Add new Ime event for desktop platforms

This commit brings new Ime event to account for preedit state of input
method, also adding `Window::set_ime_allowed` to toggle IME input on
the particular window.

This commit implements API as designed in #1497 for desktop platforms.

Co-authored-by: Artur Kovacs <kovacs.artur.barnabas@gmail.com>
Co-authored-by: Markus Siglreithmaier <m.siglreith@gmail.com>
Co-authored-by: Murarth <murarth@gmail.com>
Co-authored-by: Yusuke Kominami <yukke.konan@gmail.com>
Co-authored-by: moko256 <koutaro.mo@gmail.com>

src/platform_impl/linux/mod.rs

@@ -477,6 +477,11 @@ impl Window {
         x11_or_wayland!(match self; Window(w) => w.set_ime_position(position))
     }
 
+    #[inline]
+    pub fn set_ime_allowed(&self, allowed: bool) {
+        x11_or_wayland!(match self; Window(w) => w.set_ime_allowed(allowed))
+    }
+
     #[inline]
     pub fn focus_window(&self) {
         match self {

src/platform_impl/linux/wayland/event_loop/mod.rs

@@ -32,10 +32,9 @@ mod sink;
 mod state;
 
 pub use proxy::EventLoopProxy;
+pub use sink::EventSink;
 pub use state::WinitState;
 
-use sink::EventSink;
-
 type WinitDispatcher = calloop::Dispatcher<'static, WaylandSource, WinitState>;
 
 pub struct EventLoopWindowTarget<T> {

src/platform_impl/linux/wayland/seat/text_input/handlers.rs

@@ -5,11 +5,11 @@ use sctk::reexports::protocols::unstable::text_input::v3::client::zwp_text_input
     Event as TextInputEvent, ZwpTextInputV3,
 };
 
-use crate::event::WindowEvent;
+use crate::event::{Ime, WindowEvent};
 use crate::platform_impl::wayland;
 use crate::platform_impl::wayland::event_loop::WinitState;
 
-use super::{TextInputHandler, TextInputInner};
+use super::{Preedit, TextInputHandler, TextInputInner};
 
 #[inline]
 pub(super) fn handle_text_input(
@@ -30,8 +30,11 @@ pub(super) fn handle_text_input(
             inner.target_window_id = Some(window_id);
 
             // Enable text input on that surface.
-            text_input.enable();
-            text_input.commit();
+            if window_handle.ime_allowed.get() {
+                text_input.enable();
+                text_input.commit();
+                event_sink.push_window_event(WindowEvent::Ime(Ime::Enabled), window_id);
+            }
 
             // Notify a window we're currently over about text input handler.
             let text_input_handler = TextInputHandler {
@@ -58,19 +61,45 @@ pub(super) fn handle_text_input(
                 text_input: text_input.detach(),
             };
             window_handle.text_input_left(text_input_handler);
+            event_sink.push_window_event(WindowEvent::Ime(Ime::Disabled), window_id);
+        }
+        TextInputEvent::PreeditString {
+            text,
+            cursor_begin,
+            cursor_end,
+        } => {
+            let cursor_begin = usize::try_from(cursor_begin).ok();
+            let cursor_end = usize::try_from(cursor_end).ok();
+            let text = text.unwrap_or_default();
+            inner.pending_preedit = Some(Preedit {
+                text,
+                cursor_begin,
+                cursor_end,
+            });
         }
         TextInputEvent::CommitString { text } => {
-            // Update currenly commited string.
-            inner.commit_string = text;
+            // Update currenly commited string and reset previous preedit.
+            inner.pending_preedit = None;
+            inner.pending_commit = Some(text.unwrap_or_default());
         }
         TextInputEvent::Done { .. } => {
-            let (window_id, text) = match (inner.target_window_id, inner.commit_string.take()) {
-                (Some(window_id), Some(text)) => (window_id, text),
+            let window_id = match inner.target_window_id {
+                Some(window_id) => window_id,
                 _ => return,
             };
 
-            for ch in text.chars() {
-                event_sink.push_window_event(WindowEvent::ReceivedCharacter(ch), window_id);
+            if let Some(text) = inner.pending_commit.take() {
+                event_sink.push_window_event(WindowEvent::Ime(Ime::Commit(text)), window_id);
+            }
+
+            // Push preedit string we've got after latest commit.
+            if let Some(preedit) = inner.pending_preedit.take() {
+                let cursor_range = preedit
+                    .cursor_begin
+                    .map(|b| (b, preedit.cursor_end.unwrap_or(b)));
+
+                let event = Ime::Preedit(preedit.text, cursor_range);
+                event_sink.push_window_event(WindowEvent::Ime(event), window_id);
             }
         }
         _ => (),

src/platform_impl/linux/wayland/seat/text_input/mod.rs

@@ -20,6 +20,17 @@ impl TextInputHandler {
         self.text_input.set_cursor_rectangle(x, y, 0, 0);
         self.text_input.commit();
     }
+
+    #[inline]
+    pub fn set_input_allowed(&self, allowed: bool) {
+        if allowed {
+            self.text_input.enable();
+        } else {
+            self.text_input.disable();
+        }
+
+        self.text_input.commit();
+    }
 }
 
