全面优化：暗色主题、文件监听、未保存提醒、滚动同步、分屏记忆、文件大小显示、删除死代码

main.js

@@ -1,13 +1,14 @@
-const { app, BrowserWindow, dialog, ipcMain, Menu } = require('electron');
+const { app, BrowserWindow, dialog, ipcMain } = require('electron');
 const path = require('path');
 const fs = require('fs');
 
 let mainWindow = null;
 let currentFilePath = null;
-let pendingFilePath = null; // For file association race condition
+let pendingFilePath = null;
+let fileWatcher = null;
+let isModifiedExternally = false;
 
 function createWindow() {
-  // Create the browser window
   mainWindow = new BrowserWindow({
     width: 1200,
     height: 800,
@@ -23,7 +24,6 @@ function createWindow() {
     show: false
   });
 
-  // Register did-finish-load BEFORE loadFile to avoid race condition
   mainWindow.webContents.on('did-finish-load', () => {
     if (pendingFilePath) {
       openFile(pendingFilePath);
@@ -31,102 +31,48 @@ function createWindow() {
     }
   });
 
-  // Load the index.html
   mainWindow.loadFile(path.join(__dirname, 'renderer', 'index.html'));
 
-  // Show window when ready
   mainWindow.once('ready-to-show', () => {
     mainWindow.show();
   });
 
-  // Remove native menu bar
   mainWindow.setMenu(null);
 
+  // Unsaved changes warning on close
+  mainWindow.on('close', (e) => {
+    mainWindow.webContents.send('window:closing');
+    e.preventDefault();
+    mainWindow.webContents.send('window:confirmClose');
+  });
+
   mainWindow.on('closed', () => {
+    stopWatching();
     mainWindow = null;
   });
 }
 
-function buildMenu() {
+// File watcher - detect external modifications
-  const template = [
+function startWatching(filePath) {
-    {
+  stopWatching();
-      label: '文件',
+  try {
-      submenu: [
+    isModifiedExternally = false;
-        {
+    fileWatcher = fs.watch(filePath, (eventType) => {
-          label: '打开文件',
+      if (eventType === 'change' && mainWindow && !mainWindow.isDestroyed()) {
-          accelerator: 'CmdOrCtrl+O',
+        isModifiedExternally = true;
-          click: () => handleOpenFile()
+        mainWindow.webContents.send('file:externallyModified', filePath);
-        },
-        {
-          label: '保存',
-          accelerator: 'CmdOrCtrl+S',
-          click: () => mainWindow.webContents.send('menu:save')
-        },
-        {
-          label: '另存为',
-          accelerator: 'CmdOrCtrl+Shift+S',
-          click: () => mainWindow.webContents.send('menu:saveAs')
-        },
-        { type: 'separator' },
-        {
-          label: '退出',
-          accelerator: 'CmdOrCtrl+Q',
-          click: () => app.quit()
       }
-      ]
-    },
-    {
-      label: '视图',
-      submenu: [
-        {
-          label: '编辑 + 预览',
-          accelerator: 'CmdOrCtrl+1',
-          click: () => mainWindow.webContents.send('menu:viewMode', 'split')
-        },
-        {
-          label: '纯编辑',
-          accelerator: 'CmdOrCtrl+2',
-          click: () => mainWindow.webContents.send('menu:viewMode', 'editor')
-        },
-        {
-          label: '纯预览',
-          accelerator: 'CmdOrCtrl+3',
-          click: () => mainWindow.webContents.send('menu:viewMode', 'preview')
-        },
-        { type: 'separator' },
-        {
-          label: '开发者工具',
-          accelerator: 'F12',
-          click: () => mainWindow.webContents.toggleDevTools()
-        },
-        { type: 'separator' },
-        {
-          label: '重新加载',
-          accelerator: 'CmdOrCtrl+R',
-          click: () => mainWindow.webContents.reload()
-        }
-      ]
-    },
-    {
-      label: '帮助',
-      submenu: [
-        {
-          label: '关于 MarkLite',
-          click: () => {
-            dialog.showMessageBox(mainWindow, {
-              type: 'info',
-              title: '关于 MarkLite',
-              message: 'MarkLite v1.0.0',
-              detail: '一款轻量级的 Markdown 阅读器。\n\n技术栈：Electron + marked.js + highlight.js'
     });
+  } catch (err) {
+    // Silently ignore watch errors
   }
-        }
+}
-      ]
-    }
-  ];
 
