robert
/
xjs


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Animal.js Documentation</title>
    <link rel="stylesheet" href="../xjs.css">
    <style>
        :root {
            --sidebar-bg: #111;
            --main-bg: #111;
            --border-color: #222;
            --text-color: #888;
            --text-hover: #ccc;
            --active-color: #ff4b4b; /* Red/Orange for active item */
            --header-color: #666;
            --middle-col-bg: #161616;
            --tree-line-color: #333;
            --accent-color: #ff9f43;
        }
        
        body {
            margin: 0;
            padding: 0;
            height: 100vh;
            display: flex;
            background: var(--main-bg);
            color: var(--text-color);
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
            overflow: hidden;
            font-size: 14px;
        }

        /* 1. LEFT SIDEBAR - MAIN NAVIGATION */
        .sidebar-left {
            width: 260px;
            background: var(--sidebar-bg);
          
            display: flex;
            flex-direction: column;
            overflow-y: auto;
            flex-shrink: 0;
            padding-bottom: 40px;
        }

        .logo-area {
            padding: 24px 20px;
            font-size: 18px;
            font-weight: bold;
            color: #fff;
            display: flex;
            align-items: center;
            gap: 10px;
            margin-bottom: 10px;
        }
        .logo-circle {
            width: 10px;
            height: 10px;
            background: #fff;
            border-radius: 50%;
        }

        /* Tree Structure */
        .nav-tree {
            padding: 0 20px;
        }

        .tree-group {
            margin-bottom: 5px;
        }

        .tree-header {
            padding: 8px 0;
            color: var(--header-color);
            font-weight: 600;
            cursor: pointer;
            transition: color 0.2s;
            display: flex;
            align-items: center;
            justify-content: space-between;
        }
        
        .tree-header:hover {
            color: var(--text-hover);
        }
        
        .tree-header.active-header {
            color: #e69f3c; /* Highlight parent if needed, usually just children */
        }

        .tree-children {
            padding-left: 14px; /* Indent */
            border-left: 1px solid var(--tree-line-color);
            margin-left: 2px;
            display: none; /* Collapsed by default */
            flex-direction: column;
        }
        
        .tree-children.expanded {
            display: flex;
        }

        .nav-item {
            display: block;
            padding: 6px 0 6px 15px;
            color: var(--text-color);
            text-decoration: none;
            cursor: pointer;
            transition: all 0.2s;
            position: relative;
        }

        .nav-item:hover {
            color: var(--text-hover);
        }

        /* Active Item Style (Reference: Red text, maybe red border left overlaying the gray line?) */
        .nav-item.active {
            color: var(--active-color);
        }
        
        /* Optional: Active marker on the left line */
        .nav-item.active::before {
            content: '';
            position: absolute;
            left: -1px; /* Overlap the border */
            top: 0;
            bottom: 0;
            width: 2px;
            background: var(--active-color);
        }

        /* Flat menu section title */
        .nav-section-title {
            margin-top: 18px;
            padding: 10px 0 6px 0;
            color: #7a7a7a;
            font-size: 11px;
            font-weight: 800;
            letter-spacing: 1px;
            text-transform: uppercase;
            opacity: 0.9;
        }

        /* Search Box in sidebar */
        .sidebar-search {
            margin: 0 20px 20px 20px;
            background: #1a1a1a;
            border: 1px solid #333;
            border-radius: 4px;
            padding: 8px 12px;
            color: #fff;
            font-size: 13px;
            cursor: pointer;
        }
        .sidebar-search:hover {
            border-color: #555;
        }

        /* 2. MIDDLE SIDEBAR */
        .sidebar-middle {
            width: 320px;
            background: var(--middle-col-bg);
           
            display: flex;
            flex-direction: column;
            overflow: hidden;
            flex-shrink: 0;
        }
        #middle-frame {
            width: 100%;
            height: 100%;
            border: none;
            background: transparent;
        }

