DOS Text Editor

中文 | English

A character-mode text editor inspired by MS-DOS Edit, written in C17 with zero third-party dependencies. Runs on Windows CMD, Linux terminals, and FreeDOS.

Features

• Pure C17, zero third-party dependencies
• Windows Console API / POSIX termios / DOS BIOS platform backends
• Double-buffered rendering (minimal flicker, dirty-region diff)
• Char-wrap and horizontal-scroll display modes
• Visual vertical scrollbar (rightmost column) with click and drag
• Visual horizontal scrollbar (bottom row, horizontal-scroll mode only) with click and drag
• Multi-level undo / redo
• Find and replace (case-sensitive or insensitive)
• Full mouse support: click, double-click (word), triple-click (line), drag, wheel, right-click menu
• Menu bar (Alt+letter or mouse click to open; dropdown items clickable by mouse)
• Right-click context menu: Cut / Copy / Paste / Select All / Find Selected
• Line number display (toggle via View menu)
• Internal clipboard (cross-platform, no OS clipboard dependency)
• UTF-8 multi-byte editing — CJK and other Unicode characters, codepoint-aware cursor movement, wide-character (2-column) display
• GBK / UTF-8 auto-detection — files are detected as UTF-8 or GBK on open, converted internally to UTF-8, and written back in the original encoding on save
• Tab expansion — \t is expanded to spaces aligned at configurable tab stops (display only; stored as literal \t)
• Syntax highlighting — rule-based colorization driven by external INI files; ships with C/C++, Python, Markdown, JavaScript, HTML, CSS, JSON, Batch; fully customizable without recompiling
• Manual language switch — View > Set Language... opens a scrollable list to choose syntax highlighting for the current file (or disable it)
• TUI file/directory browser — Open and Save show a full directory browser dialog; navigate with keyboard, mouse, scroll wheel, and double-click; press /, \, ~, Ctrl+G or click the path bar to jump directly to any path
• Configurable extension→syntax mapping — add syntax_ext_<ext>=<ini> entries in config.ini to map any file extension to any syntax INI, no recompile needed
• Default filename — status bar shows Untitle when no file is open

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Code Stats

Category	Files	Lines
C source (src/, tests/)	31	~7,500
Headers (include/, src/platform/)	17	~1,050
Syntax rules (INI)	8	~440
Total	56	~9,000

Excludes cmake-build/. ~303 automated unit tests.

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Build (CMake)

Requirements

• CMake 3.16+
• Visual Studio 2026 Enterprise (Windows) or GCC/Clang (Linux/macOS)

Windows — quick build

cmake_build.bat          # configure + build (Release)
cmake_build.bat test     # build + run all ~303 unit tests
cmake_build.bat clean    # remove cmake-build/
cmake_build.bat rebuild  # clean + rebuild

Output: cmake-build\bin\Release\edit.exe

Manual CMake — Windows (Visual Studio 2026 not auto-detected)

cmake -S . -B cmake-build -G "Visual Studio 18 2026" -A x64 ^
      -DCMAKE_GENERATOR_INSTANCE="C:\Program Files\Microsoft Visual Studio\18\Enterprise"
cmake --build cmake-build --config Release
cmake --build cmake-build --config Release --target test_runner
cmake-build\bin\Release\test_runner.exe

Manual CMake — cross-platform

cmake -S . -B cmake-build
cmake --build cmake-build --config Release
cmake --build cmake-build --config Release --target test_runner
cmake-build/bin/Release/test_runner

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Usage

cmake-build\bin\Release\edit.exe [filename]

If filename does not exist, a new file is created with that name on first save.

When opening a file with a recognized extension (.c, .cpp, .h, .py, .md, etc.) the editor automatically applies syntax highlighting. Highlighting rules are loaded from the syntax/ folder next to the executable — copy or edit the INI files to customize colors.

