rockbox/apps/gesture.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 *
 * Copyright (C) 2022 by Aidan MacDonald
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/

#include "gesture.h"
#include "button.h"
#include "viewport.h"
#include "system.h"

/* could be a setting */
#define TOUCH_LONG_PRESS_TIME (30 * HZ / 100)

void gesture_reset(struct gesture *g)
{
    g->flags = 0;
}

void gesture_process(struct gesture *g, const struct touchevent *ev)
{
    /* wait for the first press if we haven't seen it */
    if (!gesture_is_pressed(g) && ev->type != TOUCHEVENT_PRESS)
        return;

    int dx, dy, dist_sqr;
    switch (ev->type)
    {
    case TOUCHEVENT_PRESS:
        g->flags |= GESTURE_F_PRESSED | GESTURE_F_VALID;
        g->id = GESTURE_NONE;
        g->ox = g->x = ev->x;
        g->oy = g->y = ev->y;
        g->start_tick = ev->tick;
        g->last_tick = ev->tick;
        break;

    case TOUCHEVENT_CONTACT:
        g->x = ev->x;
        g->y = ev->y;
        g->last_tick = ev->tick;

        if (g->id == GESTURE_LONG_PRESS)
            g->id = GESTURE_HOLD;
        else if (g->id == GESTURE_DRAGSTART)
            g->id = GESTURE_DRAG;
        else if (g->id != GESTURE_DRAG)
        {
            dx = ev->x - g->ox;
            dy = ev->y - g->oy;
            dist_sqr = dx*dx + dy*dy;

            /* if squared distance exceeds a threshold, report as a DRAG. */
            const int thresh = touchscreen_get_scroll_threshold();
            if (dist_sqr > thresh*thresh)
                g->id = GESTURE_DRAGSTART;

            /* report a LONG_PRESS if no motion occurs within a timeout */
            if (g->id == GESTURE_NONE &&
                TIME_AFTER(ev->tick, g->start_tick + TOUCH_LONG_PRESS_TIME))
                g->id = GESTURE_LONG_PRESS;
        }

        break;

    case TOUCHEVENT_RELEASE:
        /* report a RELEASE event after a continuous HOLD or DRAG */
        if (g->id == GESTURE_HOLD ||
            g->id == GESTURE_DRAGSTART ||
            g->id == GESTURE_DRAG)
            g->id = GESTURE_RELEASE;

        /* report a TAP event if we got a press & release without
         * triggering any other gestures */
        else if (g->id == GESTURE_NONE)
            g->id = GESTURE_TAP;

        g->flags &= ~GESTURE_F_PRESSED;
        g->last_tick = ev->tick;
        break;
    }
}

bool gesture_get_event_in_vp(struct gesture *g, struct gesture_event *gevt,
                             const struct viewport *vp)
{
    if (!gesture_is_valid(g))
        return false;

    gevt->id = g->id;
    gevt->x = g->x;
    gevt->y = g->y;
    gevt->ox = g->ox;
    gevt->oy = g->oy;
    gevt->start_tick = g->start_tick;
    gevt->last_tick = g->last_tick;

    if (vp) {
        gevt->x -= vp->x;
        gevt->y -= vp->y;
        gevt->ox -= vp->x;
        gevt->oy -= vp->y;
    }

    return !vp || viewport_point_within_vp(vp, g->ox, g->oy);
}

/*
 * gesture velocity helper
 */

void gesture_vel_reset(struct gesture_vel *gv)
{
    gv->idx = 0;
    gv->cnt = 0;
}

void gesture_vel_process(struct gesture_vel *gv, const struct touchevent *ev)
{
    if (ev->type != TOUCHEVENT_PRESS &&
        ev->type != TOUCHEVENT_CONTACT)
        return;

    gv->xsamp[gv->idx] = ev->x;
    gv->ysamp[gv->idx] = ev->y;
    gv->tsamp[gv->idx] = ev->tick;

    gv->idx++;
    gv->cnt++;

    if (gv->idx >= ARRAYLEN(gv->xsamp))
        gv->idx = 0;
}

bool gesture_vel_get(struct gesture_vel *gv, int *xvel, int *yvel)
{
    if (gv->cnt <= 1) {
        *xvel = 0;
        *yvel = 0;
        return false;
    }

    int dx = 0, dy = 0, dt = 0;
    size_t n = MIN(gv->cnt, ARRAYLEN(gv->xsamp)) - 1;
    size_t i = gv->cnt < ARRAYLEN(gv->xsamp) ? 0 : gv->idx;
    size_t ip = i + 1;
    while (n-- > 0) {
        if (ip >= ARRAYLEN(gv->xsamp))
            ip = 0;

        dx += gv->xsamp[ip] - gv->xsamp[i];
        dy += gv->ysamp[ip] - gv->ysamp[i];
        dt += gv->tsamp[ip] - gv->tsamp[i];

        i = ip;
        ip++;
    }

    if (dt == 0) {
        *xvel = 0;
        *yvel = 0;
    } else {
        *xvel = dx * HZ / dt;
        *yvel = dy * HZ / dt;
    }

    return gv->cnt >= ARRAYLEN(gv->xsamp);
}

/*
 * flick detector
 */

int gesture_flick_get_in_vp(const struct gesture_event *gevt,
                            const struct viewport *vp)
{
    const int vp_height = vp ? vp->height : LCD_HEIGHT;
    const int vp_width = vp ? vp->width : LCD_WIDTH;

    /* margin at edge where flicks must originate */
    const int margin = touchscreen_get_scroll_threshold() * 2;

    /* minimum distance from edge before a flick is reported */
    const int x_dist = 1 + vp_width/4;
    const int y_dist = 1 + vp_height/4;

    /* a flick only triggers if the velocity along the main axis
     * exceeds the minimum and the velocity on the other axis is
     * below the maximum */
    const int xv_min = 2*vp_width;
    const int xv_max = vp_width;
    const int yv_min = 2*vp_height;
    const int yv_max = vp_height;

    /* a flick is only detected if it occurs within this timeout */
    const long timeout = HZ/2;

    long dt = gevt->last_tick - gevt->start_tick;
    if (dt <= 0 || dt > timeout)
        return GESTURE_FLICK_NONE;

    int xvel = (gevt->x - gevt->ox) * HZ / dt;
    int yvel = (gevt->y - gevt->oy) * HZ / dt;

    if (gevt->ox < margin && gevt->x >= x_dist &&
        xvel >= xv_min && abs(yvel) <= yv_max)
        return GESTURE_FLICK_LEFT;

    if (gevt->ox >= LCD_WIDTH - margin &&
        gevt->x < LCD_WIDTH - x_dist &&
        xvel <= -xv_min && abs(yvel) <= yv_max)
        return GESTURE_FLICK_RIGHT;

    if (gevt->oy < margin && gevt->y >= y_dist &&
        yvel >= yv_min && abs(xvel) <= xv_max)
        return GESTURE_FLICK_TOP;

    if (gevt->oy >= LCD_HEIGHT - margin &&
        gevt->y < LCD_HEIGHT - y_dist &&
        yvel <= -yv_min && abs(xvel) < xv_max)
        return GESTURE_FLICK_BOTTOM;

    return GESTURE_FLICK_NONE;
}