Support multi-purpose keys in modmap

README.md

@@ -15,7 +15,8 @@
 
 * You can remap any keys, e.g. Ctrl or CapsLock.
 * You can remap any key combination to another, even to a key sequence.
-* You can also remap a key sequence as well. You could do something like Emacs's `C-x C-c`.
+* You can remap a key sequence as well. You could do something like Emacs's `C-x C-c`.
+* You can remap a key to two different keys depending on whether it's pressed alone or held.
 * Application-specific remapping. Even if it's not supported by your application, xremap can.
 
 ## Prerequisite
@@ -105,7 +106,12 @@ is supported only in `modmap` since `keymap` handles modifier keys differently.
 modmap:
   - name: Name # Required
     remap: # Required
-      KEY_XXX: KEY_YYY
+      KEY_XXX: KEY_YYY # Required
+      # or
+      KEY_XXX:
+        held: KEY_YYY # Required
+        alone: KEY_ZZZ # Required
+        alone_timeout_millis: 1000 # Optional
     application: # Optional
       not: [Application, ...]
       # or
@@ -116,6 +122,10 @@ For `KEY_XXX` and `KEY_YYY`, use [these names](https://github.com/emberian/evdev
 You can skip `KEY_` and the name is case-insensitive. So `KEY_CAPSLOCK`, `CAPSLOCK`, and `CapsLock` are the same thing.
 Some [custom aliases](src/config/key.rs) like `SHIFT_R`, `CONTROL_L`, etc. are provided.
 
+If you specify a map containing `held` and `alone`, you can use the key for two purposes.
+The key is considered `alone` if it's pressed and released within `alone_timeout_millis` (default: 1000)
+before any other key is pressed. Otherwise it's considered `held`.
+
 ### keymap
 
 `keymap` is for remapping a sequence of key combinations to another sequence of key combinations or other actions.

example/test.yml

@@ -1,10 +1,7 @@
-# modmap:
-#   - name: Global
-#     remap:
-#       a: b
-keymap:
-  - name: Global
-    application:
-      only: Slack
+modmap:
+  - name: SandS
     remap:
-      C-i: C-u
+      Space:
+        held: Shift_L
+        alone: Space
+        alone_timeout_millis: 500

src/config/action.rs

@@ -7,6 +7,7 @@ use serde::de::{MapAccess, Visitor};
 use serde::{Deserialize, Deserializer};
 use std::fmt::{Debug, Formatter};
 
+// Values in `keymap.remap`
 #[derive(Clone, Debug)]
 pub enum Action {
     KeyPress(KeyPress),
@@ -70,7 +71,7 @@ impl<'de> Deserialize<'de> for Action {
     }
 }
 
-fn serde_error<'de, V, M>(message: &str) -> Result<V, M::Error>
+pub fn serde_error<'de, V, M>(message: &str) -> Result<V, M::Error>
 where
     M: MapAccess<'de>,
 {

