2nd/10_Wiki/Topic_CSS/CSS_User_Interface.md

---
id: css-user-interface
title: "CSS User Interface"
category: "Frontend"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["resize property", "outline-offset", "resizable element", "user interface properties", "resize textarea", "CSS UI"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.88
created_at: 2026-06-23
updated_at: 2026-06-23
review_reason: ""
merge_history: []
tags: ["css", "web", "frontend", "w3schools", "user-interface", "resize", "outline"]
raw_sources: ["https://www.w3schools.com/css/css3_user_interface.asp"]
applied_in: []
github_commit: ""
---

# [[CSS User Interface]]

## 🎯 한 줄 통찰 (One-line insight)
The CSS user-interface properties cover `resize` (whether and how a user can drag-resize an element) and `outline-offset` (the gap between an outline and the element's border), where the outline sits outside the box and does not affect the element's dimensions. [S1]

## 🧠 핵심 개념 (Core concepts)
- **resize** — the `resize` property specifies if (and how) an element can be resized by a user. [S1]
- **resize values** — `horizontal` (resize the width), `vertical` (resize the height), `both` (resize in both directions), and `none` (not resizable). [S1]
- **outline-offset** — the `outline-offset` property adds a space between an outline and the edge/border of an element. [S1]
- **Outline is not a border** — unlike a border, the outline is drawn outside the element's border, may overlap other content, and is NOT part of the element's dimensions — the element's total width and height are not affected by the outline width. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Resize needs overflow** — `resize` is paired with `overflow: auto;` so the resizable box scrolls its content correctly. [S1]
- **Lock textarea sizing** — `textarea { resize: none; }` disables the browser default that lets users drag-resize a textarea. [S1]
- **Spaced highlight ring** — `outline` + `outline-offset` produces a detached highlight ring around an element without changing its layout box. [S1]

## 📖 세부 내용 (Details)
**CSS Resize** [S1]
The `resize` property specifies if (and how) an element can be resized by a user. Its values are:
- `horizontal` — the user can resize the element horizontally (the width).
- `vertical` — the user can resize the element vertically (the height).
- `both` — the user can resize the element both vertically and horizontally.
- `none` — the user cannot resize the element.

Resize only the width:
```css
div {
  resize: horizontal;
  overflow: auto;
}
```
Resize only the height:
```css
div {
  resize: vertical;
  overflow: auto;
}
```
Resize both width and height:
```css
div {
  resize: both;
  overflow: auto;
}
```
Disable resize in a textarea (browsers normally let users resize it):
```css
textarea {
  resize: none;
}
```

**CSS Outline Offset** [S1]
The `outline-offset` property adds a space between an outline and the edge/border of an element.

> Note: Outline differs from borders! Unlike border, the outline is drawn outside the element's border, and may overlap other content. Also, the outline is NOT a part of the element's dimensions; the element's total width and height is not affected by the width of the outline.

```css
div.ex1 {
  margin: 20px;
  border: 1px solid black;
  outline: 4px solid red;
  outline-offset: 15px;
}

div.ex2 {
  margin: 10px;
  border: 1px solid black;
  outline: 5px dashed blue;
  outline-offset: 5px;
}
```

**CSS User Interface Properties** [S1]

| Property | Description |
|----------|-------------|
| outline-offset | Adds space between an outline and the edge or border of an element |
| resize | Specifies whether or not an element is resizable by the user |

## 🛠️ 적용 사례 (Applied in summary)
The page's examples are the applied cases: `div` elements made resizable horizontally / vertically / both (each with `overflow: auto`), a `textarea` with resize disabled, and two `div`s demonstrating offset outlines. No external project/commit applications found in the source.

## 💻 코드 패턴 (Code patterns)
Resizable element (language: CSS):
```css
div {
  resize: both;
  overflow: auto;
}
```
Disable textarea resize (language: CSS):
```css
textarea {
  resize: none;
}
```
Offset outline (language: CSS):
```css
div.ex1 {
  border: 1px solid black;
  outline: 4px solid red;
  outline-offset: 15px;
}
```

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
No contradictions found in the source.

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual (실제 적용 사례 발견 시 applied/validated로 승격 가능)
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.88
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[CSS Tutorial]]
- **관련 개념:** [[CSS Outline]], [[CSS Overflow]], [[CSS Forms]], [[CSS Box Model]]
- **참조 맥락:** Referenced when controlling user-resizable boxes or drawing spaced focus/highlight outlines.

## 📚 출처 (Sources)
- [S1] W3Schools — CSS User Interface — https://www.w3schools.com/css/css3_user_interface.asp

## 📝 변경 이력 (Change history)
- 2026-06-23: Initial draft synthesized from the W3Schools "CSS User Interface" page (Astra wiki-curation, P-Reinforce v3.1 format).