

 <!--
============================================================================
 本网站使用了以下开源项目，特此致谢并遵循其许可证要求。
============================================================================

1. SYZOJ 项目 (原始上游代码)
   - 项目地址: https://github.com/syzoj/syzoj
   - 版权持有人: Menci
   - 许可证: MIT License
   - 完整许可证文本如下：

MIT License

Copyright (c) 2021 Menci

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

============================================================================

2. AlgoBeatOnlineJudge 项目，工单系统的一部分等(基于 SYZOJ 的修改和新增部分)
   - 项目地址: https://github.com/ZemuZzz/AlgoBeatOnlineJudge
   - 版权持有人: 请参考该项目仓库 (https://github.com/ZemuZzz/AlgoBeatOnlineJudge)
   - 许可证: Apache License 2.0
   - 完整许可证文本如下：

                                 Apache License
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				$(document).ready(function() {
				    updateUnreadCount();
				    updateNotificationCount();
				    loadForceNotifications();
				    setInterval(updateUnreadCount, 30000);
				    setInterval(updateNotificationCount, 30000);
				});
				
				// ========== 深色/浅色模式核心管理器（基于旧版 + 统一子主题） ==========
				(function() {
				    const COOKIE_KEY = 'theme_mode';
				    const STORAGE_KEYS = {
				        dark_sub: 'dark_sub_theme',
				        light_sub: 'light_sub_theme'
				    };
				    const DARK_SUB_THEMES = ['warm', 'mint', 'deep', 'oled', 'purple'];  // 与 CSS 中 class 对应
				    const LIGHT_SUB_THEMES = ['ng','warm', 'mint', 'oled', 'purple'];         // 亮色主题变体（暂时只有这些）
				
				    const icons = { light: { cls: 'sun' }, dark: { cls: 'moon' }, auto: { cls: 'adjust' } };
				    // 判断当前应该使用深色模式（true）还是浅色模式（false）
				    function shouldUseDarkMode() {
				        const mode = window.__themeMode || 'auto';
				        if (mode === 'dark') return true;
				        if (mode === 'light') return false;
				        // auto 模式：根据系统偏好
				        return window.matchMedia('(prefers-color-scheme: dark)').matches;
				    }
				    function getCurrentColorMode() {
				        return shouldUseDarkMode() ? 'dark' : 'light';
				    }
				    function setThemeMode(mode, updateCookie = true) {
				        if (updateCookie) {
				            document.cookie = COOKIE_KEY + '=' + mode + '; path=/; max-age=31536000';
				        }
				        window.__themeMode = mode;
				    }
				    function isSystemDark() {
				        return window.matchMedia('(prefers-color-scheme: dark)').matches;
				    }
				    function applyThemeClass(ss) {
				        let mode = getCurrentColorMode();
				        console.log(mode)
				        const htmlElem = document.documentElement;
				        if (mode == "dark") {
				            setDarkSubTheme(getDarkSubTheme());
				        } else {
				        console.log("applyThemeClass",localStorage,getLightSubTheme())
				            setLightSubTheme(getLightSubTheme());
				        }
				        return mode;
				    }
				    function refreshTheme(mode) {
				        const finalMode = shouldUseDarkMode();
				        if (mode) setThemeMode(mode, true);
				        applyThemeClass(finalMode);
				    }
				
				    // ----- 深色子主题管理 -----
				    function getDarkSubTheme() {
				        return localStorage.getItem(STORAGE_KEYS.dark_sub)==undefined ? 'default':localStorage.getItem(STORAGE_KEYS.dark_sub);
				    }
				    function setDarkSubTheme(themeName) {
				        console.log("setdark",themeName)
				        const html = document.documentElement;
				        DARK_SUB_THEMES.forEach(t => html.classList.remove(`dark-${t}`));
				        LIGHT_SUB_THEMES.forEach(t => html.classList.remove(`light-${t}`));
				        html.classList.add(`theme`);
				        html.classList.add(`dark`);
				        if (themeName !== 'default') {
				            html.classList.add(`dark-${themeName}`);
				        }
				        localStorage.setItem(STORAGE_KEYS.dark_sub, themeName);
				    }
				    // ----- 亮色子主题管理 -----
				    function getLightSubTheme() {
				    console.log(localStorage.getItem(STORAGE_KEYS.light_sub))
				        return localStorage.getItem(STORAGE_KEYS.light_sub)==undefined ? 'ng':localStorage.getItem(STORAGE_KEYS.light_sub);
				    }
				    function setLightSubTheme(themeName) {
				        console.log("setlight",`light-${themeName}`)
				        const html = document.documentElement;
				        DARK_SUB_THEMES.forEach(t => html.classList.remove(`dark-${t}`));
				        LIGHT_SUB_THEMES.forEach(t => html.classList.remove(`light-${t}`));
				        html.classList.remove(`dark`);
				        if (themeName !== 'default') {
				            html.classList.add(`theme`);
				            html.classList.add(`light-${themeName}`);
				        }
				        else html.classList.remove(`theme`);
				        localStorage.setItem(STORAGE_KEYS.light_sub, themeName);
				        console.log(localStorage)
				    }
				
				    // 切换子主题（供菜单调用）
				    window.switchSubTheme = function(themeName) {
				    console.log("sub",themeName)
				        const isDark = getCurrentColorMode() == 'dark';
				        if (isDark) {
				            setDarkSubTheme(themeName);
				        } else {
				            setLightSubTheme(themeName);
				        }
				        Swal.fire({
				            toast: true,
				            icon: 'success',
				            title: '主题已切换',
				            timer: 1500,
				            theme: window.__themeMode,
				            showConfirmButton: false,
				            position: 'top-end'
				        });
				    };
				
				    // ----- 动态填充统一下拉菜单（根据当前模式显示不同的主题列表）-----
				    function populateThemeMenu() {
				    console.log(-1)
				        const $menu = $('#theme-subtheme-menu');
				        if (!$menu.length) return;
				        const isDark = getCurrentColorMode() == 'dark';
				        // 定义主题列表（显示名称、图标、对应的 theme id）
				        let themes;
				        if (isDark) {
				            themes = [
				                { id: 'default', name: '暗蓝', icon: 'moon' },
				                { id: 'warm',    name: '暖橙',     icon: 'fire' },
				                { id: 'mint',    name: '墨绿',     icon: 'leaf' },
				                { id: 'deep',    name: '深邃',     icon: 'magic' },
				                { id: 'oled',    name: 'OLED黑',   icon: 'adjust' },
				                { id: 'purple',  name: '紫罗兰',   icon: 'star' }
				            ];
				        } else {
				            themes = [
				            	{ id: 'default', name: '原生', icon: 'sun' },

				                { id: 'ng', name: '新版', icon: 'rocket' },
				                { id: 'warm',    name: '暖橙',     icon: 'fire' },
				                { id: 'mint',    name: '薄荷',     icon: 'leaf' },
				                { id: 'oled',    name: '高亮白',   icon: 'adjust' },
				                { id: 'purple',  name: '紫罗兰',   icon: 'star' }
				            ];
				        }
				        let html = '';
				        themes.forEach(t => {
				            html += `<div class="item" data-theme="${t.id}">
				                        <i class="${t.icon} icon"></i> ${t.name}</div>`;
				        });
				        $menu.html(html);
				    }
				
