Overhaul the Keyboard API

Overhaul the keyboard API in winit to mimic the W3C specification
to achieve better crossplatform parity. The `KeyboardInput` event
is now uses `KeyEvent` which consists of:

  - `physical_key` - a cross platform way to refer to scancodes;
  - `logical_key`  - keysym value, which shows your key respecting the
                     layout;
  - `text`         - the text produced by this keypress;
  - `location`     - the location of the key on the keyboard;
  - `repeat`       - whether the key was produced by the repeat.

And also a `platform_specific` field which encapsulates extra
information on desktop platforms, like key without modifiers
and text with all modifiers.

The `Modifiers` were also slightly reworked as in, the information
whether the left or right modifier is pressed is now also exposed
on platforms where it could be queried reliably. The support was
also added for the web and orbital platforms finishing the API
change.

This change made the `OptionAsAlt` API on macOS redundant thus it
was removed all together.

Co-authored-by: Artúr Kovács <kovacs.artur.barnabas@gmail.com>
Co-authored-by: Kirill Chibisov <contact@kchibisov.com>
Co-authored-by: daxpedda <daxpedda@gmail.com>
Fixes: #2631.
Fixes: #2055.
Fixes: #2032.
Fixes: #1904.
Fixes: #1810.
Fixes: #1700.
Fixes: #1443.
Fixes: #1343.
Fixes: #1208.
Fixes: #1151.
Fixes: #812.
Fixes: #600.
Fixes: #361.
Fixes: #343.

src/platform_impl/linux/common/xkb_state.rs

@@ -0,0 +1,668 @@
+use std::convert::TryInto;
+use std::env;
+use std::ffi::CString;
+use std::os::raw::c_char;
+use std::os::unix::ffi::OsStringExt;
+use std::ptr;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+use smol_str::SmolStr;
+use xkbcommon_dl::{
+    self as ffi, xkb_state_component, XKBCOMMON_COMPOSE_HANDLE as XKBCH, XKBCOMMON_HANDLE as XKBH,
+};
+#[cfg(feature = "wayland")]
+use {memmap2::MmapOptions, wayland_backend::io_lifetimes::OwnedFd};
+#[cfg(feature = "x11")]
+use {x11_dl::xlib_xcb::xcb_connection_t, xkbcommon_dl::x11::XKBCOMMON_X11_HANDLE as XKBXH};
+
+use crate::event::KeyEvent;
+use crate::platform_impl::common::keymap;
+use crate::platform_impl::KeyEventExtra;
+use crate::{
+    event::ElementState,
+    keyboard::{Key, KeyCode, KeyLocation},
+};
+
+// TODO: Wire this up without using a static `AtomicBool`.
+static RESET_DEAD_KEYS: AtomicBool = AtomicBool::new(false);
+
+#[inline(always)]
+pub fn reset_dead_keys() {
+    RESET_DEAD_KEYS.store(true, Ordering::SeqCst);
+}
+
+#[derive(Debug)]
+pub struct KbdState {
+    #[cfg(feature = "x11")]
+    xcb_connection: *mut xcb_connection_t,
+    xkb_context: *mut ffi::xkb_context,
+    xkb_keymap: *mut ffi::xkb_keymap,
+    xkb_state: *mut ffi::xkb_state,
+    xkb_compose_table: *mut ffi::xkb_compose_table,
+    xkb_compose_state: *mut ffi::xkb_compose_state,
+    xkb_compose_state_2: *mut ffi::xkb_compose_state,
+    mods_state: ModifiersState,
+    #[cfg(feature = "x11")]
+    pub core_keyboard_id: i32,
+    scratch_buffer: Vec<u8>,
+}
+
+impl KbdState {
+    pub fn update_modifiers(
+        &mut self,
+        mods_depressed: u32,
+        mods_latched: u32,
+        mods_locked: u32,
+        depressed_group: u32,
+        latched_group: u32,
