✓ Stable v2.0

📄 facsimile

Terminal text editor written in modern Fortran with LSP integration

A sophisticated text editor built entirely in Fortran 2003+, demonstrating that Fortran can handle modern application development. Features VSCode-style keybindings, gap buffer text storage, multi-pane editing, full LSP support, and a git-aware file tree. No external UI dependencies - pure ANSI escape sequences for rendering.

View on GitHub Download RPM

🎯 RPM Available 🏛️ AUR Available

Features

✓
Pure Fortran
57 source files, minimal C (termios only)
✓
Gap Buffer
O(1) insertions at cursor position
✓
Full LSP Support
Completion, diagnostics, go-to-definition, rename
✓
Multi-Pane Editing
Horizontal and vertical splits with independent viewports
✓
Multi-Cursor
Select next match, add cursors above/below
✓
Git-Aware File Tree
Stage/unstage files, status indicators
✓
Workspace Persistence
Restores tabs, panes, cursors across sessions
✓
VSCode Keybindings
Familiar shortcuts for modern developers

Installation

RPM (Fedora/RHEL/CentOS)

terminal

$sudo dnf config-manager --add-repo https://repos.musicsian.com/musicsian.repo

$sudo dnf install facsimile

AUR (Arch Linux)

terminal

$yay -S facsimile

Homebrew (macOS)

terminal

$brew tap FortranGoingOnForty/fortran

$brew install facsimile

Build from Source

terminal

$git clone https://github.com/FortranGoingOnForty/facsimile.git

$cd facsimile

$make

$sudo make install

Build Dependencies: gfortran (or flang-new)

Binary name: fac

Quick Start

Open a File

terminal

$fac main.f90

Open a Directory (Workspace Mode)

terminal

$fac ~/projects/myapp

Opens the directory as a workspace with persistent state. Press Ctrl+B to toggle the file tree.

Launch with Fortress Navigator

terminal

$fac

Fortress - Workspace Navigator ────────────────────────────── Recent Workspaces: 1. ~/projects/myapp 2. ~/src/facsimile 3. ~/documents/notes Favorites: * ~/projects/myapp (pinned) [j/k] Navigate [Enter] Open [f] Toggle favorite [q] Quit

Essential Keybindings

Action	Keybinding
Save	Ctrl+S
Open file browser	Ctrl+O
Toggle file tree	Ctrl+B
Search/Replace	Ctrl+F
Go to line	Ctrl+G
Command palette	Ctrl+P
Show help	Ctrl+/
Quit	Ctrl+Q

LSP Setup

facsimile automatically detects and connects to language servers. Install the appropriate server for your language:

Language	Server
Python	pip install python-lsp-server
Rust	rustup component add rust-analyzer
JavaScript/TypeScript	npm i -g typescript-language-server
Go	go install golang.org/x/tools/gopls@latest
Fortran	pip install fortls

Configuration Overview

facsimile stores workspace state and user preferences in standard locations:

Directory Structure

~/.config/fac/
├── favorites.json        # Pinned workspaces
└── recents.json          # Recently opened workspaces

<workspace>/.fac/
├── workspace.json        # Workspace state (tabs, panes, cursors)
└── backups/              # Auto-backup storage
    └── filename.backup   # Backup files with metadata

Workspace State

Each workspace stores its complete editor state in .fac/workspace.json:

{
  "version": "1.0",
  "workspace_path": "/home/user/project",
  "last_opened": "2025-01-05T10:30:00Z",
  "tabs": [
    {
      "filename": "src/main.f90",
      "panes": [
        {
          "filename": "src/main.f90",
          "cursor": {"line": 42, "col": 10},
          "viewport": {"line": 30, "col": 1}
        }
      ],
      "active_pane": 0
    }
  ],
  "active_tab": 0
}

