Add IME support for native (#2046)

crates/eframe/src/native/run.rs

@@ -361,6 +361,8 @@ mod glow_integration {
             let theme = system_theme.unwrap_or(self.native_options.default_theme);
             integration.egui_ctx.set_visuals(theme.egui_visuals());
 
+            gl_window.window().set_ime_allowed(true);
+
             {
                 let event_loop_proxy = self.repaint_proxy.clone();
                 integration.egui_ctx.set_request_repaint_callback(move || {
@@ -729,6 +731,8 @@ mod wgpu_integration {
             let theme = system_theme.unwrap_or(self.native_options.default_theme);
             integration.egui_ctx.set_visuals(theme.egui_visuals());
 
+            window.set_ime_allowed(true);
+
             {
                 let event_loop_proxy = self.repaint_proxy.clone();
                 integration.egui_ctx.set_request_repaint_callback(move || {

crates/egui-winit/src/lib.rs

@@ -83,6 +83,9 @@ pub struct State {
     ///
     /// Only one touch will be interpreted as pointer at any time.
     pointer_touch_id: Option<u64>,
+
+    /// track ime state
+    input_method_editor_started: bool,
 }
 
 impl State {
@@ -109,6 +112,8 @@ impl State {
 
             simulate_touch_screen: false,
             pointer_touch_id: None,
+
+            input_method_editor_started: false,
         }
     }
 
@@ -251,6 +256,44 @@ impl State {
                     consumed,
                 }
             }
+            WindowEvent::Ime(ime) => {
+                // on Mac even Cmd-C is preessed during ime, a `c` is pushed to Preedit.
+                // So no need to check is_mac_cmd.
+                //
+                // How winit produce `Ime::Enabled` and `Ime::Disabled` differs in MacOS
+                // and Windows.
+                //
+                // - On Windows, before and after each Commit will produce an Enable/Disabled
+                // event.
+                // - On MacOS, only when user explicit enable/disable ime. No Disabled
+                // after Commit.
+                //
+                // We use input_method_editor_started to mannualy insert CompositionStart
+                // between Commits.
+                match ime {
+                    winit::event::Ime::Enabled | winit::event::Ime::Disabled => (),
+                    winit::event::Ime::Commit(text) => {
+                        self.input_method_editor_started = false;
+                        self.egui_input
+                            .events
+                            .push(egui::Event::CompositionEnd(text.clone()));
+                    }
+                    winit::event::Ime::Preedit(text, ..) => {
+                        if !self.input_method_editor_started {
+                            self.input_method_editor_started = true;
+                            self.egui_input.events.push(egui::Event::CompositionStart);
+                        }
+                        self.egui_input
+                            .events
+                            .push(egui::Event::CompositionUpdate(text.clone()));
+                    }
+                };
+
+                EventResponse {
+                    repaint: true,
+                    consumed: egui_ctx.wants_keyboard_input(),
+                }
+            }
             WindowEvent::KeyboardInput { input, .. } => {
                 self.on_keyboard_input(input);
                 let consumed = egui_ctx.wants_keyboard_input()
@@ -317,7 +360,6 @@ impl State {
             | WindowEvent::CloseRequested
             | WindowEvent::CursorEntered { .. }
             | WindowEvent::Destroyed
-            | WindowEvent::Ime(_)
             | WindowEvent::Occluded(_)
             | WindowEvent::Resized(_)
             | WindowEvent::ThemeChanged(_)

crates/egui/src/widgets/text_edit/builder.rs

@@ -618,7 +618,13 @@ impl<'t> TextEdit<'t> {
                         if interactive {
                             // eframe web uses `text_cursor_pos` when showing IME,
                             // so only set it when text is editable and visible!
-                            ui.ctx().output().text_cursor_pos = Some(cursor_pos.left_top());
+                            // But `winit` and `egui_web` differs in how to set the
+                            // position of IME.
+                            if cfg!(target_arch = "wasm32") {
+                                ui.ctx().output().text_cursor_pos = Some(cursor_pos.left_top());
+                            } else {
+                                ui.ctx().output().text_cursor_pos = Some(cursor_pos.left_bottom());
+                            }
                         }
                     }
                 }
@@ -816,26 +822,27 @@ fn events(
             }
 
             Event::CompositionUpdate(text_mark) => {
-                if !text_mark.is_empty() && text_mark != "\n" && text_mark != "\r" && state.has_ime
-                {
+                // empty prediction can be produced when user press backspace
+                // or escape during ime. We should clear current text.
+                if text_mark != "\n" && text_mark != "\r" && state.has_ime {
                     let mut ccursor = delete_selected(text, &cursor_range);
                     let start_cursor = ccursor;
-                    insert_text(&mut ccursor, text, text_mark);
+                    if !text_mark.is_empty() {
+                        insert_text(&mut ccursor, text, text_mark);
+                    }
                     Some(CCursorRange::two(start_cursor, ccursor))
                 } else {
                     None
                 }
             }
 
             Event::CompositionEnd(prediction) => {
-                if !prediction.is_empty()
-                    && prediction != "\n"
-                    && prediction != "\r"
-                    && state.has_ime
-                {
+                if prediction != "\n" && prediction != "\r" && state.has_ime {
                     state.has_ime = false;
                     let mut ccursor = delete_selected(text, &cursor_range);
-                    insert_text(&mut ccursor, text, prediction);
+                    if !prediction.is_empty() {
+                        insert_text(&mut ccursor, text, prediction);
+                    }
                     Some(CCursorRange::one(ccursor))
                 } else {
                     None