 /// A wrapper around text input to automatically destroy the object on `Drop`.
@@ -52,15 +63,25 @@ struct TextInputInner {
     /// Currently focused surface.
     target_window_id: Option<WindowId>,
 
-    /// Pending string to commit.
-    commit_string: Option<String>,
+    /// Pending commit event which will be dispatched on `text_input_v3::Done`.
+    pending_commit: Option<String>,
+
+    /// Pending preedit event which will be dispatched on `text_input_v3::Done`.
+    pending_preedit: Option<Preedit>,
+}
+
+struct Preedit {
+    text: String,
+    cursor_begin: Option<usize>,
+    cursor_end: Option<usize>,
 }
 
 impl TextInputInner {
     fn new() -> Self {
         Self {
             target_window_id: None,
-            commit_string: None,
+            pending_commit: None,
+            pending_preedit: None,
         }
     }
 }

src/platform_impl/linux/wayland/window/mod.rs

@@ -496,7 +496,12 @@ impl Window {
     pub fn set_ime_position(&self, position: Position) {
         let scale_factor = self.scale_factor() as f64;
         let position = position.to_logical(scale_factor);
-        self.send_request(WindowRequest::IMEPosition(position));
+        self.send_request(WindowRequest::ImePosition(position));
+    }
+
+    #[inline]
+    pub fn set_ime_allowed(&self, allowed: bool) {
+        self.send_request(WindowRequest::AllowIme(allowed));
     }
 
     #[inline]

src/platform_impl/linux/wayland/window/shim.rs

@@ -12,10 +12,10 @@ use sctk::window::{Decorations, FallbackFrame, Window};
 
 use crate::dpi::{LogicalPosition, LogicalSize};
 
-use crate::event::WindowEvent;
+use crate::event::{Ime, WindowEvent};
 use crate::platform_impl::wayland;
 use crate::platform_impl::wayland::env::WinitEnv;
-use crate::platform_impl::wayland::event_loop::WinitState;
+use crate::platform_impl::wayland::event_loop::{EventSink, WinitState};
 use crate::platform_impl::wayland::seat::pointer::WinitPointer;
 use crate::platform_impl::wayland::seat::text_input::TextInputHandler;
 use crate::platform_impl::wayland::WindowId;
@@ -69,7 +69,10 @@ pub enum WindowRequest {
     FrameSize(LogicalSize<u32>),
 
     /// Set IME window position.
-    IMEPosition(LogicalPosition<u32>),
+    ImePosition(LogicalPosition<u32>),
+
+    /// Enable IME on the given window.
+    AllowIme(bool),
 
     /// Request Attention.
     ///
@@ -157,6 +160,9 @@ pub struct WindowHandle {
     /// Whether the window is resizable.
     pub is_resizable: Cell<bool>,
 
+    /// Allow IME events for that window.
+    pub ime_allowed: Cell<bool>,
+
     /// Visible cursor or not.
     cursor_visible: Cell<bool>,
 
@@ -204,6 +210,7 @@ impl WindowHandle {
             xdg_activation,
             attention_requested: Cell::new(false),
             compositor,
+            ime_allowed: Cell::new(false),
         }
     }
 
@@ -333,6 +340,27 @@ impl WindowHandle {
         }
     }
 
+    pub fn set_ime_allowed(&self, allowed: bool, event_sink: &mut EventSink) {
+        if self.ime_allowed.get() == allowed {
+            return;
+        }
+
+        self.ime_allowed.replace(allowed);
+        let window_id = wayland::make_wid(self.window.surface());
+
+        for text_input in self.text_inputs.iter() {
+            text_input.set_input_allowed(allowed);
+        }
+
+        let event = if allowed {
+            WindowEvent::Ime(Ime::Enabled)
+        } else {
+            WindowEvent::Ime(Ime::Disabled)
+        };
+
+        event_sink.push_window_event(event, window_id);
+    }
+
     pub fn set_cursor_visible(&self, visible: bool) {
         self.cursor_visible.replace(visible);
         let cursor_icon = match visible {
@@ -387,9 +415,13 @@ pub fn handle_window_requests(winit_state: &mut WinitState) {
                 WindowRequest::NewCursorIcon(cursor_icon) => {
                     window_handle.set_cursor_icon(cursor_icon);
                 }
-                WindowRequest::IMEPosition(position) => {
+                WindowRequest::ImePosition(position) => {
                     window_handle.set_ime_position(position);
                 }
+                WindowRequest::AllowIme(allow) => {
+                    let event_sink = &mut winit_state.event_sink;
+                    window_handle.set_ime_allowed(allow, event_sink);
+                }
                 WindowRequest::GrabCursor(grab) => {
                     window_handle.set_cursor_grab(grab);
                 }

src/platform_impl/linux/x11/event_processor.rs

@@ -12,10 +12,12 @@ use super::{
 
 use util::modifiers::{ModifierKeyState, ModifierKeymap};
 