+        locked_group: u32,
+    ) {
+        if !self.ready() {
+            return;
+        }
+        let mask = unsafe {
+            (XKBH.xkb_state_update_mask)(
+                self.xkb_state,
+                mods_depressed,
+                mods_latched,
+                mods_locked,
+                depressed_group,
+                latched_group,
+                locked_group,
+            )
+        };
+        if mask.contains(xkb_state_component::XKB_STATE_MODS_EFFECTIVE) {
+            // effective value of mods have changed, we need to update our state
+            self.mods_state.update_with(self.xkb_state);
+        }
+    }
+
+    pub fn get_one_sym_raw(&mut self, keycode: u32) -> u32 {
+        if !self.ready() {
+            return 0;
+        }
+        unsafe { (XKBH.xkb_state_key_get_one_sym)(self.xkb_state, keycode) }
+    }
+
+    pub fn get_utf8_raw(&mut self, keycode: u32) -> Option<SmolStr> {
+        if !self.ready() {
+            return None;
+        }
+        let xkb_state = self.xkb_state;
+        self.make_string_with({
+            |ptr, len| unsafe { (XKBH.xkb_state_key_get_utf8)(xkb_state, keycode, ptr, len) }
+        })
+    }
+
+    fn compose_feed_normal(&mut self, keysym: u32) -> Option<ffi::xkb_compose_feed_result> {
+        self.compose_feed(self.xkb_compose_state, keysym)
+    }
+
+    fn compose_feed_2(&mut self, keysym: u32) -> Option<ffi::xkb_compose_feed_result> {
+        self.compose_feed(self.xkb_compose_state_2, keysym)
+    }
+
+    fn compose_feed(
+        &mut self,
+        xkb_compose_state: *mut ffi::xkb_compose_state,
+        keysym: u32,
+    ) -> Option<ffi::xkb_compose_feed_result> {
+        if !self.ready() || self.xkb_compose_state.is_null() {
+            return None;
+        }
+        if RESET_DEAD_KEYS.swap(false, Ordering::SeqCst) {
+            unsafe { self.init_compose() };
+        }
+        Some(unsafe { (XKBCH.xkb_compose_state_feed)(xkb_compose_state, keysym) })
+    }
+
+    fn compose_status_normal(&mut self) -> Option<ffi::xkb_compose_status> {
+        self.compose_status(self.xkb_compose_state)
+    }
+
+    fn compose_status(
+        &mut self,
+        xkb_compose_state: *mut ffi::xkb_compose_state,
+    ) -> Option<ffi::xkb_compose_status> {
+        if !self.ready() || xkb_compose_state.is_null() {
+            return None;
+        }
+        Some(unsafe { (XKBCH.xkb_compose_state_get_status)(xkb_compose_state) })
+    }
+
+    fn compose_get_utf8_normal(&mut self) -> Option<SmolStr> {
+        self.compose_get_utf8(self.xkb_compose_state)
+    }
+
+    fn compose_get_utf8_2(&mut self) -> Option<SmolStr> {
+        self.compose_get_utf8(self.xkb_compose_state_2)
+    }
+
+    fn compose_get_utf8(
+        &mut self,
+        xkb_compose_state: *mut ffi::xkb_compose_state,
+    ) -> Option<SmolStr> {
+        if !self.ready() || xkb_compose_state.is_null() {
+            return None;
+        }
+        self.make_string_with(|ptr, len| unsafe {
+            (XKBCH.xkb_compose_state_get_utf8)(xkb_compose_state, ptr, len)
+        })
+    }
+
+    /// Shared logic for constructing a string with `xkb_compose_state_get_utf8` and
+    /// `xkb_state_key_get_utf8`.
