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/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,
         }
     }
 }