[PATCH] dix: fix scale_to_desktop for edge ABS events

[Chase Douglas]

On 07/20/2012 04:41 PM, Yufeng Shen wrote:
> Scale_to_desktop() converts ABS events from device coordinates
> to screen coordinates:
> [dev_X_min, dev_X_max]  -> [screen_X_min, screen_X_max]
> [dev_Y_min, dev_Y_max]  -> [screen_Y_min, screen_Y_max]
>
> An edge ABS event with X = dev_X_max (e.g., generated from the
> edge of a touchscreen) will be converted to have screen X value
> = screen_X_max, which, however, will be filterd out when xserver
> tries to find proper Window to receive the event, because the
> range check for a Window to receive events is
>         window_X_min <= event_screen_X < window_X_max
> Events with event_screen_X = screen_X_max will fail the test get
> and rejected by the Window.
>
> To fix this, we change the device to screen coordinates mapping to
> [dev_X_min, dev_X_max]  -> [screen_X_min, screen_X_max-1]
> [dev_Y_min, dev_Y_max]  -> [screen_Y_min, screen_Y_max-1]
>
> Signed-off-by: Yufeng Shen <miletus at chromium.org>
> ---
>   dix/getevents.c |    4 ++--
>   1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/dix/getevents.c b/dix/getevents.c
> index b78d5ce..9898c6a 100644
> --- a/dix/getevents.c
> +++ b/dix/getevents.c
> @@ -890,9 +890,9 @@ scale_to_desktop(DeviceIntPtr dev, ValuatorMask *mask,
>
>       /* scale x&y to desktop coordinates */
>       *screenx = rescaleValuatorAxis(x, dev->valuator->axes + 0, NULL,
> -                                   screenInfo.x, screenInfo.width);
> +                                   screenInfo.x, screenInfo.width - 1);
>       *screeny = rescaleValuatorAxis(y, dev->valuator->axes + 1, NULL,
> -                                   screenInfo.y, screenInfo.height);
> +                                   screenInfo.y, screenInfo.height - 1);
>
>       *devx = x;
>       *devy = y;

The logic seems correct to me. We need to map to:

[screen_min, screen_max)

for each axis.

Reviewed-by: Chase Douglas <chase.douglas at canonical.com>