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10_Wiki/Topics 대규모 정리: - 오류 캡처/미완성 stub 문서 227개 제거 - 교차폴더 중복 43클러스터 병합 (63파일 → redirect) - 링크명 정규화: 깨진 링크 수정·redirect 직결·개념 매핑 ~2,400건 - 카테고리 MOC 6개 신규 생성 - Graph 섹션 미해결 related-keyword 링크 10,058건 제거 Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
153 lines
5.1 KiB
Markdown
153 lines
5.1 KiB
Markdown
---
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id: wiki-2026-0508-render-tree
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title: Render Tree
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category: 10_Wiki/Topics
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status: verified
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canonical_id: self
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aliases: [Browser-Render-Tree, Layout-Tree]
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duplicate_of: none
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source_trust_level: A
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confidence_score: 0.9
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verification_status: applied
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tags: [browser, rendering, performance, web]
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raw_sources: []
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last_reinforced: 2026-05-10
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github_commit: pending
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tech_stack:
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language: javascript
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framework: web-platform
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---
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# Render Tree
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## 매 한 줄
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> **"매 DOM × CSSOM = Render Tree"**. Browser는 매 parsed HTML (DOM) 과 매 styles (CSSOM) 을 매 merge — visible nodes만 매 골라 layout, paint, composite의 input 으로 사용. 2026 Chromium은 매 LayoutNG + RenderingNG로 매 진화.
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## 매 핵심
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### 매 Pipeline (Critical Rendering Path)
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1. **HTML → DOM** (tokenize + tree construct).
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2. **CSS → CSSOM** (parse stylesheets, compute cascade).
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3. **DOM + CSSOM → Render Tree** — 매 `display: none` 노드는 매 제외, `::before`/`::after` 매 포함.
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4. **Layout (Reflow)** — geometry 계산.
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5. **Paint** — pixel commands → layers.
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6. **Composite** — GPU layer merge → screen.
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### 매 Render Tree ≠ DOM
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- DOM 의 모든 노드 의 X. `<head>`, `<script>`, `display:none` 매 제외.
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- `visibility: hidden` 의 매 포함됨 (매 space 차지).
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- Pseudo-elements (`::before`) 매 추가됨 (DOM 에 없음).
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### 매 Blocking
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- **CSS 의 render-blocking by default**: CSSOM 완성 전에는 매 render tree 못 만듦.
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- `<script>` 의 parser-blocking — `defer`/`async`로 완화.
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- `<link rel="preload">` + `media` query 매 selective load.
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### 매 2026 modern state (RenderingNG)
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- **LayoutNG** — fragment tree로 매 incremental, isolation.
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- **CompositeAfterPaint (CAP)** — paint ordering 의 매 composite 단계로 통합.
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- **Off-main-thread scrolling/animation** — composite-only properties (`transform`, `opacity`) 매 main thread skip.
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- **CSS Containment** (`contain: layout paint`) — subtree isolation.
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- **content-visibility: auto** — 매 viewport 외 subtree skip layout/paint.
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### 매 응용
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1. Critical CSS inline → 매 first paint 단축.
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2. `content-visibility: auto` 매 long page virtualization.
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3. `will-change: transform` 매 layer promotion hint.
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## 💻 패턴
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### Critical CSS inline
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```html
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<head>
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<style>
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/* above-the-fold only */
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.hero { font-size: 3rem; color: #111; }
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</style>
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<link rel="preload" href="/main.css" as="style" onload="this.rel='stylesheet'">
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</head>
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```
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### content-visibility virtualization
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```css
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article.long-section {
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content-visibility: auto;
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contain-intrinsic-size: 0 1000px; /* placeholder size */
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}
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```
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### Composite-only animation (avoid layout/paint)
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```css
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.menu { transform: translateX(-100%); transition: transform 200ms ease; }
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.menu.open { transform: translateX(0); }
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/* GPU composites; main thread free */
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```
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### Avoid layout thrashing
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```javascript
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// BAD: read-write-read-write triggers sync layout each iter
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for (const el of items) {
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el.style.width = el.offsetWidth + 10 + 'px';
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}
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// GOOD: batch reads, then batch writes
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const widths = items.map(el => el.offsetWidth);
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items.forEach((el, i) => { el.style.width = widths[i] + 10 + 'px'; });
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```
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### CSS Containment
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```css
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.card {
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contain: layout style paint;
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/* descendant changes can't affect outside */
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}
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```
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### Render-blocking analysis
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```javascript
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// Find render-blocking resources via PerformanceObserver
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new PerformanceObserver((list) => {
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for (const entry of list.getEntries()) {
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if (entry.renderBlockingStatus === 'blocking') {
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console.warn('blocking:', entry.name);
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}
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}
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}).observe({ type: 'resource', buffered: true });
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```
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## 매 결정 기준
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| 상황 | Approach |
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| First-paint 단축 | Critical CSS inline + async/defer JS |
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| Long scrollable page | `content-visibility: auto` |
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| Smooth animation | Composite-only (transform/opacity) + `will-change` |
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| Widget isolation | `contain: layout paint` |
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| Hidden tab UI | `display: none` (full skip) vs `visibility: hidden` (preserve space) |
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**기본값**: composite-only animations, defer non-critical CSS/JS, contain on widgets.
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## 🔗 Graph
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- 부모: [[Browser-Rendering]] · [[Critical-Rendering-Path]]
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- 응용: [[Web-Performance]] · [[Core Web Vitals Optimization (INP, LCP 개선)|Core-Web-Vitals]]
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- Adjacent: [[Reflow_and_Repaint]] · [[CSSOM]] · [[DOM]]
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## 🤖 LLM 활용
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**언제**: performance audit explanations, CSS-perf debugging.
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**언제 X**: production profiling은 매 real Chrome DevTools / Lighthouse / WebPageTest 사용 — LLM의 매 verification은 X.
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## ❌ 안티패턴
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- **Layout thrashing**: read/write 매 interleave → forced synchronous layout.
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- **`top`/`left` animation**: triggers layout per frame; use `transform`.
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- **거대 inline `<style>`**: matched HTML cache의 invalidation. Critical only.
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- **`will-change` overuse**: 매 모든 element 에 적용 → memory blow-up.
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## 🧪 검증 / 중복
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- Verified (web.dev rendering performance, Chromium RenderingNG docs, MDN CRP).
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- 신뢰도 A.
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## 🕓 Changelog
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| 날짜 | 변경 |
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|---|---|
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| 2026-05-08 | Phase 1 |
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| 2026-05-10 | Manual cleanup — full rewrite covering DOM/CSSOM merge, blocking, modern RenderingNG |
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