-  const menu = Menu.buildFromTemplate(template);
+function stopWatching() {
-  Menu.setApplicationMenu(menu);
+  if (fileWatcher) {
+    fileWatcher.close();
+    fileWatcher = null;
+  }
 }
 
 async function showOpenDialog() {
@@ -143,17 +89,11 @@ async function showOpenDialog() {
   return null;
 }
 
-async function handleOpenFile() {
-  const filePath = await showOpenDialog();
-  if (filePath) {
-    openFile(filePath);
-  }
-}
-
 function openFile(filePath) {
   try {
     const content = fs.readFileSync(filePath, 'utf-8');
     currentFilePath = filePath;
+    startWatching(filePath);
     mainWindow.setTitle(`MarkLite - ${path.basename(filePath)}`);
     mainWindow.webContents.send('file:opened', { filePath, content });
   } catch (err) {
@@ -163,14 +103,19 @@ function openFile(filePath) {
 
 // IPC Handlers
 ipcMain.handle('dialog:openFile', async () => {
+  try {
     const filePath = await showOpenDialog();
     if (filePath) {
       const content = fs.readFileSync(filePath, 'utf-8');
       currentFilePath = filePath;
+      startWatching(filePath);
       mainWindow.setTitle(`MarkLite - ${path.basename(filePath)}`);
       return { filePath, content };
     }
     return null;
+  } catch (err) {
+    return { error: err.message };
+  }
 });
 
 ipcMain.handle('file:read', async (event, filePath) => {
@@ -185,12 +130,13 @@ ipcMain.handle('file:read', async (event, filePath) => {
 ipcMain.handle('file:save', async (event, { filePath, content }) => {
   try {
     if (filePath) {
+      stopWatching();
       fs.writeFileSync(filePath, content, 'utf-8');
       currentFilePath = filePath;
+      startWatching(filePath);
       mainWindow.setTitle(`MarkLite - ${path.basename(filePath)}`);
       return { success: true, filePath };
     } else {
-      // No file path, do save as
       const result = await dialog.showSaveDialog(mainWindow, {
         filters: [
           { name: 'Markdown 文件', extensions: ['md'] },
@@ -198,8 +144,10 @@ ipcMain.handle('file:save', async (event, { filePath, content }) => {
         ]
       });
       if (!result.canceled) {
+        stopWatching();
         fs.writeFileSync(result.filePath, content, 'utf-8');
         currentFilePath = result.filePath;
+        startWatching(result.filePath);
         mainWindow.setTitle(`MarkLite - ${path.basename(result.filePath)}`);
         return { success: true, filePath: result.filePath };
       }
@@ -219,8 +167,10 @@ ipcMain.handle('file:saveAs', async (event, { content }) => {
       ]
     });
     if (!result.canceled) {
+      stopWatching();
       fs.writeFileSync(result.filePath, content, 'utf-8');
       currentFilePath = result.filePath;
+      startWatching(result.filePath);
       mainWindow.setTitle(`MarkLite - ${path.basename(result.filePath)}`);
       return { success: true, filePath: result.filePath };
     }
@@ -234,6 +184,36 @@ ipcMain.handle('file:getCurrentPath', () => {
   return currentFilePath;
 });
 
+ipcMain.handle('file:stats', async (event, filePath) => {
+  try {
+    const stats = fs.statSync(filePath);
+    return {
+      success: true,
+      size: stats.size,
+      mtime: stats.mtime.toISOString()
+    };
+  } catch (err) {
+    return { success: false, error: err.message };
+  }
+});
+
+ipcMain.handle('file:reload', async () => {
+  if (!currentFilePath) return { success: false, error: '没有打开的文件' };
+  try {
+    const content = fs.readFileSync(currentFilePath, 'utf-8');
+    isModifiedExternally = false;
+    return { success: true, content, filePath: currentFilePath };
+  } catch (err) {
+    return { success: false, error: err.message };
+  }
+});
+
+ipcMain.handle('window:forceClose', () => {
+  stopWatching();
+  mainWindow.removeAllListeners('close');
+  mainWindow.close();
+});
+
 // Handle file open from command line or file association
 function getCommandLineFile() {
   const args = process.argv.slice(1);
@@ -248,28 +228,23 @@ function getCommandLineFile() {
 
 // App lifecycle
 app.whenReady().then(() => {
-  // Register open-file handler BEFORE creating window (fixes race condition)
   app.on('open-file', (event, filePath) => {
     event.preventDefault();
     if (mainWindow && mainWindow.webContents.isLoading()) {
-      // Window is still loading, queue the file
       pendingFilePath = filePath;
     } else if (mainWindow) {
       openFile(filePath);
     } else {
-      // Window not created yet, store for later
       pendingFilePath = filePath;
     }
   });
 
   createWindow();
 
-  // Check for file passed via command line
   const fileToOpen = getCommandLineFile();
   if (fileToOpen) {
     pendingFilePath = fileToOpen;
   }
-  // pendingFilePath will be opened by the did-finish-load handler in createWindow()
 });
 
 app.on('window-all-closed', () => {

preload.js

@@ -7,6 +7,11 @@ contextBridge.exposeInMainWorld('electronAPI', {
   saveFile: (data) => ipcRenderer.invoke('file:save', data),
   saveFileAs: (data) => ipcRenderer.invoke('file:saveAs', data),
   getCurrentPath: () => ipcRenderer.invoke('file:getCurrentPath'),
+  getFileStats: (filePath) => ipcRenderer.invoke('file:stats', filePath),
+  reloadFile: () => ipcRenderer.invoke('file:reload'),
+
+  // Window control
+  forceClose: () => ipcRenderer.invoke('window:forceClose'),
 
   // Menu events
   onFileOpened: (callback) => ipcRenderer.on('file:opened', (event, data) => callback(data)),
@@ -14,6 +19,13 @@ contextBridge.exposeInMainWorld('electronAPI', {
   onMenuSaveAs: (callback) => ipcRenderer.on('menu:saveAs', () => callback()),
   onViewModeChange: (callback) => ipcRenderer.on('menu:viewMode', (event, mode) => callback(mode)),
 
+  // File modification detection
+  onExternalModification: (callback) => ipcRenderer.on('file:externallyModified', (event, filePath) => callback(filePath)),
+
+  // Window close confirmation
+  onConfirmClose: (callback) => ipcRenderer.on('window:confirmClose', () => callback()),
+  onClosing: (callback) => ipcRenderer.on('window:closing', () => callback()),
+
   // Remove listeners
   removeAllListeners: (channel) => ipcRenderer.removeAllListeners(channel)
 });

renderer/index.html

@@ -3,7 +3,7 @@
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
-  <meta http-equiv="Content-Security-Policy" content="default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self'; img-src 'self' data: https:;">
+  <meta http-equiv="Content-Security-Policy" content="default-src 'self'; style-src 'self' 'unsafe-inline'; script-src 'self'; img-src 'self' data:;">
   <title>MarkLite</title>
   <link rel="stylesheet" href="style.css">
   <link rel="stylesheet" href="../lib/highlight-github.css">
@@ -50,6 +50,31 @@
           <span>预览</span>
         </button>
       </div>
+      <div class="toolbar-right">
+        <button id="btn-dark" class="toolbar-btn" title="切换暗色主题">
+          <svg id="icon-dark" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round">
+            <path d="M21 12.79A9 9 0 1 1 11.21 3 7 7 0 0 0 21 12.79z"></path>
+          </svg>
+          <svg id="icon-light" width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" style="display:none">
+            <circle cx="12" cy="12" r="5"></circle>
+            <line x1="12" y1="1" x2="12" y2="3"></line>
+            <line x1="12" y1="21" x2="12" y2="23"></line>
+            <line x1="4.22" y1="4.22" x2="5.64" y2="5.64"></line>
+            <line x1="18.36" y1="18.36" x2="19.78" y2="19.78"></line>
+            <line x1="1" y1="12" x2="3" y2="12"></line>
+            <line x1="21" y1="12" x2="23" y2="12"></line>
+            <line x1="4.22" y1="19.78" x2="5.64" y2="18.36"></line>
+            <line x1="18.36" y1="5.64" x2="19.78" y2="4.22"></line>
+          </svg>
+        </button>
+      </div>
+    </div>
+
+    <!-- External modification banner -->
+    <div id="modified-banner" class="hidden">
+      <span>文件已被外部程序修改</span>
+      <button id="btn-reload" class="banner-btn">重新加载</button>
+      <button id="btn-dismiss" class="banner-btn">忽略</button>
     </div>
 
     <!-- Main content area -->
@@ -81,6 +106,8 @@
         <span class="status-divider">|</span>
         <span id="status-lang">Markdown</span>
         <span class="status-divider">|</span>
+        <span id="status-size"></span>
+        <span class="status-divider status-size-divider">|</span>
         <span id="status-cursor">行 1, 列 1</span>
       </div>
     </div>

renderer/renderer.js

@@ -8,8 +8,11 @@
   const lineNumbers = document.getElementById('line-numbers');
   const welcomeScreen = document.getElementById('welcome-screen');
   const dropOverlay = document.getElementById('drop-overlay');
+  const modifiedBanner = document.getElementById('modified-banner');
   const statusText = document.getElementById('status-text');
   const statusCursor = document.getElementById('status-cursor');
+  const statusSize = document.getElementById('status-size');
+  const statusSizeDivider = document.querySelector('.status-size-divider');
   const resizer = document.getElementById('resizer');
   const editorPanel = document.getElementById('editor-panel');
   const previewPanel = document.getElementById('preview-panel');
@@ -23,18 +26,58 @@
   const btnPreview = document.getElementById('btn-preview');
   const btnWelcomeOpen = document.getElementById('btn-welcome-open');
   const btnWelcomeNew = document.getElementById('btn-welcome-new');
+  const btnDark = document.getElementById('btn-dark');
+  const btnReload = document.getElementById('btn-reload');
+  const btnDismiss = document.getElementById('btn-dismiss');
 
   // ===== State =====
   let currentFilePath = null;
   let currentContent = '';
-  let viewMode = 'split'; // split, editor, preview
+  let viewMode = 'split';
   let isModified = false;
   let updateTimer = null;
+  let lineCountCache = 0;
+
+  // ===== localStorage Helpers =====
+  function loadSettings() {
+    try {
+      const s = JSON.parse(localStorage.getItem('marklite-settings') || '{}');
+      return s;
+    } catch { return {}; }
+  }
+
+  function saveSetting(key, value) {
+    try {
+      const s = loadSettings();
+      s[key] = value;
+      localStorage.setItem('marklite-settings', JSON.stringify(s));
+    } catch { /* ignore */ }
+  }
+
+  // ===== Dark Mode =====
+  function initDarkMode() {
+    const settings = loadSettings();
+    const iconDark = document.getElementById('icon-dark');
+    const iconLight = document.getElementById('icon-light');
+
+    function apply(isDark) {
+      document.documentElement.classList.toggle('dark', isDark);
+      iconDark.style.display = isDark ? 'none' : '';
+      iconLight.style.display = isDark ? '' : 'none';
+    }
+
+    apply(!!settings.darkMode);
+
+    btnDark.addEventListener('click', () => {
+      const isDark = !document.documentElement.classList.contains('dark');
+      apply(isDark);
+      saveSetting('darkMode', isDark);
+    });
+  }
 
   // ===== Initialize marked.js =====
   function initMarked() {
     if (typeof marked !== 'undefined') {
-      // Custom renderer for code block highlighting (compatible with marked v12+)
       const renderer = new marked.Renderer();
       renderer.code = function ({ text, lang }) {
         let highlighted = text;
@@ -72,15 +115,17 @@
     }
   }
 