+    fn make_string_with<F>(&mut self, mut f: F) -> Option<SmolStr>
+    where
+        F: FnMut(*mut i8, usize) -> i32,
+    {
+        let size = f(ptr::null_mut(), 0);
+        if size == 0 {
+            return None;
+        }
+        let size = usize::try_from(size).unwrap();
+        self.scratch_buffer.clear();
+        // The allocated buffer must include space for the null-terminator
+        self.scratch_buffer.reserve(size + 1);
+        unsafe {
+            let written = f(
+                self.scratch_buffer.as_mut_ptr().cast(),
+                self.scratch_buffer.capacity(),
+            );
+            if usize::try_from(written).unwrap() != size {
+                // This will likely never happen
+                return None;
+            }
+            self.scratch_buffer.set_len(size);
+        };
+        byte_slice_to_smol_str(&self.scratch_buffer)
+    }
+
+    pub fn new() -> Result<Self, Error> {
+        if ffi::XKBCOMMON_OPTION.as_ref().is_none() {
+            return Err(Error::XKBNotFound);
+        }
+
+        let context =
+            unsafe { (XKBH.xkb_context_new)(ffi::xkb_context_flags::XKB_CONTEXT_NO_FLAGS) };
+        if context.is_null() {
+            return Err(Error::XKBNotFound);
+        }
+
+        let mut me = Self {
+            #[cfg(feature = "x11")]
+            xcb_connection: ptr::null_mut(),
+            xkb_context: context,
+            xkb_keymap: ptr::null_mut(),
+            xkb_state: ptr::null_mut(),
+            xkb_compose_table: ptr::null_mut(),
+            xkb_compose_state: ptr::null_mut(),
+            xkb_compose_state_2: ptr::null_mut(),
+            mods_state: ModifiersState::new(),
+            #[cfg(feature = "x11")]
+            core_keyboard_id: 0,
+            scratch_buffer: Vec::new(),
+        };
+
+        unsafe { me.init_compose() };
+
+        Ok(me)
+    }
+
+    #[cfg(feature = "x11")]
+    pub fn from_x11_xkb(connection: *mut xcb_connection_t) -> Result<Self, Error> {
+        let mut me = Self::new()?;
+        me.xcb_connection = connection;
+
+        let result = unsafe {
+            (XKBXH.xkb_x11_setup_xkb_extension)(
+                connection,
+                1,
+                2,
+                xkbcommon_dl::x11::xkb_x11_setup_xkb_extension_flags::XKB_X11_SETUP_XKB_EXTENSION_NO_FLAGS,
+                ptr::null_mut(),
+                ptr::null_mut(),
+                ptr::null_mut(),
+                ptr::null_mut(),
+            )
+        };
+        assert_eq!(result, 1, "Failed to initialize libxkbcommon");
+
+        unsafe { me.init_with_x11_keymap() };
+
+        Ok(me)
+    }
+
+    unsafe fn init_compose(&mut self) {
+        let locale = env::var_os("LC_ALL")
+            .and_then(|v| if v.is_empty() { None } else { Some(v) })
+            .or_else(|| env::var_os("LC_CTYPE"))
+            .and_then(|v| if v.is_empty() { None } else { Some(v) })
+            .or_else(|| env::var_os("LANG"))
+            .and_then(|v| if v.is_empty() { None } else { Some(v) })
+            .unwrap_or_else(|| "C".into());
+        let locale = CString::new(locale.into_vec()).unwrap();
+
+        let compose_table = (XKBCH.xkb_compose_table_new_from_locale)(
+            self.xkb_context,
+            locale.as_ptr(),
+            ffi::xkb_compose_compile_flags::XKB_COMPOSE_COMPILE_NO_FLAGS,
+        );
+
+        if compose_table.is_null() {
+            // init of compose table failed, continue without compose
+            return;
+        }
+
+        let compose_state = (XKBCH.xkb_compose_state_new)(
+            compose_table,
+            ffi::xkb_compose_state_flags::XKB_COMPOSE_STATE_NO_FLAGS,
+        );
+
+        if compose_state.is_null() {
+            // init of compose state failed, continue without compose
+            (XKBCH.xkb_compose_table_unref)(compose_table);
+            return;
+        }
+
+        let compose_state_2 = (XKBCH.xkb_compose_state_new)(
+            compose_table,
+            ffi::xkb_compose_state_flags::XKB_COMPOSE_STATE_NO_FLAGS,
+        );
+
+        if compose_state_2.is_null() {
+            // init of compose state failed, continue without compose
+            (XKBCH.xkb_compose_table_unref)(compose_table);
+            (XKBCH.xkb_compose_state_unref)(compose_state);
+            return;
+        }
+
+        self.xkb_compose_table = compose_table;
+        self.xkb_compose_state = compose_state;
+        self.xkb_compose_state_2 = compose_state_2;
+    }
+
+    unsafe fn post_init(&mut self, state: *mut ffi::xkb_state, keymap: *mut ffi::xkb_keymap) {
+        self.xkb_keymap = keymap;
+        self.xkb_state = state;
+        self.mods_state.update_with(state);
+    }
+
+    unsafe fn de_init(&mut self) {
+        (XKBH.xkb_state_unref)(self.xkb_state);
+        self.xkb_state = ptr::null_mut();
+        (XKBH.xkb_keymap_unref)(self.xkb_keymap);
+        self.xkb_keymap = ptr::null_mut();
+    }
+
+    #[cfg(feature = "x11")]
+    pub unsafe fn init_with_x11_keymap(&mut self) {
+        if !self.xkb_keymap.is_null() {
+            self.de_init();
+        }
+
+        // TODO: Support keyboards other than the "virtual core keyboard device".