				    // 初始化下拉菜单（使用 Semantic UI dropdown 并绑定事件）
				    function initThemeDropdown() {
				        const $dropdown = $('#theme-subtheme-dropdown');
				        if (!$dropdown.length) return;
				        // 每次打开前重新填充菜单，确保与当前模式同步
				        $('#theme-subtheme-dropdown').dropdown({
				            direction: 'downward',
				            on: 'click',          // 强制 click 触发（移动端默认就是 click）
				            // 可选：添加触摸优化
				            touch: true,
				            onShow: function() {
				                populateThemeMenu();
				            }
				        });
				        $('#theme-subtheme-dropdown').dropdown({
				            direction: 'downward',
				            on: 'hover',          // 强制 click 触发（移动端默认就是 click）
				            // 可选：添加触摸优化
				            touch: true,
				            onShow: function() {
				                populateThemeMenu();
				            }
				        });
				        // 菜单项点击事件（委托）
				        $(document).on('click', '#theme-subtheme-menu .item', function(e) {
				            e.preventDefault();
				            console.log("hd")
				            const theme = $(this).data('theme');
				            console.log(theme)
				            window.switchSubTheme(theme);
				        });
				        // 首次填充
				        populateThemeMenu();
				    }
				
				    // ----- 监听系统深色模式变化（仅 auto 模式）-----
				    const systemDarkMq = window.matchMedia('(prefers-color-scheme: dark)');
				    function onSystemChange(e) {
				        const currentMode = window.__themeMode;
				        if (currentMode === 'auto') {
				            applyThemeClass('auto');
				        }
				    }
				    if (systemDarkMq.addEventListener) {
				        systemDarkMq.addEventListener('change', onSystemChange);
				    } else if (systemDarkMq.addListener) {
				        systemDarkMq.addListener(onSystemChange);
				    }
				
				    // 绑定主题切换按钮 (light/dark/auto 循环)
				    function initButtonIcon() {
				        var mode = window.__themeMode;
				        var btn = document.getElementById('theme-toggle');
				        if (!btn) return;
				        var iconDef = icons[mode] || icons.light;
				        btn.innerHTML = '<i class="' + iconDef.cls + ' icon" style="margin: 0;"></i>';
				    }
				    function bindThemeToggle() {
				        const toggleBtn = document.getElementById('theme-toggle');
				        if (!toggleBtn) return;
				        toggleBtn.addEventListener('click', function(e) {
				            e.preventDefault();
				            let mode = window.__themeMode;
				            if (mode === 'light') mode = 'dark';
				            else if (mode === 'dark') mode = 'auto';
				            else mode = 'light';
				            refreshTheme(mode);
				            initButtonIcon(mode)
				            // 刷新后，下拉菜单内容会随着 populateThemeMenu 更新（下一次打开时）
				        });
				    }
				
				    // 页面加载完成后初始化
				    $(document).ready(function() {
				        // 初始化深色/浅色模式
				        initButtonIcon();
				        bindThemeToggle();
				        // 初始化统一主题下拉菜单
				        initThemeDropdown();
				        // 监听 class 变化，当深色模式被外部修改时（如通过其他方式），重新应用子主题并刷新菜单
				        const observer = new MutationObserver(function(mutations) {
				            mutations.forEach(function(mutation) {
				                if (mutation.attributeName === 'class') {
				                    const html = document.documentElement;
				                    const isDarkNow = html.classList.contains('theme');
				                    if (isDarkNow !== window._wasDark) {
				                        window._wasDark = isDarkNow;
				                        populateThemeMenu();
				                    }
				                }
				            });
				        });
				        observer.observe(document.documentElement, { attributes: true });
				        window._wasDark = document.documentElement.classList.contains('theme');
				    });
				})();
			</script>
<link rel="stylesheet" href="/self/dark/draw.css">

<style>
    /* 基础布局调整，保证画板填充分配合理 */
    * {
        user-select: none;
        -webkit-tap-highlight-color: transparent;
    }
    .drawing-app {
        width: 100%;
        height: 700px;
        background: #f5f5f5;
        border-radius: 8px;
        overflow: hidden;
        box-shadow: 0 2px 12px rgba(0,0,0,0.1);
        display: flex;
        flex-direction: column;
    }
    /* 工具栏采用 Semantic UI 的紧凑菜单样式，但保留原有flex布局使其更灵活 */
    .toolbar {
        background: #ffffff;
        padding: 12px 16px;
        border-bottom: 1px solid #ddd;
        display: flex;
        align-items: center;
        gap: 16px;
        flex-wrap: wrap;
    }
    .tool-group {
        display: flex;
        align-items: center;
        gap: 8px;
        padding-right: 16px;
        border-right: 1px solid #e9e9e9;
    }
    .tool-group:last-child {
        border-right: none;
        padding-right: 0;
    }
    .tool-group-label {
        font-size: 0.9rem;
        color: #4a4a4a;
        font-weight: 500;
        margin-right: 4px;
    }
    /* 自定义按钮激活状态，与 Semantic UI 的 primary 风格匹配 */
    .tool-button.active {
        background: #2185d0 !important;
        color: white !important;
        border-color: #2185d0 !important;
        box-shadow: 0 0 0 1px #2185d0 inset !important;
    }
    /* 颜色色块样式保留，稍微适配 Semantic 圆角 */
    .color-picker {
        display: flex;
        align-items: center;
        gap: 8px;
    }
    .color-option {
        width: 32px;
        height: 32px;
        border-radius: 4px;
        border: 2px solid transparent;
        cursor: pointer;
        transition: 0.2s;
        box-shadow: 0 1px 3px rgba(0,0,0,0.1);
    }
    .color-option:hover {
        transform: scale(1.08);
    }
    .color-option.active {
        border-color: white;
        box-shadow: 0 0 0 2px #2185d0, 0 2px 6px rgba(0,0,0,0.2);
    }
    .custom-color-wrapper {
        position: relative;
        width: 32px;
        height: 32px;
    }
    #custom-color {
        width: 100%;
        height: 100%;
        border-radius: 4px;
        border: 1px solid #ccc;
        cursor: pointer;
        opacity: 0;
        position: absolute;
        top: 0;
        left: 0;
        z-index: 2;
    }
    .custom-color-preview {
        width: 100%;
        height: 100%;
        border-radius: 4px;
        background: linear-gradient(45deg, #2185d0, #21ba45);
        position: absolute;
        top: 0;
        left: 0;
        pointer-events: none;
        border: 1px solid #ddd;
    }
    /* 滑块容器，保持原生 range 但加一点 Semantic 风格 */
    .slider-container {
        display: flex;
        align-items: center;
        gap: 12px;
        min-width: 200px;
    }
    .slider-label {
        font-size: 0.85rem;
        color: #555;
    }
    #brush-size, #zoom-range {
        flex: 1;
        height: 4px;
        border-radius: 3px;
        background: #ddd;
        outline: none;
        -webkit-appearance: none;
    }
    #brush-size::-webkit-slider-thumb, #zoom-range::-webkit-slider-thumb {
        -webkit-appearance: none;
        width: 16px;
        height: 16px;
        border-radius: 50%;
        background: #2185d0;
        cursor: pointer;
        border: none;
        box-shadow: 0 1px 3px rgba(0,0,0,0.2);
    }
    .slider-value {
        font-size: 0.85rem;
        font-weight: 600;
        color: #2c3e50;
        min-width: 40px;
        text-align: center;
    }
    .canvas-container {
        flex: 1;
        position: relative;
        overflow: hidden;
        background: #f0f0f0;
    }
    #drawing-canvas {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: white;
        cursor: crosshair;
        display: block;
    }
    .status-bar {
        background: #f9f9f9;
        padding: 8px 16px;
        border-top: 1px solid #e0e0e0;
        display: flex;
        align-items: center;
        gap: 20px;
        font-size: 0.85rem;
        color: #5a5a5a;
    }
    .status-item {
        display: flex;
        align-items: center;
        gap: 6px;
    }
    .color-indicator {
        width: 18px;
        height: 18px;
        border-radius: 3px;
        border: 1px solid #ccc;
    }
    .shortcut-hint {
        font-size: 0.7rem;
        opacity: 0.7;
        margin-left: 4px;
    }
    .canvas-loading {
        position: absolute;
        top: 50%;
        left: 50%;
        transform: translate(-50%, -50%);
        background: rgba(255,255,255,0.9);
        padding: 20px 28px;
        border-radius: 12px;
        text-align: center;
        z-index: 10;
        backdrop-filter: blur(4px);
        box-shadow: 0 2px 12px rgba(0,0,0,0.1);
        display: flex;
        flex-direction: column;
        align-items: center;
        gap: 12px;
        color: #2185d0;
        pointer-events: none;
    }
    .loading-spinner {
        width: 40px;
        height: 40px;
        border: 3px solid #e0e0e0;
        border-top-color: #2185d0;
        border-radius: 50%;
        animation: spin 0.8s linear infinite;
    }
    @keyframes spin { to { transform: rotate(360deg); } }
    @media (max-width: 768px) {
        .drawing-app { height: 600px; }
        .toolbar { padding: 10px 12px; gap: 10px; }
        .tool-group { padding-right: 10px; gap: 6px; }
        .slider-container { min-width: 160px; }
    }
    @media (max-width: 480px) {
        .drawing-app { height: 550px; }
        .toolbar { gap: 8px; }
        .tool-button { padding: 8px !important; }
        .status-bar { font-size: 0.75rem; gap: 12px; flex-wrap: wrap; }
    }
    /* 确保 Semantic 按钮与原有图标大小协调 */
    .ui.icon.button {
        padding: 0.7em;
        background: white;
        color: #4a4a4a;
        transition: 0.15s;
    }
    .ui.icon.button i.icon {
        margin: 0 !important;
        font-size: 1.1em;
    }
    .action-button.ui.button {
        display: inline-flex;
        align-items: center;
        gap: 6px;
    }
</style>