Favorites & Recents

The Fortress navigator tracks your workspaces:

favorites.json

{
  "favorites": [
    {"path": "/home/user/projects/myapp", "name": "My App"},
    {"path": "/home/user/src/facsimile", "name": "facsimile"}
  ]
}

recents.json

{
  "recents": [
    {"path": "/home/user/projects/myapp", "count": 15, "last_opened": "2025-01-05T10:30:00Z"},
    {"path": "/home/user/documents/notes", "count": 8, "last_opened": "2025-01-04T15:00:00Z"}
  ]
}

Backup System

When quitting with unsaved changes and choosing "don't save", facsimile creates backups in .fac/backups/:

Backup files preserve the original content
Metadata file tracks backup info and timestamps
On next open, prompts to restore, ignore, or diff
Keeps only the most recent backup per file

LSP Configuration

facsimile uses standard language server configurations. Configure servers through their own config files:

Language	Config Location
Python (pylsp)	~/.config/pylsp/config.json
Rust	rustfmt.toml in project
JavaScript/TypeScript	.prettierrc, tsconfig.json
Fortran	.fortls in project

Overview

facsimile (binary: fac) is a terminal text editor written entirely in modern Fortran. It demonstrates that Fortran can handle sophisticated application development beyond numerical computing.

Key design principles:

Pure implementation - Minimal external dependencies (C termios only)
Gap buffer - Efficient text storage with O(1) cursor insertions
VSCode keybindings - Familiar shortcuts for modern developers
Full LSP - Code intelligence through Language Server Protocol
Workspace mode - Persistent state across sessions

System Overview

facsimile is written in modern Fortran (2003+) with minimal C bindings. The codebase consists of 57 Fortran source files organized into modules.

Module Organization

Module	Responsibility
editor_state_module	Central state: tabs, panes, cursors, LSP
text_buffer_module	Gap buffer text storage
command_handler_module	Keybinding to action mapping (~7000 lines)
input_handler_module	Raw terminal input parsing
renderer_module	ANSI escape sequence rendering
lsp_server_manager_module	Language server lifecycle
json_module	Custom JSON parser (no deps)

Gap Buffer

Data Structure

facsimile uses a gap buffer for text storage, providing O(1) insertions at the cursor position:

type :: buffer_t
    character(len=:), allocatable :: data    ! Text content
    integer :: gap_start                      ! Position of gap
    integer :: gap_end                        ! End of gap
    integer :: size                           ! Total allocated
    logical :: modified                       ! Unsaved changes
end type

The gap is a reserved space in the buffer that moves with the cursor. Insertions at the cursor simply fill the gap - no data movement required.

Operations

Insert at cursor - O(1), fills gap
Delete at cursor - O(1), expands gap
Move cursor - O(distance), shifts gap
Buffer growth - O(n), 2x expansion when full

UTF-8 Handling

All cursor positions use CHARACTER indices (not byte positions) for correct handling of multi-byte UTF-8 sequences:

! utf8_module provides conversions:
function utf8_char_count(str)           ! Count characters in string
function buffer_byte_to_char_col(...)   ! Byte position -> character position
function buffer_char_to_byte_col(...)   ! Character position -> byte position

This ensures correct cursor placement with emoji, accented characters, and other multi-byte sequences.

LSP Client

facsimile implements a full LSP client with JSON-RPC communication:

facsimile Editor
    ↓ (JSON-RPC over stdio)
Language Server (e.g., pylsp, rust-analyzer)
    ↓
Code analysis, completions, diagnostics

The editor includes a custom JSON parser written in Fortran - no external JSON library dependencies.

Multi-server support: Each tab can connect to multiple language servers (e.g., Python type checker + linter).

