resolver.c

#include "time_util.h"
#include "resolver.h"
#include "names.h"

#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>

void resolver_init(struct resolver *r, key_action_t *root_keymap,
        send_t send, void *send_data){
    *r = (struct resolver){0};
    r->send = send;
    r->send_data = send_data;
    r->root_keymap = root_keymap;
    r->current_keymap = root_keymap;
}


// call on each "natural" TAP resolution (which happens upon key release)
static void track_last_tap(struct resolver *r, struct input_event release_ev){
    r->last_tap_code = release_ev.code;
    r->last_tap_time = release_ev.time;
}

// call on each non-natural-TAP dual-key resolution
static void invalidate_last_tap(struct resolver *r){
    r->last_tap_code = -1;
}

// call on each incoming keypress
static void maybe_invalidate_last_tap(struct resolver *r, int code){
    if(code != r->last_tap_code){
        r->last_tap_code = -1;
    }
}

// returns bool ok
bool resolve_dedup_input(struct resolver *r, struct input_event ev){
    if(ev.type != EV_KEY) return true;
    if(ev.code > KEY_MAX) return true;
    if(ev.value == 0){
        // ignore non-final release of a key
        if(r->input_counts[ev.code] == 0){
            fprintf(stderr,
                "invalid key release of %s in resolve_dedup_input\n",
                get_input_name(ev.code)
            );
            return false;
        }
        return --r->input_counts[ev.code] == 0;
    }
    if(ev.value == 1){
        // ignore non-first press of a key;
        return r->input_counts[ev.code]++ == 0;
    }
    return true;
}

/* Given a pressed dual-key X, check unresolved events to decide tap or hold.
   The first condition met from the list below indicates the correct mode:
     - X has been double-tapped (tap mode)
     - X has timed out (hold mode)
     - X has been released (tap mode)
     - another key has been pressed and released (hold mode)
     - actually, neither has happened yet (resolvable time will be set) */
enum waveform {
    WAVEFORM_TAP,
    WAVEFORM_HOLD,
    WAVEFORM_NONE_YET,
};
enum waveform check_waveform(struct resolver *r, struct input_event ev,
        key_dual_t dual){
    // is the keypress old enough to be a hold?
    if(msec_diff(timeval_now(), ev.time) > dual.hold_ms){
        // only on time-based holds do we check doubletap behavior.
        long dtms = dual.double_tap_ms;
        if(dtms > -1){
            // check for double tap conditions
            if(r->last_tap_code == ev.code){
                if(dtms == 0 || msec_diff(ev.time, r->last_tap_time) < dtms){
                    // not a natural tap
                    invalidate_last_tap(r);
                    return WAVEFORM_TAP;
                }
            }
        }
        invalidate_last_tap(r);
        return WAVEFORM_HOLD;
    }
    // in TIMEOUT_ONLY, we don't have to check any further
    if(dual.mode == DUAL_MODE_TIMEOUT_ONLY){
        return WAVEFORM_NONE_YET;
    }

    int keys_pressed[KEY_MAX] = {0};
    for(size_t i = 1; i < r->ur_len; i++){
        struct input_event ev2 = r->unresolved[(r->ur_start + i) % URMAX];
        // only consider key events
        if(ev2.type != EV_KEY) continue;
        // was the main key released?
        if(ev2.value == 0 && ev2.code == ev.code){
            track_last_tap(r, ev2);
            return WAVEFORM_TAP;
        }
        // in HOLD_ON_ROLLOVER mode, any other keypress is HOLD
        if(dual.mode == DUAL_MODE_HOLD_ON_ROLLOVER
                && ev2.type == EV_KEY && ev2.value == 1){
            invalidate_last_tap(r);
            return WAVEFORM_HOLD;
        }
        // on press, record the pressed state of the key
        if(ev2.value == 1 && ev2.code < KEY_MAX){
            keys_pressed[ev2.code] = 1;
            // any secondary press prevents a doubletap
            invalidate_last_tap(r);
        }
        // some other key was pressed and released, main key is a HOLD
        if(ev2.value == 0 && ev2.code < KEY_MAX && keys_pressed[ev2.code]){
            invalidate_last_tap(r);
            return WAVEFORM_HOLD;
        }
    }

