Writer

A unified writing suite for the Precursor device with three modes: Markdown Editor, Journal, and Typewriter.

Features

Markdown Editor

A multi-document text editor with line-level markdown styling and preview mode.

• Multi-document management — create, open, delete documents
• Line-level syntax styling in edit mode:
  • Headings → Large/Bold GlyphStyle
  • Code blocks → Monospace GlyphStyle
  • Block quotes → indented with left bar
  • Lists → bullet/number prefix preserved
  • Horizontal rules → drawn line
• Preview mode — rendered markdown with stripped prefixes
• Word/character count in status bar
• Export — TCP push (port 7879) or USB keyboard autotype
• Auto-save on exit and focus loss

Controls (Edit Mode):

Key	Action
Printable chars	Insert at cursor
Enter	New line
Backspace	Delete backward
Arrows	Move cursor
Home	Start of line
Esc then p	Toggle preview
Esc then s	Save document
Esc then e	Export menu
Esc then f	File menu
Esc then q	Back to doc list

Controls (Document List):

Key	Action
Enter	Open selected
n	New document
d	Delete selected
Up/Down	Navigate
q	Back to mode select

Journal

One entry per day, automatically keyed by date with date navigation.

• Auto-creates today's entry on open
• Date navigation — previous/next day via Esc+[ / Esc+]
• Auto-saves on date change or exit
• Search across all entries (substring match)
• Word count displayed in status bar
• Date sourced from device RTC via llio::LocalTime

Controls:

Key	Action
Printable/Enter/Backspace/Arrows	Edit entry
Esc then [	Previous day
Esc then ]	Next day
Esc then t	Jump to today
Esc then /	Search entries
Esc then s	Save current entry
Esc then q	Save and back to mode select

Typewriter Mode

Full-screen forward-only text entry for free-writing and first drafts.

• No backspace/delete — once typed, it stays
• No cursor movement — always appends at end
• Session-based — starts fresh each time
• Live word counter in status bar
• Session summary on exit (words, characters, lines)
• Save option — transfer session to editor documents

Controls:

Key	Action
Printable chars	Append at end
Enter	New line
Esc then d	Done (show summary)

Summary Screen:

Key	Action
s	Save as document
q	Discard session

Export

Export documents via network or USB keyboard.

Method	Description
TCP (port 7879)	Device listens, retrieve with nc <ip> 7879 > doc.md
USB Keyboard Autotype	Types document character-by-character on connected computer

Installation

Clone into your xous-core apps directory:

cd xous-core/apps
git clone https://github.com/tbcolby/precursor-writer.git writer

Register the app in your workspace. Add to xous-core/Cargo.toml members:

"apps/writer",
"apps/writer/writer-core",

Register in apps/manifest.json:

"writer": {
    "context_name": "Writer",
    "menu_name": {
        "appmenu.writer": {
            "en": "Writer",
            "en-tts": "Writer"
        }
    }
}

Build and run:

cargo xtask renode-image writer

Architecture

writer-core/            Pure text logic (no Xous deps, host-testable)
src/
  main.rs               Event loop, state machine, key dispatch
  editor.rs             Markdown editor state
  journal.rs            Journal mode (date-keyed entries)
  typewriter.rs         Typewriter mode (append-only)
  render.rs             Drawing: line-by-line with GlyphStyle
  storage.rs            PDDB operations (docs, journal)
  export.rs             TCP push + USB keyboard autotype
  ui.rs                 Shared UI utilities

writer-core Library

The writer-core crate provides platform-independent text editing logic, testable on the host:

• TextBuffer struct: cursor, viewport scrolling, insert/delete/move operations
• LineKind markdown classifier: headings, code blocks, quotes, lists, rules
• strip_prefix for preview mode rendering
• Date utilities: epoch ms ↔ YYYY-MM-DD, prev/next day navigation
• Binary serialization for PDDB document storage

Run tests: cargo test -p writer-core

Key Design Decisions

1. Line-level styling — One GlyphStyle per TextView. Whole-line classification avoids pixel-level text splitting.

2. Esc-prefix commands — All printable characters go to the buffer. Esc followed by one letter triggers commands (similar to vim leader key).

3. Separate PDDB dictionaries — writer.docs and writer.journal keep concerns isolated.

4. Forward-only typewriter — Cursor always at end, no editing. Forces free-writing flow.

5. TCP export — Simpler than USB mass storage. Proven pattern from other Precursor apps.

PDDB Storage

All persistent data stored in two dictionaries:

Dictionary	Key Pattern	Format
writer.docs	doc_{name}	Binary: [u16 title_len][title_utf8][content_utf8]
writer.docs	_index	Binary: [u32 count][u16 name_len][name_utf8]...
writer.journal	YYYY-MM-DD	Raw UTF-8 text (entry content)
writer.journal	_index	Newline-separated list of dates

Testing

# Run writer-core unit tests on host (40 tests)
cargo test -p writer-core

# Build for Renode emulation
cargo xtask renode-image writer

Development

This app was developed using the methodology described in xous-dev-toolkit — an LLM-assisted approach to Precursor app development on macOS ARM64.

Author

Made by Tyler Colby — Colby's Data Movers, LLC

Contact: tyler@colbysdatamovers.com | GitHub Issues

License

Licensed under the Apache License, Version 2.0.