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Keyboard Shortcuts

Action	Shortcut
New	Ctrl+N
Open	Ctrl+O
Save	Ctrl+S or F2
Save As	Ctrl+Shift+S
Exit	Alt+X
Undo	Ctrl+Z
Redo	Ctrl+Y
Cut	Ctrl+X
Copy	Ctrl+C
Paste	Ctrl+V
Select All	Ctrl+A
Find	Ctrl+F
Find Next	F3
Find Prev	Shift+F3
Replace	Ctrl+H
Toggle Wrap / HScroll	Ctrl+W
Horizontal scroll (HScroll mode)	Ctrl+← / Ctrl+→
Toggle Insert / Overwrite	Insert
Help	F1

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Mouse Operations

Gesture	Effect
Left-click	Move cursor to position
Double-click	Select word under cursor
Triple-click	Select entire line
Left-drag	Extend selection; auto-scrolls when dragged to top/bottom edge
Mouse wheel	Scroll viewport (cursor stays in place), 3 lines per tick
Right-click	Open context menu: Cut / Copy / Paste / Select All / Find Selected
Click menu bar item	Open dropdown
Click dropdown item	Execute command
Click vertical scrollbar track	Page up / page down
Drag vertical scrollbar thumb	Scroll to any position
Click horizontal scrollbar track	Pan left / right by half-page (HScroll mode only)
Drag horizontal scrollbar thumb	Pan to any horizontal position (HScroll mode only)

Screen layout

┌─ Menu bar ──────────────────────────────────────────┐  row 0
│ File(F)  Edit(E)  Search(S)  View(V)  Help(H)        │
├─ Edit area ──────────────────────────────────── │v│  │  rows 1…N-2
│ (file content, line numbers optional)           │e│  │
│                                                 │r│  │
│                                                 │t│  │
├─ H-scrollbar (WRAP_NONE mode only) ─────────────┤ ├──│  row N-2
│ [======#####=================================]  │+│  │
├─ Status bar ────────────────────────────────────┴─┤  │  row N-1
│  filename  Ln:1 Col:1 / 42 lines  INS  NWRP        │
└──────────────────────────────────────────────────┘

• Vertical scrollbar (rightmost column): | = track, # = thumb. Always visible.
• Horizontal scrollbar (second-to-last row, WRAP_NONE only): = = track, # = thumb. The + corner cell connects both scrollbars.

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Project Structure

TextEditor/
├── src/
│   ├── main.c            # event loop, keyboard & mouse dispatch, entry point
│   ├── editor.c          # cursor, selection, text editing, scroll, syntax ctx
│   ├── document.c        # line array, undo/redo, encoding fields
│   ├── display.c         # double-buffered Unicode cell screen layer
│   ├── viewport.c        # layout, tab-aware coord mapping, scrollbar, syntax render
│   ├── input.c           # normalized input events (keyboard + mouse + wheel)
│   ├── menu.c            # menu bar rendering, dropdown navigation, commands
│   ├── dialog.c          # modal dialogs: input, confirm, find, replace, help,
│   │                     #   right-click context menu
│   ├── search.c          # incremental find & replace (forward / backward)
│   ├── clipboard.c       # internal clipboard (platform-independent)
│   ├── config.c          # INI config file parser (config.ini)
│   ├── util.c            # memory, string, and path utilities
│   ├── utf8.c            # UTF-8 decode/encode, width calc, codepoint cursor move
│   ├── encoding.c        # GBK/UTF-8 auto-detection and conversion (Windows API)
│   ├── regex_simple.c    # lightweight NFA regex: . * + ? [] \d\w\s ^ $ \b
│   ├── syntax.c          # INI-driven syntax highlighting engine
│   └── platform/
│       ├── platform.h        # platform abstraction interface
│       ├── platform_win.c    # Windows Console API (Unicode, mouse wheel)
│       ├── platform_nix.c    # POSIX termios + ANSI escape sequences
│       └── platform_dos.c    # DOS INT 10h/16h (skeleton)
├── include/              # public header files (types.h, editor.h, …)
│   ├── types.h           # Cell, WrapMode, color/attr macros
│   ├── editor.h          # Editor struct (incl. SyntaxContext), full API
│   ├── document.h        # Document struct (incl. encoding), full API
│   ├── viewport.h        # Viewport, Selection, viewport_render (+ SyntaxContext)
│   ├── syntax.h          # SyntaxDef, SyntaxRule, SyntaxContext, highlight API
│   ├── encoding.h        # FileEncoding, encoding_detect, gbk↔utf8 convert
│   ├── regex_simple.h    # regex_match / regex_search
│   └── utf8.h            # utf8_decode/encode/cp_width/byte_to_col …
├── syntax/               # external syntax highlighting rules (INI format)
│   ├── c.ini             # C / C++ keywords, strings, comments, preprocessor
│   ├── python.ini        # Python keywords, strings, comments, decorators
│   ├── markdown.ini      # Markdown headings, bold/italic, code blocks, links
│   ├── javascript.ini    # JavaScript / TypeScript keywords, templates, decorators
│   ├── html.ini          # HTML / XML / SVG tags, attributes, entities, comments
│   ├── css.ini           # CSS / SCSS / Less selectors, properties, hex colors
│   ├── json.ini          # JSON keywords, strings; jsonc block/line comments
│   └── batch.ini         # Batch script keywords, echo, set, if, for
├── tests/                # ~303 unit tests, zero third-party
│   ├── test_runner.c     # test harness entry point + assertions
│   ├── test_document.c
│   ├── test_clipboard.c
│   ├── test_search.c
│   ├── test_viewport.c   # coord mapping + vertical & horizontal scrollbar hit-tests
│   ├── test_util.c
│   ├── test_config.c
│   ├── test_editor.c     # scroll_view, sel_word, sel_line, find_selected flow
│   ├── test_utf8.c       # UTF-8 decode/encode/width/cursor-move (18 cases)
│   ├── test_encoding.c   # encoding_detect + GBK↔UTF-8 roundtrip (10 cases)
│   ├── test_syntax.c     # highlight_line: keyword/comment/string/number/priority
│   └── mocks/
│       └── mock_display.c    # stub display layer for headless test builds
├── docs/                  # project documentation (specs, requirements, tests)
├── CMakeLists.txt
├── cmake_build.bat       # Windows quick-build / test / clean / rebuild
└── config.ini            # runtime configuration (wrap mode, line numbers, …)

