Processing optically encoder knobs

switches.c

void
update_cursor(int cursor_num)
{
    struct cursor_data_struct *cursor;
    uint32_t timer;
    int x, y;
    int16_t delta;
    int c_limit;
    int16_t cur;

    /* invalid cursor */
    if ((cursor_num < 0) || (cursor_num >= MAX_CURSORS)) {
        return;
    }

    cursor = &cursor_data[cursor_num];
    c_limit = (cursor->hv == IS_HORIZ) ? 240 : 300; /* reticule width */
    timer = cursor->timer;

    /* if timer is non-null figure out if the user has turned the knob */
    if (timer) {
        cur = timer_get_counter(timer);
        delta = cur - cursor->prev;
        if (delta) {
            printf("Delta : %d\n", delta);
        }
        /* scaling function */
        if (delta != 0) {
            if (abs(delta) < 10) {
                delta = (delta < 0) ? -1 : 1;
            } else if (abs(delta) < 100) {
                delta = (delta < 0) ? -5 : 5;
            } else {
                delta = (delta < 0) ? -20 : 20;
            }
        }
        cursor->prev = cur;
        cursor->ndx += delta;
        cursor->ndx = (cursor->ndx < 0) ? 0 : cursor->ndx;
        cursor->ndx = (cursor->ndx >= c_limit) ? c_limit - 1 : cursor->ndx;
    }
    if (cursor->hv == IS_HORIZ) {
        x = 0;
        y = cursor->ndx;
    } else {
        x = cursor->ndx;
        y = 0;
    }
        
    eve_move_to(x, y);
    eve_set_color(cursor->color);
    eve_draw_bitmap(cursor->bitmap);
}