+        self.core_keyboard_id = (XKBXH.xkb_x11_get_core_keyboard_device_id)(self.xcb_connection);
+        let keymap = (XKBXH.xkb_x11_keymap_new_from_device)(
+            self.xkb_context,
+            self.xcb_connection,
+            self.core_keyboard_id,
+            xkbcommon_dl::xkb_keymap_compile_flags::XKB_KEYMAP_COMPILE_NO_FLAGS,
+        );
+        if keymap.is_null() {
+            panic!("Failed to get keymap from X11 server.");
+        }
+
+        let state = (XKBXH.xkb_x11_state_new_from_device)(
+            keymap,
+            self.xcb_connection,
+            self.core_keyboard_id,
+        );
+        self.post_init(state, keymap);
+    }
+
+    #[cfg(feature = "wayland")]
+    pub unsafe fn init_with_fd(&mut self, fd: OwnedFd, size: usize) {
+        if !self.xkb_keymap.is_null() {
+            self.de_init();
+        }
+
+        let map = MmapOptions::new()
+            .len(size)
+            .map_copy_read_only(&fd)
+            .unwrap();
+
+        let keymap = (XKBH.xkb_keymap_new_from_string)(
+            self.xkb_context,
+            map.as_ptr() as *const _,
+            ffi::xkb_keymap_format::XKB_KEYMAP_FORMAT_TEXT_V1,
+            ffi::xkb_keymap_compile_flags::XKB_KEYMAP_COMPILE_NO_FLAGS,
+        );
+
+        if keymap.is_null() {
+            panic!("Received invalid keymap from compositor.");
+        }
+
+        let state = (XKBH.xkb_state_new)(keymap);
+        self.post_init(state, keymap);
+    }
+
+    #[cfg(feature = "wayland")]
+    pub fn key_repeats(&mut self, keycode: ffi::xkb_keycode_t) -> bool {
+        unsafe { (XKBH.xkb_keymap_key_repeats)(self.xkb_keymap, keycode) == 1 }
+    }
+
+    #[inline]
+    pub fn ready(&self) -> bool {
+        !self.xkb_state.is_null()
+    }
+
+    #[inline]
+    pub fn mods_state(&self) -> ModifiersState {
+        self.mods_state
+    }
+
+    pub fn process_key_event(
+        &mut self,
+        keycode: u32,
+        state: ElementState,
+        repeat: bool,
+    ) -> KeyEvent {
+        let mut event =
+            KeyEventResults::new(self, keycode, !repeat && state == ElementState::Pressed);
+        let physical_key = event.keycode();
+        let (logical_key, location) = event.key();
+        let text = event.text();
+        let (key_without_modifiers, _) = event.key_without_modifiers();
+        let text_with_all_modifiers = event.text_with_all_modifiers();
+
+        let platform_specific = KeyEventExtra {
+            key_without_modifiers,
+            text_with_all_modifiers,
+        };
+
+        KeyEvent {
+            physical_key,
+            logical_key,
+            text,
+            location,
+            state,
+            repeat,
+            platform_specific,
+        }
+    }
+
+    fn keysym_to_utf8_raw(&mut self, keysym: u32) -> Option<SmolStr> {
+        self.scratch_buffer.clear();
+        self.scratch_buffer.reserve(8);
+        loop {
+            let bytes_written = unsafe {
+                (XKBH.xkb_keysym_to_utf8)(
+                    keysym,
+                    self.scratch_buffer.as_mut_ptr().cast(),
+                    self.scratch_buffer.capacity(),
+                )
+            };
+            if bytes_written == 0 {
+                return None;
+            } else if bytes_written == -1 {
+                self.scratch_buffer.reserve(8);
+            } else {
+                unsafe {
+                    self.scratch_buffer
+                        .set_len(bytes_written.try_into().unwrap())
+                };
+                break;
+            }
+        }
+
+        // Remove the null-terminator
+        self.scratch_buffer.pop();
+        byte_slice_to_smol_str(&self.scratch_buffer)
+    }
+}
+
+impl Drop for KbdState {
+    fn drop(&mut self) {
+        unsafe {
+            if !self.xkb_compose_state.is_null() {
+                (XKBCH.xkb_compose_state_unref)(self.xkb_compose_state);
+            }
+            if !self.xkb_compose_state_2.is_null() {
+                (XKBCH.xkb_compose_state_unref)(self.xkb_compose_state_2);
+            }
+            if !self.xkb_compose_table.is_null() {
+                (XKBCH.xkb_compose_table_unref)(self.xkb_compose_table);
+            }
+            if !self.xkb_state.is_null() {
+                (XKBH.xkb_state_unref)(self.xkb_state);
+            }
+            if !self.xkb_keymap.is_null() {
+                (XKBH.xkb_keymap_unref)(self.xkb_keymap);
+            }
+            (XKBH.xkb_context_unref)(self.xkb_context);
+        }
+    }
+}
+
+struct KeyEventResults<'a> {
+    state: &'a mut KbdState,
+    keycode: u32,
+    keysym: u32,
+    compose: Option<XkbCompose>,
+}
+
+impl<'a> KeyEventResults<'a> {
+    fn new(state: &'a mut KbdState, keycode: u32, compose: bool) -> Self {
+        let keysym = state.get_one_sym_raw(keycode);
+
+        let compose = if compose {
+            Some(match state.compose_feed_normal(keysym) {
+                Some(ffi::xkb_compose_feed_result::XKB_COMPOSE_FEED_ACCEPTED) => {
+                    // Unwrapping is safe here, as `compose_feed` returns `None` when composition is uninitialized.
