qemu/blob/master/hw/input/virtio-input-hid.c :
31-32.  On an Arch guest, evtest shows an "ImExPS/2 Generic Explorer
Mouse" or a "QEMU Virtio Mouse", both of which list the event codes as
supported.  On Windows 7 guest, Device Manager can be manually set to
a "Microsoft - Microsoft PS/2 Mouse" instead of the default "Microsoft
- PS/2 Compatible Mouse" driver, which forces IntelliMouse Explorer
mode to allow usage of the extra buttons.

"remote-viewer --spice-debug" shows the events:

(remote-viewer:14226): GSpice-DEBUG: 17:09:00.043: spice-widget.c:2007
0:0 button_event press: button 8, state 0x10
(remote-viewer:14226): GSpice-DEBUG: 17:09:00.414: spice-widget.c:2007
0:0 button_event release: button 8, state 0x10
(remote-viewer:14226): GSpice-DEBUG: 17:09:01.045: spice-widget.c:2007
0:0 button_event press: button 9, state 0x10
(remote-viewer:14226): GSpice-DEBUG: 17:09:01.473: spice-widget.c:2007
0:0 button_event release: button 9, state 0x10

But, the guest never receives them, because spice doesn't appear to handle them.

It doesn't look like adding support for these should be many lines.  I
was trying to write a patch, but got a bit lost.


spice-protocol::spice/enums.h only gives SpiceMouseButton types of
LEFT, MIDDLE, RIGHT, UP, and DOWN.  _SIDE and _EXTRA need to be added
here.  If they're merely added, in c, they'd be represented by ints 6
and 7.  I'm not sure if (2) _INVALID types would need to be left in
the middle to make their internal representation match the button
numbers that "remote-viewer --spice-debug" is showing.  (That's mainly
because I'm not sure where these values are ultimately "decoded" into
causing QEMU mouse events.)

spice-gtk::src/spice-widget.c::button_event() calls:

* button_gdk_to_spice() which also only gives the same 5 button types
and returns 0 for button 8 or 9, so the event winds up never getting
passing along.  _SIDE and _EXTRA need to be added here.  I'm not sure
if they should be sequentially added as ints 6 and 7, or if (2)
_INVALID types need to be added here for padding as well.

* button_mask_gdk_to_spice() which might also need something added.
I'm not sure why a mask is being used regarding the button state, let
alone how to convert it.

* spice_inputs_channel_button_{press,release}() which might also need
state mask handling in its switch().

>From there, msg->marshallers->msgc_inputs_mouse_{press,release}() are
called.  Those threw me, and during the build process are generated as
src/spice-gtk/subprojects/spice-common/common/generated_client_marshellers.c.
They don't look like they need to be modified.

I'm not sure where that message is received, or where it generates (I
presume) a mouse event through QEMU.