+use crate::platform_impl::platform::x11::ime::{ImeEvent, ImeEventReceiver, ImeRequest};
 use crate::{
     dpi::{PhysicalPosition, PhysicalSize},
     event::{
-        DeviceEvent, ElementState, Event, KeyboardInput, ModifiersState, TouchPhase, WindowEvent,
+        DeviceEvent, ElementState, Event, Ime, KeyboardInput, ModifiersState, TouchPhase,
+        WindowEvent,
     },
     event_loop::EventLoopWindowTarget as RootELW,
 };
@@ -26,6 +28,7 @@ const KEYCODE_OFFSET: u8 = 8;
 pub(super) struct EventProcessor<T: 'static> {
     pub(super) dnd: Dnd,
     pub(super) ime_receiver: ImeReceiver,
+    pub(super) ime_event_receiver: ImeEventReceiver,
     pub(super) randr_event_offset: c_int,
     pub(super) devices: RefCell<HashMap<DeviceId, Device>>,
     pub(super) xi2ext: XExtension,
@@ -37,6 +40,7 @@ pub(super) struct EventProcessor<T: 'static> {
     pub(super) first_touch: Option<u64>,
     // Currently focused window belonging to this process
     pub(super) active_window: Option<ffi::Window>,
+    pub(super) is_composing: bool,
 }
 
 impl<T: 'static> EventProcessor<T> {
@@ -567,7 +571,7 @@ impl<T: 'static> EventProcessor<T> {
 
                 // When a compose sequence or IME pre-edit is finished, it ends in a KeyPress with
                 // a keycode of 0.
-                if keycode != 0 {
+                if keycode != 0 && !self.is_composing {
                     let scancode = keycode - KEYCODE_OFFSET as u32;
                     let keysym = wt.xconn.lookup_keysym(xkev);
                     let virtual_keycode = events::keysym_to_element(keysym as c_uint);
@@ -602,12 +606,25 @@ impl<T: 'static> EventProcessor<T> {
                         return;
                     };
 
-                    for chr in written.chars() {
+                    // If we're composing right now, send the string we've got from X11 via
+                    // Ime::Commit.
+                    if self.is_composing && keycode == 0 && !written.is_empty() {
                         let event = Event::WindowEvent {
                             window_id,
-                            event: WindowEvent::ReceivedCharacter(chr),
+                            event: WindowEvent::Ime(Ime::Commit(written)),
                         };
+
+                        self.is_composing = false;
                         callback(event);
+                    } else {
+                        for chr in written.chars() {
+                            let event = Event::WindowEvent {
+                                window_id,
+                                event: WindowEvent::ReceivedCharacter(chr),
+                            };
+
+                            callback(event);
+                        }
                     }
                 }
             }
@@ -1223,8 +1240,59 @@ impl<T: 'static> EventProcessor<T> {
             }
         }
 
-        if let Ok((window_id, x, y)) = self.ime_receiver.try_recv() {
-            wt.ime.borrow_mut().send_xim_spot(window_id, x, y);
+        // Handle IME requests.
+        if let Ok(request) = self.ime_receiver.try_recv() {
+            let mut ime = wt.ime.borrow_mut();
+            match request {
+                ImeRequest::Position(window_id, x, y) => {
+                    ime.send_xim_spot(window_id, x, y);
+                }
+                ImeRequest::Allow(window_id, allowed) => {
+                    ime.set_ime_allowed(window_id, allowed);
+                }
+            }
+        }
+
+        match self.ime_event_receiver.try_recv() {
+            Ok((window, event)) => match event {
+                ImeEvent::Enabled => {
+                    callback(Event::WindowEvent {
+                        window_id: mkwid(window),
+                        event: WindowEvent::Ime(Ime::Enabled),
+                    });
+                }
+                ImeEvent::Start => {
+                    self.is_composing = true;
+                    callback(Event::WindowEvent {
+                        window_id: mkwid(window),
+                        event: WindowEvent::Ime(Ime::Preedit("".to_owned(), None)),
+                    });
+                }
+                ImeEvent::Update(text, position) => {
+                    if self.is_composing {
+                        callback(Event::WindowEvent {
+                            window_id: mkwid(window),
+                            event: WindowEvent::Ime(Ime::Preedit(text, Some((position, position)))),
+                        });
+                    }
+                }
+                ImeEvent::End => {
+                    self.is_composing = false;
+                    // Issue empty preedit on `Done`.
+                    callback(Event::WindowEvent {
+                        window_id: mkwid(window),
+                        event: WindowEvent::Ime(Ime::Preedit(String::new(), None)),
+                    });
+                }
+                ImeEvent::Disabled => {
+                    self.is_composing = false;
+                    callback(Event::WindowEvent {
+                        window_id: mkwid(window),
+                        event: WindowEvent::Ime(Ime::Disabled),
+                    });
+                }
+            },
+            Err(_) => (),
         }
     }
 

src/platform_impl/linux/x11/ime/callbacks.rs

@@ -108,8 +108,19 @@ unsafe fn replace_im(inner: *mut ImeInner) -> Result<(), ReplaceImError> {
     let mut new_contexts = HashMap::new();
     for (window, old_context) in (*inner).contexts.iter() {
         let spot = old_context.as_ref().map(|old_context| old_context.ic_spot);
+        let is_allowed = old_context
+            .as_ref()
+            .map(|old_context| old_context.is_allowed)
+            .unwrap_or_default();
         let new_context = {
-            let result = ImeContext::new(xconn, new_im.im, *window, spot);
+            let result = ImeContext::new(
+                xconn,
+                new_im.im,
+                *window,
+                spot,
+                is_allowed,
+                (*inner).event_sender.clone(),
+            );
             if result.is_err() {
                 let _ = close_im(xconn, new_im.im);
             }

src/platform_impl/linux/x11/ime/context.rs

@@ -1,41 +1,196 @@
-use std::{
-    os::raw::{c_short, c_void},
-    ptr,
-    sync::Arc,
-};
+use std::mem::transmute;
+use std::os::raw::c_short;
+use std::ptr;
+use std::sync::Arc;
 
 use super::{ffi, util, XConnection, XError};
+use crate::platform_impl::platform::x11::ime::{ImeEvent, ImeEventSender};
+use std::ffi::CStr;
+use x11_dl::xlib::{XIMCallback, XIMPreeditCaretCallbackStruct, XIMPreeditDrawCallbackStruct};
 
+/// IME creation error.
 #[derive(Debug)]
 pub enum ImeContextCreationError {
+    /// Got the error from Xlib.
     XError(XError),
+
+    /// Got null pointer from Xlib but without exact reason.
     Null,
 }
 
-unsafe fn create_pre_edit_attr<'a>(
-    xconn: &'a Arc<XConnection>,
-    ic_spot: &'a ffi::XPoint,
-) -> util::XSmartPointer<'a, c_void> {
-    util::XSmartPointer::new(
-        xconn,
-        (xconn.xlib.XVaCreateNestedList)(
-            0,
-            ffi::XNSpotLocation_0.as_ptr() as *const _,
-            ic_spot,
-            ptr::null_mut::<()>(),
-        ),
-    )
-    .expect("XVaCreateNestedList returned NULL")
+/// The callback used by XIM preedit functions.
+type XIMProcNonnull = unsafe extern "C" fn(ffi::XIM, ffi::XPointer, ffi::XPointer);
+
+/// Wrapper for creating XIM callbacks.
+#[inline]
+fn create_xim_callback(client_data: ffi::XPointer, callback: XIMProcNonnull) -> ffi::XIMCallback {
+    XIMCallback {
+        client_data,
+        callback: Some(callback),
+    }
 }
 
