Highlight Bad Unicode Characters

[notpeter]

Check for existing issues

• [X] Completed

Describe the feature

Working with a document that had some invisible U+200D zero-width joiner characters which resulted in some odd rendering bugs.

Zed should highlight these and optionally potentially other classes of "bad" characters:

• U+200B (Zero Width Space), U+200C Zero Width Non-joiner, U+200D (Zero Width Joiner)
• Bidirectional text control characters (U+200E, U+200F)
• Control characters (U+0000 to U+001F, U+007F to U+009F)
• Combining characters (U+20E3, U+20DD)

Additionally it might be helpful to optionally support highlighting "maybe bad" characters:

• Smart quotes (left/right of single/double)
• Emdash / Endash – —
• Elipses: … (U+2026)
• Unicode Ligatures, etc

Vscode: Zed:

VSCode includes a bunch of settings which help control this behavior `editor.unicodeHighlight.* as inspirations for how to control this behavior.

If applicable, add mockups / screenshots to help present your vision of the feature