src/config/key_action.rs

@@ -0,0 +1,102 @@
+use crate::config::action::serde_error;
+use crate::config::key::parse_key;
+use evdev::Key;
+use serde::de::{MapAccess, Visitor};
+use serde::{Deserialize, Deserializer};
+use std::fmt::Formatter;
+use std::time::Duration;
+
+static DEFAULT_ALONE_TIMEOUT_MILLIS: u64 = 1000;
+
+// Values in `modmap.remap`
+#[derive(Clone, Debug)]
+pub enum KeyAction {
+    Key(Key),
+    MultiPurposeKey(MultiPurposeKey),
+}
+
+#[derive(Clone, Debug)]
+pub struct MultiPurposeKey {
+    pub held: Key,
+    pub alone: Key,
+    pub alone_timeout: Duration,
+}
+
+impl<'de> Deserialize<'de> for KeyAction {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct KeyActionVisitor;
+
+        impl<'de> Visitor<'de> for KeyActionVisitor {
+            type Value = KeyAction;
+
+            fn expecting(&self, formatter: &mut Formatter) -> std::fmt::Result {
+                formatter.write_str("string or map")
+            }
+
+            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+            where
+                E: serde::de::Error,
+            {
+                let key = parse_key(value).map_err(serde::de::Error::custom)?;
+                Ok(KeyAction::Key(key))
+            }
+
+            fn visit_map<M>(self, mut map: M) -> Result<Self::Value, M::Error>
+            where
+                M: MapAccess<'de>,
+            {
+                let mut held: Option<Key> = None;
+                let mut alone: Option<Key> = None;
+                let mut alone_timeout_millis: u64 = DEFAULT_ALONE_TIMEOUT_MILLIS;
+
+                while let Some(key) = map.next_key::<String>()? {
+                    match &key[..] {
+                        "held" => {
+                            let value: String = map.next_value()?;
+                            held = Some(parse_key(&value).map_err(serde::de::Error::custom)?)
+                        }
+                        "alone" => {
+                            let value: String = map.next_value()?;
+                            alone = Some(parse_key(&value).map_err(serde::de::Error::custom)?)
+                        }
+                        "alone_timeout_millis" => alone_timeout_millis = map.next_value()?,
+                        key => {
+                            return serde_error::<Self::Value, M>(&format!(
+                                "held, alone, or alone_timeout_ms is expected, but got: {}",
+                                key
+                            ))
+                        }
+                    }
+                }
+
+                let held = match held {
+                    Some(held) => held,
+                    None => {
+                        return serde_error::<Self::Value, M>(
+                            "held is not specified in a multi-purpose remap of modmap",
+                        )
+                    }
+                };
+                let alone = match alone {
+                    Some(alone) => alone,
+                    None => {
+                        return serde_error::<Self::Value, M>(
+                            "alone is not specified in a multi-purpose remap of modmap",
+                        )
+                    }
+                };
+                let multi_purpose_key = MultiPurposeKey {
+                    held,
+                    alone,
+                    alone_timeout: Duration::from_millis(alone_timeout_millis),
+                };
+                Ok(KeyAction::MultiPurposeKey(multi_purpose_key))
+            }
+        }
+
+        deserializer.deserialize_any(KeyActionVisitor)
+    }
+}

src/config/mod.rs

@@ -2,6 +2,7 @@ pub mod action;
 mod actions;
 pub mod application;
 mod key;
+pub mod key_action;
 pub mod key_press;
 mod keymap;
 mod modmap;

src/config/modmap.rs

@@ -1,5 +1,6 @@
 use crate::config::application::Application;
 use crate::config::key::parse_key;
+use crate::config::key_action::KeyAction;
 use evdev::Key;
 use serde::de::{value, Error, MapAccess, Visitor};
 use serde::{Deserialize, Deserializer};
@@ -11,18 +12,18 @@ use std::fmt;
 pub struct Modmap {
     pub name: String,
     #[serde(deserialize_with = "modmap_remap")]
-    pub remap: HashMap<Key, Key>,
+    pub remap: HashMap<Key, KeyAction>,
     pub application: Option<Application>,
 }
 
-fn modmap_remap<'de, D>(deserializer: D) -> Result<HashMap<Key, Key>, D::Error>
+fn modmap_remap<'de, D>(deserializer: D) -> Result<HashMap<Key, KeyAction>, D::Error>
 where
     D: Deserializer<'de>,
 {
     struct ModmapRemap;
 
     impl<'de> Visitor<'de> for ModmapRemap {
-        type Value = HashMap<Key, Key>;
+        type Value = HashMap<Key, KeyAction>;
 
         fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
             formatter.write_str("map from string to string")
@@ -32,13 +33,12 @@ where
         where
             M: MapAccess<'de>,
         {
-            let remap: HashMap<String, String> = Deserialize::deserialize(value::MapAccessDeserializer::new(map))?;
+            let remap: HashMap<String, KeyAction> = Deserialize::deserialize(value::MapAccessDeserializer::new(map))?;
             let mut modmap = HashMap::new();
 
-            for (from, to) in remap.iter() {
+            for (from, to) in remap.into_iter() {
                 let from_key = parse_key(&from).map_err(M::Error::custom)?;
-                let to_key = parse_key(&to).map_err(M::Error::custom)?;
-                modmap.insert(from_key, to_key);
+                modmap.insert(from_key, to);
             }
 
