feat(terminal): Chinese / IME input (P3)

Implement IME composition support and migrate regular character input to
a hidden textarea, matching the xterm.js approach.

Key changes:
- Add a hidden, absolutely-positioned `<textarea>` inside `.terminal-screen`
  that follows the terminal cursor cell. It receives focus on click, connect,
  and resize so the OS/browser IME candidate window appears at the cursor.
- `on:input` now sends regular printable characters; `on:keydown` only handles
  special keys (arrows, Enter, Esc, Backspace, F-keys, Ctrl combos).
- `on:compositionstart/end` track IME sessions and send the final composed
  string at the end, avoiding partial pinyin/jamo/kana leaks.
- Move `on:paste` and `on:keydown` from `.terminal-screen` to the textarea so
  focus stays on the IME target.
- Replace `.terminal-screen:focus` with `:focus-within` since the screen div
  no longer holds focus.
- Add `is_regular_text_input` helper and unit test.

Web-sys features extended with `InputEvent` and `CompositionEvent`.

Tests: 24/24 pass, clippy clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.toml

@@ -42,6 +42,7 @@ web-sys = { version = "0.3", default-features = false, features = [
     "Clipboard",
     "ClipboardEvent",
     "CloseEvent",
+    "CompositionEvent",
     "console",
     "DataTransfer",
     "Document",
@@ -52,6 +53,7 @@ web-sys = { version = "0.3", default-features = false, features = [
     "Event",
     "EventTarget",
     "HtmlElement",
+    "InputEvent",
     "KeyboardEvent",
     "Location",
     "MessageEvent",

TERMINAL_ROADMAP.md

@@ -36,6 +36,7 @@
 | 粘贴（Ctrl-V / Ctrl-Shift-V / 右键菜单，含 bracketed paste） | `component.rs::handle_paste` / `prepare_paste` |
 | 文本选区 + 复制（自建模型，Ctrl-Shift-C / 选区存在时 Ctrl+C，跨滚动） | `component.rs` 鼠标处理 / `core.rs::selection_text` |
 | 鼠标上报（vim/htop/tmux 鼠标，SGR/Default/UTF-8 编码，滚轮） | `component.rs` 鼠标处理 / `encode_mouse_report` |
+| 中文 / IME 输入（拼音/日文/韩文，隐藏 textarea + composition 事件） | `component.rs::handle_input` / `handle_composition_*` |
 
 ---
 
@@ -111,33 +112,45 @@
 
 ---
 
-### P3 — 中文 / IME 输入
+### P3 — 中文 / IME 输入 ✅ 已完成
 
-**现状**：`map_key_to_terminal_input` 只处理 `key.chars().count() == 1` 的单字符，IME 组合输入（拼音候选）完全没接。
+**现状**：已实现。拼音、日文、韩文等 IME 组合输入可以正常工作；普通英文/数字输入也迁到了 `textarea` 的 `input` 事件，确保和 IME 走同一条路径。
 
-**计划实现**：
+**已实现**：
-1. 改用 **`composition` 事件 + 隐藏 `<textarea>`** 的标准方案（xterm.js 也是这套）：
+1. **隐藏 `<textarea>` IME 载体**（`component.rs` view）
-   - 一个 1×1 透明、跟随光标的 `textarea` 承接 IME。
+   - 绝对定位、透明、无边框、大小跟随终端光标单元格。
-   - 监听 `compositionstart` / `compositionupdate` / `compositionend`。
+   - 通过 `tabindex="0"` 成为焦点目标；`terminal-screen` 改用 `:focus-within` 显示焦点环。
-   - 组合进行中不发字节；`compositionend` 时把最终文本一次性作为 Input 发送。
+2. **事件模型迁移**
-   - 普通 `input` 事件（非组合）也走这个 textarea，替代部分 `keydown` 逐字符逻辑。
+   - `on:input`：普通字符/数字/空格输入，读取 textarea value 后清空并发送。
-2. 光标定位：把隐藏 textarea 定位到终端光标处，让候选框出现在正确位置。
+   - `on:compositionstart` / `on:compositionend`：IME 组合期间不发字节，`compositionend` 时发送最终文本。
+   - `on:keydown`：仍处理方向键、Enter、Esc、Backspace、F 键、Ctrl 组合等**非打印键**。
+   - `on:paste`：从 `terminal-screen` 移到 textarea，确保 focus 在 textarea 时右键/菜单粘贴也能触发。
+3. **焦点管理**
+   - 点击 terminal-screen、WebSocket 连接成功、窗口 resize 后都聚焦 IME textarea。
+4. **测试**：新增 `is_regular_text_input_detects_printable_keys` 单测，确保打印字符被正确交给 textarea；24 个 terminal 测试全过，clippy 干净。
 