<!-- 画板主容器 -->
<div class="drawing-app">
    <div class="toolbar">
        <!-- 工具组: 画笔/橡皮擦/形状 -->
        <div class="tool-group">
            <span class="tool-group-label">工具</span>
            <button class="ui icon button tool-button active" id="brush-btn" title="画笔">
                <i class="icon pencil"></i>
            </button>
            <button class="ui icon button tool-button" id="eraser-btn" title="橡皮擦">
                <i class="icon eraser"></i>
            </button>
            <button class="ui icon button tool-button" id="line-btn" title="直线">
                <i class="icon window minimize outline"></i>
            </button>
            <button class="ui icon button tool-button" id="rectangle-btn" title="矩形 (点击切换实心/空心)">
                <i class="icon square outline"></i>
            </button>
            <button class="ui icon button tool-button" id="circle-btn" title="圆形 (点击切换实心/空心)">
                <i class="icon circle outline"></i>
            </button>
        </div>
        
        <!-- 视图控制组 -->
        <div class="tool-group">
            <span class="tool-group-label">视图</span>
            <button class="ui icon button tool-button" id="pan-btn" title="平移画布">
                <i class="icon hand paper"></i>
            </button>
            <div class="slider-container" style="min-width: 130px;">
                <span class="slider-label">缩放</span>
                <input type="range" id="zoom-range" min="0.2" max="3" step="0.01" value="1">
                <span class="slider-value" id="zoom-value">100%</span>
            </div>
            <button class="ui icon button tool-button" id="reset-view-btn" title="重置视图">
                <i class="icon home"></i>
            </button>
        </div>
        
        <!-- 颜色组 -->
        <div class="tool-group">
            <span class="tool-group-label">颜色</span>
            <div class="color-picker">
                <div class="color-option active" style="background-color: #000000;" data-color="#000000" title="黑色"></div>
                <div class="color-option" style="background-color: #ef4444;" data-color="#ef4444" title="红色"></div>
                <div class="color-option" style="background-color: #3b82f6;" data-color="#3b82f6" title="蓝色"></div>
                <div class="color-option" style="background-color: #10b981;" data-color="#10b981" title="绿色"></div>
                <div class="color-option" style="background-color: #f59e0b;" data-color="#f59e0b" title="橙色"></div>
                <div class="color-option" style="background-color: #8b5cf6;" data-color="#8b5cf6" title="紫色"></div>
                <div class="color-option" style="background-color: #ffffff;" data-color="#ffffff" title="白色"></div>
                <div class="custom-color-wrapper">
                    <input type="color" id="custom-color" value="#2185d0">
                    <div class="custom-color-preview"></div>
                </div>
            </div>
        </div>
        
        <!-- 画笔大小控制 -->
        <div class="tool-group">
            <div class="slider-container">
                <span class="slider-label">画笔大小</span>
                <input type="range" id="brush-size" min="1" max="40" value="8">
                <span class="slider-value" id="brush-size-value">8px</span>
            </div>
        </div>
        
        <!-- 操作按钮组 -->
        <div class="action-buttons" style="display: flex; gap: 8px; margin-left: auto;">
            <button class="ui primary button icon labeled action-button" id="undo-btn">
                <i class="icon undo"></i> 撤销
                <span class="shortcut-hint">Ctrl+Z</span>
            </button>
            <button class="ui primary button icon labeled action-button" id="redo-btn">
                <i class="icon redo"></i> 重做
                <span class="shortcut-hint">Ctrl+Y</span>
            </button>
            <button class="ui red button icon labeled action-button" id="clear-btn">
                <i class="icon trash"></i> 清空
            </button>
            <button class="ui green button icon labeled action-button" id="save-btn">
                <i class="icon download"></i> 保存
            </button>
            <button class="ui button icon labeled action-button" id="help-btn">
                <i class="icon help circle"></i> 帮助
            </button>
        </div>
    </div>
    
    <div class="canvas-container">
        <div class="canvas-loading" id="loading-overlay">
            <div class="loading-spinner"></div>
            <span>初始化画布...</span>
        </div>
        <canvas id="drawing-canvas"></canvas>
    </div>
    
    <div class="status-bar">
        <div class="status-item"><i class="icon pencil"></i> 工具: <span id="current-tool" class="status-value">画笔</span></div>
        <div class="status-item"><i class="icon paint brush"></i> 大小: <span id="current-size" class="status-value">8px</span></div>
        <div class="status-item"><i class="icon eyedropper"></i> 颜色: <div id="current-color" class="color-indicator" style="background-color: #000000;"></div></div>
        <div class="status-item"><i class="icon hashtag"></i> 笔画: <span id="stroke-count" class="status-value">0</span></div>
    </div>
</div>

<script>
    (function(){
        // ==================== DOM 元素 ====================
        const canvas = document.getElementById('drawing-canvas');
        const ctx = canvas.getContext('2d');
        const loadingOverlay = document.getElementById('loading-overlay');
        
        // ==================== 绘画状态 ====================
        let isDrawing = false;
        let currentTool = 'brush';
        let currentColor = '#000000';
        let brushSize = 8;
        let strokes = [];
        let historyStack = [];      // 存储所有历史状态（深拷贝数组）
        let historyIndex = -1;      // 当前所在历史位置的索引
        let currentStroke = null;
        let ctrlPressed = false;
        let erasingStrokeIds = new Set();
        let currentEraseRadius = brushSize;
        let eraserPreviewPoints = [];
        let eraserPreviewActive = false;
        let eraserPreviewTimer = null;
        let eraserPreviewAlpha = 0.6;
        let shiftPressed = false;
        const MAX_HISTORY = 500;
        // 填充模式状态 (分别针对矩形和圆形)
        let rectFillMode = false;    // false: 空心, true: 实心
        let circleFillMode = false;  // false: 空心, true: 实心
        