-// WARNING: this struct doesn't destroy its XIC resource when dropped.
+/// The server started preedit.
+extern "C" fn preedit_start_callback(
+    _xim: ffi::XIM,
+    client_data: ffi::XPointer,
+    _call_data: ffi::XPointer,
+) -> i32 {
+    let client_data = unsafe { &mut *(client_data as *mut ImeContextClientData) };
+
+    client_data.text.clear();
+    client_data.cursor_pos = 0;
+    client_data
+        .event_sender
+        .send((client_data.window, ImeEvent::Start))
+        .expect("failed to send preedit start event");
+    -1
+}
+
+/// Done callback is used when the preedit should be hidden.
+extern "C" fn preedit_done_callback(
+    _xim: ffi::XIM,
+    client_data: ffi::XPointer,
+    _call_data: ffi::XPointer,
+) {
+    let client_data = unsafe { &mut *(client_data as *mut ImeContextClientData) };
+
+    // Drop text buffer and reset cursor position on done.
+    client_data.text = Vec::new();
+    client_data.cursor_pos = 0;
+
+    client_data
+        .event_sender
+        .send((client_data.window, ImeEvent::End))
+        .expect("failed to send preedit end event");
+}
+
+fn calc_byte_position(text: &Vec<char>, pos: usize) -> usize {
+    let mut byte_pos = 0;
+    for i in 0..pos {
+        byte_pos += text[i].len_utf8();
+    }
+    byte_pos
+}
+
+/// Preedit text information to be drawn inline by the client.
+extern "C" fn preedit_draw_callback(
+    _xim: ffi::XIM,
+    client_data: ffi::XPointer,
+    call_data: ffi::XPointer,
+) {
+    let client_data = unsafe { &mut *(client_data as *mut ImeContextClientData) };
+    let call_data = unsafe { &mut *(call_data as *mut XIMPreeditDrawCallbackStruct) };
+    client_data.cursor_pos = call_data.caret as usize;
+
+    let chg_range =
+        call_data.chg_first as usize..(call_data.chg_first + call_data.chg_length) as usize;
+    if chg_range.start > client_data.text.len() || chg_range.end > client_data.text.len() {
+        warn!(
+            "invalid chg range: buffer length={}, but chg_first={} chg_lengthg={}",
+            client_data.text.len(),
+            call_data.chg_first,
+            call_data.chg_length
+        );
+        return;
+    }
+
+    // NULL indicate text deletion
+    let mut new_chars = if call_data.text.is_null() {
+        Vec::new()
+    } else {
+        let xim_text = unsafe { &mut *(call_data.text) };
+        if xim_text.encoding_is_wchar > 0 {
+            return;
+        }
+        let new_text = unsafe { CStr::from_ptr(xim_text.string.multi_byte) };
+
+        String::from(new_text.to_str().expect("Invalid UTF-8 String from IME"))
+            .chars()
+            .collect()
+    };
+    let mut old_text_tail = client_data.text.split_off(chg_range.end);
+    client_data.text.truncate(chg_range.start);
+    client_data.text.append(&mut new_chars);
+    client_data.text.append(&mut old_text_tail);
+    let cursor_byte_pos = calc_byte_position(&client_data.text, client_data.cursor_pos);
+
+    client_data
+        .event_sender
+        .send((
+            client_data.window,
+            ImeEvent::Update(client_data.text.iter().collect(), cursor_byte_pos),
+        ))
+        .expect("failed to send preedit update event");
+}
+
+/// Handling of cursor movements in preedit text.
+extern "C" fn preedit_caret_callback(
+    _xim: ffi::XIM,
+    client_data: ffi::XPointer,
+    call_data: ffi::XPointer,
+) {
+    let client_data = unsafe { &mut *(client_data as *mut ImeContextClientData) };
+    let call_data = unsafe { &mut *(call_data as *mut XIMPreeditCaretCallbackStruct) };
+
+    if call_data.direction == ffi::XIMCaretDirection::XIMAbsolutePosition {
+        client_data.cursor_pos = call_data.position as usize;
+        let cursor_byte_pos = calc_byte_position(&client_data.text, client_data.cursor_pos);
+
+        client_data
+            .event_sender
+            .send((
+                client_data.window,
+                ImeEvent::Update(client_data.text.iter().collect(), cursor_byte_pos),
+            ))
+            .expect("failed to send preedit update event");
+    }
+}
+
+/// Struct to simplify callback creation and latter passing into Xlib XIM.
+struct PreeditCallbacks {
+    start_callback: ffi::XIMCallback,
+    done_callback: ffi::XIMCallback,
+    draw_callback: ffi::XIMCallback,
+    caret_callback: ffi::XIMCallback,
+}
+
+impl PreeditCallbacks {
+    pub fn new(client_data: ffi::XPointer) -> PreeditCallbacks {
+        let start_callback = create_xim_callback(client_data, unsafe {
+            transmute(preedit_start_callback as usize)
+        });
+        let done_callback = create_xim_callback(client_data, preedit_done_callback);
+        let caret_callback = create_xim_callback(client_data, preedit_caret_callback);
+        let draw_callback = create_xim_callback(client_data, preedit_draw_callback);
+
+        PreeditCallbacks {
+            start_callback,
+            done_callback,
+            caret_callback,
+            draw_callback,
+        }
+    }
+}
+
+struct ImeContextClientData {
+    window: ffi::Window,
+    event_sender: ImeEventSender,
+    text: Vec<char>,
+    cursor_pos: usize,
+}
+
+// XXX: this struct doesn't destroy its XIC resource when dropped.
 // This is intentional, as it doesn't have enough information to know whether or not the context
 // still exists on the server. Since `ImeInner` has that awareness, destruction must be handled
 // through `ImeInner`.
-#[derive(Debug)]
 pub struct ImeContext {
-    pub ic: ffi::XIC,
-    pub ic_spot: ffi::XPoint,
+    pub(super) ic: ffi::XIC,
+    pub(super) ic_spot: ffi::XPoint,
+    pub(super) is_allowed: bool,
+    // Since the data is passed shared between X11 XIM callbacks, but couldn't be direclty free from
+    // there we keep the pointer to automatically deallocate it.
+    _client_data: Box<ImeContextClientData>,
 }
 
 impl ImeContext {
@@ -44,66 +199,111 @@ impl ImeContext {
         im: ffi::XIM,
         window: ffi::Window,
         ic_spot: Option<ffi::XPoint>,
+        is_allowed: bool,
+        event_sender: ImeEventSender,
     ) -> Result<Self, ImeContextCreationError> {
-        let ic = if let Some(ic_spot) = ic_spot {
-            ImeContext::create_ic_with_spot(xconn, im, window, ic_spot)
+        let client_data = Box::into_raw(Box::new(ImeContextClientData {
+            window,
+            event_sender,
+            text: Vec::new(),
+            cursor_pos: 0,
+        }));
+
+        let ic = if is_allowed {
+            ImeContext::create_ic(xconn, im, window, client_data as ffi::XPointer)
+                .ok_or(ImeContextCreationError::Null)?
         } else {
-            ImeContext::create_ic(xconn, im, window)
+            ImeContext::create_none_ic(xconn, im, window).ok_or(ImeContextCreationError::Null)?
         };
 
-        let ic = ic.ok_or(ImeContextCreationError::Null)?;
         xconn
             .check_errors()
             .map_err(ImeContextCreationError::XError)?;
 