    return WAVEFORM_NONE_YET;
}

void do_keypress(struct resolver *r, struct input_event ev, key_action_t *ka){
    switch(ka->type){
        case KT_DUAL:
            fprintf(stderr, "can't call do_keypress() on a dual-mode key\n");
            exit(1);
            break;
        case KT_NONE:
            fprintf(stderr, "can't call do_keypress() on a none-type key\n");
            exit(1);
            break;
        case KT_SIMPLE:
            // remember how to release the key
            r->release_map[ev.code] = ka->key.simple;
            // send the modified key
            ev.code = ka->key.simple;
            r->send(r->send_data, ev);
            break;
        case KT_MACRO:
            // send the whole chain of macros
            for(key_macro_t *m = ka->key.macro; m; m = m->next){
                struct input_event ev = {
                    .type = EV_KEY,
                    .value = m->press,
                    .code = m->code,
                };
                r->send(r->send_data, ev);

                struct input_event syn_ev = {
                    .type = EV_SYN,
                    .code = SYN_REPORT,
                    .value = 0,
                };
                r->send(r->send_data, syn_ev);
            }
            break;
        case KT_MAP:
            // set the keymap
            r->current_keymap = ka;
            // reset the keymap on release
            r->release_map[ev.code] = RESET_KEYMAP;
            // send nothing
            break;
    }
}

bool resolve_press(struct resolver *r, struct input_event ev){
    maybe_invalidate_last_tap(r, ev.code);
    // get the key action from the map
    key_action_t *ka = key_action_get(r->current_keymap, ev.code);
    switch(ka->type){
        case KT_MAP:
        case KT_MACRO:
        case KT_SIMPLE:
            do_keypress(r, ev, ka);
            return true;
        case KT_DUAL:
            switch(check_waveform(r, ev, ka->key.dual)){
                // .tap and .hold must not be KT_DUALs
                case WAVEFORM_TAP:
                    do_keypress(r, ev, ka->key.dual.tap);
                    return true;
                case WAVEFORM_HOLD:
                    do_keypress(r, ev, ka->key.dual.hold);
                    return true;
                case WAVEFORM_NONE_YET:
                    // wait for a timeout to resolve this event
                    r->resolvable_time = msec_after(
                        ev.time, ka->key.dual.hold_ms
                    );
                    r->use_resolvable_time=true;
                    return false;
            }
        case KT_NONE:
        default:
            fprintf(stderr, "invalid key action in resolver\n");
            exit(1);
    }
}

bool resolve_release(struct resolver *r, struct input_event ev){
    /* make the code look like whatever we mapped it to when we
       resolved the initial keypress */
    int initial_code = ev.code;
    ev.code = r->release_map[initial_code];
    r->release_map[initial_code] = 0;
    switch(ev.code){
        case RESET_KEYMAP:
            r->current_keymap = r->root_keymap;
            break;
        case 0:
            // we must have sent this key release early; do nothing.
            break;
        default:
            r->send(r->send_data, ev);
    }
    return true;
}

/* helper function which tries to resolve the oldest key event.  Returns false
   if it deems the event unresolvable, setting the resolver.resolve_time as
   appropriate. */
bool resolve(struct resolver *r){
    if(r->ur_len == 0){
        return false;
    }