             Ok(modmap)

src/event_handler.rs

@@ -1,6 +1,7 @@
 use crate::client::{build_client, WMClient};
 use crate::config::action::Action;
 use crate::config::application::Application;
+use crate::config::key_action::KeyAction;
 use crate::config::key_press::{KeyPress, Modifier};
 use crate::Config;
 use evdev::uinput::VirtualDevice;
@@ -9,10 +10,12 @@ use lazy_static::lazy_static;
 use log::debug;
 use std::collections::HashMap;
 use std::error::Error;
+use std::time::Instant;
 
 pub struct EventHandler {
     device: VirtualDevice,
     wm_client: WMClient,
+    multi_purpose_keys: HashMap<Key, MultiPurposeKeyState>,
     override_remap: Option<HashMap<KeyPress, Vec<Action>>>,
     application_cache: Option<String>,
     shift: PressState,
@@ -26,6 +29,7 @@ impl EventHandler {
         EventHandler {
             device,
             wm_client: build_client(),
+            multi_purpose_keys: HashMap::new(),
             override_remap: None,
             application_cache: None,
             shift: PressState::new(false),
@@ -38,32 +42,31 @@ impl EventHandler {
     // Handle EventType::KEY
     pub fn on_event(&mut self, event: InputEvent, config: &Config) -> Result<(), Box<dyn Error>> {
         self.application_cache = None; // expire cache
-        let mut key = Key::new(event.code());
+        let key = Key::new(event.code());
         debug!("=> {}: {:?}", event.value(), &key);
 
         // Apply modmap
-        for modmap in &config.modmap {
-            if let Some(modmap_key) = modmap.remap.get(&key) {
-                if let Some(wm_class_matcher) = &modmap.application {
-                    if !self.match_wm_class(wm_class_matcher) {
-                        continue;
-                    }
-                }
-                key = modmap_key.clone();
-                break;
-            }
+        let mut key_values = if let Some(key_action) = self.find_modmap(&config, &key) {
+            self.dispatch_keys(key_action, key, event.value())
+        } else {
+            vec![(key, event.value())]
+        };
+        if !self.multi_purpose_keys.is_empty() {
+            key_values = self.flush_timeout_keys(key_values);
         }
 
         // Apply keymap
-        if MODIFIER_KEYS.contains(&key.code()) {
-            self.update_modifier(key.code(), event.value());
-        } else if let Some(actions) = self.find_keymap(config, &key, event.value()) {
-            for action in &actions {
-                self.dispatch_action(action)?;
+        for (key, value) in key_values.into_iter() {
+            if MODIFIER_KEYS.contains(&key.code()) {
+                self.update_modifier(key.code(), value);
+            } else if let Some(actions) = self.find_keymap(config, &key, value) {
+                for action in &actions {
+                    self.dispatch_action(action)?;
+                }
+                return Ok(());
             }
-            return Ok(());
+            self.send_key(&key, value)?;
         }
-        self.send_key(&key, event.value())?;
         Ok(())
     }
 
@@ -79,6 +82,72 @@ impl EventHandler {
         self.send_event(event)
     }
 
+    fn dispatch_keys(&mut self, key_action: KeyAction, key: Key, value: i32) -> Vec<(Key, i32)> {
+        match key_action {
+            KeyAction::Key(modmap_key) => vec![(modmap_key.clone(), value)],
+            KeyAction::MultiPurposeKey(multi_purpose_key) => {
+                if value == PRESS {
+                    self.multi_purpose_keys.insert(
+                        key.clone(),
+                        MultiPurposeKeyState {
+                            held: multi_purpose_key.held,
+                            alone: multi_purpose_key.alone,
+                            alone_timeout_at: Some(Instant::now() + multi_purpose_key.alone_timeout),
+                        },
+                    );
+                    return vec![]; // delay the press
+                } else if value == REPEAT {
+                    if let Some(state) = self.multi_purpose_keys.get_mut(&key) {
+                        return state.repeat();
+                    }
+                } else if value == RELEASE {
+                    if let Some(state) = self.multi_purpose_keys.remove(&key) {
+                        return state.release();
+                    }
+                } else {
+                    panic!("unexpected key event value: {}", value);
+                }
+                // fallthrough on state discrepancy
+                vec![(key, value)]
+            }
+        }
+    }
+
+    fn flush_timeout_keys(&mut self, key_values: Vec<(Key, i32)>) -> Vec<(Key, i32)> {
+        let mut flush = false;
+        for (_, value) in key_values.iter() {
+            if *value == PRESS {
+                flush = true;
+                break;
+            }
+        }
+
+        if flush {
+            let mut flushed: Vec<(Key, i32)> = vec![];
+            for (_, state) in self.multi_purpose_keys.iter_mut() {
+                flushed.extend(state.force_held());
+            }
+            flushed.extend(key_values);
+            flushed
+        } else {
+            key_values
+        }
+    }
+
+    fn find_modmap(&mut self, config: &Config, key: &Key) -> Option<KeyAction> {
+        for modmap in &config.modmap {
+            if let Some(key_action) = modmap.remap.get(&key) {
+                if let Some(application_matcher) = &modmap.application {
+                    if !self.match_application(application_matcher) {
+                        continue;
+                    }
+                }
+                return Some(key_action.clone());
+            }
+        }
+        None
+    }
+
     fn find_keymap(&mut self, config: &Config, key: &Key, value: i32) -> Option<Vec<Action>> {
         if !is_pressed(value) {
             return None;
@@ -100,8 +169,8 @@ impl EventHandler {
         }
         for keymap in &config.keymap {
             if let Some(actions) = keymap.remap.get(&key_press) {
-                if let Some(wm_class_matcher) = &keymap.application {
-                    if !self.match_wm_class(wm_class_matcher) {
+                if let Some(application_matcher) = &keymap.application {
+                    if !self.match_application(application_matcher) {
                         continue;
                     }
                 }
@@ -212,7 +281,7 @@ impl EventHandler {
         }
     }
 
