Re: [PATCH] ui/sdl: Mouse event optimization

[BALATON Zoltan <balaton@eik.bme.hu>]

On Fri, 25 Oct 2024, Lei Huang wrote:
> Use a convergence factor to make the VM's input
> global coordinates more closely approach the global
> coordinates of DOM0.

Dom0 is some Xen terminology. Do you mean "host" which is more often used 
in QEMU?

> Change-Id: I2c3f12f1fe7dfb9306d1fc40c4fd4d299937f4c6
> Signed-off-by: Lei Huang <Lei.Huang@amd.com>
> ---
> ui/sdl2.c | 32 ++++++++++++++++++++++++++++++--
> 1 file changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/ui/sdl2.c b/ui/sdl2.c
> index bd4f5a9da14..8f504dd8727 100644
> --- a/ui/sdl2.c
> +++ b/ui/sdl2.c
> @@ -303,6 +303,34 @@ static void sdl_mouse_mode_change(Notifier *notify, void *data)
>     }
> }
>
> +/*
> + *guest_x and guest_y represent the global coordinates on the VM side,
> + *while x and y represent the global coordinates on the dom0 side.
> + *The goal of this entire process is to align the global coordinates of
> + *the VM with those of dom0 using dx and dy. The current approach aims
> + *for precise calibration in once attempt; however, because guest_x

"in one attempt" also add a space after the * at the beginning of lines.

> + *and guest_y are non-zero values, they are not accurate values when
> + *they are counted out to become negative.Therefore, achieving perfect
> + *alignment in one attempt is impossible.Since the same calibration method
> + *is used each time, repeated attempts cannot achieve alignment either.
> + *By introducing a convergence factor, guest_x and guest_y can be made to
> + *approach dom0's x and y indefinitely.
> + *
> + *                   QEMU                       (dx,dy)  VM
> + *calculates dx and dy using guest_x and guest_y ---->  input driver
> + *           ^                                            |
> + *           |                                            |
> + *           |                                            V
> + *           |     update
> + *           | guest_x,guest_y              input dispatcher ---> WindowManager
> + *           |                                            |                 |
> + *           |                                            |                 |
> + *           |                 libdrm                     V                 |
> + *       virtio-gpu  <------ drmModeMoveCursor <------ compositor <-------  |
> + *                           (guest_x,guest_y)   calculates guest_x and
> + *                                               guest_y dy using dx and dy
> + */

What about other display devices than virtio-gpu? Does this work with 
those or do they need some update? If this is independent of graphics 
device maybe add a note that virtio-gpu is an example and could be any 
graphics device.

Regards,
BALATON Zoltan

> +#define CONVERGENCE_FACTOR 3
> static void sdl_send_mouse_event(struct sdl2_console *scon, int dx, int dy,
>                                  int x, int y, int state)
> {
> @@ -331,8 +359,8 @@ static void sdl_send_mouse_event(struct sdl2_console *scon, int dx, int dy,
>             y -= guest_y;
>             guest_x += x;
>             guest_y += y;
> -            dx = x;
> -            dy = y;
> +            dx = x / CONVERGENCE_FACTOR;
> +            dy = y / CONVERGENCE_FACTOR;
>         }
>         qemu_input_queue_rel(scon->dcl.con, INPUT_AXIS_X, dx);
>         qemu_input_queue_rel(scon->dcl.con, INPUT_AXIS_Y, dy);
> -- 
> 2.45.2
>
>
>