        /* 3. RIGHT CONTENT */
        .content-right {
            flex: 1;
            display: flex;
            flex-direction: column;
            background: #000;
            overflow: hidden;
        }
        #content-frame {
            flex: 1;
            border: none;
            width: 100%;
            height: 100%;
        }

        /* Connection line between middle and right columns */
        .column-connection-line {
            position: fixed;
            inset: 0;
            width: 100vw;
            height: 100vh;
            pointer-events: none;
            z-index: 20;
            opacity: 0.85;
        }

        .column-connection-path {
            stroke: var(--accent-color);
            stroke-width: 2;
            stroke-dasharray: 6 6;
            stroke-linecap: round;
            fill: none;
            opacity: 0.35;
            animation: dashFlow 1.1s linear infinite;
            filter: drop-shadow(0 0 2px rgba(255, 159, 67, 0.25));
        }

        @keyframes dashFlow {
            to { stroke-dashoffset: -12; }
        }

    </style>
</head>
<body>

    <!-- 1. Left Sidebar -->
    <div class="sidebar-left">
        <div class="logo-area">
            <div class="logo-circle"></div>
            Animal.js
        </div>
        
        <div class="sidebar-search" onclick="selectCategory('search.html', 'test_on_update.html', null)">
            Search
        </div>
        
        <div class="nav-tree" aria-label="主菜单（扁平化）">
            <div class="nav-section-title">Animal.js 动画</div>
            <div class="nav-item active" data-list="targets/list.html" data-default="targets/overview.html" onclick="selectCategory('targets/list.html', 'targets/overview.html', this)">目标 Targets</div>
            <div class="nav-item" data-list="animatable_properties/list.html" data-default="animatable_properties/test_transforms.html" onclick="selectCategory('animatable_properties/list.html', 'animatable_properties/test_transforms.html', this)">可动画属性 Properties</div>
            <div class="nav-item" data-list="tween_value_types/list.html" data-default="tween_value_types/test_numerical.html" onclick="selectCategory('tween_value_types/list.html', 'tween_value_types/test_numerical.html', this)">补间值类型 Tween 值</div>
            <div class="nav-item" data-list="tween_parameters/list.html" data-default="tween_parameters/overview.html" onclick="selectCategory('tween_parameters/list.html', 'tween_parameters/overview.html', this)">补间参数 Tween 参数</div>
            <div class="nav-item" data-list="svg/list.html" data-default="svg/overview.html" onclick="selectCategory('svg/list.html', 'svg/overview.html', this)">SVG 动画</div>
            <div class="nav-item" data-list="list_callbacks.html" data-default="test_on_update.html" onclick="selectCategory('list_callbacks.html', 'test_on_update.html', this)">回调 Callbacks</div>
            <div class="nav-item" data-list="examples/list.html" data-default="examples/controls.html" onclick="selectCategory('examples/list.html', 'examples/controls.html', this)">示例 Examples</div>

            <div class="nav-section-title">Layer 弹窗</div>
            <div class="tree-group" data-tree="layer">
                <div class="tree-header" onclick="toggleTree(this)">Layer 子菜单</div>
                <div class="tree-children expanded">
                    <div class="nav-item" data-list="layer/list.html" data-default="layer/overview.html" onclick="selectCategory('layer/list.html', 'layer/overview.html', this)">Layer API / Tests</div>
                    <div class="nav-item" data-list="layer/custom_list.html" data-default="layer/test_custom_animation.html" onclick="selectCategory('layer/custom_list.html', 'layer/test_custom_animation.html', this)">自定义动画</div>
                    <div class="nav-item" data-list="examples/list.html" data-default="examples/layer.html" onclick="selectCategory('examples/list.html', 'examples/layer.html', this)">交互示例（Layer + 动画）</div>
                </div>
            </div>