-        Ok(ImeContext {
+        let mut context = ImeContext {
             ic,
-            ic_spot: ic_spot.unwrap_or(ffi::XPoint { x: 0, y: 0 }),
-        })
+            ic_spot: ffi::XPoint { x: 0, y: 0 },
+            is_allowed,
+            _client_data: Box::from_raw(client_data),
+        };
+
+        // Set the spot location, if it's present.
+        if let Some(ic_spot) = ic_spot {
+            context.set_spot(xconn, ic_spot.x, ic_spot.y)
+        }
+
+        Ok(context)
+    }
+
+    unsafe fn create_none_ic(
+        xconn: &Arc<XConnection>,
+        im: ffi::XIM,
+        window: ffi::Window,
+    ) -> Option<ffi::XIC> {
+        let ic = (xconn.xlib.XCreateIC)(
+            im,
+            ffi::XNInputStyle_0.as_ptr() as *const _,
+            ffi::XIMPreeditNone | ffi::XIMStatusNone,
+            ffi::XNClientWindow_0.as_ptr() as *const _,
+            window,
+            ptr::null_mut::<()>(),
+        );
+
+        (!ic.is_null()).then(|| ic)
     }
 
     unsafe fn create_ic(
         xconn: &Arc<XConnection>,
         im: ffi::XIM,
         window: ffi::Window,
+        client_data: ffi::XPointer,
     ) -> Option<ffi::XIC> {
-        let ic = (xconn.xlib.XCreateIC)(
-            im,
-            ffi::XNInputStyle_0.as_ptr() as *const _,
-            ffi::XIMPreeditNothing | ffi::XIMStatusNothing,
-            ffi::XNClientWindow_0.as_ptr() as *const _,
-            window,
-            ptr::null_mut::<()>(),
-        );
-        if ic.is_null() {
-            None
-        } else {
-            Some(ic)
-        }
-    }
+        let preedit_callbacks = PreeditCallbacks::new(client_data);
+        let preedit_attr = util::XSmartPointer::new(
+            xconn,
+            (xconn.xlib.XVaCreateNestedList)(
+                0,
+                ffi::XNPreeditStartCallback_0.as_ptr() as *const _,
+                &(preedit_callbacks.start_callback) as *const _,
+                ffi::XNPreeditDoneCallback_0.as_ptr() as *const _,
+                &(preedit_callbacks.done_callback) as *const _,
+                ffi::XNPreeditCaretCallback_0.as_ptr() as *const _,
+                &(preedit_callbacks.caret_callback) as *const _,
+                ffi::XNPreeditDrawCallback_0.as_ptr() as *const _,
+                &(preedit_callbacks.draw_callback) as *const _,
+                ptr::null_mut::<()>(),
+            ),
+        )
+        .expect("XVaCreateNestedList returned NULL");
 
-    unsafe fn create_ic_with_spot(
-        xconn: &Arc<XConnection>,
-        im: ffi::XIM,
-        window: ffi::Window,
-        ic_spot: ffi::XPoint,
-    ) -> Option<ffi::XIC> {
-        let pre_edit_attr = create_pre_edit_attr(xconn, &ic_spot);
-        let ic = (xconn.xlib.XCreateIC)(
-            im,
-            ffi::XNInputStyle_0.as_ptr() as *const _,
-            ffi::XIMPreeditNothing | ffi::XIMStatusNothing,
-            ffi::XNClientWindow_0.as_ptr() as *const _,
-            window,
-            ffi::XNPreeditAttributes_0.as_ptr() as *const _,
-            pre_edit_attr.ptr,
-            ptr::null_mut::<()>(),
-        );
-        if ic.is_null() {
-            None
-        } else {
-            Some(ic)
-        }
+        let ic = {
+            let ic = (xconn.xlib.XCreateIC)(
+                im,
+                ffi::XNInputStyle_0.as_ptr() as *const _,
+                ffi::XIMPreeditCallbacks | ffi::XIMStatusNothing,
+                ffi::XNClientWindow_0.as_ptr() as *const _,
+                window,
+                ffi::XNPreeditAttributes_0.as_ptr() as *const _,
+                preedit_attr.ptr,
+                ptr::null_mut::<()>(),
+            );
+
+            // If we've failed to create IC with preedit callbacks fallback to normal one.
+            if ic.is_null() {
+                (xconn.xlib.XCreateIC)(
+                    im,
+                    ffi::XNInputStyle_0.as_ptr() as *const _,
+                    ffi::XIMPreeditNothing | ffi::XIMStatusNothing,
+                    ffi::XNClientWindow_0.as_ptr() as *const _,
+                    window,
+                    ptr::null_mut::<()>(),
+                )
+            } else {
+                ic
+            }
+        };
+
+        (!ic.is_null()).then(|| ic)
     }
 
     pub fn focus(&self, xconn: &Arc<XConnection>) -> Result<(), XError> {
@@ -120,18 +320,34 @@ impl ImeContext {
         xconn.check_errors()
     }
 
