Warning

This is an internal project, and is not intended for public use. No support or stability guarantees are provided.

Enhance Code Emphasis

The enhanceCodeEmphasis source enhancer adds visual emphasis to specific lines in code examples by marking them with a data-hl attribute. This allows you to highlight important code patterns or call attention to specific sections in demos using simple comment annotations.

Features

Single-line emphasis with @highlight comments
Multi-line emphasis blocks with @highlight-start / @highlight-end pairs
Text highlighting within a line with @highlight-text "text"
Optional descriptions in quoted strings (e.g., @highlight "description")
Strong emphasis with ! at the end of descriptions (e.g., @highlight "We must do this!")
Automatic strong emphasis for nested blocks - lines inside multiple emphasis ranges are automatically marked as strong
Works with all code languages that support comments
Compatible with both inline and block comment styles

Basic Usage

import { enhanceCodeEmphasis } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';

// Use as a source enhancer
const sourceEnhancers = [enhanceCodeEmphasis];

// Pass to CodeHighlighter or use with enhanceCode

The enhancer processes @highlight comments in your source files and adds data-hl to the corresponding line elements in the HAST tree.

Comment Patterns

Single Line Emphasis

Emphasize the line containing the comment:

export default function Button() {
  return (
    <button className="primary">Click me</button> {/* @highlight */}
  );
}

The line with the <button> element will be emphasized.

Single Line with Description

Add context about what's being emphasized:

export default function Component() {
  const [count, setCount] = useState(0); // @highlight "We track state"

  return <div>{count}</div>;
}

Strong Emphasis

End a description with ! to mark it as strong emphasis (data-hl="strong"):

export default function Component() {
  const apiKey = process.env.API_KEY; // @highlight "We must provide the API key!"

  return <div>...</div>;
}

Strong emphasis is useful for highlighting critical code that users must pay attention to or modify.

Multi-line Emphasis

Emphasize a range of lines between start and end markers:

export default function Component() {
  return (
    // @highlight-start
    <div>
      <h1>Heading 1</h1>
      <p>Some content</p>
    </div>
    // @highlight-end
  );
}

Lines 4-7 (from <div> through </div>) will be emphasized. The range starts at the first line after @highlight-start and ends at the last line before @highlight-end.

Multi-line with Description

Explain what the emphasized section demonstrates:

export default function Component() {
  return (
    // @highlight-start "We add a heading with an h1"
    <div>
      <h1>Heading 1</h1>
    </div>
    // @highlight-end
  );
}

Text Highlighting

Highlight specific text within a line:

export default function Component() {
  return (
    <div>
      <h1>Heading 1</h1> {/* @highlight-text "Heading 1" */}
    </div>
  );
}

This wraps the specified text in a <span data-hl=""> element, allowing you to highlight a specific word or phrase within a line rather than the entire line.

Comment Syntax

Supported Formats

The enhancer recognizes these comment patterns:

Pattern	Effect
`@highlight`	Emphasize current line
`@highlight "description"`	Emphasize with description
`@highlight-start`	Start multi-line block
`@highlight-start "desc"`	Start block with description
`@highlight-end`	End multi-line block
`@highlight-text "text"`	Highlight specific text within the line

Description Format

Descriptions are provided as quoted strings:

// @highlight "We initialize the state"
const [value, setValue] = useState(0);

// @highlight-start "We render the component"
<div>
  <p>Content</p>
</div>;
// @highlight-end

Displaying Comments in Documentation

By default, @highlight comments are stripped from the rendered code. To show the comment syntax in documentation (while still applying the emphasis), use the displayComments code block attribute:

```jsx displayComments
export default function Button() {
  return (
    <button className="primary">Click me</button> {/* @highlight */}
  );
}
```

This is useful for documentation pages where you want to show users the comment syntax itself.