Navigation

Option	Type	Default	Description
`Arrow Keys`	binding	-	Move cursor
`Home / Ctrl+A`	binding	-	Line start (smart toggle)
`End / Ctrl+E`	binding	-	Line end
`Ctrl+Home`	binding	-	File start
`Ctrl+End`	binding	-	File end
`Alt+Left / Alt+Right`	binding	-	Jump by word
`PageUp / PageDown`	binding	-	Page scroll
`Alt+[ / Alt+]`	binding	-	Jump to matching bracket

Editing

Option	Type	Default	Description
`Backspace / Ctrl+H`	binding	-	Delete backward
`Delete`	binding	-	Delete forward
`Tab`	binding	-	Insert 4 spaces / indent selection
`Shift+Tab`	binding	-	Dedent selection/line
`Ctrl+K`	binding	-	Kill line forward (to yank stack)
`Ctrl+U`	binding	-	Kill line backward (to yank stack)
`Ctrl+W / Alt+Backspace`	binding	-	Delete word backward
`Alt+D / Alt+Delete`	binding	-	Delete word forward
`Ctrl+T`	binding	-	Transpose characters
`Ctrl+J`	binding	-	Join lines

Clipboard & Yank Stack

Option	Type	Default	Description
`Ctrl+X`	binding	-	Cut line/selection (to yank stack)
`Ctrl+C`	binding	-	Copy to clipboard
`Ctrl+V`	binding	-	Paste from clipboard
`Ctrl+Y`	binding	-	Yank from stack (cycle history)
`Ctrl+Shift+V`	binding	-	Cycle yank stack

Line Operations

Option	Type	Default	Description
`Alt+Up / Alt+Down`	binding	-	Move line up/down
`Alt+Shift+Up/Down`	binding	-	Duplicate line

Selection & Multi-Cursor

Option	Type	Default	Description
`Shift+Arrows`	binding	-	Character selection
`Shift+Alt+Left/Right`	binding	-	Word selection
`Shift+Ctrl+A/E`	binding	-	Select to line boundaries
`Shift+PageUp/Down`	binding	-	Page selection
`Ctrl+D`	binding	-	Select next match (multi-cursor)
`Alt+Click`	binding	-	Add/remove cursor at position
`Ctrl+Alt+Up/Down`	binding	-	Add cursor above/below
`Escape`	binding	-	Clear selection / exit multi-cursor

Search & Replace

Option	Type	Default	Description
`Ctrl+F`	binding	-	Unified search/replace prompt
`Ctrl+G`	binding	-	Go to line
`n / Ctrl+N`	binding	-	Next match (in search mode)
`N / Ctrl+P`	binding	-	Previous match (in search mode)
`r`	binding	-	Replace one (in search mode)
`a`	binding	-	Replace all (in search mode)
`Ctrl+R`	binding	-	Toggle regex (in search mode)
`Ctrl+C`	binding	-	Toggle case sensitivity (in search)
`Ctrl+W`	binding	-	Toggle whole-word (in search)

File Operations

Option	Type	Default	Description
`Ctrl+S`	binding	-	Save file
`Ctrl+O`	binding	-	Open file (Fortress navigator)
`Ctrl+N`	binding	-	New untitled buffer
`Ctrl+Q`	binding	-	Quit

Tab Management

Option	Type	Default	Description
`Ctrl+T`	binding	-	Create new tab
`Ctrl+PageDown / Ctrl+Alt+Right`	binding	-	Next tab
`Ctrl+PageUp / Ctrl+Alt+Left`	binding	-	Previous tab
`Alt+1 to Alt+9`	binding	-	Jump to specific tab
`Ctrl+W`	binding	-	Close current pane/tab

Pane Management

Option	Type	Default	Description
`Alt+V`	binding	-	Split vertically (right pane)
`Alt+S`	binding	-	Split horizontally (bottom pane)
`Alt+H / Ctrl+Shift+Left`	binding	-	Move to left pane
`Alt+L / Ctrl+Shift+Right`	binding	-	Move to right pane
`Alt+K / Ctrl+Shift+Up`	binding	-	Move to pane above
`Alt+J / Ctrl+Shift+Down`	binding	-	Move to pane below
`Alt+Q`	binding	-	Close current pane only

