ViewMD

A lightweight, feature-rich Markdown reader and editor built with Avalonia UI and .NET 8.

Features

Markdown Support

• CommonMark + GitHub Flavored Markdown (GFM)
• All basic syntax: headings, bold, italic, strikethrough
• Lists (ordered, unordered, nested)
• Links and images
• Code blocks with syntax highlighting
• Tables with alignment
• Task lists (checkboxes)
• Blockquotes
• Horizontal rules
• Footnotes
• Definition lists
• Abbreviations
• Emoji support (:smile: :heart:)
• Math expressions (LaTeX/KaTeX)
• Mermaid diagrams (flowcharts, sequence, class, etc.)
• HTML embedding

Editor Features

• Syntax-highlighted editor using AvaloniaEdit with TextMate
• Live preview with debounced rendering (300ms)
• Split-pane layout with resizable splitter
• Line numbers
• Word and character count
• Auto-save support
• Keyboard shortcuts for common operations

File Operations

• Create new documents (Ctrl+N)
• Open markdown files (Ctrl+O)
• Save and Save As (Ctrl+S, Ctrl+Shift+S)
• Export to HTML and PDF
• Recent files tracking
• Multi-tab document management

UI/UX

• 11 Beautiful Themes including Glass Light/Dark, Acrylic Light/Dark, Pure Dark, Ocean Breeze, Forest Canopy, Sunset Glow, Midnight Purple, Rose Gold, and Arctic Mint
• Clean, modern interface with acrylic blur effects
• Read mode for distraction-free reading
• Zoom controls for preview
• Status bar with document stats
• Right-click context menu with copy options
• Beautiful typography and styling

Keyboard Shortcuts

File Operations

• Ctrl+N - New file
• Ctrl+O - Open file
• Ctrl+S - Save
• Ctrl+Shift+S - Save As
• Alt+F4 - Exit

Editing

• Ctrl+B - Insert bold
• Ctrl+I - Insert italic
• Ctrl+K - Insert link
• Ctrl+Shift+I - Insert image
• Ctrl+Shift+C - Insert code block
• Ctrl+T - Insert table

View

• F6 - Toggle read mode
• Ctrl+Shift+H - Copy HTML to clipboard
• Ctrl+W - Close active tab
• Ctrl+Shift+W - Close all tabs
• Ctrl+Tab - Next tab
• Ctrl+Shift+Tab - Previous tab

Architecture

Technology Stack

• .NET 8 - Modern, cross-platform framework
• Avalonia UI 11.3 - Cross-platform UI framework
• Markdig - Fast, extensible Markdown processor
• AvaloniaEdit - Syntax-highlighted text editor
• CommunityToolkit.Mvvm - MVVM helpers and code generation

Project Structure

MarkdownViewer/
├── Models/           # Data models
├── ViewModels/       # MVVM view models
├── Views/            # Avalonia XAML views
├── Services/         # Business logic services
└── Assets/           # Resources and styles

Design Patterns

• MVVM - Model-View-ViewModel architecture
• Dependency Injection - Microsoft.Extensions.DependencyInjection
• Service Layer - Separation of concerns
• Observable Pattern - CommunityToolkit.Mvvm

Building from Source

Prerequisites

• .NET 8.0 SDK or later
• Any OS: Windows, macOS, or Linux

Build Instructions

# Clone the repository
git clone <repository-url>
cd Markdown_viewer

# Restore dependencies
dotnet restore

# Build the project
dotnet build

# Run the application
dotnet run

Development

# Build in Release mode
dotnet build -c Release

# Publish for your platform
dotnet publish -c Release -r win-x64 --self-contained
dotnet publish -c Release -r linux-x64 --self-contained
dotnet publish -c Release -r osx-x64 --self-contained

Markdown Feature Support

Basic Syntax ✅

• Headings (H1-H6)
• Paragraphs and line breaks
• Bold, italic, strikethrough
• Lists (ordered, unordered, nested)
• Links and images
• Code (inline and blocks)
• Blockquotes
• Horizontal rules

Extended Syntax ✅

• Tables
• Task lists
• Footnotes
• Definition lists
• Abbreviations
• Subscript and superscript

GitHub Flavored Markdown ✅

• Syntax highlighting in code blocks
• Autolinks
• Strikethrough
• Tables
• Task lists
• Emoji support

Advanced Features ✅

• Math expressions (LaTeX/KaTeX)
• Mermaid diagrams
• HTML embedding
• Front matter (YAML)

Known Limitations

1. Image Handling: Images must be accessible via file path or URL.

2. Text Selection: Cross-element text selection in preview is limited. Use the right-click context menu to copy markdown or plain text.