-**风险**：中高。事件模型要从「keydown 逐键」迁一部分到「textarea + composition」，需保证不回归现有按键。建议**先把 P1 功能键做完再动这块**，避免两套输入逻辑互相打架。
+**已知限制**：
+- 主屏幕 scrollback 滚动后，光标可能位于可见区域下方，IME 候选框位置会对应到光标逻辑位置（可能偏下）。IME 主要用于当前输入， scrolled-back 场景输入较少见。
+- 目前不支持 textarea 自动滚动延伸选区（和 P0 同一限制）。
 
 ---
 
-## 3. 其余缺口（暂不排期，记录备查）
+### P4 — Canvas / WebGL 渲染器（性能目标）
 
-xterm.js 还有这些，本项目暂列「按需再做」：
+**现状**：DOM 渲染。常规 80×24–160×40 终端流畅，但大终端（≥200×100）或高刷新率连续输出时，DOM 节点多、重排重绘开销大。
 
-- **链接检测**（点 URL 打开）、**搜索 / 查找**（Ctrl-F 高亮）
+**计划实现**：
-- **光标样式**：块 / 竖线 / 下划线 + 闪烁（目前固定块状反色）
+1. **Canvas 2D 渲染器（先做）**
-- **Canvas / WebGL 渲染器**：当前是 DOM 渲染，够用但不如 Canvas 快；超大终端 + 高刷新率场景才需要 → **已纳入长期性能目标，P3 后推进**
+   - 一屏单元格一次 `fillText` / `fillRect` 绘制，减少 DOM 节点。
-- **sixel / 图片协议**、**字形连字控制**
+   - 保留现有 `TerminalCore` 数据模型，渲染层换成 Canvas。
-- **Unicode 11/15 宽度表**：目前依赖 vt100 的宽度判断，极端 emoji / 新字符可能不准
+   - 文本选区用 Canvas 半透明矩形；光标用 Canvas 反色或额外 DOM overlay。
-- **无障碍**（屏幕阅读器 live region）
+2. **WebGL 渲染器（后做）**
-- **公开 API / 插件系统 / 配置项**：当前是项目内定制组件，无对外 API
+   - 把字符集预渲染到 texture atlas，用 shader 批量绘制。
+   - 适合超大终端 + 高刷新率场景，但实现复杂度高。
+3. **可切换**
+   - 默认 DOM，提供 prop/api 切到 Canvas/WebGL。
+
+**风险**：高。需要重新实现渲染层、文本测量、选区高亮、滚动逻辑，同时保证和现有 `TerminalCore` 数据模型兼容。
 
 ---
 

app/src/terminal/component.rs

@@ -7,9 +7,9 @@ use wasm_bindgen::JsCast;
 use wasm_bindgen::closure::Closure;
 use web_sys::js_sys::{Array, Function};
 use web_sys::{
-    BinaryType, ClipboardEvent, ErrorEvent, Event, HtmlElement, KeyboardEvent,
+    BinaryType, ClipboardEvent, CompositionEvent, ErrorEvent, Event, HtmlElement,
-    MessageEvent, MouseEvent, ResizeObserver, ResizeObserverEntry, WebSocket,
+    InputEvent, KeyboardEvent, MessageEvent, MouseEvent, ResizeObserver,
-    WheelEvent,
+    ResizeObserverEntry, WebSocket, WheelEvent,
 };
 
 use super::core::{
@@ -87,6 +87,7 @@ impl Default for TerminalViewport {
 #[component]
 pub fn TerminalPanel() -> impl IntoView {
     let terminal_ref = NodeRef::<html::Div>::new();
+    let ime_ref = NodeRef::<html::Textarea>::new();
     let measure_ref = NodeRef::<html::Span>::new();
     let connection_status = RwSignal::new("Connecting".to_owned());
     let ws_signal = RwSignal::new(None::<WebSocket>);
@@ -121,6 +122,10 @@ pub fn TerminalPanel() -> impl IntoView {
     let selection = RwSignal::new(None::<Selection>);
     let selecting = RwSignal::new(false);
 