        // 视图变换
        let viewZoom = 1.0;
        let viewOffsetX = 0;
        let viewOffsetY = 0;
        let isPanning = false;
        let panStartX = 0, panStartY = 0;
        let lastOffsetX = 0, lastOffsetY = 0;
        let panActive = false;
        
        // UI 元素
        const brushBtn = document.getElementById('brush-btn');
        const eraserBtn = document.getElementById('eraser-btn');
        const lineBtn = document.getElementById('line-btn');
        const rectangleBtn = document.getElementById('rectangle-btn');
        const circleBtn = document.getElementById('circle-btn');
        const undoBtn = document.getElementById('undo-btn');
        const clearBtn = document.getElementById('clear-btn');
        const saveBtn = document.getElementById('save-btn');
        const colorOptions = document.querySelectorAll('.color-option');
        const customColorInput = document.getElementById('custom-color');
        const customColorPreview = document.querySelector('.custom-color-preview');
        const brushSizeSlider = document.getElementById('brush-size');
        const brushSizeValue = document.getElementById('brush-size-value');
        const currentSizeSpan = document.getElementById('current-size');
        const currentToolSpan = document.getElementById('current-tool');
        const currentColorSpan = document.getElementById('current-color');
        const strokeCountSpan = document.getElementById('stroke-count');
        const panBtn = document.getElementById('pan-btn');
        const zoomRange = document.getElementById('zoom-range');
        const zoomValue = document.getElementById('zoom-value');
        const resetViewBtn = document.getElementById('reset-view-btn');
        
        // ==================== 辅助函数更新按钮图标 ====================
        function updateRectButtonIcon() {
            const iconEl = rectangleBtn.querySelector('i.icon');
            if (rectFillMode) {
                iconEl.className = 'icon square';  // 实心方形图标
            } else {
                iconEl.className = 'icon square outline';
            }
        }
        
        function updateCircleButtonIcon() {
            const iconEl = circleBtn.querySelector('i.icon');
            if (circleFillMode) {
                iconEl.className = 'icon circle';   // 实心圆形图标
            } else {
                iconEl.className = 'icon circle outline';
            }
        }
        
        // 获取当前活动形状工具的填充模式
        function getCurrentShapeFillMode() {
            if (currentTool === 'rectangle') return rectFillMode;
            if (currentTool === 'circle') return circleFillMode;
            return false;
        }
        
        // ==================== 数据结构 ====================
        class Stroke {
            constructor(tool, color, size, points = [], fillMode = false) {
                this.tool = tool;
                this.color = tool === 'eraser' ? '#ffffff' : color;
                this.size = size;
                this.points = points;
                this.shapeData = null;
                this.id = Date.now() + Math.random();
                this.timestamp = Date.now();
                this.fillMode = fillMode;  // 用于矩形/圆形的实心/空心模式
            }
            addPoint(x, y) { this.points.push({x, y}); }
            setShapeData(data) { this.shapeData = data; }
        }
        
        // 保存当前状态到历史（在每次绘制完成后调用）
        function pushToHistory() {
            // 删除当前位置之后的所有历史
            historyStack = historyStack.slice(0, historyIndex + 1);
            // 深拷贝当前 strokes
            const copy = strokes.map(s => {
                const newStroke = new Stroke(s.tool, s.color, s.size, [...s.points], s.fillMode);
                if (s.shapeData) newStroke.setShapeData({ ...s.shapeData });
                newStroke.id = s.id;
                newStroke.timestamp = s.timestamp;
                return newStroke;
            });
            historyStack.push(copy);
            // 限制历史长度
            if (historyStack.length > MAX_HISTORY) historyStack.shift();
            else historyIndex = historyStack.length - 1;
        }
        
        // 恢复到指定的历史索引
        function restoreFromHistory(index) {
            if (index < 0 || index >= historyStack.length) return false;
            strokes = historyStack[index].map(s => {
                const newStroke = new Stroke(s.tool, s.color, s.size, [...s.points], s.fillMode);
                if (s.shapeData) newStroke.setShapeData({ ...s.shapeData });
                newStroke.id = s.id;
                newStroke.timestamp = s.timestamp;
                return newStroke;
            });
            historyIndex = index;
            redrawCanvas();
            updateStrokeCount();
            return true;
        }
        function getRawMousePos(e) {
            const rect = canvas.getBoundingClientRect();
            let clientX, clientY;
            if (e.type.includes('touch')) {
                clientX = e.touches[0].clientX;
                clientY = e.touches[0].clientY;
            } else {
                clientX = e.clientX;
                clientY = e.clientY;
            }
            let canvasX = (clientX - rect.left) * (canvas.width / rect.width);
            let canvasY = (clientY - rect.top) * (canvas.height / rect.height);
            return { x: canvasX, y: canvasY };
        }
        
        function getWorldPos(e) {
            const raw = getRawMousePos(e);
            let worldX = (raw.x - viewOffsetX) / viewZoom;
            let worldY = (raw.y - viewOffsetY) / viewZoom;
            return { x: worldX, y: worldY };
        }
        
        function setDrawingStyle() {
            if (currentTool === 'eraser') {
                ctx.strokeStyle = '#ffffff';
                ctx.fillStyle = '#ffffff';
            } else {
                ctx.strokeStyle = currentColor;
                ctx.fillStyle = currentColor;
            }
            ctx.lineWidth = brushSize;
            ctx.lineCap = 'round';
            ctx.lineJoin = 'round';
        }
        
        // 绘制单个笔画 (支持实心/空心)
        function drawStrokeToContext(stroke) {
            if (stroke.tool === 'eraser') {
                ctx.strokeStyle = '#ffffff';
                ctx.fillStyle = '#ffffff';
            } else {
                ctx.strokeStyle = stroke.color;
                ctx.fillStyle = stroke.color;
            }
            ctx.lineWidth = stroke.size;
            ctx.lineCap = 'round';
            ctx.lineJoin = 'round';
            
            if (stroke.tool === 'brush' || stroke.tool === 'eraser') {
                if (stroke.points.length < 2) {
                    if (stroke.points[0]) {
                        ctx.beginPath();
                        ctx.arc(stroke.points[0].x, stroke.points[0].y, stroke.size / 2, 0, Math.PI * 2);
                        ctx.fill();
                    }
                    return;
                }
                ctx.beginPath();
                ctx.moveTo(stroke.points[0].x, stroke.points[0].y);
                for (let i = 1; i < stroke.points.length; i++) ctx.lineTo(stroke.points[i].x, stroke.points[i].y);
                ctx.stroke();
            } else if (stroke.tool === 'line' && stroke.shapeData) {
                const { startX, startY, endX, endY } = stroke.shapeData;
                ctx.beginPath();
                ctx.moveTo(startX, startY);
                ctx.lineTo(endX, endY);
                ctx.stroke();
            } else if (stroke.tool === 'rectangle' && stroke.shapeData) {
                const { startX, startY, endX, endY } = stroke.shapeData;
                ctx.beginPath();
                ctx.rect(startX, startY, endX - startX, endY - startY);
                if (stroke.fillMode) {
                    ctx.fill();     // 实心填充，无边框
                } else {
                    ctx.stroke();   // 空心
                }
            } else if (stroke.tool === 'circle' && stroke.shapeData) {
                const { startX, startY, endX, endY } = stroke.shapeData;
                const radius = Math.hypot(endX - startX, endY - startY);
                ctx.beginPath();
                ctx.arc(startX, startY, radius, 0, Math.PI * 2);
                if (stroke.fillMode) {
                    ctx.fill();
                } else {
                    ctx.stroke();
                }
            }
        }
        