Advanced Patterns

Multiple Single Lines

You can emphasize multiple individual lines:

export default function Form() {
  const [name, setName] = useState(''); // @highlight
  const [email, setEmail] = useState(''); // @highlight

  return (
    <form>
      <input value={name} onChange={(e) => setName(e.target.value)} />
      <input value={email} onChange={(e) => setEmail(e.target.value)} /> {/* @highlight */}
    </form>
  );
}

Nested Multi-line Blocks

The enhancer handles nested emphasis blocks using a stack-based algorithm. Lines that fall within multiple emphasis ranges are automatically marked with strong emphasis (data-hl="strong"):

export default function Component() {
  return (
    // @highlight-start "outer block"
    <div>
      <header>Title</header>
      {/* @highlight-start "inner block"  */}
      <main>
        <p>Content</p>
      </main>
      {/* @highlight-end  */}
      <footer>Footer</footer>
    </div>
    // @highlight-end
  );
}

In this example:

The outer block lines (<div>, <header>, <footer>, </div>) get normal emphasis
The inner block lines (<main>, <p>, </main>) get strong emphasis because they're nested within both ranges
Position markers (data-hl-position) are preserved from the innermost range

Mixed Single and Multi-line

Combine both patterns in the same file:

export default function Dashboard() {
  const [data, setData] = useState([]); // @highlight

  return (
    <div>
      <Header />
      {/* @highlight-start */}
      <Chart data={data} />
      <Table data={data} />
      {/* @highlight-end */}
      <Footer /> {/* @highlight */}
    </div>
  );
}

Frame Reframing

When any emphasis is present, the enhancer splits the code block's frame structure around highlighted lines. Each original frame is broken into typed sub-frames that CSS can target for collapsing, animating, or scrolling to the focused area.

How It Works

Given a 7-line code block where line 4 is highlighted, the frames are restructured:

Frame #	Lines	`data-frame-type`
1	1–3	(none)
2	4	`highlighted`
3	5–7	(none)

When padding is configured (see Configurable Padding), additional typed frames surround the focused highlight region:

Frame #	Lines	`data-frame-type`
1	1	(none)
2	2–3	`padding-top`
3	4	`highlighted`
4	5–6	`padding-bottom`
5	7	(none)

Frame Data Attributes

Attribute	Type	Description
`data-frame-type`	string	`"highlighted"` (focused region), `"highlighted-unfocused"` (non-focused regions), `"padding-top"`, or `"padding-bottom"`. Normal frames have no type attribute.
`data-frame-indent`	number	Only on `highlighted` and `highlighted-unfocused` frames. The shared indent level of the highlighted lines (min leading spaces ÷ 2).

Configurable Padding

Use createEnhanceCodeEmphasis to configure padding frames around the focused highlight region:

import { createEnhanceCodeEmphasis } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';

const sourceEnhancers = [
  createEnhanceCodeEmphasis({
    paddingFrameMaxSize: 3,
    focusFramesMaxSize: 10,
  }),
];

Option	Type	Default	Description
`paddingFrameMaxSize`	number	`0`	Maximum number of context lines above/below the focused region
`focusFramesMaxSize`	number	—	Maximum total lines in the focus area (padding + highlighted). Remaining budget is split floor/ceil (extra line goes to bottom).

When paddingFrameMaxSize is 0 (the default), no padding frames are created and only highlighted and normal frames are produced.

The `@focus` Directive

When multiple highlight regions exist, padding is added around the first region by default. Add @focus to override which region receives padding:

const theme = getTheme(); // @highlight
const config = getConfig();

// @highlight-start @focus
<ThemeProvider theme={theme}>
  <App config={config} />
</ThemeProvider>;
// @highlight-end

In this example, @focus directs the padding frames to surround the ThemeProvider block instead of the theme line.