-    fn match_wm_class(&mut self, application_matcher: &Application) -> bool {
+    fn match_application(&mut self, application_matcher: &Application) -> bool {
         // Lazily fill the wm_class cache
         if let None = self.application_cache {
             match self.wm_client.current_application() {
@@ -255,30 +324,6 @@ impl EventHandler {
     }
 }
 
-#[derive(Clone)]
-struct PressState {
-    left: bool,
-    right: bool,
-}
-
-impl PressState {
-    fn new(pressed: bool) -> PressState {
-        PressState {
-            left: pressed,
-            right: pressed,
-        }
-    }
-}
-
-fn is_pressed(value: i32) -> bool {
-    value == PRESS || value == REPEAT
-}
-
-// InputEvent#value
-static RELEASE: i32 = 0;
-static PRESS: i32 = 1;
-static REPEAT: i32 = 2;
-
 lazy_static! {
     static ref MODIFIER_KEYS: [u16; 8] = [
         // Shift
@@ -312,3 +357,76 @@ lazy_static! {
         Key::new(Key::KEY_RIGHTMETA.code()),
     ];
 }
+
+//---
+
+#[derive(Clone)]
+struct PressState {
+    left: bool,
+    right: bool,
+}
+
+impl PressState {
+    fn new(pressed: bool) -> PressState {
+        PressState {
+            left: pressed,
+            right: pressed,
+        }
+    }
+}
+
+fn is_pressed(value: i32) -> bool {
+    value == PRESS || value == REPEAT
+}
+
+// InputEvent#value
+static RELEASE: i32 = 0;
+static PRESS: i32 = 1;
+static REPEAT: i32 = 2;
+
+//---
+
+#[derive(Debug)]
+struct MultiPurposeKeyState {
+    held: Key,
+    alone: Key,
+    alone_timeout_at: Option<Instant>,
+}
+
+impl MultiPurposeKeyState {
+    fn repeat(&mut self) -> Vec<(Key, i32)> {
+        if let Some(alone_timeout_at) = &self.alone_timeout_at {
+            if Instant::now() < *alone_timeout_at {
+                vec![] // still delay the press
+            } else {
+                self.alone_timeout_at = None; // timeout
+                vec![(self.held.clone(), PRESS)]
+            }
+        } else {
+            vec![(self.held.clone(), REPEAT)]
+        }
+    }
+
+    fn release(&self) -> Vec<(Key, i32)> {
+        if let Some(alone_timeout_at) = &self.alone_timeout_at {
+            if Instant::now() < *alone_timeout_at {
+                // dispatch the delayed press and this release
+                vec![(self.alone.clone(), PRESS), (self.alone.clone(), RELEASE)]
+            } else {
+                // too late. dispatch the held key
+                vec![(self.held.clone(), PRESS), (self.held.clone(), RELEASE)]
+            }
+        } else {
+            vec![(self.held.clone(), RELEASE)]
+        }
+    }
+
+    fn force_held(&mut self) -> Vec<(Key, i32)> {
+        if self.alone_timeout_at.is_some() {
+            self.alone_timeout_at = None;
+            vec![(self.held.clone(), PRESS)]
+        } else {
+            vec![]
+        }
+    }
+}