        function redrawCanvas() {
            ctx.fillStyle = '#ffffff';
            ctx.fillRect(0, 0, canvas.width, canvas.height);
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            [...strokes].sort((a, b) => a.timestamp - b.timestamp).forEach(stroke => drawStrokeToContext(stroke));
            ctx.restore();
        }
        
        function drawDot(x, y) {
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            ctx.beginPath();
            ctx.arc(x, y, brushSize / 2, 0, Math.PI * 2);
            ctx.fill();
            ctx.restore();
        }
        
        function drawBrushStrokeSegment() {
            const points = currentStroke.points;
            if (points.length < 2) return;
            const last = points[points.length - 2];
            const curr = points[points.length - 1];
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            ctx.beginPath();
            ctx.moveTo(last.x, last.y);
            ctx.lineTo(curr.x, curr.y);
            ctx.stroke();
            ctx.restore();
        }
        
        function drawLinePreview(x, y) {
            redrawCanvas();
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            const { startX, startY } = currentStroke.shapeData;
            ctx.beginPath();
            ctx.moveTo(startX, startY);
            ctx.lineTo(x, y);
            ctx.stroke();
            ctx.restore();
        }
        function drawRectanglePreview(x, y) {
            redrawCanvas();
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            // 设置当前颜色和线宽，确保预览效果与最终绘制一致
            ctx.fillStyle = currentColor;
            ctx.strokeStyle = currentColor;
            ctx.lineWidth = brushSize;
            const { startX, startY } = currentStroke.shapeData;
            let w = x - startX, h = y - startY;
            if (shiftPressed) {
                const side = Math.max(Math.abs(w), Math.abs(h));
                w = w >= 0 ? side : -side;
                h = h >= 0 ? side : -side;
            }
            ctx.beginPath();
            ctx.rect(startX, startY, w, h);
            if (rectFillMode) {
                ctx.fill();   // 实心填充使用当前颜色
            } else {
                ctx.stroke(); // 空心描边同样使用当前颜色和线宽
            }
            ctx.restore();
        }
        
        function drawCirclePreview(x, y) {
            redrawCanvas();
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            // 设置当前颜色和线宽
            ctx.fillStyle = currentColor;
            ctx.strokeStyle = currentColor;
            ctx.lineWidth = brushSize;
            const { startX, startY } = currentStroke.shapeData;
            const radius = Math.hypot(x - startX, y - startY);
            ctx.beginPath();
            ctx.arc(startX, startY, radius, 0, Math.PI * 2);
            if (circleFillMode) {
                ctx.fill();
            } else {
                ctx.stroke();
            }
            ctx.restore();
        }
        
        function drawEraserPreview() {
            if (!eraserPreviewActive || eraserPreviewPoints.length < 2) return;
            ctx.save();
            ctx.translate(viewOffsetX, viewOffsetY);
            ctx.scale(viewZoom, viewZoom);
            ctx.globalAlpha = eraserPreviewAlpha;
            ctx.lineWidth = brushSize;
            ctx.lineCap = 'round';
            ctx.strokeStyle = 'rgba(255, 0, 0, 0.6)';
            ctx.fillStyle = 'rgba(255, 0, 0, 0.2)';
            ctx.beginPath();
            ctx.moveTo(eraserPreviewPoints[0].x, eraserPreviewPoints[0].y);
            for (let i = 1; i < eraserPreviewPoints.length; i++) ctx.lineTo(eraserPreviewPoints[i].x, eraserPreviewPoints[i].y);
            ctx.stroke();
            for (let p of eraserPreviewPoints) {
                ctx.beginPath();
                ctx.arc(p.x, p.y, brushSize / 2, 0, Math.PI * 2);
                ctx.fill();
            }
            ctx.restore();
        }
        
        function pointToSegmentDistance(a, b, p) {
            const abx = b.x - a.x, aby = b.y - a.y;
            const t = ((p.x - a.x) * abx + (p.y - a.y) * aby) / (abx * abx + aby * aby || 1);
            const clamped = Math.max(0, Math.min(1, t));
            const projX = a.x + clamped * abx, projY = a.y + clamped * aby;
            return Math.hypot(p.x - projX, p.y - projY);
        }
        
        function isPointInStrokeDetectWithRadius(stroke, px, py, tolerance) {
            if (stroke.tool === 'brush' || stroke.tool === 'eraser') {
                for (let i = 0; i < stroke.points.length; i++) {
                    const p = stroke.points[i];
                    if (Math.hypot(p.x - px, p.y - py) <= tolerance) return true;
                    if (i > 0 && pointToSegmentDistance(stroke.points[i-1], p, {x:px, y:py}) <= tolerance) return true;
                }
                return false;
            }
            else if (stroke.tool === 'line' && stroke.shapeData) {
                const { startX, startY, endX, endY } = stroke.shapeData;
                return pointToSegmentDistance({x:startX,y:startY}, {x:endX,y:endY}, {x:px,y:py}) <= tolerance;
            }
            else if (stroke.tool === 'rectangle' && stroke.shapeData) {
                let { startX, startY, endX, endY } = stroke.shapeData;
                const minX = Math.min(startX, endX) - tolerance, maxX = Math.max(startX, endX) + tolerance;
                const minY = Math.min(startY, endY) - tolerance, maxY = Math.max(startY, endY) + tolerance;
                return px >= minX && px <= maxX && py >= minY && py <= maxY;
            }
            else if (stroke.tool === 'circle' && stroke.shapeData) {
                const { startX, startY, endX, endY } = stroke.shapeData;
                const radius = Math.hypot(endX - startX, endY - startY);
                return Math.hypot(px - startX, py - startY) <= radius + tolerance/2;
            }
            return false;
        }
        
        function eraseByPreviewPath(points, radius) {
            if (!points.length) return false;
            const tolerance = radius * 1.2;
            let anyDeleted = false;
            let deletedIds = new Set();
            for (let i = strokes.length - 1; i >= 0; i--) {
                const stroke = strokes[i];
                if (deletedIds.has(stroke.id)) continue;
                let erased = false;
                for (let p of points) {
                    if (isPointInStrokeDetectWithRadius(stroke, p.x, p.y, tolerance)) { erased = true; break; }
                }
                if (!erased) {
                    for (let j = 0; j < points.length-1; j++) {
                        const mid = { x: (points[j].x + points[j+1].x)/2, y: (points[j].y + points[j+1].y)/2 };
                        if (isPointInStrokeDetectWithRadius(stroke, mid.x, mid.y, tolerance)) { erased = true; break; }
                        if (isPointInStrokeDetectWithRadius(stroke, points[j].x, points[j].y, tolerance)) { erased = true; break; }
                    }
                }
                if (erased) {
                    strokes.splice(i,1);
                    deletedIds.add(stroke.id);
                    anyDeleted = true;
                }
            }
            if (anyDeleted) {
                pushToHistory();
                redrawCanvas();
                updateStrokeCount();
            }
            return anyDeleted;
        }
        
        function startDrawing(e) {
            e.preventDefault();
            if (panActive) return;
            const { x, y } = getWorldPos(e);
            isDrawing = true;
            if (currentTool === 'eraser') {
                eraserPreviewActive = true;
                eraserPreviewPoints = [{ x, y }];
                if (eraserPreviewTimer) clearTimeout(eraserPreviewTimer);
                redrawCanvas();
                drawEraserPreview();
                return;
            }
            // 获取当前工具的填充模式 (矩形/圆形)
            let fillMode = false;
            if (currentTool === 'rectangle') fillMode = rectFillMode;
            if (currentTool === 'circle') fillMode = circleFillMode;
            