@focus can be combined with any highlight directive:

// @highlight @focus
// @highlight-start @focus
// @highlight-start @focus "We render the provider"

Styling Frame Types

Target frame types with CSS to create collapsible code blocks:

/* Normal frames and unfocused highlighted frames are hidden by default (collapsed) */
.codeBlock .frame:not([data-frame-type]),
.codeBlock .frame[data-frame-type='highlighted-unfocused'] {
  max-height: 0;
  overflow: hidden;
  opacity: 0;
  transition:
    max-height 0.3s ease,
    opacity 0.3s ease;
}

/* Padding frames appear dimmed when collapsed */
.codeBlock .frame[data-frame-type='padding-top'],
.codeBlock .frame[data-frame-type='padding-bottom'] {
  opacity: 0.5;
  transition: opacity 0.3s ease;
}

/* When expanded, show all frames */
.expanded .codeBlock .frame:not([data-frame-type]),
.expanded .codeBlock .frame[data-frame-type='highlighted-unfocused'] {
  max-height: 500px;
  overflow: visible;
  opacity: 1;
}

.expanded .codeBlock .frame[data-frame-type='padding-top'],
.expanded .codeBlock .frame[data-frame-type='padding-bottom'] {
  opacity: 1;
}

/* Use indent level to shift highlighted frames left when collapsed */
.codeBlock .frame[data-frame-type='highlighted'] {
  transition: margin-left 0.3s ease;
}

.codeBlock .frame[data-frame-type='highlighted'][data-frame-indent='1'] {
  margin-left: -2ch;
}

.codeBlock .frame[data-frame-type='highlighted'][data-frame-indent='2'] {
  margin-left: -4ch;
}

/* Reset indent shift when expanded */
.expanded .codeBlock .frame[data-frame-type='highlighted'] {
  margin-left: 0;
}

Demo: Collapsible Code Block

The following demo shows a code block that starts collapsed, revealing only the highlighted and padding frames. Click Expand to show the full source.

import * as React from 'react';
import { fetchUser } from './api';

interface User {
  name: string;
  email: string;
}

export function UserProfile({ id }: { id: string }) {
  const [user, setUser] = React.useState<User | null>(null);

  React.useEffect(() => {
    let cancelled = false;
    fetchUser(id).then((data) => {
      if (!cancelled) {
        setUser(data);
      }
    });
    return () => {
      cancelled = true;
    };
  }, [id]);

  if (!user) {
    return <p>Loading...</p>;
  }

  return (
    <div>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
    </div>
  );
}

ExpandCollapse

import * as React from 'react';
import type { Code as CodeType } from '@mui/internal-docs-infra/CodeHighlighter/types';
import { parseImportsAndComments } from '@mui/internal-docs-infra/pipeline/loaderUtils';
import { EMPHASIS_COMMENT_PREFIX } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';
import { Code } from './Code';

const source = `import * as React from 'react';
import { fetchUser } from './api';

interface User {
  name: string;
  email: string;
}

export function UserProfile({ id }: { id: string }) {
  const [user, setUser] = React.useState<User | null>(null);

  // @highlight-start
  React.useEffect(() => {
    let cancelled = false;
    fetchUser(id).then((data) => {
      if (!cancelled) {
        setUser(data);
      }
    });
    return () => {
      cancelled = true;
    };
  }, [id]);
  // @highlight-end

  if (!user) {
    return <p>Loading...</p>;
  }

  return (
    <div>
      <h2>{user.name}</h2>
      <p>{user.email}</p>
    </div>
  );
}`;

export async function CollapsibleCode() {
  const { code: strippedSource, comments } = await parseImportsAndComments(source, '/demo.tsx', {
    removeCommentsWithPrefix: [EMPHASIS_COMMENT_PREFIX],
    notableCommentsPrefix: [EMPHASIS_COMMENT_PREFIX],
  });

  const code: CodeType = {
    Default: {
      language: 'tsx',
      source: strippedSource!,
      comments,
    },
  };

  return <Code code={code} />;
}

Demo: @focus with Multiple Regions

When there are multiple highlight regions, @focus controls which region receives padding frames. In this demo, the useEffect block on the second region is focused — its surrounding lines get padding frames while the first region (formatDate call) does not.