            <div class="nav-section-title">开发者</div>
            <div class="nav-item" data-list="search.html" data-default="module.html" onclick="selectCategory('search.html', 'module.html', this)">模块开发与测试指南</div>
        </div>
    </div>

    <!-- 2. Middle Sidebar -->
    <div class="sidebar-middle">
        <iframe id="middle-frame" src="targets/list.html"></iframe>
    </div>

    <!-- 3. Right Content -->
    <div class="content-right">
        <iframe id="content-frame" src="targets/test_css_selector.html"></iframe>
    </div>

    <!-- SVG overlay for the middle→right connection line -->
    <svg id="column-connection-line" class="column-connection-line" aria-hidden="true">
        <path id="column-connection-path" class="column-connection-path" d=""></path>
    </svg>

    <script>
        // Bump this when you want to force-refresh iframe pages
        const DOC_CACHE_VERSION = '2';

        // =========================================================
        // URL state (hash routing)
        // - When navigating: write selected content page into URL: #p=<encoded>
        // - On refresh / back-forward: restore the same content page + sync left/middle
        // =========================================================
        let _docApplyingRoute = false;

        function ensureHtmlPath(u) {
            const n = normalizeDocUrl(u);
            if (!n) return null;
            return n.endsWith('.html') ? n : (n + '.html');
        }

        // New readable token:
        // - omit ".html"
        // - "/" becomes "_" (separator)
        // - existing "_" becomes "__" (escape), so it's reversible
        function routeTokenFromContentUrl(contentUrl) {
            let u = normalizeDocUrl(contentUrl);
            if (!u) return '';
            if (u.endsWith('.html')) u = u.slice(0, -5);
            // escape "_" first, then turn "/" into "_"
            return u.replace(/_/g, '__').replace(/\//g, '_');
        }

        function contentUrlFromRouteToken(token) {
            let t = String(token || '');
            if (!t) return null;
            // In case someone pasted an encoded token, be tolerant.
            try { t = decodeURIComponent(t); } catch {}

            // If it already looks like a path (legacy), keep it.
            if (t.includes('/')) return ensureHtmlPath(t);

            // Decode: "_" => "/", "__" => "_"
            let out = '';
            for (let i = 0; i < t.length; i++) {
                const ch = t[i];
                if (ch === '_') {
                    if (t[i + 1] === '_') { out += '_'; i++; }
                    else out += '/';
                } else {
                    out += ch;
                }
            }
            return ensureHtmlPath(out);
        }

        function getRouteContentUrl() {
            const h = String(location.hash || '');
            if (!h) return null;
            const hash = h.startsWith('#') ? h.slice(1) : h;
            // Legacy-friendly:
            // - "#p=<encoded path>"
            // - "#/path/to/page.html"
            // New:
            // - "#layer_overview" / "#layer_test__confirm__flow"
            if (hash.startsWith('/')) {
                const p = hash.slice(1);
                return p ? ensureHtmlPath(p) : null;
            }
            if (hash.startsWith('p=')) {
                const params = new URLSearchParams(hash);
                const p = params.get('p');
                return p ? ensureHtmlPath(p) : null;
            }
            return contentUrlFromRouteToken(hash);
        }

        function setRouteContentUrl(contentUrl, { replace = false } = {}) {
            const token = routeTokenFromContentUrl(contentUrl);
            if (!token) return;
            const nextHash = '#' + token;
            if (location.hash === nextHash) return;
            if (replace) history.replaceState(null, '', nextHash);
            else location.hash = nextHash;
        }