            currentStroke = new Stroke(currentTool, currentColor, brushSize, [], fillMode);
            currentStroke.addPoint(x, y);
            if (['line', 'rectangle', 'circle'].includes(currentTool)) currentStroke.shapeData = { startX: x, startY: y };
            if (currentTool === 'brush') drawDot(x, y);
        }
        
        function draw(e) {
            if (!isDrawing || panActive) return;
            e.preventDefault();
            const { x, y } = getWorldPos(e);
            if (currentTool === 'eraser') {
                if (eraserPreviewActive) {
                    const last = eraserPreviewPoints[eraserPreviewPoints.length-1];
                    if (Math.hypot(x - last.x, y - last.y) > brushSize * 0.3) {
                        eraserPreviewPoints.push({ x, y });
                        redrawCanvas();
                        drawEraserPreview();
                    }
                }
                return;
            }
            if (!currentStroke) return;
            currentStroke.addPoint(x, y);
            if (currentTool === 'brush') drawBrushStrokeSegment();
            else if (currentTool === 'line') drawLinePreview(x, y);
            else if (currentTool === 'rectangle') drawRectanglePreview(x, y);
            else if (currentTool === 'circle') drawCirclePreview(x, y);
        }
        
        function stopDrawing() {
            if (!isDrawing) return;
            isDrawing = false;
            if (currentTool === 'eraser' && eraserPreviewActive && eraserPreviewPoints.length > 0) {
                eraseByPreviewPath(eraserPreviewPoints, brushSize);
                // 清除预览状态
                eraserPreviewActive = false;
                eraserPreviewPoints = [];
                if (eraserPreviewTimer) clearTimeout(eraserPreviewTimer);
                // 重绘，预览轨迹消失
                redrawCanvas();
                return;
            }
            if (currentStroke && currentStroke.points.length > 0) {
                if (['line', 'rectangle', 'circle'].includes(currentTool) && currentStroke.shapeData) {
                    let lastPt = currentStroke.points[currentStroke.points.length-1];
                    let endX = lastPt.x, endY = lastPt.y;
                    if (currentTool === 'rectangle' && shiftPressed) {
                        const startX = currentStroke.shapeData.startX;
                        const startY = currentStroke.shapeData.startY;
                        let w = endX - startX, h = endY - startY;
                        const side = Math.max(Math.abs(w), Math.abs(h));
                        endX = startX + (w >= 0 ? side : -side);
                        endY = startY + (h >= 0 ? side : -side);
                    }
                    currentStroke.shapeData.endX = endX;
                    currentStroke.shapeData.endY = endY;
                }
                strokes.push(currentStroke);
                pushToHistory();  // 保存历史
                updateStrokeCount();
            }
            currentStroke = null;
        }
        
        function updateStrokeCount() { strokeCountSpan.textContent = strokes.length; }
        
        function setActiveTool(toolName, displayName) {
            if (panActive) setPanMode(false);
            [brushBtn, eraserBtn, lineBtn, rectangleBtn, circleBtn].forEach(btn => btn.classList.remove('active'));
            currentTool = toolName;
            currentToolSpan.textContent = displayName;
            if (toolName === 'brush') brushBtn.classList.add('active');
            else if (toolName === 'eraser') eraserBtn.classList.add('active');
            else if (toolName === 'line') lineBtn.classList.add('active');
            else if (toolName === 'rectangle') rectangleBtn.classList.add('active');
            else if (toolName === 'circle') circleBtn.classList.add('active');
            setDrawingStyle();
        }
        
       function handleRectangleTool() {
            // 如果当前处于平移模式，先退出平移并切换到矩形
            if (panActive) {
                setPanMode(false);
                setActiveTool('rectangle', '矩形');
                return;
            }
            // 已经是矩形工具 -> 切换空心/实心
            if (currentTool === 'rectangle') {
                rectFillMode = !rectFillMode;
                updateRectButtonIcon();
                const mode = rectFillMode ? "实心矩形" : "空心矩形";
                currentToolSpan.textContent = mode;
                setTimeout(() => {
                    if (currentTool === 'rectangle') currentToolSpan.textContent = "矩形";
                }, 800);
                if (!isDrawing) redrawCanvas();
            } else {
                // 切换到矩形工具
                setActiveTool('rectangle', '矩形');
            }
            if (isDrawing) stopDrawing();
        }
        
        function handleCircleTool() {
            // 如果当前处于平移模式，先退出平移并切换到圆形
            if (panActive) {
                setPanMode(false);
                setActiveTool('circle', '圆形');
                return;
            }
            // 已经是圆形工具 -> 切换空心/实心
            if (currentTool === 'circle') {
                circleFillMode = !circleFillMode;
                updateCircleButtonIcon();
                const mode = circleFillMode ? "实心圆形" : "空心圆形";
                currentToolSpan.textContent = mode;
                setTimeout(() => {
                    if (currentTool === 'circle') currentToolSpan.textContent = "圆形";
                }, 800);
                if (!isDrawing) redrawCanvas();
            } else {
                // 切换到圆形工具
                setActiveTool('circle', '圆形');
            }
            if (isDrawing) stopDrawing();
        }
        
        function updateBrushSizeDisplay() {
            brushSizeValue.textContent = `${brushSize}px`;
            currentSizeSpan.textContent = `${brushSize}px`;
            setDrawingStyle();
        }
        // -------------------- Toast 通知 --------------------
        function showToast(message, icon = 'info', duration = 1500) {
            const Toast = Swal.mixin({
                toast: true,
                position: 'top-end',
                showConfirmButton: false,
                theme:window.__themeMode,
                timer: duration,
                timerProgressBar: true,
                didOpen: (toast) => {
                    toast.addEventListener('mouseenter', Swal.stopTimer);
                    toast.addEventListener('mouseleave', Swal.resumeTimer);
                }
            });
            Toast.fire({
                icon: icon,
                title: message
            });
        }
        // 撤销
        function undo() {
            if (isDrawing) stopDrawing();
            if (historyIndex > 0) {
                restoreFromHistory(historyIndex - 1);
                showToast('已撤销', 'success');
            } else {
                // 提示无法撤销
                showToast('无法撤销', 'error');
            }
            setDrawingStyle();
        }
        
        // 重做
        function redo() {
            if (isDrawing) stopDrawing();
            if (historyIndex < historyStack.length - 1) {
                restoreFromHistory(historyIndex + 1);
                showToast('已重做', 'success');
            } else {
                showToast('无法重做', 'error');

            }
            setDrawingStyle();
        }

        
        async function clearCanvas() {
            if (strokes.length === 0) return;
            const result = await Swal.fire({
                title: '清空画布',
                text: '确定要清空画布吗？此操作不可撤销。',
                icon: 'warning',
                showCancelButton: true,
                theme:window.__themeMode,
                confirmButtonColor: '#dc2626',
                cancelButtonColor: '#64748b',
                confirmButtonText: '清空',
                cancelButtonText: '取消'
            });
            if (result.isConfirmed) {
                strokes = [];
                // 重置历史
                historyStack = [[]];
                historyIndex = 0;
                if (typeof resetView === 'function') resetView();
                else { viewZoom = 1; viewOffsetX = 0; viewOffsetY = 0; zoomRange.value = '1'; zoomValue.textContent = '100%'; redrawCanvas(); }
                updateStrokeCount();
                setDrawingStyle();
                Swal.fire({ title: '已清空', text: '画布已清空', icon: 'success', timer: 1500, showConfirmButton: false,theme:window.__themeMode, });
            }
        }
        
        function getStrokesBoundingBox() {
            if (strokes.length === 0) return null;
            let minX = Infinity, minY = Infinity, maxX = -Infinity, maxY = -Infinity;
            strokes.forEach(stroke => {
                if (stroke.points) stroke.points.forEach(p => { minX = Math.min(minX, p.x); minY = Math.min(minY, p.y); maxX = Math.max(maxX, p.x); maxY = Math.max(maxY, p.y); });
                if (stroke.shapeData) {
                    const { startX, startY, endX, endY } = stroke.shapeData;
                    minX = Math.min(minX, startX, endX); maxX = Math.max(maxX, startX, endX);
                    minY = Math.min(minY, startY, endY); maxY = Math.max(maxY, startY, endY);
                    if (stroke.tool === 'circle') {
                        const rad = Math.hypot(endX - startX, endY - startY);
                        minX = Math.min(minX, startX - rad); maxX = Math.max(maxX, startX + rad);
                        minY = Math.min(minY, startY - rad); maxY = Math.max(maxY, startY + rad);
                    }
                }
            });
            return { minX: minX-10, minY: minY-10, maxX: maxX+10, maxY: maxY+10, width: maxX-minX+20, height: maxY-minY+20 };
        }
        