+    // IME composition state: when true, regular `input` events are ignored and
+    // the final composed string is sent on `compositionend`.
+    let composing = RwSignal::new(false);
+
     // Mouse-reporting bookkeeping (only used while an app has enabled mouse
     // reporting).  `mouse_held_button` remembers which button is down so we can
     // emit motion events and SGR-style releases; `mouse_last_cell` throttles
@@ -130,6 +135,33 @@ pub fn TerminalPanel() -> impl IntoView {
     let mouse_last_cell: Rc<std::cell::Cell<Option<(usize, usize)>>> =
         Rc::new(std::cell::Cell::new(None));
 
+    // -- IME cursor follower -------------------------------------------------
+    //
+    // The hidden IME textarea's position is bound reactively to the terminal
+    // cursor cell so the OS/browser IME candidate window appears in the right
+    // place.  See the `style` prop on the textarea in the view below.
+    let ime_style = move || {
+        let _ = render_tick.get();
+        let Some((row, col)) = core_signal
+            .try_with_untracked(|core| {
+                if core.hide_cursor() {
+                    None
+                } else {
+                    Some(core.cursor_position())
+                }
+            })
+            .flatten()
+        else {
+            return String::new();
+        };
+        let (cell_w, cell_h) = cell_size.get();
+        let left = TERMINAL_PADDING + f64::from(col) * cell_w;
+        let top = TERMINAL_PADDING + f64::from(row) * cell_h;
+        format!(
+            "left:{left}px;top:{top}px;width:{cell_w}px;height:{cell_h}px;"
+        )
+    };
+
     // -- WebSocket lifecycle ------------------------------------------------
 
     Effect::new(move |_| {
@@ -148,6 +180,7 @@ pub fn TerminalPanel() -> impl IntoView {
         let open_ws = ws_signal;
         let open_viewport = current_viewport;
         let open_ref = terminal_ref;
+        let open_ime = ime_ref;
         let open_measure = measure_ref;
         let open_mode = view_mode;
         let open_prog_scroll = programmatic_scroll_top;
@@ -168,7 +201,7 @@ pub fn TerminalPanel() -> impl IntoView {
 
             send_resize_message(&open_socket, viewport);
             sync_scroll_to_bottom(open_ref, open_prog_scroll);
-            focus_terminal(open_ref);
+            focus_ime_textarea(&open_ime);
         });
         socket.set_onopen(Some(on_open.as_ref().unchecked_ref()));
         on_open.forget();
@@ -273,6 +306,7 @@ pub fn TerminalPanel() -> impl IntoView {
         let resize_core = core_signal;
         let resize_st = scroll_top;
         let resize_tick = render_tick;
+        let resize_ime = ime_ref;
         let callback = Closure::<dyn FnMut(Array, ResizeObserver)>::new(
             move |entries: Array, _observer: ResizeObserver| {
                 let Some(entry) = entries
@@ -314,7 +348,7 @@ pub fn TerminalPanel() -> impl IntoView {
                     send_resize_message(&resize_socket, viewport);
                 }
 
-                focus_terminal(resize_ref);
+                focus_ime_textarea(&resize_ime);
             },
         );
 
@@ -393,6 +427,19 @@ pub fn TerminalPanel() -> impl IntoView {
                 return;
             }
 
+            // Printable characters are handled by the IME textarea's `input` /
+            // `composition` events so that IME composition and dead keys work.
+            // Only special keys (arrows, Enter, Esc, Backspace, F-keys,
+            // Ctrl-combos, …) are processed here.
+            if is_regular_text_input(
+                &event.key(),
+                event.ctrl_key(),
+                event.alt_key(),
+                event.meta_key(),
+            ) {
+                return;
+            }
+
             // The terminal owns bare Ctrl+letter (no Shift/Alt/Meta) so the
             // browser doesn't intercept common shortcuts (Ctrl-W close tab,
             // Ctrl-T new tab, Ctrl-N new window, Ctrl-R reload, Ctrl-F find,
@@ -643,9 +690,6 @@ pub fn TerminalPanel() -> impl IntoView {
         let paste_core = core_signal;
 