+    // Set the spot for preedit text. Setting spot isn't working with libX11 when preedit callbacks
+    // are being used. Certain IMEs do show selection window, but it's placed in bottom left of the
+    // window and couldn't be changed.
+    //
+    // For me see: https://bugs.freedesktop.org/show_bug.cgi?id=1580.
     pub fn set_spot(&mut self, xconn: &Arc<XConnection>, x: c_short, y: c_short) {
-        if self.ic_spot.x == x && self.ic_spot.y == y {
+        if !self.is_allowed || self.ic_spot.x == x && self.ic_spot.y == y {
             return;
         }
+
         self.ic_spot = ffi::XPoint { x, y };
 
         unsafe {
-            let pre_edit_attr = create_pre_edit_attr(xconn, &self.ic_spot);
+            let preedit_attr = util::XSmartPointer::new(
+                xconn,
+                (xconn.xlib.XVaCreateNestedList)(
+                    0,
+                    ffi::XNSpotLocation_0.as_ptr(),
+                    &self.ic_spot,
+                    ptr::null_mut::<()>(),
+                ),
+            )
+            .expect("XVaCreateNestedList returned NULL");
+
             (xconn.xlib.XSetICValues)(
                 self.ic,
                 ffi::XNPreeditAttributes_0.as_ptr() as *const _,
-                pre_edit_attr.ptr,
+                preedit_attr.ptr,
                 ptr::null_mut::<()>(),
             );
         }

src/platform_impl/linux/x11/ime/inner.rs

@@ -3,6 +3,7 @@ use std::{collections::HashMap, mem, ptr, sync::Arc};
 use super::{ffi, XConnection, XError};
 
 use super::{context::ImeContext, input_method::PotentialInputMethods};
+use crate::platform_impl::platform::x11::ime::ImeEventSender;
 
 pub unsafe fn close_im(xconn: &Arc<XConnection>, im: ffi::XIM) -> Result<(), XError> {
     (xconn.xlib.XCloseIM)(im);
@@ -22,6 +23,7 @@ pub struct ImeInner {
     pub contexts: HashMap<ffi::Window, Option<ImeContext>>,
     // WARNING: this is initially zeroed!
     pub destroy_callback: ffi::XIMCallback,
+    pub event_sender: ImeEventSender,
     // Indicates whether or not the the input method was destroyed on the server end
     // (i.e. if ibus/fcitx/etc. was terminated/restarted)
     pub is_destroyed: bool,
@@ -29,13 +31,18 @@ pub struct ImeInner {
 }
 
 impl ImeInner {
-    pub fn new(xconn: Arc<XConnection>, potential_input_methods: PotentialInputMethods) -> Self {
+    pub fn new(
+        xconn: Arc<XConnection>,
+        potential_input_methods: PotentialInputMethods,
+        event_sender: ImeEventSender,
+    ) -> Self {
         ImeInner {
             xconn,
             im: ptr::null_mut(),
             potential_input_methods,
             contexts: HashMap::new(),
             destroy_callback: unsafe { mem::zeroed() },
+            event_sender,
             is_destroyed: false,
             is_fallback: false,
         }

src/platform_impl/linux/x11/ime/mod.rs

@@ -19,9 +19,29 @@ use self::{
     inner::{close_im, ImeInner},
     input_method::PotentialInputMethods,
 };
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub enum ImeEvent {
+    Enabled,
+    Start,
+    Update(String, usize),
+    End,
+    Disabled,
+}
 
-pub type ImeReceiver = Receiver<(ffi::Window, i16, i16)>;
-pub type ImeSender = Sender<(ffi::Window, i16, i16)>;
+pub type ImeReceiver = Receiver<ImeRequest>;
+pub type ImeSender = Sender<ImeRequest>;
+pub type ImeEventReceiver = Receiver<(ffi::Window, ImeEvent)>;
+pub type ImeEventSender = Sender<(ffi::Window, ImeEvent)>;
+
+/// Request to control XIM handler from the window.
+pub enum ImeRequest {
+    /// Set IME spot position for given `window_id`.
+    Position(ffi::Window, i16, i16),
+
+    /// Allow IME input for the given `window_id`.
+    Allow(ffi::Window, bool),
+}
 
 #[derive(Debug)]
 pub enum ImeCreationError {
@@ -37,11 +57,14 @@ pub struct Ime {
 }
 
 impl Ime {
-    pub fn new(xconn: Arc<XConnection>) -> Result<Self, ImeCreationError> {
+    pub fn new(
+        xconn: Arc<XConnection>,
+        event_sender: ImeEventSender,
+    ) -> Result<Self, ImeCreationError> {
         let potential_input_methods = PotentialInputMethods::new(&xconn);
 