        // 用于导出图片的绘制函数 (支持填充模式)
        function drawStrokeToContextRaw(ctx, stroke) {
            ctx.save();
            ctx.strokeStyle = stroke.tool === 'eraser' ? '#ffffff' : stroke.color;
            ctx.fillStyle = stroke.tool === 'eraser' ? '#ffffff' : stroke.color;
            ctx.lineWidth = stroke.size;
            if (stroke.tool === 'brush' || stroke.tool === 'eraser') {
                if (stroke.points.length < 2 && stroke.points[0]) { ctx.beginPath(); ctx.arc(stroke.points[0].x, stroke.points[0].y, stroke.size/2, 0, 2*Math.PI); ctx.fill(); }
                else if (stroke.points.length >= 2) { ctx.beginPath(); ctx.moveTo(stroke.points[0].x, stroke.points[0].y); for(let i=1;i<stroke.points.length;i++) ctx.lineTo(stroke.points[i].x, stroke.points[i].y); ctx.stroke(); }
            } else if (stroke.tool === 'line' && stroke.shapeData) { ctx.beginPath(); ctx.moveTo(stroke.shapeData.startX, stroke.shapeData.startY); ctx.lineTo(stroke.shapeData.endX, stroke.shapeData.endY); ctx.stroke(); }
            else if (stroke.tool === 'rectangle' && stroke.shapeData) { 
                ctx.beginPath(); 
                ctx.rect(stroke.shapeData.startX, stroke.shapeData.startY, stroke.shapeData.endX - stroke.shapeData.startX, stroke.shapeData.endY - stroke.shapeData.startY);
                if (stroke.fillMode) ctx.fill();
                else ctx.stroke();
            }
            else if (stroke.tool === 'circle' && stroke.shapeData) { 
                const rad = Math.hypot(stroke.shapeData.endX - stroke.shapeData.startX, stroke.shapeData.endY - stroke.shapeData.startY);
                ctx.beginPath(); 
                ctx.arc(stroke.shapeData.startX, stroke.shapeData.startY, rad, 0, 2*Math.PI);
                if (stroke.fillMode) ctx.fill();
                else ctx.stroke();
            }
            ctx.restore();
        }
        
        async function saveImage() {
            if (strokes.length === 0) {
                const link = document.createElement('a');
                link.download = `画板作品_${new Date().toISOString().slice(0,10)}.png`;
                link.href = canvas.toDataURL('image/png');
                link.click();
                saveBtn.innerHTML = '<i class="icon checkmark"></i> 已保存';
                setTimeout(() => saveBtn.innerHTML = '<i class="icon save"></i> 保存', 1500);
                showToast('已保存图片', 'success');
                return;
            }
            const bbox = getStrokesBoundingBox();
            if (!bbox) { const link = document.createElement('a'); link.download = `drawing.png`; link.href = canvas.toDataURL(); link.click(); return; }
            const offCanvas = document.createElement('canvas');
            offCanvas.width = bbox.width; offCanvas.height = bbox.height;
            const offCtx = offCanvas.getContext('2d');
            offCtx.fillStyle = '#ffffff'; offCtx.fillRect(0, 0, offCanvas.width, offCanvas.height);
            offCtx.save(); offCtx.translate(-bbox.minX, -bbox.minY);
            [...strokes].sort((a,b)=>a.timestamp-b.timestamp).forEach(s => drawStrokeToContextRaw(offCtx, s));
            offCtx.restore();
            const link = document.createElement('a');
            link.download = `画板作品_${new Date().toISOString().slice(0,10)}.png`;
            link.href = offCanvas.toDataURL('image/png');
            link.click();
            saveBtn.innerHTML = '<i class="icon checkmark"></i> 已保存';
            setTimeout(() => saveBtn.innerHTML = '<i class="icon save"></i> 保存', 1500);
            showToast('已保存图片', 'success');
        }
        
        function applyZoomAndRedraw() {
            const container = document.querySelector('.canvas-container');
            const rect = container.getBoundingClientRect();
            const centerX = rect.width/2, centerY = rect.height/2;
            const worldX = (centerX - viewOffsetX)/viewZoom, worldY = (centerY - viewOffsetY)/viewZoom;
            const newZoom = parseFloat(zoomRange.value);
            viewZoom = newZoom;
            viewOffsetX = centerX - worldX * viewZoom;
            viewOffsetY = centerY - worldY * viewZoom;
            zoomValue.textContent = `${Math.round(viewZoom*100)}%`;
            redrawCanvas();
        }
        
        function resetView() { viewZoom = 1; viewOffsetX = 0; viewOffsetY = 0; zoomRange.value = '1'; zoomValue.textContent = '100%'; redrawCanvas(); }
        
        let resizeTimer = null;
        function resizeCanvasAndSync() {
            if (resizeTimer) clearTimeout(resizeTimer);
            resizeTimer = setTimeout(() => {
                const container = document.querySelector('.canvas-container');
                const rect = container.getBoundingClientRect();
                const newWidth = Math.floor(rect.width), newHeight = Math.floor(rect.height);
                if (newWidth>0 && newHeight>0 && (canvas.width !== newWidth || canvas.height !== newHeight)) {
                    if (isDrawing) stopDrawing();
                    canvas.width = newWidth; canvas.height = newHeight;
                    redrawCanvas();
                    setDrawingStyle();
                }
            }, 30);
        }
        
        function initializeCanvas() {
            const container = document.querySelector('.canvas-container');
            const rect = container.getBoundingClientRect();
            canvas.width = rect.width || 800; canvas.height = rect.height || 600;
            ctx.fillStyle = '#ffffff'; ctx.fillRect(0,0,canvas.width,canvas.height);
            strokes = [];
            historyStack = [[]];
            historyIndex = 0;
            updateStrokeCount(); 
            setDrawingStyle();
            setTimeout(() => { if(loadingOverlay) { loadingOverlay.style.opacity='0'; setTimeout(()=>loadingOverlay.style.display='none',300); } }, 400);
        }
        
        function setPanMode(active) {
            panActive = active;
            if (panActive) {
                [brushBtn, eraserBtn, lineBtn, rectangleBtn, circleBtn].forEach(btn => btn.classList.remove('active'));
                currentToolSpan.textContent = '平移';
                panBtn.classList.add('active');
                canvas.style.cursor = 'grab';
            } else {
                panBtn.classList.remove('active');
                let displayName = currentTool === 'brush' ? '画笔' : currentTool === 'eraser' ? '橡皮擦' : currentTool === 'line' ? '直线' : currentTool === 'rectangle' ? '矩形' : '圆形';
                currentToolSpan.textContent = displayName;
                if (currentTool === 'brush') brushBtn.classList.add('active');
                else if (currentTool === 'eraser') eraserBtn.classList.add('active');
                else if (currentTool === 'line') lineBtn.classList.add('active');
                else if (currentTool === 'rectangle') rectangleBtn.classList.add('active');
                else if (currentTool === 'circle') circleBtn.classList.add('active');
                canvas.style.cursor = 'crosshair';
            }
        }
        
