Slidev Code Blocks

This skill covers everything about displaying code in Slidev presentations, including syntax highlighting with Shiki, line highlighting, code groups, and importing external snippets.

When to Use This Skill

Displaying code snippets in presentations
Highlighting specific lines of code
Creating step-by-step code reveals
Showing code comparisons
Importing code from external files

Basic Code Blocks

Simple Code Block

```javascript
function greet(name) {
  return `Hello, ${name}!`
}
```

With Language Specification

Shiki supports 100+ languages:

```typescript
interface User {
  id: number
  name: string
  email: string
}
```

```python
def fibonacci(n):
    if n <= 1:
        return n
    return fibonacci(n-1) + fibonacci(n-2)
```

```rust
fn main() {
    println!("Hello, Rust!");
}
```

Line Numbers

Enable Line Numbers

```typescript {lines:true}
const x = 1
const y = 2
const z = x + y
```

Global Configuration

In frontmatter:

---
lineNumbers: true
---

Starting Line Number

```typescript {startLine:5}
// This starts at line 5
const x = 1
```

Line Highlighting

Highlight Specific Lines

```typescript {2,3}
const a = 1
const b = 2  // highlighted
const c = 3  // highlighted
const d = 4
```

Highlight Ranges

```typescript {1-3,5}
line 1  // highlighted
line 2  // highlighted
line 3  // highlighted
line 4
line 5  // highlighted
```

Click-Through Highlighting

Reveal highlights step by step:

```typescript {1|2-3|5}
const name = 'Slidev'      // Click 1
const version = '0.50'     // Click 2
const author = 'Anthony'   // Click 2

console.log(name, version) // Click 3
```

Highlight All Then Focus

```typescript {*|1|2|3}
const a = 1
const b = 2
const c = 3
```

Click 0: All lines visible
Click 1: Line 1 highlighted
Click 2: Line 2 highlighted
Click 3: Line 3 highlighted

With Final State

```typescript {1|2|all}
const x = 1
const y = 2
```

Code Block Options

Maximum Height

```typescript {maxHeight:'200px'}
// Long code block
// with many lines
// ...
```

Wrapping

```typescript {wrap:true}
const veryLongLine = 'This is a very long line that would normally overflow the code block but now it wraps nicely'
```

Combined Options

```typescript {2-4|6-8}{lines:true,startLine:10,maxHeight:'300px'}
function example() {
  const a = 1
  const b = 2
  const c = 3

  return {
    sum: a + b + c
  }
}
```

Code Themes

Configure in setup/shiki.ts

// setup/shiki.ts
import { defineShikiSetup } from '@slidev/types'

export default defineShikiSetup(() => {
  return {
    themes: {
      dark: 'vitesse-dark',
      light: 'vitesse-light',
    },
  }
})

Popular Themes

vitesse-dark / vitesse-light
dracula
one-dark-pro
nord
material-theme
github-dark / github-light

Code Groups

Show multiple code variants in tabs:

```typescript {monaco}
// TypeScript version
interface User {
  name: string
}
```

```javascript
// JavaScript version
const user = {
  name: 'John'
}
```

Use <<< to create tabbed code groups (experimental):

<<< @/snippets/example.ts
<<< @/snippets/example.js

Importing External Code

Full File Import

<<< @/snippets/example.ts

With Line Range

<<< @/snippets/example.ts#L5-10

With Language Override

<<< @/snippets/config{json}

With Highlighting

<<< @/snippets/example.ts {2,4}

Diff Highlighting

Show code changes:

```typescript
function greet(name: string) {
  return `Hello, ${name}!` // [!code --]
  return `Hi, ${name}!`    // [!code ++]
}
```

Highlight Specific Changes

```typescript
const config = {
  theme: 'dark',   // [!code highlight]
  debug: false,    // [!code warning]
  timeout: 1000,   // [!code error]
}
```

TwoSlash Integration

TypeScript hover information:

```typescript twoslash
const message = 'Hello'
//    ^?
```

Hover annotations:

```typescript twoslash
interface User {
  name: string
  age: number
}

const user: User = {
  name: 'John',
  age: 30
}
//    ^?
```

Code Focus

Focus Mode

Dim non-highlighted lines:

```typescript {2}{focus}
const a = 1
const b = 2  // Focused, others dimmed
const c = 3
```

Click Focus Transitions

```typescript {1|2|3}{focus}
step1()  // First focused
step2()  // Then this
step3()  // Finally this
```

Inline Code

Simple Inline

Use the `useState` hook for state management.

Styled Inline

The function returns `true`{.text-green-500} or `false`{.text-red-500}.

Code Block Styling

Custom CSS Class

```typescript {class:'my-code'}
const x = 1
```

.my-code {
  font-size: 0.9em;
  border-radius: 8px;
}

Scoped Styles

# Code Slide

```js
const x = 1


## Best Practices

### 1. Keep Code Concise

❌ **Too much code**
````markdown
```typescript
// Full 100-line file


✓ **Focused snippet**
````markdown
```typescript
// Just the relevant function
function handleClick() {
  setState(value => value + 1)
}
```

2. Use Meaningful Highlights

❌ No context

```typescript
const x = 1
```

✓ Guided attention

```typescript {2}
const x = 1
const important = 'focus here'  // highlighted
const y = 2
```

3. Progressive Reveal for Complex Code

```typescript {1-2|4-6|8-10}
// Step 1: Define types
interface User { name: string }

// Step 2: Create function
function greet(user: User) {
  return `Hello, ${user.name}`
}

// Step 3: Usage
const greeting = greet({ name: 'World' })
console.log(greeting)
```

4. Use Comments for Context

```typescript
// BAD: Magic numbers
const delay = 1000

// GOOD: Named constants
const ANIMATION_DELAY_MS = 1000
```

Common Patterns

Before/After Comparison

```typescript
// Before
function add(a, b) {
  return a + b
}

// After
const add = (a: number, b: number): number => a + b
```

Step-by-Step Tutorial

```typescript {1|1-4|1-7|1-10}
// Step 1: Import
import { ref } from 'vue'

// Step 2: Create ref
const count = ref(0)

// Step 3: Create function
function increment() {
  count.value++
}
```

Output Format

When creating code slides, provide:

---
layout: default
---

# [Topic]

[Brief explanation of what the code does]

```[language] {[highlights]}{[options]}
[code]


**KEY DECISIONS:**
- Language: [chosen language]
- Highlighting: [which lines and why]
- Animation: [click sequence if any]
- Theme: [if non-default]

slidev-code-blocks