6.10 Extensions

6.10.1 Color Text

Create a filter to apply blue text color to fenced div.

Created a minimal local color-text filter:
- Added _quiz/_extensions/color-text/color-text.lua
- It supports the .blue class for both blocks and inline spans:
  - HTML: adds style="color: blue;"
  - PDF: wraps with LaTeX xcolor; automatically injects \usepackage{xcolor}
Updated the qmd file YAML to reference this local filter:
- filters:
  - _extensions/color-text/color-text.lua
You can use fenced divs and inline spans with .blue.

Use example

In the yaml header of your qmd file, add the following line to reference the local filter:

---
title: "Quiz: Linear Regression and Hypothesis Testing (p2)"
from: markdown+tex_math_single_backslash
params:
  # solution: false
  solution: true
filters:
  - _extensions/color-text/color-text.lua
format:
  pdf:
    include-in-header: ../latex/preamble.tex
    fontsize: 12pt
---

Use the .blue class in your markdown content:

::: {.content-visible when-meta="params.solution"}
::: {.blue}
**Solutions**
(a) The 95% confidence interval for $\beta_1$ is given by
  $$
  \hat{\beta}_1 \pm t_{0.975, n-2} \cdot SE(\hat{\beta}_1)
  $$
  Degrees of freedom: $df = n-2 = 50-2 = 48$
(b)
:::
:::

Highlight-text Quarto Extension

6.10.2 Emoji

HTML output has built-in support for emojis. You can simply insert emojis like 😀, the output will render it for you accordingly.

emoji extension supports text representations of emojis. E.g., :grinning: will be rendered as 😀 in the output.

In the yaml, add the emoji extension to the from option in document metadata.

---
title: "My Document"
from: markdown+emoji
---

For markdown formats that support text representations of emojis 😁 (e.g. :grinning:), the text version will be written. For other formats the literal emoji character will be written.

Currently, the gfm and hugo (with enableEmoji = true in the site config) formats both support text representation of emojis.

Usage: When you type :smile:, it will be rendered as 😄 in the output.

Note: This does NOT work for quarto pdf. Unsupported unicode/emoji characters will be rendered as empty boxes in pdf output.

Fix: For pdf outputs, use the twemoji or newunicodechar approach instead. See below.

twemoji for emojis
newunicodechar for unicdoe characters

twemoji

Four steps to add more emojis in the future:

Open twemoji_manifest.json and append new code points to the emoji object
- Example: "1f44d": ["👍", ":thumbsup:"]
Use the following cmd to find the code points of an emoji; replace the emoji, ‘⚠️’, in the command with the one you want to add.
```
node -e 'const s=process.argv[1]; const codes=[...s].map(ch=>ch.codePointAt(0).toString(16)); console.log(codes.join("-"))' '⚠️'
# Prints: 26a0-fe0f  → Twemoji file: assets/72x72/26a0-fe0f.png (often 26a0.png also exists)
```

Run the fetcher again:

fetch_twemoji.sh

Within the project directory:

$./emoji/fetch_twemoji.sh

From anywhere:

$'/Users/menghan/Documents/language/norsk/norskprøver/B2/exam notes/emoji/fetch_twemoji.sh'
Exists: 1f4a1.png
Exists: 1f4c8.png
Exists: 1f4dd.png
Exists: 1f539.png
Exists: 1f600.png
Exists: 1f604.png
Exists: 1f680.png
Exists: 26a0.png
Downloading: 2705.png
Done. Files saved in ~/Documents/language/norsk/norskprøver/B2/exam notes/emoji. Map to filter names as needed (already matching).

The script downloads only missing PNGs. If you add more codes to twemoji_manifest.json, just run it again.

To refresh files, delete specific PNGs (or all) in emoji and rerun.

Add to unicode_map in emoji.lua to point to the same filename.
- Example: ["⚠️"] = "26a0.png",
This ensures when you use the emoji directly, it maps to the correct image file.
Optionally add a shortcode mapping in emoji.lua’s emoji_map to point to the same filename.
- Example: [":warning:"] = "26a0.png",
This allows you to use the shortcode :warning: in addition to the direct emoji.

🎯 Usage Examples

You can now use emojis in your QMD files in two ways:

Direct Unicode: Great job! 👍 This is amazing! 🎉
Shortcodes: Great job! :thumbsup: This is amazing! :tada:

newunicodechar

newunicodechar package allows you to define a mapping from a Unicode character to a LaTeX command.

Syntax: \newunicodechar{<char>}{<code>}

<char> is the Unicode character you want to display.
<code> is the LaTeX code that will be substituted to when <char> is encountered.

For math symbols, wrap it using \ensuremath{}.

\usepackage{newunicodechar}

% Manually define the missing characters
\newunicodechar{→}{\ensuremath{\rightarrow}}
\newunicodechar{∀}{\ensuremath{\forall}}

\begin{document}
Now these will work: ∀x (Fx → Gx)
\end{document}

Appearance improvement: Use “Apple Symbols” for symbol fonts. This font is most robust for symbol display, and with good looking. Declare the mapping for unsupported characters in the mainfont.

\newfontfamily\symbolfont{Apple Symbols}  % Works for Mac, but NOT for TeX Live distribution
% \newfontfamily\symbolfont{DejaVu Sans}  % DejaVu Sans also has good unicode support, distributed with TeX Live, no additional installation needed

\newunicodechar{→}{{\symbolfont →}}       % This looks better (shorter) than the math symbol \ensuremath{\rightarrow}
\newunicodechar{♂}{{\symbolfont ♂}}
\newunicodechar{♀}{{\symbolfont ♀}}
\newunicodechar{♪}{{\symbolfont ♪}}
\newunicodechar{⬢}{{\symbolfont ⬢}}

The easiest way is to use a mainfont that has good unicode support, such as “DejaVu”. It has a wide range of unicode characters, including emojis and math symbols. This avoids the need to manually define mappings for each character.

Note: Note DejaVu Sans Mono does NOT support CJK characters, so if you have Chinese characters in your document, they will fall back to the default font, or be rendered as empty boxes.

% Select fonts that actually contain your symbols
\setmainfont{DejaVu Serif}
\setsansfont{DejaVu Sans}
\setmonofont{DejaVu Sans Mono}

\begin{document}

Serif preview: The quick brown fox jumps over the lazy dog.

\textsf{Sans-Serif preview: The quick brown fox jumps over the lazy dog.}

Residual income: 
$$ 
\begin{aligned}
RI_t &= NI - EC \\
&= NI - r \cdot BV_{t-1} \\
&= (ROE - r) \cdot BV_{t-1} 
\end{aligned}
$$

Monospace preview: 

```markdown
DejaVu Sans Mono
---------------中英文2:1---------------
|ab|cd|ef|gh|ij|kl|mn|op|qr|st|uv|wx|yz|
|这|应|该|是|中|英|文|完|美|的|2:|1等距|
|A0|1!|2@|3#|4$|5%|6^|7&|8*|9(|0)|=+|[]|
```
\end{document}

will show like this:

To fix CJK characters, use Maple Mono NF CN for CJK monofont.

\setmainfont{DejaVu Serif}
\setsansfont{DejaVu Sans}
\setmonofont{DejaVu Sans Mono}

% For CJK characters, use xeCJK package and set a CJK monospaced font
\usepackage{xeCJK}
\setCJKmonofont{Maple Mono NF CN}

will show like this:

Georgia Pro

ref: