fix: BOM处理、异步读取、10MB文件限制、滚动同步精度优化

main.js

@@ -1,6 +1,9 @@
 const { app, BrowserWindow, dialog, ipcMain } = require('electron');
 const path = require('path');
 const fs = require('fs');
+const { readFile, stat } = require('fs/promises');
+
+const MAX_FILE_SIZE = 10 * 1024 * 1024; // 10MB
 
 let mainWindow = null;
 let activeFilePath = null; // Currently active tab's file path
@@ -149,15 +152,23 @@ async function showOpenDialog() {
   return null;
 }
 
-function readFileContent(filePath) {
+async function readFileContent(filePath) {
-  return fs.readFileSync(filePath, 'utf-8');
+  // 文件大小检查
+  const stats = await stat(filePath);
+  if (stats.size > MAX_FILE_SIZE) {
+    throw new Error(`文件过大（${(stats.size / 1024 / 1024).toFixed(1)} MB），暂不支持超过 10MB 的文件`);
+  }
+  let content = await readFile(filePath, 'utf-8');
+  // 剥离 UTF-8 BOM（Windows 某些编辑器会添加）
+  if (content.charCodeAt(0) === 0xFEFF) content = content.slice(1);
+  return content;
 }
 
 // Open file in a new tab (renderer manages tabs)
-function openFileInTab(filePath) {
+async function openFileInTab(filePath) {
   if (!mainWindow || mainWindow.isDestroyed()) return;
   try {
-    const content = readFileContent(filePath);
+    const content = await readFileContent(filePath);
     activeFilePath = filePath;
     startWatching(filePath);
     mainWindow.setTitle(`MarkLite - ${path.basename(filePath)}`);
@@ -213,7 +224,7 @@ ipcMain.handle('dialog:openFile', async () => {
   try {
     const files = await showOpenDialog();
     if (files && files.length > 0) {
-      const content = readFileContent(files[0]);
+      const content = await readFileContent(files[0]);
       activeFilePath = files[0];
       startWatching(files[0]);
       mainWindow.setTitle(`MarkLite - ${path.basename(files[0])}`);
@@ -228,7 +239,7 @@ ipcMain.handle('dialog:openFile', async () => {
 
 ipcMain.handle('file:read', async (event, filePath) => {
   try {
-    const content = readFileContent(filePath);
+    const content = await readFileContent(filePath);
     return { success: true, content };
   } catch (err) {
     return { success: false, error: err.message };
@@ -277,8 +288,8 @@ ipcMain.handle('file:getCurrentPath', () => {
 
 ipcMain.handle('file:stats', async (event, filePath) => {
   try {
-    const stats = fs.statSync(filePath);
+    const fileStat = await stat(filePath);
-    return { success: true, size: stats.size, mtime: stats.mtime.toISOString() };
+    return { success: true, size: fileStat.size, mtime: fileStat.mtime.toISOString() };
   } catch (err) {
     return { success: false, error: err.message };
   }
@@ -287,7 +298,7 @@ ipcMain.handle('file:stats', async (event, filePath) => {
 ipcMain.handle('file:reload', async () => {
   if (!activeFilePath) return { success: false, error: '没有打开的文件' };
   try {
-    const content = readFileContent(activeFilePath);
+    const content = await readFileContent(activeFilePath);
     return { success: true, content, filePath: activeFilePath };
   } catch (err) {
     return { success: false, error: err.message };

renderer/renderer.js

@@ -321,12 +321,116 @@
 
   // ===== Scroll Sync =====
   let previewPositions = null;
+  let lineToPreviewMap = null; // 行号 → 预览像素位置的映射
 