        function baseDocPath(url) {
            return normalizeDocUrl(url);
        }

        function guessListUrlByContent(contentUrl) {
            const u = normalizeDocUrl(contentUrl);
            if (!u) return null;
            if (u === 'module.html' || u === 'search.html') return 'search.html';
            if (u === 'test_on_update.html') return 'list_callbacks.html';
            if (u.startsWith('targets/')) return 'targets/list.html';
            if (u.startsWith('animatable_properties/')) return 'animatable_properties/list.html';
            if (u.startsWith('tween_value_types/')) return 'tween_value_types/list.html';
            if (u.startsWith('tween_parameters/')) return 'tween_parameters/list.html';
            if (u.startsWith('svg/')) return 'svg/list.html';
            if (u === 'layer/test_custom_animation.html') return 'layer/custom_list.html';
            if (u === 'layer/test_custom_animation_banner.html') return 'layer/custom_list.html';
            if (u === 'layer/test_custom_animation_ballsorting.html') return 'layer/custom_list.html';
            if (u.startsWith('layer/')) return 'layer/list.html';
            if (u.startsWith('examples/')) return 'examples/list.html';
            return null;
        }

        function syncLeftActiveByListUrl(listUrl, contentUrl) {
            const u = normalizeDocUrl(listUrl);
            if (!u) return;
            const items = Array.from(document.querySelectorAll('.nav-item'));
            items.forEach(i => i.classList.remove('active'));

            // Prefer exact (list + default) match, then fall back to first list match
            const normContent = normalizeDocUrl(contentUrl);
            const exact = items.find(i =>
                normalizeDocUrl(i.getAttribute('data-list')) === u &&
                normalizeDocUrl(i.getAttribute('data-default')) === normContent
            );
            const any = items.find(i => normalizeDocUrl(i.getAttribute('data-list')) === u);
            (exact || any)?.classList.add('active');
            syncNavTreeState();
        }

        function ensureCategoryForContent(contentUrl) {
            const listUrl = guessListUrlByContent(contentUrl);
            if (!listUrl) return;

            // Left highlight
            syncLeftActiveByListUrl(listUrl, contentUrl);

            // Middle list
            const middleFrame = document.getElementById('middle-frame');
            if (middleFrame) {
                const current = baseDocPath(middleFrame.getAttribute('src') || '');
                if (current !== normalizeDocUrl(listUrl)) {
                    middleFrame.src = withDocVersion(listUrl);
                }
            }
        }

        function selectCategory(listUrl, defaultContentUrl, el) {
            // 1. Highlight Nav Item
            document.querySelectorAll('.nav-item').forEach(item => item.classList.remove('active'));
            if (el) el.classList.add('active');
            syncNavTreeState();

            // 2. Load Middle Column (List)
            const middleFrame = document.getElementById('middle-frame');
            const listUrlV = withDocVersion(listUrl);
            if (middleFrame.getAttribute('src') !== listUrlV) {
                middleFrame.src = listUrlV;
            }

            // 3. Load Right Column (Default Content)
            loadContent(defaultContentUrl, { updateRoute: true });
        }

        function toggleTree(headerEl) {
            if (!headerEl) return;
            const next = headerEl.nextElementSibling;
            if (!next || !next.classList.contains('tree-children')) return;
            next.classList.toggle('expanded');
            const isExpanded = next.classList.contains('expanded');
            headerEl.classList.toggle('active-header', isExpanded);
        }

        function syncNavTreeState() {
            try {
                const active = document.querySelector('.nav-item.active');
                const children = active?.closest('.tree-children');
                const header = children ? children.previousElementSibling : null;
                document.querySelectorAll('.tree-children').forEach(c => c.classList.remove('expanded'));
                document.querySelectorAll('.tree-header').forEach(h => h.classList.remove('active-header'));
                if (children) {
                    children.classList.add('expanded');
                    if (header && header.classList.contains('tree-header')) {
                        header.classList.add('active-header');
                    }
                }
            } catch {}
        }

        function withDocVersion(url) {
            const u = String(url || '');
            if (!u) return u;
            // keep explicit query params if present
            if (u.includes('?')) return u;
            return u + '?v=' + encodeURIComponent(DOC_CACHE_VERSION);
        }

        function loadContent(url, opts = {}) {
            const { updateRoute = true, replaceRoute = false } = opts || {};
            const contentFrame = document.getElementById('content-frame');
            const urlV = withDocVersion(url);
            if (contentFrame.getAttribute('src') !== urlV) {
                contentFrame.src = urlV;
            }

