[PATCH libinput 06/11] touchpad: scale thumb pressure threshold with the resolution

[Hans de Goede]

Hi,

On 22-07-15 07:09, Peter Hutterer wrote:
> On touchpads with a higher resolution we also see higher pressure values.
> Scale accordingly, but use the T440s as reference and don't go below that
> device's threshold. A false positive is worse than a false negative when it
> comes to thumb detection.
>
> https://bugs.freedesktop.org/show_bug.cgi?id=91362
>
> Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>

Tricky, feels a bit like black magic, I cannot think of a better approach though,
so lets see how this works out:

Reviewed-by: Hans de Goede <hdegoede at redhat.com>

Regards,

Hans

> ---
>   src/evdev-mt-touchpad.c | 13 ++++++++++---
>   test/touchpad.c         | 20 ++++++++++----------
>   2 files changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
> index b4399d2..c7f55c3 100644
> --- a/src/evdev-mt-touchpad.c
> +++ b/src/evdev-mt-touchpad.c
> @@ -1534,6 +1534,8 @@ tp_init_thumb(struct tp_dispatch *tp)
>   	struct evdev_device *device = tp->device;
>   	const struct input_absinfo *abs;
>   	double w = 0.0, h = 0.0;
> +	int xres, yres;
> +	double threshold;
>
>   	if (!tp->buttons.is_clickpad)
>   		return 0;
> @@ -1552,12 +1554,17 @@ tp_init_thumb(struct tp_dispatch *tp)
>   	if (h < 50)
>   		return 0;
>
> -	/* The touchpads we looked at so far have a clear thumb threshold of
> -	 * ~100, you don't reach that with a normal finger interaction.
> +	/* Our reference touchpad is the T440s with 42x42 resolution.
> +	 * Higher-res touchpads exhibit higher pressure for the same
> +	 * interaction. On the T440s, the threshold value is 100, you don't
> +	 * reach that with a normal finger interaction.
>   	 * Note: "thumb" means massive touch that should not interact, not
>   	 * "using the tip of my thumb for a pinch gestures".
>   	 */
> -	tp->thumb.threshold = 100;
> +	xres = tp->device->abs.absinfo_x->resolution;
> +	yres = tp->device->abs.absinfo_y->resolution;
> +	threshold = 100.0 * hypot(xres, yres)/hypot(42, 42);
> +	tp->thumb.threshold = max(100, threshold);
>   	tp->thumb.detect_thumbs = true;
>
>   	return 0;
> diff --git a/test/touchpad.c b/test/touchpad.c
> index 7b8324c..27485ae 100644
> --- a/test/touchpad.c
> +++ b/test/touchpad.c
> @@ -4017,7 +4017,7 @@ START_TEST(touchpad_thumb_begin_no_motion)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4041,7 +4041,7 @@ START_TEST(touchpad_thumb_update_no_motion)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4071,7 +4071,7 @@ START_TEST(touchpad_thumb_clickfinger)
>   	struct libinput_event *event;
>   	struct libinput_event_pointer *ptrev;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4128,7 +4128,7 @@ START_TEST(touchpad_thumb_btnarea)
>   	struct libinput_event *event;
>   	struct libinput_event_pointer *ptrev;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4164,7 +4164,7 @@ START_TEST(touchpad_thumb_edgescroll)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4195,7 +4195,7 @@ START_TEST(touchpad_thumb_tap_begin)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4225,7 +4225,7 @@ START_TEST(touchpad_thumb_tap_touch)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4255,7 +4255,7 @@ START_TEST(touchpad_thumb_tap_hold)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4286,7 +4286,7 @@ START_TEST(touchpad_thumb_tap_hold_2ndfg)
>   	struct litest_device *dev = litest_current_device();
>   	struct libinput *li = dev->libinput;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
> @@ -4333,7 +4333,7 @@ START_TEST(touchpad_thumb_tap_hold_2ndfg_tap)
>   	struct libinput_event *event;
>   	struct libinput_event_pointer *ptrev;
>   	struct axis_replacement axes[] = {
> -		{ ABS_MT_PRESSURE, 100 },
> +		{ ABS_MT_PRESSURE, 190 },
>   		{ -1, 0 }
>   	};
>
>