Github の Markdown アラート記法を再現する CSS

GitHub の Markdown 拡張 - Alerts

GitHub のアラートは、ブロッククォート構文に基づいた Markdown 拡張で、以下のように書くことができる。

> [!NOTE]  
> Highlights information that users should take into account, even when skimming.

> [!TIP]
> Optional information to help a user be more successful.

> [!IMPORTANT]  
> Crucial information necessary for users to succeed.

> [!WARNING]  
> Critical content demanding immediate user attention due to potential risks.

> [!CAUTION]
> Negative potential consequences of an action.

以下のようにレンダリングされる。

Alerts 表示する CSS

以下のような HTML に、

<blockquote class="markdown-alert-note">
<p>Useful information that users should know, even when skimming content.</p>
</blockquote>

以下のような CSS 当てれば、

blockquote {
  margin: 0;
  margin-bottom: 1rem;
  padding: 1px 1rem 1px 1rem;
  border-left: .25rem solid #e5e5e5;
}

blockquote p::before {
  font-weight: bold;
  white-space: pre;
  padding-left: 2rem;
  background-repeat: no-repeat;
}

blockquote.markdown-alert-note {
  border-left: .25em solid #0969da;
}
blockquote.markdown-alert-note p::before {
  content: 'Note\a\a';
  color: #0969da;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='%230969da' viewBox='0 0 16 16'%3E %3Cpath d='M0 8a8 8 0 1 1 16 0A8 8 0 0 1 0 8Zm8-6.5a6.5 6.5 0 1 0 0 13 6.5 6.5 0 0 0 0-13ZM6.5 7.75A.75.75 0 0 1 7.25 7h1a.75.75 0 0 1 .75.75v2.75h.25a.75.75 0 0 1 0 1.5h-2a.75.75 0 0 1 0-1.5h.25v-2h-.25a.75.75 0 0 1-.75-.75ZM8 6a1 1 0 1 1 0-2 1 1 0 0 1 0 2Z'/%3E %3C/svg%3E");
}

以下のように表示できる。

その他も追加すれば、

blockquote.markdown-alert-tip {
  border-left: .25em solid #1a7f37;
}
blockquote.markdown-alert-tip p::before {
  content: 'Tip\a\a';
  color: #1a7f37;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='%231a7f37' viewBox='0 0 16 16'%3E %3Cpath d='M8 1.5c-2.363 0-4 1.69-4 3.75 0 .984.424 1.625.984 2.304l.214.253c.223.264.47.556.673.848.284.411.537.896.621 1.49a.75.75 0 0 1-1.484.211c-.04-.282-.163-.547-.37-.847a8.456 8.456 0 0 0-.542-.68c-.084-.1-.173-.205-.268-.32C3.201 7.75 2.5 6.766 2.5 5.25 2.5 2.31 4.863 0 8 0s5.5 2.31 5.5 5.25c0 1.516-.701 2.5-1.328 3.259-.095.115-.184.22-.268.319-.207.245-.383.453-.541.681-.208.3-.33.565-.37.847a.751.751 0 0 1-1.485-.212c.084-.593.337-1.078.621-1.489.203-.292.45-.584.673-.848.075-.088.147-.173.213-.253.561-.679.985-1.32.985-2.304 0-2.06-1.637-3.75-4-3.75ZM5.75 12h4.5a.75.75 0 0 1 0 1.5h-4.5a.75.75 0 0 1 0-1.5ZM6 15.25a.75.75 0 0 1 .75-.75h2.5a.75.75 0 0 1 0 1.5h-2.5a.75.75 0 0 1-.75-.75Z'/%3E %3C/svg%3E");
}

blockquote.markdown-alert-important {
  border-left: .25em solid #8250df;
}
blockquote.markdown-alert-important p::before {
  content: 'Important\a\a';
  color: #8250df;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='%238250df' viewBox='0 0 16 16'%3E %3Cpath d='M0 1.75C0 .784.784 0 1.75 0h12.5C15.216 0 16 .784 16 1.75v9.5A1.75 1.75 0 0 1 14.25 13H8.06l-2.573 2.573A1.458 1.458 0 0 1 3 14.543V13H1.75A1.75 1.75 0 0 1 0 11.25Zm1.75-.25a.25.25 0 0 0-.25.25v9.5c0 .138.112.25.25.25h2a.75.75 0 0 1 .75.75v2.19l2.72-2.72a.749.749 0 0 1 .53-.22h6.5a.25.25 0 0 0 .25-.25v-9.5a.25.25 0 0 0-.25-.25Zm7 2.25v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 9a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z'/%3E %3C/svg%3E");
}

blockquote.markdown-alert-warning {
  border-left: .25em solid #9a6700;
}
blockquote.markdown-alert-warning p::before {
  content: 'Warning\a\a';
  color: #9a6700;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='%239a6700' viewBox='0 0 16 16'%3E %3Cpath d='M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z'/%3E %3C/svg%3E");
}

blockquote.markdown-alert-caution {
  border-left: .25em solid #cf222e;
}
blockquote.markdown-alert-caution p::before {
  content: 'Caution\a\a';
  color: #cf222e;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='%23cf222e' viewBox='0 0 16 16'%3E %3Cpath d='M6.457 1.047c.659-1.234 2.427-1.234 3.086 0l6.082 11.378A1.75 1.75 0 0 1 14.082 15H1.918a1.75 1.75 0 0 1-1.543-2.575Zm1.763.707a.25.25 0 0 0-.44 0L1.698 13.132a.25.25 0 0 0 .22.368h12.164a.25.25 0 0 0 .22-.368Zm.53 3.996v2.5a.75.75 0 0 1-1.5 0v-2.5a.75.75 0 0 1 1.5 0ZM9 11a1 1 0 1 1-2 0 1 1 0 0 1 2 0Z'/%3E %3C/svg%3E");
}

以下のような HTML で、

<blockquote>
<p>Simple blockquote content.</p>
</blockquote>

<blockquote class="markdown-alert-note">
<p>Useful information that users should know, even when skimming content.</p>
</blockquote>

<blockquote class="markdown-alert-tip">
<p>Helpful advice for doing things better or more easily.</p>
</blockquote>

<blockquote class="markdown-alert-important">
<p>Key information users need to know to achieve their goal.</p>
</blockquote>

<blockquote class="markdown-alert-warning">
<p>Urgent info that needs immediate user attention to avoid problems.</p>
</blockquote>

<blockquote class="markdown-alert-caution">
<p>Advises about risks or negative outcomes of certain actions.</p>
</blockquote>

以下のように表示できる。

おしまい。