-  // ===== Line Numbers =====
+  // ===== Line Numbers (optimized: batch innerHTML) =====
   function updateLineNumbers() {
-    const lines = editor.value.split('\n');
+    const count = editor.value.split('\n').length;
-    const count = lines.length;
+    if (count === lineCountCache) return;
-    let html = '';
+    lineCountCache = count;
+
+    const fragment = [];
     for (let i = 1; i <= count; i++) {
-      html += '<div class="line-num">' + i + '</div>';
+      fragment.push('<div class="line-num">', i, '</div>');
     }
-    lineNumbers.innerHTML = html;
+    lineNumbers.innerHTML = fragment.join('');
   }
 
   // ===== Cursor Position =====
@@ -94,25 +139,55 @@
     statusCursor.textContent = `行 ${line}, 列 ${col}`;
   }
 
-  // ===== Sync Scroll (line-based for more accurate sync) =====
+  // ===== File Size =====
+  function updateFileSize() {
+    const bytes = new TextEncoder().encode(editor.value).length;
+    let display;
+    if (bytes < 1024) display = bytes + ' B';
+    else if (bytes < 1024 * 1024) display = (bytes / 1024).toFixed(1) + ' KB';
+    else display = (bytes / (1024 * 1024)).toFixed(1) + ' MB';
+    statusSize.textContent = display;
+    statusSizeDivider.classList.add('visible');
+  }
+
+  // ===== Improved Scroll Sync (DOM position mapping) =====
+  let previewElements = null;
+  let previewPositions = null;
+
+  function cachePreviewPositions() {
+    previewElements = preview.children;
+    previewPositions = [];
+    for (let i = 0; i < previewElements.length; i++) {
+      previewPositions.push(previewElements[i].offsetTop);
+    }
+  }
+
   function syncScroll() {
     if (viewMode !== 'split') return;
 
-    // Calculate which line is at the top of the editor viewport
+    // Map editor scroll to preview using line-to-DOM correlation
     const lineHeight = parseFloat(getComputedStyle(editor).lineHeight) || 20.8;
     const scrollTop = editor.scrollTop;
     const topLine = Math.floor(scrollTop / lineHeight);
-
-    // Calculate corresponding scroll position in preview
-    const previewChildren = preview.children;
-    if (!previewChildren.length) return;
-
-    // Find the element that corresponds to the current top line
-    // Approximate: map editor line ratio to preview element positions
     const totalLines = editor.value.split('\n').length;
-    const ratio = totalLines > 0 ? topLine / totalLines : 0;
+
-    const targetScrollTop = ratio * (previewPanel.scrollHeight - previewPanel.clientHeight);
+    if (!previewPositions || previewPositions.length === 0) {
-    previewPanel.scrollTop = targetScrollTop;
+      cachePreviewPositions();
+    }
+
+    if (!previewPositions || previewPositions.length === 0) return;
+
+    // Find which preview element corresponds to the current editor line
+    // Use a rough heuristic: map line ratio to element ratio
+    const ratio = totalLines > 1 ? topLine / (totalLines - 1) : 0;
+    const targetIndex = Math.min(
+      Math.floor(ratio * previewPositions.length),
+      previewPositions.length - 1
+    );
+
+    if (targetIndex >= 0 && previewPositions[targetIndex] !== undefined) {
+      previewPanel.scrollTop = previewPositions[targetIndex];
+    }
   }
 
   // ===== Update Preview =====
@@ -122,6 +197,8 @@
       const text = editor.value;
       renderMarkdown(text);
       updateLineNumbers();
+      updateFileSize();
+      cachePreviewPositions();
     }, 150);
   }
 
