Re: [PATCH] vnc,ps2: fix the PS/2 mouse work badly when connect VNC

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

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Hi Shiyuan

On Mon, Jul 17, 2023 at 7:16 AM Shiyuan Gao <gaoshiyuan@baidu.com> wrote:

> When only use PS/2 mouse without usb-tablet, the mouse pointer of the
> guest on the VNC will work badly that the cursor of VNC is inconsistent
> with the mouse pointer of guest.
>
>
Afaik, VNC doesn't support client-side drawing of guest mouse (there are no
message to set guest mouse position). So the guest mouse should be drawn by
the server, and currently QEMU doesn't do it.


> The reason is the PS/2 mouse use relative coordinates and we can't know
> the initial position of the guest mouse pointer.
>

It's not just about the initial position.


>
>
So move the guest mouse pointer to (0, 0) of the screen when connect the
> VNC, and then move the mouse pointer to the cursor of VNC(absolute
> coordinates are also relative coordinates).
>
>
It's hardly a solution, you still have no clue what will be the guest mouse
position.


> On windows VM, also need disable "Enhance Pointer Precision" Option in
> "Pointer Options" (Control Panel -> Mouse).
>
>
Apparently, this option doesn't have much to do with relative mouse motion.
Can you explain what it does with this change?


Which guest OS are you using? Hopefully they all support either usb-tablet
or vmmouse extension for absolute positioning. Otherwise, I'd suggest using
Spice, which has those messages for client side guest-mouse drawing.



> Signed-off-by: Shiyuan Gao <gaoshiyuan@baidu.com>
> ---
>  hw/input/ps2.c | 2 +-
>  ui/vnc.c       | 5 +++++
>  2 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/hw/input/ps2.c b/hw/input/ps2.c
> index 45af76a837..e1f44bd298 100644
> --- a/hw/input/ps2.c
> +++ b/hw/input/ps2.c
> @@ -77,7 +77,7 @@
>  #define MOUSE_STATUS_ENABLED    0x20
>  #define MOUSE_STATUS_SCALE21    0x10
>
> -#define PS2_QUEUE_SIZE      16  /* Queue size required by PS/2 protocol */
> +#define PS2_QUEUE_SIZE      32  /* Queue size required by PS/2 protocol */
>  #define PS2_QUEUE_HEADROOM  8   /* Queue size for keyboard command
> replies */
>
>  /* Bits for 'modifiers' field in PS2KbdState */
> diff --git a/ui/vnc.c b/ui/vnc.c
> index 92964dcc0c..a1a6048ee4 100644
> --- a/ui/vnc.c
> +++ b/ui/vnc.c
> @@ -1816,6 +1816,11 @@ static void pointer_event(VncState *vs, int
> button_mask, int x, int y)
>          if (vs->last_x != -1) {
>              qemu_input_queue_rel(con, INPUT_AXIS_X, x - vs->last_x);
>              qemu_input_queue_rel(con, INPUT_AXIS_Y, y - vs->last_y);
> +        } else {
> +            qemu_input_queue_rel(con, INPUT_AXIS_X, 0 - width);
> +            qemu_input_queue_rel(con, INPUT_AXIS_Y, 0 - height);
> +            x = 0;
> +            y = 0;
>          }
>          vs->last_x = x;
>          vs->last_y = y;
> --
> 2.27.0
>
>

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