    // grab the oldest event
    struct input_event ev = r->unresolved[r->ur_start % URMAX];

    bool resolved = false;
    r->use_resolvable_time = false;

    if(ev.type == EV_KEY){
        // invalid key code
        if(ev.code > KEY_MAX){
            fprintf(stderr, "Dropping too-high keycode %d\n", ev.code);
            resolved = true;
        }
        // key released
        else if(ev.value == 0){
            // printf("%.10s of %.10s\n", "release", get_input_name(ev.code));
            resolved = resolve_release(r, ev);
        }
        // key pressed
        else if(ev.value == 1){
            // printf("%.10s of %.10s\n", "press", get_input_name(ev.code));
            resolved = resolve_press(r, ev);
        }
        // key repeated
        else if(ev.value == 2){
            // printf("%.10s of %.10s\n", "repeat", get_input_name(ev.code));
            /* make the code look like whatever we mapped it to when we
               resolved the initial keypress */
            ev.code = r->release_map[ev.code];
            if(ev.code != 0 && ev.code != RESET_KEYMAP){
                /* TODO: generate fake repeats to avoid the situation where
                         where a key is pressed twice and we can't tell which
                         repeat is from the first press and which one is
                         irrelevant.  For now, X handles its own key repeats
                         so these don't really even matter. */
                r->send(r->send_data, ev);
            }
            resolved = true;
        }else{
            fprintf(stderr,
                "dropping invalid ev.value %d in resolver\n", ev.value
            );
            resolved = true;
        }
    }else if(ev.type == EV_SYN){
        // printf("EV_SYN\n");
        r->send(r->send_data, ev);
        resolved = true;
    }else{
        // other ev.types are passed through unchanged
        r->send(r->send_data, ev);
        resolved = true;
    }

    if(resolved){
        // one less element
        r->ur_len--;
        // but we start one later
        r->ur_start = (r->ur_start + 1) % URMAX;
    }else{
        /* if we decided we couldn't resolve the oldest event, but the newest
           event is a key release, emit the key release immediately.  We know
           that the initial press must have been resolved because if the
           initial press had come after the unresolvable key, then now that
           we have the release the unresolvable key would be resolvable. */
        ev = r->unresolved[(r->ur_start + r->ur_len - 1) % URMAX];
        if(ev.value == 0 && ev.code < KEY_MAX){
            /* make the code look like whatever we mapped it to when we
               resolved the initial keypress */
            ev.code = r->release_map[ev.code];
            switch(ev.code){
                case RESET_KEYMAP:
                    // return to root keymap
                    r->current_keymap = r->root_keymap;
                    // one less element
                    r->ur_len--;
                    break;
                case KEY_LEFTALT:
                case KEY_RIGHTALT:
                case KEY_LEFTCTRL:
                case KEY_RIGHTCTRL:
                case KEY_LEFTMETA:
                case KEY_RIGHTMETA:
                case KEY_LEFTSHIFT:
                case KEY_RIGHTSHIFT:
                    // modifier keys don't get resolved early
                    break;
                default:
                    r->send(r->send_data, ev);
                    // send a sync event for this generated key event
                    struct input_event syn_ev = {
                        .type = EV_SYN,
                        .code = SYN_REPORT,
                        .value = 0,
                    };
                    r->send(r->send_data, syn_ev);
                    // one less element
                    r->ur_len--;
            }
        }
    }
    return resolved;
}

// returns the timeout to be used for select(), which is either out or NULL
struct timeval *select_timeout(struct resolver *r, struct timeval *out){
    // don't pass a timeout if none is valid.
    if(!r->use_resolvable_time){
        return NULL;
    }

    struct timespec now_timespec;
    clock_gettime(CLOCK_REALTIME, &now_timespec);
    struct timeval now;
    TIMESPEC_TO_TIMEVAL(&now, &now_timespec);

    long mdiff = msec_diff(r->resolvable_time, now);
    if(mdiff < 0){
        // somehow the timeout has expired, zero length timeout
        out->tv_sec = 0;
        out->tv_usec = 0;
    }else{
        out->tv_sec = mdiff / 1000;
        out->tv_usec = (mdiff % 1000) * 1000;
    }
    return out;
}