import * as React from 'react';
import { formatDate } from './formatDate';
import { fetchEvents } from './fetchEvents';

const today = formatDate(new Date());

export function Calendar() {
  const [events, setEvents] = React.useState([]);

  React.useEffect(() => {
    fetchEvents(today).then(setEvents);
  }, []);

  return (
    <div className="calendar">
      <h2>{today}</h2>
      <ul>
        {events.map((event) => (
          <li key={event.id}>{event.title}</li>
        ))}
      </ul>
    </div>
  );
}

ExpandCollapse

import * as React from 'react';
import type { Code as CodeType } from '@mui/internal-docs-infra/CodeHighlighter/types';
import { parseImportsAndComments } from '@mui/internal-docs-infra/pipeline/loaderUtils';
import { EMPHASIS_COMMENT_PREFIX } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';
import { Code } from './Code';

const source = `import * as React from 'react';
import { formatDate } from './formatDate';
import { fetchEvents } from './fetchEvents';

const today = formatDate(new Date()); // @highlight

export function Calendar() {
  const [events, setEvents] = React.useState([]);

  // @highlight-start @focus
  React.useEffect(() => {
    fetchEvents(today).then(setEvents);
  }, []);
  // @highlight-end

  return (
    <div className="calendar">
      <h2>{today}</h2>
      <ul>
        {events.map((event) => (
          <li key={event.id}>{event.title}</li>
        ))}
      </ul>
    </div>
  );
}`;

export async function FocusCode() {
  const { code: strippedSource, comments } = await parseImportsAndComments(source, '/demo.tsx', {
    removeCommentsWithPrefix: [EMPHASIS_COMMENT_PREFIX],
    notableCommentsPrefix: [EMPHASIS_COMMENT_PREFIX],
  });

  const code: CodeType = {
    Default: {
      language: 'tsx',
      source: strippedSource!,
      comments,
    },
  };

  return <Code code={code} />;
}

Demo: Indent Shifting

With no padding configured, only highlighted and normal frames are produced. The data-frame-indent attribute on highlighted frames tells CSS how far the code is indented. This demo highlights an import statement (indent 0) and the deeply nested <DatePicker> usage (indent 3). When collapsed, the JSX frame shifts left by 6ch so it aligns with the left edge, then resets when expanded.

import * as React from 'react';
import { DatePicker } from './DatePicker';

export function ScheduleView() {
  const [date, setDate] = React.useState(null);

  return (
    <main>
      <header>
        <h1>Schedule</h1>
      </header>
      <section>
        <form>
          <label htmlFor="date">Pick a date</label>
          <DatePicker
            id="date"
            value={date}
            onChange={setDate}
            minDate={new Date()}
            format="MM/dd/yyyy"
          />
        </form>
      </section>
      <footer>
        <p>All times shown in UTC</p>
      </footer>
    </main>
  );
}

import * as React from 'react';
import type { Code as CodeType } from '@mui/internal-docs-infra/CodeHighlighter/types';
import { parseImportsAndComments } from '@mui/internal-docs-infra/pipeline/loaderUtils';
import { EMPHASIS_COMMENT_PREFIX } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';
import { CodeIndent } from './CodeIndent';

const source = `import * as React from 'react';
import { DatePicker } from './DatePicker'; // @highlight

export function ScheduleView() {
  const [date, setDate] = React.useState(null);

  return (
    <main>
      <header>
        <h1>Schedule</h1>
      </header>
      <section>
        <form>
          <label htmlFor="date">Pick a date</label>
          {/* @highlight-start @focus */}
          <DatePicker
            id="date"
            value={date}
            onChange={setDate}
            minDate={new Date()}
            format="MM/dd/yyyy"
          />
          {/* @highlight-end */}
        </form>
      </section>
      <footer>
        <p>All times shown in UTC</p>
      </footer>
    </main>
  );
}`;