         move |event: ClipboardEvent| {
-            let Some(socket) = ws_signal.get_untracked() else {
-                return;
-            };
             let Some(raw) = event
                 .clipboard_data()
                 .and_then(|dt| dt.get_data("text").ok())
@@ -660,18 +704,78 @@ pub fn TerminalPanel() -> impl IntoView {
                 .try_with_untracked(|core| core.bracketed_paste())
                 == Some(true);
             let data = prepare_paste(&raw, bracketed);
-
+            send_input_data(
-            // Pasting is an interaction at the prompt → return to live view.
+                data,
-            if !paste_mode.get_untracked().is_live() {
+                ws_signal,
-                paste_mode.set(ViewMode::Live);
+                paste_mode,
-                sync_scroll_to_bottom(terminal_ref, paste_prog_scroll);
+                terminal_ref,
-            }
+                paste_prog_scroll,
-
-            event.prevent_default();
-            send_terminal_message(
-                &socket,
-                &ClientTerminalMessage::Input { data },
             );
+            event.prevent_default();
+        }
+    };
+
+    // -- IME input ------------------------------------------------------------
+    //
+    // Regular characters and IME composition are handled through a hidden
+    // textarea that sits on top of the terminal cursor.  Special keys
+    // (arrows, Enter, Esc, F-keys, Ctrl-combos) still go through keydown.
+    let handle_input = {
+        let input_mode = view_mode;
+        let input_prog_scroll = programmatic_scroll_top;
+        let input_composing = composing;
+        let input_ime = ime_ref;
+        move |event: Event| {
+            let Ok(_event) = event.dyn_into::<InputEvent>() else {
+                return;
+            };
+            if input_composing.get_untracked() {
+                return;
+            }
+            let Some(text) = ime_ref_text(&input_ime) else {
+                return;
+            };
+            if text.is_empty() {
+                return;
+            }
+            clear_ime_textarea(&input_ime);
+            send_input_data(
+                text,
+                ws_signal,
+                input_mode,
+                terminal_ref,
+                input_prog_scroll,
+            );
+        }
+    };
+
+    let handle_composition_start = move |_: CompositionEvent| {
+        composing.set(true);
+    };
+
+    let handle_composition_end = {
+        let end_mode = view_mode;
+        let end_prog_scroll = programmatic_scroll_top;
+        let end_composing = composing;
+        let end_ime = ime_ref;
+        move |event: CompositionEvent| {
+            if !end_composing.get_untracked() {
+                clear_ime_textarea(&end_ime);
+                return;
+            }
+            end_composing.set(false);
+            if let Some(text) = event.data()
+                && !text.is_empty()
+            {
+                send_input_data(
+                    text,
+                    ws_signal,
+                    end_mode,
+                    terminal_ref,
+                    end_prog_scroll,
+                );
+            }
+            clear_ime_textarea(&end_ime);
         }
     };
 
@@ -909,7 +1013,7 @@ pub fn TerminalPanel() -> impl IntoView {
     };
 
     let handle_click = move |_| {
-        focus_terminal(terminal_ref);
+        focus_ime_textarea(&ime_ref);
     };
 
     // -- View ---------------------------------------------------------------
@@ -954,16 +1058,27 @@ pub fn TerminalPanel() -> impl IntoView {
             <div
                 node_ref=terminal_ref
                 class="terminal-screen"
-                tabindex="0"
                 on:click=handle_click
-                on:keydown=handle_keydown
                 on:scroll=handle_scroll
                 on:wheel=handle_wheel
-                on:paste=handle_paste
                 on:mousedown=handle_mousedown
                 on:mousemove=handle_mousemove
                 on:mouseup=handle_mouseup
             >
+                <textarea
+                    node_ref=ime_ref
+                    class="terminal-ime"
+                    tabindex="0"
+                    autocomplete="off"
+                    autocapitalize="off"
+                    spellcheck="false"
+                    style=ime_style
+                    on:keydown=handle_keydown
+                    on:input=handle_input
+                    on:compositionstart=handle_composition_start
+                    on:compositionend=handle_composition_end
+                    on:paste=handle_paste
+                ></textarea>
                 <span node_ref=measure_ref class="terminal-measure" aria-hidden="true">
                     {MEASURE_SAMPLE_TEXT}
                 </span>
@@ -1402,8 +1517,9 @@ fn point_to_cell(
     )
 }
 