            // Keep middle list selection in sync when possible
            try {
                setMiddleActive(url);
            } catch {}

            // Keep left + middle category consistent even if navigation came from middle list / prev-next
            try {
                ensureCategoryForContent(url);
            } catch {}

            // Persist current selection in URL (so refresh stays on same page)
            if (updateRoute) {
                try { setRouteContentUrl(url, { replace: !!replaceRoute }); } catch {}
            }

            // Update connection line after navigation
            scheduleConnectionLineUpdate();
        }

        // Called by content iframe pages (and also internally after navigation)
        function setMiddleActive(contentUrl) {
            const middleFrame = document.getElementById('middle-frame');
            if (!middleFrame) return;
            const win = middleFrame.contentWindow;
            if (win && typeof win.setActiveByContentUrl === 'function') {
                win.setActiveByContentUrl(contentUrl);
            }

            // Update connection line when active item changes
            scheduleConnectionLineUpdate();
        }

        // =========================================================
        // Global Prev/Next（组内顺序 + 跨组跳转，由路由表统一驱动）
        // =========================================================
        const DOC_PAGES = [
            // Targets
            { group: 'Targets', title: 'Targets 概览', url: 'targets/overview.html' },
            { group: 'Targets', title: 'CSS Selector', url: 'targets/test_css_selector.html' },
            { group: 'Targets', title: 'DOM Elements', url: 'targets/test_dom_elements.html' },
            { group: 'Targets', title: 'JavaScript Objects', url: 'targets/test_js_objects.html' },
            { group: 'Targets', title: 'Array of targets', url: 'targets/test_array_targets.html' },

            // Animatable properties
            { group: 'Properties', title: 'Transforms', url: 'animatable_properties/test_transforms.html' },
            { group: 'Properties', title: 'CSS Properties', url: 'animatable_properties/test_css_props.html' },
            { group: 'Properties', title: 'CSS Variables', url: 'animatable_properties/test_css_vars.html' },
            { group: 'Properties', title: 'JS Properties', url: 'animatable_properties/test_js_props.html' },

            // Tween value types
            { group: 'Tween 值', title: 'Numerical', url: 'tween_value_types/test_numerical.html' },
            { group: 'Tween 值', title: 'Unit', url: 'tween_value_types/test_unit.html' },
            { group: 'Tween 值', title: 'Relative', url: 'tween_value_types/test_relative.html' },
            { group: 'Tween 值', title: 'Colors', url: 'tween_value_types/test_colors.html' },

            // Tween parameters
            { group: 'Tween 参数', title: 'Tween parameters 概览', url: 'tween_parameters/overview.html' },
            { group: 'Tween 参数', title: 'duration / delay', url: 'tween_parameters/test_duration_delay.html' },

            // SVG
            { group: 'SVG', title: 'SVG 概览', url: 'svg/overview.html' },
            { group: 'SVG', title: 'draw() 路径描边', url: 'svg/test_draw_path.html' },
            { group: 'SVG', title: 'Motion Path', url: 'svg/test_motion_path.html' },
            { group: 'SVG', title: 'SVG 属性动画', url: 'svg/test_svg_attributes.html' },
            { group: 'SVG', title: 'SVG transform', url: 'svg/test_svg_transforms.html' },
            { group: 'SVG', title: 'Morph（points）', url: 'svg/test_morph_points.html' },
            { group: 'SVG', title: 'Morph（path d）', url: 'svg/test_morph_path.html' },

            // Callbacks
            { group: 'Callbacks', title: 'onUpdate', url: 'test_on_update.html' },