export async function IndentCode() {
  const { code: strippedSource, comments } = await parseImportsAndComments(source, '/demo.tsx', {
    removeCommentsWithPrefix: [EMPHASIS_COMMENT_PREFIX],
    notableCommentsPrefix: [EMPHASIS_COMMENT_PREFIX],
  });

  const code: CodeType = {
    Default: {
      language: 'tsx',
      source: strippedSource!,
      comments,
    },
  };

  return <CodeIndent code={code} />;
}

Implementation Details

How It Works

Comment Extraction: Comments are extracted during parsing with notableCommentsPrefix: ['@highlight']
Directive Parsing: The enhancer scans comments for @highlight, @highlight-start, @highlight-end, and @highlight-text patterns
Line Calculation: Single-line directives mark their own line; multi-line directives mark all lines from the first line after @highlight-start to the last line before @highlight-end
Nested Detection: Lines inside multiple ranges are automatically marked as strong emphasis
HAST Modification: The enhancer traverses the HAST tree and adds dataHl: '' (or dataHl: 'strong' for nested lines or descriptions ending with !) to line elements

HAST Structure

Lines in the HAST tree have this structure after enhancement:

{
  type: 'element',
  tagName: 'span',
  properties: {
    className: 'line',
    dataLn: 3,                              // Line number
    dataHl: '',                             // Added by enhancer (or 'strong' for nested/!)
    dataHlDescription: 'We track state',    // Optional description
    dataHlPosition: 'single',               // 'single' | 'start' | 'end' for line position
  },
  children: [/* code tokens */]
}

For text highlighting with @highlight-text "text", the specified text within the line is wrapped in a span:

{
  type: 'element',
  tagName: 'span',
  properties: { dataHl: '' },
  children: [{ type: 'text', value: 'text' }]
}

Data Attributes

The enhancer adds these attributes to line elements:

Attribute	Type	Description
`data-hl`	string	`""` for normal, `"strong"` if description ends with `!` or line is nested
`data-hl-description`	string	Description text (if provided in comment)
`data-hl-position`	string	`"single"` for single-line, `"start"` or `"end"` for multiline range bounds (from innermost range)

For single-line emphasis with @highlight:

data-hl is set (or data-hl="strong" if description ends with !)
data-hl-description is set if a description was provided
data-hl-position="single" is set to distinguish from multiline range boundaries

For multi-line emphasis with @highlight-start / @highlight-end:

data-hl is set on all lines in the range (or data-hl="strong" if description ends with ! or line is nested)
data-hl-description is set on the first line (if provided)
data-hl-position="start" is set on the first line (only for ranges with more than one line)
data-hl-position="end" is set on the last line (only for ranges with more than one line)

For text highlighting with @highlight-text "text":

The specified text within the line is wrapped in a <span data-hl=""> element
The line element itself does not receive any additional attributes

Stack-Based Pairing

Multi-line directives are paired using a stack:

@highlight-start pushes onto the stack
@highlight-end pops from the stack and emphasizes the range
Inner (nested) ranges are processed before outer ranges
Lines that appear in multiple ranges are automatically marked as strong emphasis
Position markers from inner ranges are preserved when outer ranges are processed

Configuration

Adding to Source Enhancers

Configure in your webpack loader or server-side loading:

import { enhanceCodeEmphasis } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';
import { createLoadServerSource } from '@mui/internal-docs-infra/pipeline/loadServerSource';
import { loadCodeVariant } from '@mui/internal-docs-infra/pipeline/loadCodeVariant';

const sourceEnhancers = [enhanceCodeEmphasis];

For configurable padding, use the factory:

import { createEnhanceCodeEmphasis } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';

const sourceEnhancers = [
  createEnhanceCodeEmphasis({
    paddingFrameMaxSize: 3,
    focusFramesMaxSize: 10,
  }),
];

Then pass to your loading pipeline:

// Create a loadSource that extracts emphasis comments
const loadSource = createLoadServerSource({
  notableCommentsPrefix: ['@highlight'],
  removeCommentsWithPrefix: ['@highlight'],
});

// Use with loadCodeVariant
const { code } = await loadCodeVariant(url, variantName, variant, {
  loadSource,
  sourceEnhancers,
  sourceParser,
});

// Or with CodeHighlighter
<CodeHighlighter
  sourceEnhancers={sourceEnhancers}
  // ... other props
/>

// Or with useCode
const { selectedFile } = useCode(props, {
  sourceEnhancers,
});

Comment Prefix

The default comment prefix is @highlight, exported as EMPHASIS_COMMENT_PREFIX:

import { EMPHASIS_COMMENT_PREFIX } from '@mui/internal-docs-infra/pipeline/enhanceCodeEmphasis';

console.log(EMPHASIS_COMMENT_PREFIX); // '@highlight'

To use a different prefix, you would need to create a custom enhancer based on this implementation.

Styling Emphasized Lines

The data-hl attribute can be targeted with CSS. First, ensure lines are displayed as blocks for proper highlighting:

/* Required: Display lines as blocks for line-based highlighting */
.frame[data-lined] {
  display: block;
  white-space: normal;
}

.frame[data-lined] .line {
  display: block;
  white-space: pre;
}

/* Highlight emphasized lines */
.line[data-hl] {
  background-color: rgba(255, 255, 0, 0.1);
  border-left: 2px solid #ffd700;
  padding-left: 8px;
}

/* Strong emphasis for critical lines (descriptions ending with !) */
.line[data-hl='strong'] {
  background-color: rgba(255, 100, 100, 0.15);
  border-left: 3px solid #ff4444;
}

/* Single-line emphasis - rounded on all corners */
.line[data-hl-position='single'] {
  border-radius: 4px;
}

/* Multiline block start - rounded top corners */
.line[data-hl-position='start'] {
  border-top-left-radius: 4px;
  border-top-right-radius: 4px;
}

/* Multiline block end - rounded bottom corners */
.line[data-hl-position='end'] {
  border-bottom-left-radius: 4px;
  border-bottom-right-radius: 4px;
}

/* Dark mode variant */
@media (prefers-color-scheme: dark) {
  .line[data-hl] {
    background-color: rgba(255, 255, 0, 0.05);
    border-left-color: #b8860b;
  }

  .line[data-hl='strong'] {
    background-color: rgba(255, 100, 100, 0.1);
    border-left-color: #cc3333;
  }
}

Showing Descriptions

You can display the description using CSS ::before:

/* Show description as tooltip */
.line[data-hl-description]::before {
  content: attr(data-hl-description);
  position: absolute;
  /* ... tooltip styles */
}

Best Practices

Be Specific

Use single-line emphasis for specific statements:

// ✓ Good - highlights the important line
const result = await fetchData();

// ✗ Avoid - too vague
function processData() {
  const result = await fetchData();
  return result;
}

Use Descriptions

Add context when the emphasis isn't obvious:

// ✓ Good - explains what to notice
<div className="container"> {/* @highlight "We add the container class" */}

// ✗ Less helpful - just marks the line
<div className="container"> {/* @highlight */}

Use multi-line emphasis for logical code blocks:

// ✓ Good - emphasizes the complete pattern
// @highlight-start "We handle the form submission"
<form onSubmit={handleSubmit}>
  <input type="text" value={name} onChange={handleChange} />
  <button type="submit">Submit</button>
</form>
// @highlight-end

Match Comment Style

Use the appropriate comment style for your language:

// JSX/TSX - use {/* */} for inline, // for block
<div>{/* @highlight */}</div>
// @highlight-start

// JavaScript/TypeScript - use //
const x = 42; // @highlight

// CSS - use /* */
.button {
  color: blue; /* @highlight */
}

Troubleshooting

Lines Not Being Emphasized

Check that:

Comments are being extracted with notableCommentsPrefix: ['@highlight']
The comment syntax exactly matches the expected patterns
Multi-line pairs have matching start/end markers
Line numbers in the HAST tree match your source

Unmatched Multi-line Pairs

If you have unmatched @highlight-start or @highlight-end:

Extra @highlight-end → ignored (no effect)
Extra @highlight-start → ignored (no matching end)

Check your code for balanced pairs.