LSP Features

Option	Type	Default	Description
`F12 / Ctrl+\ / Alt+G`	binding	-	Go to Definition
`Shift+F12 / Alt+R`	binding	-	Find References
`F2`	binding	-	Rename Symbol
`F10 / Alt+.`	binding	-	Code Actions (quick fixes)
`F8 / Alt+E`	binding	-	Diagnostics Panel
`F4 / Alt+O`	binding	-	Document Symbols (outline)
`F6 / Alt+P`	binding	-	Workspace Symbols (search)
`Shift+Alt+F`	binding	-	Format Document
`Alt+,`	binding	-	Jump Back (navigation history)
`Ctrl+P`	binding	-	Command Palette

File Tree (Fuss Mode)

Option	Type	Default	Description
`j / Down`	binding	-	Move down in tree
`k / Up`	binding	-	Move up in tree
`Right`	binding	-	Enter directory
`Left`	binding	-	Exit to parent
`Enter / o`	binding	-	Open file in new tab
`.`	binding	-	Toggle dotfiles/gitignored
`a`	binding	-	Stage file (git add)
`u`	binding	-	Unstage file (git restore)
`Escape`	binding	-	Exit fuss mode

Miscellaneous

Option	Type	Default	Description
`Alt+'`	binding	-	Cycle quotes: " -> ' -> `
`Alt+Shift+'`	binding	-	Remove surrounding brackets/quotes
`Ctrl+Z`	binding	-	Undo
`Ctrl+] / Ctrl+Shift+Z`	binding	-	Redo
`Ctrl+L`	binding	-	Clear/redraw screen
`Ctrl+/ or Ctrl+?`	binding	-	Show help/keybindings
`Ctrl+B / F3`	binding	-	Toggle file tree (Fuss mode)

Common Issues

Alt key combinations not working

Terminal may intercept Alt keys for its own menus.

Solutions:

Configure terminal to pass Alt through
Use Escape as prefix (Escape+V for Alt+V)

LSP not working

Language server may not be installed or in PATH.

Solutions:

Verify server is installed: which pylsp
Check server is executable and in PATH
Look for error messages in status bar

Workspace not restoring

State may be corrupted or directory mismatch.

Solutions:

Open exact directory (not subdirectory)
Check .fac/workspace.json exists
Remove corrupted file to start fresh

Display corruption

Terminal rendering issues.

Solutions:

Press Ctrl+L to redraw
Resize terminal window
Ensure terminal supports ANSI escape sequences

Getting Help

Press Ctrl+/ for keybinding help
Press Ctrl+P for command palette
Check GitHub Issues

📄 facsimile

Features

Installation

RPM (Fedora/RHEL/CentOS)

AUR (Arch Linux)

Homebrew (macOS)

Build from Source

Quick Start

Open a File

Open a Directory (Workspace Mode)

Launch with Fortress Navigator

Essential Keybindings

LSP Setup

Configuration Overview

Directory Structure

Workspace State

Favorites & Recents

favorites.json

recents.json

Backup System

LSP Configuration

Overview

Editing

Multi-Cursor

Selection

Yank Stack

Navigation

Cursor Movement

Search & Replace

Go to Line

Workspace

Tab Management

Pane Splitting

File Tree (Fuss Mode)

LSP Features

Auto-Completion

Diagnostics

Code Navigation

Syntax Highlighting

System Overview

Module Organization

Gap Buffer

Data Structure

Operations

UTF-8 Handling

Rendering System

LSP Client

Undo/Redo System

Workspace Persistence

Navigation

Editing

Clipboard & Yank Stack

Line Operations

Selection & Multi-Cursor

Search & Replace

File Operations

Tab Management

Pane Management

LSP Features

File Tree (Fuss Mode)

Miscellaneous

Common Issues

Alt key combinations not working

LSP not working

Workspace not restoring

Display corruption

Getting Help