insert_char() and key_down/key_up should be unified, and use keysyms directly

[narodnik]

In my code, I need smooth repeating keys. We do this with a special gadget that takes miniquad key events, and tracks the time. This allows add an initial delay and time between actions.

struct PressedKeysSmoothRepeat {
    /// When holding keys, we track from start and last sent time.
    /// This is useful for initial delay and smooth scrolling.
    pressed_keys: HashMap<String, RepeatingKeyTimer>,
    /// Initial delay before allowing keys
    start_delay: u32,
    /// Minimum time between repeated keys
    step_time: u32,
}

impl PressedKeysSmoothRepeat {
    fn new(start_delay: u32, step_time: u32) -> Self {
        Self { pressed_keys: HashMap::new(), start_delay, step_time }
    }

    fn key_down(&mut self, key: &str, repeat: bool) -> u32 {
        if !repeat {
            return 1;
        }

        // Insert key if not exists
        if !self.pressed_keys.contains_key(key) {
            self.pressed_keys.insert(key.to_string(), RepeatingKeyTimer::new());
        }

        let repeater = self.pressed_keys.get_mut(key).expect("repeat map");
        repeater.update(self.start_delay, self.step_time)
    }

    fn key_up(&mut self, key: &str) {
        self.pressed_keys.remove(key);
    }
}

struct RepeatingKeyTimer {
    start: Instant,
    actions: u32,
}

impl RepeatingKeyTimer {
    fn new() -> Self {
        Self { start: Instant::now(), actions: 0 }
    }

    fn update(&mut self, start_delay: u32, step_time: u32) -> u32 {
        let elapsed = self.start.elapsed().as_millis();
        if elapsed < start_delay as u128 {
            return 0
        }
        let total_actions = ((elapsed - start_delay as u128) / step_time as u128) as u32;
        let remaining_actions = total_actions - self.actions;
        self.actions = total_actions;
        remaining_actions
    }
}

We need the key_up event to remove the key from the hashmap - see PressedKeysSmoothRepeat::key_up(), but there is no key up event for insert_char.

What if insert_char is deprecated, and we replace KeyCodes in key_up/key_down with xkb keysyms?

[narodnik]

Right now I'm using the repeat flag to detect key ups.