Wrong Lines Emphasized

Verify that:

Comments are on the correct lines in your source
Line numbers in HAST tree match (check dataLn properties)
Comment extraction isn't removing the comments from the source

Types

Default source enhancer that adds emphasis to code lines based on @highlight comments. Uses no padding frames by default. Use createEnhanceCodeEmphasis for configurable padding.

Parameter	Type	Description
root	`HastRoot`
comments	`SourceComments \| undefined`
fileName	`string`

Return Type

HastRoot | Promise<HastRoot>

EMPHASIS_COMMENT_PREFIX

The prefix used to identify emphasis comments in source code. Comments starting with this prefix will be processed for emphasis.

type EMPHASIS_COMMENT_PREFIX = '@highlight'

EmphasisMeta

Metadata for an emphasized line.

type EmphasisMeta = {
  /** Optional description for this emphasis */
  description?: string;
  /** Position: 'single' for single-line, 'start'/'end' for multiline range bounds, undefined for middle */
  position?: 'single' | 'start' | 'end';
  /** Whether this is a strong emphasis (description ended with !) */
  strong?: boolean;
  /** For text highlighting: the specific text to highlight within the line */
  highlightText?: string;
  /** Whether this line's region is the focused region (for padding) */
  focus?: boolean;
}

EnhanceCodeEmphasisOptions

Options for the enhance code emphasis factory.

type EnhanceCodeEmphasisOptions = {
  /**
   * Maximum number of padding lines above and below the focused highlight region.
   * Padding frames provide surrounding context for the highlighted code.
   * Set to 0 or omit to disable padding frames.
   */
  paddingFrameMaxSize?: number;
  /**
   * Maximum total number of lines in the focus area (padding-top + highlighted + padding-bottom).
   * When set, padding sizes are reduced so the total focus area fits within this limit.
   * The remainder after subtracting the highlighted size is split: floor(remainder/2) for
   * padding-top and ceil(remainder/2) for padding-bottom.
   */
  focusFramesMaxSize?: number;
}

FrameRange

A range of lines that forms a frame in the output.

type FrameRange = {
  /** First line number (1-based, inclusive) */
  startLine: number;
  /** Last line number (1-based, inclusive) */
  endLine: number;
  /** The type of frame */
  type:
    | 'normal'
    | 'padding-top'
    | 'highlighted'
    | 'highlighted-unfocused'
    | 'padding-bottom'
    | 'comment';
}

Parse Source - Syntax highlighting and HAST generation
HAST Utilities - Converting HAST to React JSX
Load Server Source - Loading source files with enhancers
Code Highlighter - Displaying code with emphasis

Enhance Code Emphasis

Features

Basic Usage

Comment Patterns

Single Line Emphasis

Single Line with Description

Strong Emphasis

Multi-line Emphasis

Multi-line with Description

Text Highlighting

Comment Syntax

Supported Formats

Description Format

Displaying Comments in Documentation

Advanced Patterns

Multiple Single Lines

Nested Multi-line Blocks

Mixed Single and Multi-line

Frame Reframing

How It Works

Frame Data Attributes

Configurable Padding

The @focus Directive

Styling Frame Types

Demo: Collapsible Code Block

Demo: @focus with Multiple Regions

Demo: Indent Shifting

Implementation Details

How It Works

HAST Structure

Data Attributes

Stack-Based Pairing

Configuration

Adding to Source Enhancers

Comment Prefix

Styling Emphasized Lines

Showing Descriptions

Best Practices

Be Specific

Use Descriptions

Group Related Lines

Match Comment Style

Troubleshooting

Lines Not Being Emphasized

Unmatched Multi-line Pairs

Wrong Lines Emphasized

Types

Related

The `@focus` Directive