         let (mut inner, client_data) = {
-            let mut inner = Box::new(ImeInner::new(xconn, potential_input_methods));
+            let mut inner = Box::new(ImeInner::new(xconn, potential_input_methods, event_sender));
             let inner_ptr = Box::into_raw(inner);
             let client_data = inner_ptr as _;
             let destroy_callback = ffi::XIMCallback {
@@ -88,12 +111,37 @@ impl Ime {
     // Ok(_) indicates that nothing went wrong internally
     // Ok(true) indicates that the action was actually performed
     // Ok(false) indicates that the action is not presently applicable
-    pub fn create_context(&mut self, window: ffi::Window) -> Result<bool, ImeContextCreationError> {
+    pub fn create_context(
+        &mut self,
+        window: ffi::Window,
+        with_preedit: bool,
+    ) -> Result<bool, ImeContextCreationError> {
         let context = if self.is_destroyed() {
             // Create empty entry in map, so that when IME is rebuilt, this window has a context.
             None
         } else {
-            Some(unsafe { ImeContext::new(&self.inner.xconn, self.inner.im, window, None) }?)
+            let event = if with_preedit {
+                ImeEvent::Enabled
+            } else {
+                // There's no IME without preedit.
+                ImeEvent::Disabled
+            };
+
+            self.inner
+                .event_sender
+                .send((window, event))
+                .expect("Failed to send enabled event");
+
+            Some(unsafe {
+                ImeContext::new(
+                    &self.inner.xconn,
+                    self.inner.im,
+                    window,
+                    None,
+                    with_preedit,
+                    self.inner.event_sender.clone(),
+                )
+            }?)
         };
         self.inner.contexts.insert(window, context);
         Ok(!self.is_destroyed())
@@ -151,6 +199,24 @@ impl Ime {
             context.set_spot(&self.xconn, x as _, y as _);
         }
     }
+
+    pub fn set_ime_allowed(&mut self, window: ffi::Window, allowed: bool) {
+        if self.is_destroyed() {
+            return;
+        }
+
+        if let Some(&mut Some(ref mut context)) = self.inner.contexts.get_mut(&window) {
+            if allowed == context.is_allowed {
+                return;
+            }
+        }
+
+        // Remove context for that window.
+        let _ = self.remove_context(window);
+
+        // Create new context supporting IME input.
+        let _ = self.create_context(window, allowed);
+    }
 }
 
 impl Drop for Ime {

src/platform_impl/linux/x11/mod.rs

@@ -44,7 +44,7 @@ use mio::{unix::SourceFd, Events, Interest, Poll, Token, Waker};
 use self::{
     dnd::{Dnd, DndState},
     event_processor::EventProcessor,
-    ime::{Ime, ImeCreationError, ImeReceiver, ImeSender},
+    ime::{Ime, ImeCreationError, ImeReceiver, ImeRequest, ImeSender},
     util::modifiers::ModifierKeymap,
 };
 use crate::{
@@ -144,6 +144,7 @@ impl<T: 'static> EventLoop<T> {
             .expect("Failed to call XInternAtoms when initializing drag and drop");
 
         let (ime_sender, ime_receiver) = mpsc::channel();
+        let (ime_event_sender, ime_event_receiver) = mpsc::channel();
         // Input methods will open successfully without setting the locale, but it won't be
         // possible to actually commit pre-edit sequences.
         unsafe {
@@ -168,7 +169,7 @@ impl<T: 'static> EventLoop<T> {
             }
         }
         let ime = RefCell::new({
-            let result = Ime::new(Arc::clone(&xconn));
+            let result = Ime::new(Arc::clone(&xconn), ime_event_sender);
             if let Err(ImeCreationError::OpenFailure(ref state)) = result {
                 panic!("Failed to open input method: {:#?}", state);
             }
@@ -252,12 +253,14 @@ impl<T: 'static> EventLoop<T> {
             devices: Default::default(),
             randr_event_offset,
             ime_receiver,
+            ime_event_receiver,
             xi2ext,
             mod_keymap,
             device_mod_state: Default::default(),
             num_touch: 0,
             first_touch: None,
             active_window: None,
+            is_composing: false,
         };
 
         // Register for device hotplug events

src/platform_impl/linux/x11/window.rs

@@ -26,7 +26,8 @@ use crate::{
 };
 
 use super::{
-    ffi, util, EventLoopWindowTarget, ImeSender, WakeSender, WindowId, XConnection, XError,
+    ffi, util, EventLoopWindowTarget, ImeRequest, ImeSender, WakeSender, WindowId, XConnection,
+    XError,
 };
 
 #[derive(Debug)]
@@ -453,7 +454,10 @@ impl UnownedWindow {
                 .queue();
 
             {
-                let result = event_loop.ime.borrow_mut().create_context(window.xwindow);
+                let result = event_loop
+                    .ime
+                    .borrow_mut()
+                    .create_context(window.xwindow, false);
                 if let Err(err) = result {
                     let e = match err {
                         ImeContextCreationError::XError(err) => OsError::XError(err),
@@ -1410,17 +1414,21 @@ impl UnownedWindow {
             .map_err(|err| ExternalError::Os(os_error!(OsError::XError(err))))
     }
 
-    pub(crate) fn set_ime_position_physical(&self, x: i32, y: i32) {
-        let _ = self
-            .ime_sender
-            .lock()
-            .send((self.xwindow, x as i16, y as i16));
-    }
-
     #[inline]
     pub fn set_ime_position(&self, spot: Position) {
         let (x, y) = spot.to_physical::<i32>(self.scale_factor()).into();
-        self.set_ime_position_physical(x, y);
+        let _ = self
+            .ime_sender
+            .lock()
+            .send(ImeRequest::Position(self.xwindow, x, y));
+    }
+
+    #[inline]
+    pub fn set_ime_allowed(&self, allowed: bool) {
+        let _ = self
+            .ime_sender
+            .lock()
+            .send(ImeRequest::Allow(self.xwindow, allowed));
     }
 
     #[inline]