   function cachePreviewPositions() {
     previewPositions = [];
     for (let i = 0; i < preview.children.length; i++) {
       previewPositions.push(preview.children[i].offsetTop);
     }
+    // 构建行号→预览位置的映射表
+    buildLineToPreviewMap();
+  }
+
+  // 通过分析原始 Markdown 文本，建立编辑器行号到预览 DOM 位置的映射
+  function buildLineToPreviewMap() {
+    if (!previewPositions || previewPositions.length === 0) {
+      lineToPreviewMap = null;
+      return;
+    }
+
+    const text = editor.value;
+    const lines = text.split('\n');
+    const totalLines = lines.length;
+
+    // 找出每个"块级元素"在编辑器中的起始行
+    // 块级元素：标题、段落、代码块、列表、引用、表格、水平线
+    const blockStartLines = [];
+    let inCodeBlock = false;
+
+    for (let i = 0; i < totalLines; i++) {
+      const line = lines[i];
+      const trimmed = line.trimStart();
+
+      // 围栏代码块边界
+      if (trimmed.startsWith('```')) {
+        if (!inCodeBlock) {
+          blockStartLines.push(i);
+          inCodeBlock = true;
+        } else {
+          inCodeBlock = false;
+        }
+        continue;
+      }
+
+      if (inCodeBlock) continue;
+
+      // 块级元素起始行
+      if (
+        trimmed.startsWith('#') ||           // 标题
+        trimmed.startsWith('- ') ||           // 无序列表
+        trimmed.startsWith('* ') ||           // 无序列表
+        trimmed.startsWith('+ ') ||           // 无序列表
+        /^\d+\.\s/.test(trimmed) ||           // 有序列表
+        trimmed.startsWith('> ') ||           // 引用
+        trimmed.startsWith('|') ||            // 表格
+        trimmed.startsWith('---') ||          // 水平线
+        trimmed.startsWith('***') ||          // 水平线
+        trimmed.startsWith('___') ||          // 水平线
+        (trimmed === '' && i > 0 && lines[i - 1].trim() === '') // 连续空行=段落分隔
+      ) {
+        blockStartLines.push(i);
+      }
+    }
+
+    // 去重并排序
+    const uniqueStarts = [...new Set(blockStartLines)].sort((a, b) => a - b);
+
+    // 将编辑器行号映射到预览 DOM 位置
+    // 每个块的起始行对应一个预览元素，用线性插值填充中间行
+    lineToPreviewMap = new Float32Array(totalLines);
+
+    if (uniqueStarts.length === 0) {
+      // 没有找到块边界，回退到线性映射
+      for (let i = 0; i < totalLines; i++) {
+        lineToPreviewMap[i] = (i / Math.max(1, totalLines - 1)) * previewPositions[previewPositions.length - 1];
+      }
+      return;
+    }
+
+    // 将块起始行映射到预览 DOM 索引
+    const domCount = previewPositions.length;
+    for (let i = 0; i < uniqueStarts.length; i++) {
+      const lineIdx = uniqueStarts[i];
+      const domIdx = Math.min(Math.floor((i / uniqueStarts.length) * domCount), domCount - 1);
+      lineToPreviewMap[lineIdx] = previewPositions[domIdx];
+    }
+
+    // 线性插值填充所有行
+    for (let i = 0; i < totalLines; i++) {
+      if (lineToPreviewMap[i] !== 0 && uniqueStarts.includes(i)) continue;
+
+      // 找到前后最近的已映射行
+      let prevLine = -1, nextLine = -1;
+      for (let j = i - 1; j >= 0; j--) {
+        if (lineToPreviewMap[j] !== 0 || uniqueStarts.includes(j)) { prevLine = j; break; }
+      }
+      for (let j = i + 1; j < totalLines; j++) {
+        if (lineToPreviewMap[j] !== 0 || uniqueStarts.includes(j)) { nextLine = j; break; }
+      }
+
+      if (prevLine === -1 && nextLine === -1) {
+        lineToPreviewMap[i] = 0;
+      } else if (prevLine === -1) {
+        lineToPreviewMap[i] = lineToPreviewMap[nextLine];
+      } else if (nextLine === -1) {
+        lineToPreviewMap[i] = lineToPreviewMap[prevLine];
+      } else {
+        // 线性插值
+        const ratio = (i - prevLine) / (nextLine - prevLine);
+        lineToPreviewMap[i] = lineToPreviewMap[prevLine] + ratio * (lineToPreviewMap[nextLine] - lineToPreviewMap[prevLine]);
+      }
+    }
   }
 
   function syncScroll() {
@@ -334,17 +438,23 @@
     const lineHeight = parseFloat(getComputedStyle(editor).lineHeight) || 20.8;
     const scrollTop = editor.scrollTop;
     const topLine = Math.floor(scrollTop / lineHeight);
-    const totalLines = editor.value.split('\n').length;
 
     if (!previewPositions || previewPositions.length === 0) cachePreviewPositions();
     if (!previewPositions || previewPositions.length === 0) return;
 
+    // 使用行号→预览位置映射表
+    if (lineToPreviewMap && topLine >= 0 && topLine < lineToPreviewMap.length) {
+      previewPanel.scrollTop = lineToPreviewMap[topLine];
+    } else {
+      // fallback: 线性比例映射
+      const totalLines = editor.value.split('\n').length;
       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];
       }
     }
+  }
 
   // ===== Schedule Update =====
   function scheduleUpdate() {
@@ -549,6 +659,15 @@
     updateTitle();
   }
 
+  // ===== File Size Limit =====
+  const MAX_FILE_SIZE = 10 * 1024 * 1024; // 10MB
+
+  function formatFileSize(bytes) {
+    if (bytes < 1024) return bytes + ' B';
+    if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' KB';
+    return (bytes / (1024 * 1024)).toFixed(1) + ' MB';
+  }
+
   // ===== File Operations =====
   async function handleOpenFile() {
     if (typeof window.electronAPI !== 'undefined') {
@@ -565,6 +684,10 @@
         Array.from(e.target.files).forEach(file => {
           const ext = file.name.substring(file.name.lastIndexOf('.')).toLowerCase();
           if (!['.md', '.markdown', '.txt'].includes(ext)) return;
+          if (file.size > MAX_FILE_SIZE) {
+            alert(`"${file.name}" 过大（${formatFileSize(file.size)}），暂不支持超过 10MB 的文件`);
+            return;
+          }
           const reader = new FileReader();
           reader.onload = (ev) => {
             createNewTab(file.name, ev.target.result);
@@ -725,6 +848,11 @@
         const filePath = file.path;
         const ext = filePath ? filePath.substring(filePath.lastIndexOf('.')).toLowerCase() : '';
         if (!allowedExts.includes(ext)) continue;
+        // Electron 主进程已有文件大小检查，此处为浏览器模式兜底
+        if (file.size > MAX_FILE_SIZE) {
+          alert(`"${file.name}" 过大（${formatFileSize(file.size)}），暂不支持超过 10MB 的文件`);
+          continue;
+        }
         if (filePath && typeof window.electronAPI !== 'undefined') {
           const result = await window.electronAPI.readFile(filePath);
           if (result.success) {