Send empty Ime::Preedit before the Ime::Commit

This should help downstream to automatically clear it.

CHANGELOG.md

@@ -25,6 +25,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Windows, fixed ALT+Space shortcut to open window menu.
 - On Wayland, fixed `Ime::Preedit` not being sent on IME reset.
 - Fixed unbound version specified for `raw-window-handle` leading to compilation failures.
+- Empty `Ime::Preedit` event will be sent before `Ime::Commit` to help clearing preedit.
 
 # 0.27.2 (2022-8-12)
 

src/event.rs

@@ -841,8 +841,9 @@ pub struct KeyboardInput {
 /// the character you want to apply the accent to. This will generate the following event sequence:
 /// ```ignore
 /// // Press "`" key
-/// Ime::Preedit("`", Some(0), Some(0))
+/// Ime::Preedit("`", Some((0, 0)))
 /// // Press "E" key
+/// Ime::Preedit("", None) // Synthetic event generated by winit to clear preedit.
 /// Ime::Commit("é")
 /// ```
 ///
@@ -853,14 +854,15 @@ pub struct KeyboardInput {
 /// sequence could be obtained:
 /// ```ignore
 /// // Press "A" key
-/// Ime::Preedit("a", Some(1), Some(1))
+/// Ime::Preedit("a", Some((1, 1)))
 /// // Press "B" key
-/// Ime::Preedit("a b", Some(3), Some(3))
+/// Ime::Preedit("a b", Some((3, 3)))
 /// // Press left arrow key
-/// Ime::Preedit("a b", Some(1), Some(1))
+/// Ime::Preedit("a b", Some((1, 1)))
 /// // Press space key
-/// Ime::Preedit("啊b", Some(3), Some(3))
+/// Ime::Preedit("啊b", Some((3, 3)))
 /// // Press space key
+/// Ime::Preedit("", None) // Synthetic event generated by winit to clear preedit.
 /// Ime::Commit("啊不")
 /// ```
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -876,20 +878,21 @@ pub enum Ime {
     /// Notifies when a new composing text should be set at the cursor position.
     ///
     /// The value represents a pair of the preedit string and the cursor begin position and end
-    /// position. When it's `None`, the cursor should be hidden.
+    /// position. When it's `None`, the cursor should be hidden. When `String` is an empty string
+    /// this indicates that preedit was cleared.
     ///
     /// The cursor position is byte-wise indexed.
     Preedit(String, Option<(usize, usize)>),
 
     /// Notifies when text should be inserted into the editor widget.
     ///
-    /// Any pending [`Preedit`](Self::Preedit) must be cleared.
+    /// Right before this event winit will send empty [`Self::Preedit`] event.
     Commit(String),
 
     /// Notifies when the IME was disabled.
     ///
     /// After receiving this event you won't get any more [`Preedit`](Self::Preedit) or
-    /// [`Commit`](Self::Commit) events until the next [`Enabled`](Self::Enabled) event. You can
+    /// [`Commit`](Self::Commit) events until the next [`Enabled`](Self::Enabled) event. You should
     /// also stop issuing IME related requests like [`Window::set_ime_position`] and clear pending
     /// preedit text.
     Disabled,

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

@@ -88,25 +88,28 @@ pub(super) fn handle_text_input(
                 _ => return,
             };
 
+            // Clear preedit at the start of `Done`.
+            event_sink.push_window_event(
+                WindowEvent::Ime(Ime::Preedit(String::new(), None)),
+                window_id,
+            );
+
+            // Send `Commit`.
             if let Some(text) = inner.pending_commit.take() {
                 event_sink.push_window_event(WindowEvent::Ime(Ime::Commit(text)), window_id);
             }
 
-            // Always send preedit on `Done` events.
-            let (text, range) = inner
-                .pending_preedit
-                .take()
-                .map(|preedit| {
-                    let cursor_range = preedit
-                        .cursor_begin
-                        .map(|b| (b, preedit.cursor_end.unwrap_or(b)));
+            // Send preedit.
+            if let Some(preedit) = inner.pending_preedit.take() {
+                let cursor_range = preedit
+                    .cursor_begin
+                    .map(|b| (b, preedit.cursor_end.unwrap_or(b)));
 
-                    (preedit.text, cursor_range)
-                })
-                .unwrap_or_default();
-
-            let event = Ime::Preedit(text, range);
-            event_sink.push_window_event(WindowEvent::Ime(event), window_id);
+                event_sink.push_window_event(
+                    WindowEvent::Ime(Ime::Preedit(preedit.text, cursor_range)),
+                    window_id,
+                );
+            }
         }
         _ => (),
     }

src/platform_impl/linux/x11/event_processor.rs

@@ -621,6 +621,12 @@ impl<T: 'static> EventProcessor<T> {
                     // 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::Ime(Ime::Preedit(String::new(), None)),
+                        };
+                        callback(event);
+
                         let event = Event::WindowEvent {
                             window_id,
                             event: WindowEvent::Ime(Ime::Commit(written)),

src/platform_impl/macos/view.rs

@@ -431,6 +431,10 @@ declare_class!(
             let is_control = string.chars().next().map_or(false, |c| c.is_control());
 
             if self.is_ime_enabled() && !is_control {
+                AppState::queue_event(EventWrapper::StaticEvent(Event::WindowEvent {
+                    window_id: self.window_id(),
+                    event: WindowEvent::Ime(Ime::Preedit(String::new(), None)),
+                }));
                 AppState::queue_event(EventWrapper::StaticEvent(Event::WindowEvent {
                     window_id: self.window_id(),
                     event: WindowEvent::Ime(Ime::Commit(string)),

src/platform_impl/windows/event_loop.rs

@@ -1262,6 +1262,10 @@ unsafe fn public_window_callback_inner<T: 'static>(
                     if let Some(text) = ime_context.get_composed_text() {
                         userdata.window_state_lock().ime_state = ImeState::Enabled;
 
+                        userdata.send_event(Event::WindowEvent {
+                            window_id: RootWindowId(WindowId(window)),
+                            event: WindowEvent::Ime(Ime::Preedit(String::new(), None)),
+                        });
                         userdata.send_event(Event::WindowEvent {
                             window_id: RootWindowId(WindowId(window)),
                             event: WindowEvent::Ime(Ime::Commit(text)),
@@ -1298,6 +1302,10 @@ unsafe fn public_window_callback_inner<T: 'static>(
                     // trying receiving composing result and commit if exists.
                     let ime_context = ImeContext::current(window);
                     if let Some(text) = ime_context.get_composed_text() {
+                        userdata.send_event(Event::WindowEvent {
+                            window_id: RootWindowId(WindowId(window)),
+                            event: WindowEvent::Ime(Ime::Preedit(String::new(), None)),
+                        });
                         userdata.send_event(Event::WindowEvent {
                             window_id: RootWindowId(WindowId(window)),
                             event: WindowEvent::Ime(Ime::Commit(text)),