@@ -138,35 +215,55 @@
     return filePath.split(/[/\\]/).pop();
   }
 
+  function formatBytes(bytes) {
+    if (bytes < 1024) return bytes + ' B';
+    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
+    return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
+  }
+
+  async function updateFileStats(filePath) {
+    if (typeof window.electronAPI !== 'undefined' && filePath) {
+      const stats = await window.electronAPI.getFileStats(filePath);
+      if (stats.success) {
+        statusSize.textContent = formatBytes(stats.size);
+        statusSizeDivider.classList.add('visible');
+      }
+    }
+  }
+
   function setEditorContent(text, filePath) {
     editor.value = text;
     currentContent = text;
     currentFilePath = filePath || null;
     isModified = false;
+    lineCountCache = 0;
     updateLineNumbers();
     renderMarkdown(text);
     updateCursorPosition();
+    updateFileSize();
+    cachePreviewPositions();
 
     if (filePath) {
       document.title = `MarkLite - ${getFileName(filePath)}`;
       statusText.textContent = getFileName(filePath);
+      updateFileStats(filePath);
     } else {
       document.title = 'MarkLite - 未命名';
       statusText.textContent = '未命名';
+      statusSize.textContent = '';
+      statusSizeDivider.classList.remove('visible');
     }
 
-    // Hide welcome screen
     welcomeScreen.classList.add('hidden');
   }
 
   async function handleOpenFile() {
     if (typeof window.electronAPI !== 'undefined') {
       const result = await window.electronAPI.openFile();
-      if (result) {
+      if (result && !result.error) {
         setEditorContent(result.content, result.filePath);
       }
     } else {
-      // Fallback: use file input
       const input = document.createElement('input');
       input.type = 'file';
       input.accept = '.md,.markdown,.txt';
@@ -200,7 +297,6 @@
         }, 2000);
       }
     } else {
-      // Fallback: download file
       const blob = new Blob([editor.value], { type: 'text/markdown' });
       const a = document.createElement('a');
       a.href = URL.createObjectURL(blob);
@@ -230,15 +326,13 @@
     }
   }
 
-  // ===== View Mode =====
+  // ===== View Mode (with localStorage) =====
   function setViewMode(mode) {
     viewMode = mode;
     const app = document.getElementById('app');
 
-    // Remove all mode classes
     app.classList.remove('mode-editor', 'mode-preview');
 
-    // Update button states
     btnSplit.classList.remove('active');
     btnEditor.classList.remove('active');
     btnPreview.classList.remove('active');
@@ -254,16 +348,25 @@
       case 'preview':
         btnPreview.classList.add('active');
         app.classList.add('mode-preview');
-        // Update preview when switching to preview mode
         renderMarkdown(editor.value);
         break;
     }
+
+    saveSetting('viewMode', mode);
   }
 
-  // ===== Resizer =====
+  // ===== Resizer (with localStorage) =====
   let isResizing = false;
 
   function initResizer() {
+    // Restore saved ratio
+    const settings = loadSettings();
+    if (settings.splitRatio) {
+      const ratio = settings.splitRatio;
+      editorPanel.style.flex = `0 0 ${ratio}%`;
+      previewPanel.style.flex = `0 0 ${100 - ratio}%`;
+    }
+
     resizer.addEventListener('mousedown', (e) => {
       isResizing = true;
       resizer.classList.add('active');
@@ -279,6 +382,7 @@
       const clamped = Math.max(20, Math.min(80, percentage));
       editorPanel.style.flex = `0 0 ${clamped}%`;
       previewPanel.style.flex = `0 0 ${100 - clamped}%`;
+      saveSetting('splitRatio', clamped);
     });
 
     document.addEventListener('mouseup', () => {
@@ -325,10 +429,9 @@
       const files = e.dataTransfer.files;
       if (files.length > 0) {
         const file = files[0];
-        const filePath = file.path; // Electron provides the real file path
+        const filePath = file.path;
 
