[PATCH libinput 07/11] touchpad: only try thumb detection in the lowest 15/8mm

[Hans de Goede]

Hi,

On 22-07-15 07:09, Peter Hutterer wrote:
> That's the most likely area it will be resting in, if it's sitting anywhere
> above that it's likely part of an interaction.
>
> A thumb in the lowest 15mm needs to trigger the pressure threshold before it's
> labelled a thumb. A thumb in the lowest 8mm is considered a thumb if it
> remains there for 300ms. Regardless of the pressure, since we can't reliably
> get pressure here. If a thumb moves out of the area, or starts outside of that
> area it is never a thumb.

"If a thumb moves out of the area" -> not so in the code:

<snip>

>   static void
> -tp_thumb_detect(struct tp_dispatch *tp, struct tp_touch *t)
> +tp_thumb_detect(struct tp_dispatch *tp, struct tp_touch *t, uint64_t time)
>   {
> -	/* once a thumb, always a thumb */
> -	if (!tp->thumb.detect_thumbs || t->is_thumb)
> +	enum tp_thumb_state state = t->thumb.state;
> +
> +	/* once a thumb, always a thumb, once ruled out always ruled out */
> +	if (!tp->thumb.detect_thumbs ||
> +	    t->thumb.state != THUMB_STATE_MAYBE)
>   		return;
>

This check make it so that a touch labeled a thumb (THUMB_STATE_YES)
will stay a thumb even if it moves above the upper_thumb_line.

> +	if (t->point.y < tp->thumb.upper_thumb_line) {
> +		/* if a potential thumb is above the line, it won't ever
> +		 * label as thumb */
> +		t->thumb.state = THUMB_STATE_NO;
> +		goto out;
> +	}
> +

This can be fixed by moving this check above the previous one.

Otherwise looks good.

Regards,

Hans