            // Examples
            { group: 'Examples', title: 'Controls', url: 'examples/controls.html' },
            { group: 'Examples', title: 'Layer', url: 'examples/layer.html' },

            // Layer
            { group: 'Layer', title: 'Layer 概览', url: 'layer/overview.html' },
            { group: 'Layer', title: '自定义动画', url: 'layer/test_custom_animation.html' },
            { group: 'Layer', title: '自定义动画（Banner）', url: 'layer/test_custom_animation_banner.html' },
            { group: 'Layer', title: '自定义动画（BallSorting）', url: 'layer/test_custom_animation_ballsorting.html' },
            { group: 'Layer', title: 'SVG Icon animation', url: 'layer/test_icons_svg_animation.html' },
            { group: 'Layer', title: 'Confirm flow', url: 'layer/test_confirm_flow.html' },
            { group: 'Layer', title: 'Selection.layer + dataset', url: 'layer/test_selection_layer_dataset.html' },
            { group: 'Layer', title: 'Static API / Builder API', url: 'layer/test_static_fire.html' },
            { group: 'Layer', title: 'DOM content + Step flow', url: 'layer/test_dom_steps.html' },

            // Developer
            { group: 'Developer', title: '模块开发与测试指南', url: 'module.html' }
        ];

        function normalizeDocUrl(url) {
            const raw = String(url || '');
            const noHash = raw.split('#')[0];
            const noQuery = noHash.split('?')[0];
            return String(noQuery || '')
                .replace(/^[#/]+/, '')
                .replace(/^\.\//, '')
                .replace(/^\/+/, '');
        }

        function docFindIndex(currentUrl) {
            const u = normalizeDocUrl(currentUrl);
            if (!u) return -1;
            return DOC_PAGES.findIndex(p => u === p.url || u.endsWith(p.url));
        }

        function docGetPrevNext(currentUrl) {
            const idx = docFindIndex(currentUrl);
            if (idx < 0) return { idx: -1, prev: null, next: null, current: null };
            const prev = (idx > 0) ? DOC_PAGES[idx - 1] : null;
            const next = (idx < DOC_PAGES.length - 1) ? DOC_PAGES[idx + 1] : null;
            return { idx, prev, next, current: DOC_PAGES[idx] };
        }

        function docNavigatePrev(currentUrl) {
            const { prev } = docGetPrevNext(currentUrl);
            if (prev) loadContent(prev.url);
        }

        function docNavigateNext(currentUrl) {
            const { next } = docGetPrevNext(currentUrl);
            if (next) loadContent(next.url);
        }

        // Expose to iframes (same origin)
        window.docGetPrevNext = docGetPrevNext;
        window.docNavigatePrev = docNavigatePrev;
        window.docNavigateNext = docNavigateNext;

        // =============================
        // Middle ↔ Right connection line
        // =============================
        const connectionSvg = document.getElementById('column-connection-line');
        const connectionPath = document.getElementById('column-connection-path');
        let _connRaf = 0;

        function scheduleConnectionLineUpdate() {
            if (_connRaf) return;
            _connRaf = requestAnimationFrame(() => {
                _connRaf = 0;
                updateConnectionLine();
            });
        }

        function getActiveElementInFrame(frameEl) {
            try {
                const doc = frameEl?.contentDocument;
                if (!doc) return null;
                // Middle list pages use .card.active / .header-card.active; fall back to .active
                return (
                    doc.querySelector('.card.active') ||
                    doc.querySelector('.header-card.active') ||
                    doc.querySelector('.nav-item.active') ||
                    doc.querySelector('.active')
                );
            } catch {
                return null;
            }
        }