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Configuration (config.ini)

Key	Default	Description
wrap_mode	0	0 = Char-wrap, 1 = Horizontal-scroll
show_lineno	false	Show line numbers in edit area
tab_size	4	Tab stop width (display only; stored as \t in the file)
max_file_size	524288	Maximum file size to open (bytes)
syntax_ext_<ext>	—	Map a file extension to a syntax INI, e.g. syntax_ext_xyz=c.ini

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Syntax Highlighting

Rules are loaded from syntax/<lang>.ini files next to the executable. The editor matches the file extension automatically; if no match is found, highlighting is disabled.

Rule types

Type	Description
keyword	Word-boundary keyword list
string	Quoted string literal (configurable delimiter and escape)
line_comment	From prefix to end of line (e.g. //, #)
block_comment	Multi-line delimited span (e.g. /* … */)
number	Integer, hex (0x…), float, with optional suffixes
line_start	Entire line if it starts with a given prefix (e.g. #include)
regex	Custom pattern using the built-in lightweight regex engine

Supported regex features

. * + ? [abc] [a-z] [^…] \d \w \s ^ $ \b

Example INI snippet

[meta]
name       = C
extensions = .c .cpp .h .hpp

[rule.keywords]
type     = keyword
color    = cyan
priority = 10
words    = int char void if else for while return struct typedef

[rule.line_comment]
type     = line_comment
color    = green
priority = 20
prefix   = //

[rule.block_comment]
type  = block_comment
color = green
start = /*
end   = */

Add or edit INI files in syntax/ to support new languages — no recompile needed.

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Roadmap

• Phase 1: editing, file I/O, menus, basic mouse (click + drag)
• Phase 2: selection, clipboard, find/replace, undo/redo
• Phase 3: wrap/scroll modes, line numbers, status bar
• Phase 4: full mouse support (wheel, double/triple-click, right-click menu, scrollbars), horizontal scrollbar
• Phase 5: UTF-8 / GBK multi-byte editing, wide-character display, codepoint-aware cursor
• Phase 6: tab expansion, GBK auto-detect & convert, lightweight regex, INI-driven syntax highlighting (C / Python / Markdown)
• Phase 7: status bar encoding / language indicator, syntax incremental refresh, manual language switch dialog, more syntax INI files (JavaScript, HTML, CSS, JSON, Batch)
• Phase 8: TUI directory browser for Open/Save, path quick-jump (/ \ ~ Ctrl+G), configurable extension→syntax mapping, default filename Untitle

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Documentation

Document	中文	English
Code structure	代码文件结构	CODE_STRUCTURE
Functional requirements	功能需求文档	FUNCTIONAL_REQUIREMENTS
Functional test spec	功能测试规范	FUNCTIONAL_TEST_SPEC