-fn focus_terminal(terminal_ref: NodeRef<html::Div>) {
+/// Focus the hidden IME textarea so keyboard input and composition go there.
-    if let Some(element) = terminal_ref.get_untracked() {
+fn focus_ime_textarea(ime_ref: &NodeRef<html::Textarea>) {
+    if let Some(element) = ime_ref.get_untracked() {
         let _ = element.focus();
     }
 }
@@ -1430,6 +1546,42 @@ fn copy_current_selection(selection: RwSignal<Option<Selection>>, core: RwSignal
     }
 }
 
+/// Send a string as terminal input, scrolling to the bottom if needed.
+fn send_input_data(
+    data: String,
+    socket_signal: RwSignal<Option<WebSocket>>,
+    mode_signal: RwSignal<ViewMode>,
+    terminal_ref: NodeRef<html::Div>,
+    prog_scroll: RwSignal<i32>,
+) {
+    if data.is_empty() {
+        return;
+    }
+    let Some(socket) = socket_signal.get_untracked() else {
+        return;
+    };
+    if !mode_signal.get_untracked().is_live() {
+        mode_signal.set(ViewMode::Live);
+        sync_scroll_to_bottom(terminal_ref, prog_scroll);
+    }
+    send_terminal_message(
+        &socket,
+        &ClientTerminalMessage::Input { data },
+    );
+}
+
+/// Read the current value of the hidden IME textarea.
+fn ime_ref_text(ime_ref: &NodeRef<html::Textarea>) -> Option<String> {
+    ime_ref.get_untracked().map(|t| t.value())
+}
+
+/// Clear the hidden IME textarea after sending composed/typed text.
+fn clear_ime_textarea(ime_ref: &NodeRef<html::Textarea>) {
+    if let Some(t) = ime_ref.get_untracked() {
+        t.set_value("");
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Key mapping
 // ---------------------------------------------------------------------------
@@ -1668,6 +1820,14 @@ fn map_key_to_terminal_input(
     )
 }
 
+/// Whether a keydown event represents a regular printable character that
+/// should be handled by the IME textarea's `input` event, rather than sent
+/// directly from `keydown`.  This lets the browser manage IME composition,
+/// dead keys, and upper/lower case before we see the final text.
+fn is_regular_text_input(key: &str, ctrl: bool, alt: bool, meta: bool) -> bool {
+    key.chars().count() == 1 && !ctrl && !alt && !meta
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -1854,6 +2014,19 @@ mod tests {
         assert!(selection_rects(None, 0, 30, cols, cw).is_empty());
     }
 
+    #[test]
+    fn is_regular_text_input_detects_printable_keys() {
+        assert!(is_regular_text_input("a", false, false, false));
+        assert!(is_regular_text_input("A", false, false, false)); // Shift handled by browser
+        assert!(is_regular_text_input(" ", false, false, false));
+        assert!(!is_regular_text_input("Enter", false, false, false));
+        assert!(!is_regular_text_input("ArrowUp", false, false, false));
+        assert!(!is_regular_text_input("a", true, false, false)); // Ctrl+a
+        assert!(!is_regular_text_input("a", false, true, false)); // Alt+a
+        assert!(!is_regular_text_input("a", false, false, true)); // Meta+a
+        assert!(!is_regular_text_input("Dead", false, false, false));
+    }
+
     #[test]
     fn key_to_bytes_table() {
         // --- basic printable / control keys ---

style/tailwind.css

@@ -610,13 +610,32 @@
     scrollbar-color: rgb(148 163 184 / 60%) transparent;
   }
 
-  .terminal-screen:focus {
+  .terminal-screen:focus-within {
     border-color: #38bdf8;
     box-shadow:
       inset 0 1px 0 rgb(255 255 255 / 4%),
       0 0 0 3px rgb(56 189 248 / 15%);
   }
 
+  .terminal-ime {
+    position: absolute;
+    z-index: 100;
+    opacity: 0;
+    background: transparent;
+    color: transparent;
+    caret-color: transparent;
+    border: none;
+    outline: none;
+    resize: none;
+    padding: 0;
+    margin: 0;
+    overflow: hidden;
+    pointer-events: auto;
+    font-family: inherit;
+    font-size: 1px;
+    line-height: 1px;
+  }
+
   .terminal-text {
     margin: 0;
     min-height: 100%;