        function bindEvents() {
            canvas.addEventListener('mousedown', startDrawing); canvas.addEventListener('mousemove', draw); canvas.addEventListener('mouseup', stopDrawing); canvas.addEventListener('mouseout', stopDrawing);
            canvas.addEventListener('touchstart', startDrawing, {passive:false}); canvas.addEventListener('touchmove', draw, {passive:false}); canvas.addEventListener('touchend', stopDrawing);
            brushBtn.addEventListener('click', ()=>setActiveTool('brush','画笔'));
            eraserBtn.addEventListener('click', ()=>setActiveTool('eraser','橡皮擦'));
            lineBtn.addEventListener('click', ()=>setActiveTool('line','直线'));
            rectangleBtn.addEventListener('click', handleRectangleTool);
            circleBtn.addEventListener('click', handleCircleTool);
            colorOptions.forEach(btn => { btn.addEventListener('click',()=>{ colorOptions.forEach(b=>b.classList.remove('active')); btn.classList.add('active'); currentColor = btn.dataset.color; currentColorSpan.style.backgroundColor = currentColor; if(customColorPreview) customColorPreview.style.background = currentColor; setDrawingStyle(); }); });
            customColorInput.addEventListener('input',(e)=>{ currentColor = e.target.value; colorOptions.forEach(b=>b.classList.remove('active')); currentColorSpan.style.backgroundColor = currentColor; customColorPreview.style.background = currentColor; setDrawingStyle(); });
            brushSizeSlider.addEventListener('input',()=>{ brushSize = parseInt(brushSizeSlider.value); updateBrushSizeDisplay(); });
            undoBtn.addEventListener('click', undo); clearBtn.addEventListener('click', clearCanvas); saveBtn.addEventListener('click', saveImage);
            if(panBtn) panBtn.addEventListener('click',()=>setPanMode(!panActive));
            canvas.addEventListener('mousedown',(e)=>{ if(panActive){ e.preventDefault(); isPanning=true; const raw=getRawMousePos(e); panStartX=raw.x; panStartY=raw.y; lastOffsetX=viewOffsetX; lastOffsetY=viewOffsetY; canvas.style.cursor='grabbing'; } });
            window.addEventListener('mousemove',(e)=>{ if(isPanning && panActive){ const raw=getRawMousePos(e); viewOffsetX = lastOffsetX + (raw.x - panStartX); viewOffsetY = lastOffsetY + (raw.y - panStartY); redrawCanvas(); } });
            window.addEventListener('mouseup',()=>{ if(isPanning){ isPanning=false; canvas.style.cursor=panActive?'grab':'crosshair'; } });
            canvas.addEventListener('touchstart',(e)=>{ if(panActive){ e.preventDefault(); isPanning=true; const raw=getRawMousePos(e); panStartX=raw.x; panStartY=raw.y; lastOffsetX=viewOffsetX; lastOffsetY=viewOffsetY; } });
            window.addEventListener('touchmove',(e)=>{ if(isPanning && panActive){ e.preventDefault(); const raw=getRawMousePos(e); viewOffsetX = lastOffsetX + (raw.x - panStartX); viewOffsetY = lastOffsetY + (raw.y - panStartY); redrawCanvas(); } });
            window.addEventListener('touchend',()=>{ isPanning=false; });
            if(zoomRange) zoomRange.addEventListener('input', applyZoomAndRedraw);
            if(resetViewBtn) resetViewBtn.addEventListener('click', resetView);
            const redoBtn = document.getElementById('redo-btn');
            if (redoBtn) redoBtn.addEventListener('click', redo);
            window.addEventListener('resize', ()=>resizeCanvasAndSync());
            document.addEventListener('keydown', (e) => {
                if (e.key === 'Shift') shiftPressed = true;
                if (e.key === 'Control' || e.key === 'Meta') ctrlPressed = true;
                // 撤销 Ctrl+Z
                if ((e.key === 'z' || e.key === 'Z') && ctrlPressed && !e.shiftKey) {
                    e.preventDefault();
                    undo();
                }
                // 重做 Ctrl+Y 或 Ctrl+Shift+Z
                if ((e.key === 'y' || e.key === 'Y') && ctrlPressed ||
                    ((e.key === 'z' || e.key === 'Z') && ctrlPressed && e.shiftKey)) {
                    e.preventDefault();
                    redo();
                }
            });
            document.addEventListener('keyup',(e)=>{ if(e.key==='Shift') shiftPressed=false; if(e.key==='Control'||e.key==='Meta') ctrlPressed=false; });
            canvas.addEventListener('contextmenu', (e) => e.preventDefault());
            const helpBtn = document.getElementById('help-btn');
            if (helpBtn) {
                helpBtn.addEventListener('click', () => {
                    Swal.fire({
                        title: '画板使用帮助',
                        theme:window.__themeMode,
                        html: `
                            <div style="text-align: left;">
                                <h4>🎨 绘图工具</h4>
                                <ul style="margin-bottom: 12px;">
                                    <li><strong>画笔</strong>：自由绘制，大小可调</li>
                                    <li><strong>橡皮擦</strong>：擦除笔画（轨迹擦除）</li>
                                    <li><strong>直线</strong>：拖动绘制直线</li>
                                    <li><strong>矩形 / 圆形</strong>：点击工具按钮可在<strong>空心/实心</strong>之间切换，绘制时按住 <kbd>Shift</kbd> 可得到正方形/圆形</li>
                                </ul>
                                <h4>⌨️ 快捷键</h4>
                                <ul style="margin-bottom: 12px;">
                                    <li><kbd>Ctrl + Z</kbd> 撤销</li>
                                    <li>绘制矩形/圆形时按住 <kbd>Shift</kbd> → 正比例图形</li>
                                </ul>
                                <h4>🖱️ 视图操作</h4>
                                <ul style="margin-bottom: 12px;">
                                    <li><strong>平移</strong>：点击“平移”按钮后拖动画布</li>
                                    <li><strong>缩放</strong>：拖动缩放滑块或点击重置视图</li>
                                </ul>
                                <h4>🎨 颜色/大小</h4>
                                <ul>
                                    <li>颜色：点击预设色块或使用自定义颜色选择器</li>
                                    <li>画笔大小：拖动滑块调整</li>
                                </ul>
                                <h4>💾 其他操作</h4>
                                <ul>
                                    <li>保存：保存为 PNG 图片（自动裁剪至内容区域）</li>
                                    <li>清空：清除所有绘制内容</li>
                                </ul>
                            </div>
                        `,
                        icon: 'info',
                        confirmButtonText: '知道了',
                        confirmButtonColor: '#2185d0',
                        width: '600px'
                    });
                });
            }
        }
        
        window.addEventListener('load',()=>{ 
            initializeCanvas(); 
            bindEvents(); 
            customColorPreview.style.background='#2185d0'; 
            currentColorSpan.style.backgroundColor='#000000'; 
            setDrawingStyle(); 
            if(zoomRange){ zoomRange.value='1'; zoomValue.textContent='100%'; }
            updateRectButtonIcon();
            updateCircleButtonIcon();
        });
    })();
</script>
</div>
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      <div class="ui center aligned container">
        <span style="color: #999;">coco6de Based on <a href="https://github.com/syzoj/syzoj" target="_blank">SYZOJ</a>.</span>
      </div>
    </div>
</div>
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