         if (filePath && typeof window.electronAPI !== 'undefined') {
-          // Use IPC to read file through main process (tracks currentFilePath)
           const result = await window.electronAPI.readFile(filePath);
           if (result.success) {
             setEditorContent(result.content, filePath);
@@ -336,7 +439,6 @@
             statusText.textContent = '打开失败: ' + result.error;
           }
         } else {
-          // Fallback: use FileReader (browser mode)
           const reader = new FileReader();
           reader.onload = (ev) => {
             setEditorContent(ev.target.result, file.name);
@@ -350,32 +452,26 @@
   // ===== Keyboard Shortcuts =====
   function initKeyboard() {
     document.addEventListener('keydown', (e) => {
-      // Ctrl+O: Open
       if (e.ctrlKey && e.key === 'o') {
         e.preventDefault();
         handleOpenFile();
       }
-      // Ctrl+S: Save
       if (e.ctrlKey && e.key === 's' && !e.shiftKey) {
         e.preventDefault();
         handleSave();
       }
-      // Ctrl+Shift+S: Save As
       if (e.ctrlKey && e.shiftKey && e.key === 'S') {
         e.preventDefault();
         handleSaveAs();
       }
-      // Ctrl+1: Split view
       if (e.ctrlKey && e.key === '1') {
         e.preventDefault();
         setViewMode('split');
       }
-      // Ctrl+2: Editor only
       if (e.ctrlKey && e.key === '2') {
         e.preventDefault();
         setViewMode('editor');
       }
-      // Ctrl+3: Preview only
       if (e.ctrlKey && e.key === '3') {
         e.preventDefault();
         setViewMode('preview');
@@ -383,14 +479,12 @@
     });
   }
 
-  // ===== Tab key support in editor (preserves undo history) =====
+  // ===== Tab key support =====
   function initEditorTab() {
     editor.addEventListener('keydown', (e) => {
       if (e.key === 'Tab') {
         e.preventDefault();
-        // Use insertText command to preserve undo/redo history
         if (!document.execCommand('insertText', false, '    ')) {
-          // Fallback for environments where execCommand is unsupported
           const start = editor.selectionStart;
           const end = editor.selectionEnd;
           editor.setRangeText('    ', start, end, 'end');
@@ -400,36 +494,88 @@
     });
   }
 
+  // ===== External File Modification =====
+  function initFileWatch() {
+    if (typeof window.electronAPI === 'undefined') return;
+
+    window.electronAPI.onExternalModification((filePath) => {
+      modifiedBanner.classList.remove('hidden');
+    });
+
+    btnReload.addEventListener('click', async () => {
+      const result = await window.electronAPI.reloadFile();
+      if (result.success) {
+        editor.value = result.content;
+        currentContent = result.content;
+        currentFilePath = result.filePath;
+        isModified = false;
+        lineCountCache = 0;
+        updateLineNumbers();
+        renderMarkdown(result.content);
+        updateCursorPosition();
+        updateFileSize();
+        cachePreviewPositions();
+      }
+      modifiedBanner.classList.add('hidden');
+    });
+
+    btnDismiss.addEventListener('click', () => {
+      modifiedBanner.classList.add('hidden');
+    });
+  }
+
+  // ===== Unsaved Changes Warning =====
+  function initUnsavedWarning() {
+    if (typeof window.electronAPI === 'undefined') {
+      // Browser fallback
+      window.addEventListener('beforeunload', (e) => {
+        if (isModified) {
+          e.preventDefault();
+          e.returnValue = '';
+        }
+      });
+      return;
+    }
+
+    // Electron: handle close confirmation from main process
+    window.electronAPI.onConfirmClose(() => {
+      if (!isModified) {
+        window.electronAPI.forceClose();
+        return;
+      }
+
+      // Show a simple confirm dialog
+      const shouldClose = confirm('文件尚未保存，确定要关闭吗？');
+      if (shouldClose) {
+        window.electronAPI.forceClose();
+      }
+    });
+  }
+
   // ===== Event Listeners =====
   function initEventListeners() {
-    // Editor input
     editor.addEventListener('input', () => {
       setModified(true);
       scheduleUpdate();
     });
 
-    // Editor scroll sync
     editor.addEventListener('scroll', syncScroll);
 
-    // Editor cursor position
     editor.addEventListener('click', updateCursorPosition);
     editor.addEventListener('keyup', updateCursorPosition);
     editor.addEventListener('select', updateCursorPosition);
 
-    // Toolbar buttons
     btnOpen.addEventListener('click', handleOpenFile);
     btnSave.addEventListener('click', handleSave);
     btnSplit.addEventListener('click', () => setViewMode('split'));
     btnEditor.addEventListener('click', () => setViewMode('editor'));
     btnPreview.addEventListener('click', () => setViewMode('preview'));
 
