Need a way to handle keys pressed at keypad init

[aseanwatson]

Context from Discord:

Todbot said:

What if keypad generated synthetic press events for any buttons not in the value_when_pressed state on init?

DanH replied:

That is an interesting idea. I was thinking of a __get_item__ or a current_state(i), but generatig some initial events is probably not hard and requires no new API. Also I don't think it would cause issues with any current use cases that I can think of.

[aseanwatson]

More context...

Zero is an odd initial value for debounce_counter; you're liable to get weird events if there is noise at startup.

If you initialized to -debounce_threshold there needs to be some debouncing before you see an event. (Yes, I know the default debounce _threshold is 1.) And, if the keys are pressed you'd get pressed events.

You kind of get the opposite after a reset() call. (debounce_counter gets memset to debounce_threshold, so you get a bunch of release events for anything not pressed. But, contrary to the docs no event for keys which are pressed.)

And:

**TL;DR: ** You could have keypad_construct_common memset(self->debounce_counter, -self->debounce_threshold, key_count); and do the thing todbot suggested.

Or you could:

 void keypad_construct_common(keypad_scanner_obj_t *self, mp_float_t interval, size_t max_events, uint8_t debounce_threshold) {
     size_t key_count = common_hal_keypad_generic_get_key_count(self);
     self->debounce_counter = (int8_t *)m_malloc(sizeof(int8_t) * key_count);
 
     self->interval_ticks = (mp_uint_t)(interval * 1024);   // interval * 1000 * (1024/1000)
 
     keypad_eventqueue_obj_t *events = mp_obj_malloc(keypad_eventqueue_obj_t, &keypad_eventqueue_type);
     common_hal_keypad_eventqueue_construct(events, max_events);
     self->events = events;
 
     self->debounce_threshold = debounce_threshold;
 
     self->never_reset = false;
 
     // Add self to the list of active keypad scanners.
     keypad_register_scanner(self);
-    keypad_scan_now(self, port_get_raw_ticks(NULL));
+    common_hal_keypad_generic_reset(self);
 }

And:

 void common_hal_keypad_generic_reset(void *self_in) {
     keypad_scanner_obj_t *self = self_in;
     size_t key_count = common_hal_keypad_generic_get_key_count(self);
-    memset(self->debounce_counter, self->debounce_threshold, key_count);
+    memset(self->debounce_counter, -self->debounce_threshold, key_count);
     keypad_scan_now(self, port_get_raw_ticks(NULL));
 }

That'd also fix the implementation of reset() to do what the docs say it does.