        function getAnchorElementInContentFrame(frameEl) {
            try {
                const doc = frameEl?.contentDocument;
                if (!doc) return null;
                // Prefer a *visible* code area anchor (in-viewport), then fall back
                const candidates = [
                    '.box-container .box-header',
                    '.code-view.active, .html-view.active, .css-view.active',
                    '.box-container',
                    'h1',
                    '.container',
                    'body'
                ];
                for (const sel of candidates) {
                    const el = doc.querySelector(sel);
                    if (!el) continue;
                    // If it's visible in the iframe viewport, use it; else keep looking
                    const r = el.getBoundingClientRect();
                    const vh = frameEl?.clientHeight || 0;
                    if (!vh) return el;
                    const visibleTop = Math.max(0, r.top);
                    const visibleBottom = Math.min(vh, r.bottom);
                    if (visibleBottom - visibleTop > 8) return el;
                }
                return doc.body;
            } catch {
                return null;
            }
        }

        function clamp(n, min, max) {
            return Math.min(Math.max(n, min), max);
        }

        function getVisibleCenterInFrame(frameEl, elRect) {
            const w = frameEl?.clientWidth || 0;
            const h = frameEl?.clientHeight || 0;
            if (!w || !h) return null;

            const visibleLeft = Math.max(0, elRect.left);
            const visibleRight = Math.min(w, elRect.right);
            const visibleTop = Math.max(0, elRect.top);
            const visibleBottom = Math.min(h, elRect.bottom);

            if (visibleRight - visibleLeft <= 1 || visibleBottom - visibleTop <= 1) {
                return null;
            }

            return {
                x: (visibleLeft + visibleRight) / 2,
                y: (visibleTop + visibleBottom) / 2
            };
        }

        function updateConnectionLine() {
            if (!connectionSvg || !connectionPath) return;

            const middleFrame = document.getElementById('middle-frame');
            const contentFrame = document.getElementById('content-frame');
            if (!middleFrame || !contentFrame) return;

            const midRect = middleFrame.getBoundingClientRect();
            const rightRect = contentFrame.getBoundingClientRect();

            const active = getActiveElementInFrame(middleFrame);
            const anchor = getAnchorElementInContentFrame(contentFrame);
            if (!active || !anchor) {
                connectionPath.setAttribute('d', '');
                connectionSvg.style.opacity = '0';
                return;
            }

            const activeRect = active.getBoundingClientRect();
            const anchorRect = anchor.getBoundingClientRect();

            // Use the *visible* part of the element within its iframe viewport
            const activeCenter = getVisibleCenterInFrame(middleFrame, activeRect);
            const anchorCenter = getVisibleCenterInFrame(contentFrame, anchorRect);
            if (!activeCenter || !anchorCenter) {
                // If either side isn't visible in its iframe, hide the line (prevents weird drifting)
                connectionPath.setAttribute('d', '');
                connectionSvg.style.opacity = '0';
                return;
            }

            // Convert iframe-viewport coordinates to parent viewport coordinates
            const startX = midRect.left + clamp(activeRect.right, 0, middleFrame.clientWidth);
            const startY = midRect.top + activeCenter.y;

            // Stop just before the content block (avoid entering the dark code area)
            const endX = rightRect.left + clamp(anchorRect.left - 2, 6, contentFrame.clientWidth - 12);
            const endY = rightRect.top + anchorCenter.y;

            // Draw an L-shaped polyline.
            // Keep the vertical segment aligned with the column divider (middle ↔ right).
            const dividerX = rightRect.left + 0.5; // half-pixel for crisper stroke alignment
            const x1 = Math.max(startX + 12, dividerX);
            const d = [
                `M ${startX} ${startY}`,
                `L ${x1} ${startY}`,
                `L ${x1} ${endY}`,
                `L ${endX} ${endY}`
            ].join(' ');

            connectionPath.setAttribute('d', d);
            connectionSvg.style.opacity = '0.85';
        }