+                    XkbCompose::Accepted(state.compose_status_normal().unwrap())
+                }
+                Some(ffi::xkb_compose_feed_result::XKB_COMPOSE_FEED_IGNORED) => XkbCompose::Ignored,
+                None => XkbCompose::Uninitialized,
+            })
+        } else {
+            None
+        };
+
+        KeyEventResults {
+            state,
+            keycode,
+            keysym,
+            compose,
+        }
+    }
+
+    fn keycode(&mut self) -> KeyCode {
+        keymap::raw_keycode_to_keycode(self.keycode)
+    }
+
+    pub fn key(&mut self) -> (Key, KeyLocation) {
+        self.keysym_to_key(self.keysym)
+            .unwrap_or_else(|(key, location)| match self.compose {
+                Some(XkbCompose::Accepted(ffi::xkb_compose_status::XKB_COMPOSE_COMPOSING)) => {
+                    // When pressing a dead key twice, the non-combining variant of that character will be
+                    // produced. Since this function only concerns itself with a single keypress, we simulate
+                    // this double press here by feeding the keysym to the compose state twice.
+                    self.state.compose_feed_2(self.keysym);
+                    match self.state.compose_feed_2(self.keysym) {
+                        Some(ffi::xkb_compose_feed_result::XKB_COMPOSE_FEED_ACCEPTED) => (
+                            // Extracting only a single `char` here *should* be fine, assuming that no dead
+                            // key's non-combining variant ever occupies more than one `char`.
+                            Key::Dead(
+                                self.state
+                                    .compose_get_utf8_2()
+                                    .map(|s| s.chars().next().unwrap()),
+                            ),
+                            location,
+                        ),
+                        _ => (key, location),
+                    }
+                }
+                _ => (
+                    self.composed_text()
+                        .unwrap_or_else(|_| self.state.keysym_to_utf8_raw(self.keysym))
+                        .map(Key::Character)
+                        .unwrap_or(key),
+                    location,
+                ),
+            })
+    }
+
+    pub fn key_without_modifiers(&mut self) -> (Key, KeyLocation) {
+        // This will become a pointer to an array which libxkbcommon owns, so we don't need to deallocate it.
+        let mut keysyms = ptr::null();
+        let keysym_count = unsafe {
+            (XKBH.xkb_keymap_key_get_syms_by_level)(
+                self.state.xkb_keymap,
+                self.keycode,
+                0,
+                0,
+                &mut keysyms,
+            )
+        };
+        let keysym = if keysym_count == 1 {
+            unsafe { *keysyms }
+        } else {
+            0
+        };
+        self.keysym_to_key(keysym)
+            .unwrap_or_else(|(key, location)| {
+                (
+                    self.state
+                        .keysym_to_utf8_raw(keysym)
+                        .map(Key::Character)
+                        .unwrap_or(key),
+                    location,
+                )
+            })
+    }
+
+    fn keysym_to_key(&mut self, keysym: u32) -> Result<(Key, KeyLocation), (Key, KeyLocation)> {
+        let location = super::keymap::keysym_location(keysym);
+        let key = super::keymap::keysym_to_key(keysym);
+        if matches!(key, Key::Unidentified(_)) {
+            Err((key, location))
+        } else {
+            Ok((key, location))
+        }
+    }
+
+    pub fn text(&mut self) -> Option<SmolStr> {
+        self.composed_text()
+            .unwrap_or_else(|_| self.state.keysym_to_utf8_raw(self.keysym))
+    }
+
+    pub fn text_with_all_modifiers(&mut self) -> Option<SmolStr> {
+        // The current behaviour makes it so composing a character overrides attempts to input a
+        // control character with the `Ctrl` key. We can potentially add a configuration option
+        // if someone specifically wants the oppsite behaviour.