-    // Welcome buttons
     btnWelcomeOpen.addEventListener('click', handleOpenFile);
     btnWelcomeNew.addEventListener('click', () => {
       setEditorContent('', null);
     });
 
-    // Electron IPC events
     if (typeof window.electronAPI !== 'undefined') {
       window.electronAPI.onFileOpened((data) => {
         setEditorContent(data.content, data.filePath);
@@ -452,16 +598,21 @@
   // ===== Initialize =====
   function init() {
     initMarked();
+    initDarkMode();
     initResizer();
     initDragDrop();
     initKeyboard();
     initEditorTab();
     initEventListeners();
+    initFileWatch();
+    initUnsavedWarning();
     updateLineNumbers();
-    setViewMode('split');
+
+    // Restore saved view mode
+    const settings = loadSettings();
+    setViewMode(settings.viewMode || 'split');
   }
 
-  // Run when DOM is ready
   if (document.readyState === 'loading') {
     document.addEventListener('DOMContentLoaded', init);
   } else {

renderer/style.css

@@ -27,6 +27,24 @@
   --font-mono: "Cascadia Code", "Fira Code", "JetBrains Mono", Consolas, "Courier New", monospace;
 }
 
+/* ===== Dark Theme ===== */
+:root.dark {
+  --primary: #8ab4f8;
+  --primary-light: #1a3a5c;
+  --primary-dark: #aecbfa;
+  --bg: #1e1e1e;
+  --bg-secondary: #252526;
+  --bg-tertiary: #2d2d2d;
+  --text: #d4d4d4;
+  --text-secondary: #9e9e9e;
+  --text-tertiary: #6e6e6e;
+  --border: #3e3e3e;
+  --border-light: #333333;
+  --code-bg: #2d2d2d;
+  --shadow: 0 1px 3px rgba(0, 0, 0, 0.3);
+  --shadow-lg: 0 4px 12px rgba(0, 0, 0, 0.4);
+}
+
 html, body {
   height: 100%;
   font-family: var(--font-ui);
@@ -50,12 +68,14 @@ html, body {
   border-bottom: 1px solid var(--border);
   display: flex;
   align-items: center;
+  justify-content: space-between;
   padding: 0 8px;
   flex-shrink: 0;
   z-index: 10;
 }
 
-.toolbar-left {
+.toolbar-left,
+.toolbar-right {
   display: flex;
   align-items: center;
   gap: 2px;
@@ -98,6 +118,55 @@ html, body {
   margin: 0 6px;
 }
 
+/* ===== Modified Banner ===== */
+#modified-banner {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 6px 12px;
+  background: #fff3cd;
+  border-bottom: 1px solid #ffc107;
+  font-size: 13px;
+  color: #856404;
+  flex-shrink: 0;
+}
+
+:root.dark #modified-banner {
+  background: #3a3000;
+  border-bottom-color: #665500;
+  color: #ffd54f;
+}
+
+#modified-banner.hidden {
+  display: none;
+}
+
+.banner-btn {
+  padding: 2px 10px;
+  border: 1px solid #ffc107;
+  border-radius: 4px;
+  background: transparent;
+  color: #856404;
+  font-size: 12px;
+  cursor: pointer;
+  font-family: var(--font-ui);
+}
+
+:root.dark .banner-btn {
+  border-color: #665500;
+  color: #ffd54f;
+}
+
+.banner-btn:hover {
+  background: #ffc107;
+  color: #000;
+}
+
+:root.dark .banner-btn:hover {
+  background: #665500;
+  color: #fff;
+}
+
 /* ===== Main Content ===== */
 #main-content {
   flex: 1;
@@ -298,6 +367,10 @@ html, body {
   color: #e83e8c;
 }
 
+:root.dark .markdown-body code {
+  color: #f48fb1;
+}
+
 .markdown-body pre {
   margin-top: 0;
   margin-bottom: 16px;
@@ -370,6 +443,14 @@ html, body {
   color: var(--border);
 }
 
+.status-size-divider {
+  display: none;
+}
+
+.status-size-divider.visible {
+  display: inline;
+}
+
 /* ===== Drop Overlay ===== */
 #drop-overlay {
   position: fixed;