        function attachFrameScrollListeners(frameEl) {
            if (!frameEl) return;
            const onScroll = () => {
                markFrameScrolling(frameEl);
                scheduleConnectionLineUpdate();
            };
            try {
                // Window scroll inside iframe
                frameEl.contentWindow?.addEventListener('scroll', onScroll, { passive: true });
                // Some pages scroll on document/body; capture to be safe
                frameEl.contentDocument?.addEventListener('scroll', onScroll, true);
                frameEl.contentDocument?.documentElement?.addEventListener?.('scroll', onScroll, { passive: true });
                frameEl.contentDocument?.body?.addEventListener?.('scroll', onScroll, { passive: true });
            } catch {}
        }

        const _scrollHideTimers = new WeakMap();
        function markFrameScrolling(frameEl) {
            try {
                const doc = frameEl?.contentDocument;
                if (!doc) return;
                doc.documentElement?.classList.add('scrolling');
                doc.body?.classList.add('scrolling');
                const prev = _scrollHideTimers.get(frameEl);
                if (prev) clearTimeout(prev);
                _scrollHideTimers.set(frameEl, setTimeout(() => {
                    try {
                        doc.documentElement?.classList.remove('scrolling');
                        doc.body?.classList.remove('scrolling');
                    } catch {}
                }, 500));
            } catch {}
        }

        // Always-on lightweight loop to keep the line aligned even
        // if iframe scroll events were missed due to timing.
        let _connLoopStarted = false;
        function startConnectionLineLoop() {
            if (_connLoopStarted) return;
            _connLoopStarted = true;
            const loop = () => {
                // Only bother when we have a path (avoids work when hidden)
                if (connectionPath?.getAttribute('d')) {
                    scheduleConnectionLineUpdate();
                }
                requestAnimationFrame(loop);
            };
            requestAnimationFrame(loop);
        }

        // Make initial active state robust against iframe load ordering
        window.addEventListener('load', () => {
            // Restore route (if present) before doing any extra syncing
            try {
                const routeUrl = getRouteContentUrl();
                if (routeUrl) {
                    _docApplyingRoute = true;
                    ensureCategoryForContent(routeUrl);
                    loadContent(routeUrl, { updateRoute: false });
                } else {
                    // No route: persist current default content into URL (so first refresh is stable)
                    const current = baseDocPath(document.getElementById('content-frame')?.getAttribute('src') || '');
                    if (current) setRouteContentUrl(current, { replace: true });
                }
            } catch {}
            _docApplyingRoute = false;

            const contentFrame = document.getElementById('content-frame');
            const src = contentFrame?.getAttribute('src');
            if (src) setMiddleActive(src);

            const middleFrame = document.getElementById('middle-frame');
            if (middleFrame) {
                middleFrame.addEventListener('load', () => {
                    const current = document.getElementById('content-frame')?.getAttribute('src');
                    if (current) setMiddleActive(current);
                    attachFrameScrollListeners(middleFrame);
                    scheduleConnectionLineUpdate();
                });
            }

            if (contentFrame) {
                contentFrame.addEventListener('load', () => {
                    const current = contentFrame.getAttribute('src');
                    if (current) setMiddleActive(current);
                    attachFrameScrollListeners(contentFrame);
                    scheduleConnectionLineUpdate();
                });
            }

            // If the iframes were already loaded before we attached 'load' listeners,
            // still attach scroll listeners immediately.
            attachFrameScrollListeners(middleFrame);
            attachFrameScrollListeners(contentFrame);

            window.addEventListener('resize', scheduleConnectionLineUpdate, { passive: true });
            scheduleConnectionLineUpdate();
            startConnectionLineLoop();
        });

        // Back/forward + manual hash edits: restore selection
        window.addEventListener('hashchange', () => {
            if (_docApplyingRoute) return;
            const routeUrl = getRouteContentUrl();
            if (!routeUrl) return;
            _docApplyingRoute = true;
            try {
                ensureCategoryForContent(routeUrl);
                loadContent(routeUrl, { updateRoute: false });
            } finally {
                _docApplyingRoute = false;
            }
        });
    </script>
</body>
</html>