+        self.composed_text()
+            .unwrap_or_else(|_| self.state.get_utf8_raw(self.keycode))
+    }
+
+    fn composed_text(&mut self) -> Result<Option<SmolStr>, ()> {
+        if let Some(compose) = &self.compose {
+            match compose {
+                XkbCompose::Accepted(status) => match status {
+                    ffi::xkb_compose_status::XKB_COMPOSE_COMPOSED => {
+                        Ok(self.state.compose_get_utf8_normal())
+                    }
+                    ffi::xkb_compose_status::XKB_COMPOSE_NOTHING => Err(()),
+                    _ => Ok(None),
+                },
+                XkbCompose::Ignored | XkbCompose::Uninitialized => Err(()),
+            }
+        } else {
+            Err(())
+        }
+    }
+}
+
+/// Represents the current state of the keyboard modifiers
+///
+/// Each field of this struct represents a modifier and is `true` if this modifier is active.
+///
+/// For some modifiers, this means that the key is currently pressed, others are toggled
+/// (like caps lock).
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
+pub struct ModifiersState {
+    /// The "control" key
+    pub ctrl: bool,
+    /// The "alt" key
+    pub alt: bool,
+    /// The "shift" key
+    pub shift: bool,
+    /// The "Caps lock" key
+    pub caps_lock: bool,
+    /// The "logo" key
+    ///
+    /// Also known as the "windows" key on most keyboards
+    pub logo: bool,
+    /// The "Num lock" key
+    pub num_lock: bool,
+}
+
+impl ModifiersState {
+    fn new() -> Self {
+        Self::default()
+    }
+
+    fn update_with(&mut self, state: *mut ffi::xkb_state) {
+        let mod_name_is_active = |mod_name: &[u8]| unsafe {
+            (XKBH.xkb_state_mod_name_is_active)(
+                state,
+                mod_name.as_ptr() as *const c_char,
+                xkb_state_component::XKB_STATE_MODS_EFFECTIVE,
+            ) > 0
+        };
+        self.ctrl = mod_name_is_active(ffi::XKB_MOD_NAME_CTRL);
+        self.alt = mod_name_is_active(ffi::XKB_MOD_NAME_ALT);
+        self.shift = mod_name_is_active(ffi::XKB_MOD_NAME_SHIFT);
+        self.caps_lock = mod_name_is_active(ffi::XKB_MOD_NAME_CAPS);
+        self.logo = mod_name_is_active(ffi::XKB_MOD_NAME_LOGO);
+        self.num_lock = mod_name_is_active(ffi::XKB_MOD_NAME_NUM);
+    }
+}
+
+impl From<ModifiersState> for crate::keyboard::ModifiersState {
+    fn from(mods: ModifiersState) -> crate::keyboard::ModifiersState {
+        let mut to_mods = crate::keyboard::ModifiersState::empty();
+        to_mods.set(crate::keyboard::ModifiersState::SHIFT, mods.shift);
+        to_mods.set(crate::keyboard::ModifiersState::CONTROL, mods.ctrl);
+        to_mods.set(crate::keyboard::ModifiersState::ALT, mods.alt);
+        to_mods.set(crate::keyboard::ModifiersState::SUPER, mods.logo);
+        to_mods
+    }
+}
+
+#[derive(Debug)]
+pub enum Error {
+    /// libxkbcommon is not available
+    XKBNotFound,
+}
+
+#[derive(Copy, Clone, Debug)]
+enum XkbCompose {
+    Accepted(ffi::xkb_compose_status),
+    Ignored,
+    Uninitialized,
+}
+
+// Note: This is track_caller so we can have more informative line numbers when logging
+#[track_caller]
+fn byte_slice_to_smol_str(bytes: &[u8]) -> Option<SmolStr> {
+    std::str::from_utf8(bytes)
+        .map(SmolStr::new)
+        .map_err(|e| {
+            warn!(
+                "UTF-8 received from libxkbcommon ({:?}) was invalid: {e}",
+                bytes
+            )
+        })
+        .ok()
+}