Future Enhancements

• Custom CSS theme editor
• Advanced find and replace
• Outline/Table of contents navigation
• Git integration for version control
• Spell checker
• Custom keyboard shortcuts configuration

License

This project is open source and available under the MIT License.

Credits

Built with:

• Avalonia UI
• Markdig
• AvaloniaEdit
• CommunityToolkit.Mvvm

File association (Windows)

To make .md files open with this app when double-clicked on Windows, you can register a file association. There are two common ways:

1. During installer/publish: add a file-association entry in your installer (recommended).

2. Per-user registration script: run scripts/register-md-association.ps1 with the path to your installed exe. This registers entries under HKCU so “Open with” works and lets you set ViewMD as default in Windows Settings.

pwsh -ExecutionPolicy Bypass -File .\scripts\register-md-association.ps1 -ExePath "C:\\Program Files\\ViewMD\\MarkdownViewer.exe" -SetDefault

3. Manual registry merge: a .reg file is provided in docs/associate-md.reg as an example. Edit the executable path in that file to point to your installed MarkdownViewer.exe, then double-click the .reg file to merge it into the registry (requires appropriate permissions).

Example usage (for testing):

1. Build and publish the app for Windows (self-contained recommended):

dotnet publish -c Release -r win-x64 --self-contained -o publish\win-x64

2. Edit docs\associate-md.reg to point to the published executable path (or copy the EXE into C:\Program Files\\ViewMD\\).

3. Double-click the .reg file to merge it. After that, double-clicking a .md file should start ViewMD and open the file.

4. Alternatively for testing without registry edits, you can run the app with a file path argument:

dotnet run -- "C:\path\to\example.md"
# or run the published exe directly:
publish\win-x64\MarkdownViewer.exe "C:\path\to\example.md"

To undo the per-user registration:

pwsh -ExecutionPolicy Bypass -File .\scripts\unregister-md-association.ps1

Security: editing the registry affects your system configuration — only run scripts/merge .reg files you trust. Installer-based registration is safer for end users.

Packaging / Installers

Inno Setup (EXE installer)

An Inno Setup script is provided at installer/inno-setup.iss which:

• Copies the published binaries to Program Files
• Registers .md file associations (optional task during install)
• Adds the app to "Open with"

Steps:

1. Publish your app to publish\win-x64:

   dotnet publish -c Release -r win-x64 --self-contained -o publish\win-x64 MarkdownViewer.csproj

2. Open installer\inno-setup.iss in Inno Setup and build the installer.
3. Run the generated MarkdownViewer-Setup.exe. Choose the file association task if desired.

MSIX (AppX) package

An MSIX AppxManifest.xml template is under installer/ with file type associations for .md, .markdown, and .txt, and full-trust desktop process enabled.

Notes:

• You’ll need to sign the package and supply required assets (icons) referenced in the manifest.
• The app runs as a full-trust desktop app; ensure the executable path in the manifest matches your package layout.

Quick MSIX packaging guide

1. Generate stub icons (optional) and validate assets:

pwsh -ExecutionPolicy Bypass -File .\scripts\advanced\create-stub-icons.ps1
pwsh -ExecutionPolicy Bypass -File .\scripts\advanced\check-msix-assets.ps1

2. Build and create a signed MSIX (optional signing):

# Unsigned (for quick local testing, may require sideloading)
pwsh -ExecutionPolicy Bypass -File .\scripts\advanced\package-msix.ps1 -Configuration Release -Runtime win-x64 -MsixPath ViewMD.msix

# Signed (provide your PFX and password securely)
$sec = Read-Host -AsSecureString "PFX password"
pwsh -ExecutionPolicy Bypass -File .\scripts\advanced\package-msix.ps1 -Configuration Release -Runtime win-x64 -MsixPath ViewMD.msix -PfxPath ".\signing-test.pfx" -PfxPassword $sec

3. Install the MSIX

• Double-click the .msix file.
• If signed with a self-signed cert, install the cert to CurrentUser\Trusted People first.
• Ensure sideloading is enabled if required.

Troubleshooting

• Icons missing: run the asset check script and ensure all listed files exist under Assets/.
• Default app choice: Windows manages default apps; your file associations appear, but users may need to confirm defaults in Settings.
• Packaging tools: Make sure MakeAppx.exe and signtool.exe are available (Windows SDK).

Developer quick start

• Run the app for debugging:

   pwsh -ExecutionPolicy Bypass -File .\scripts\dev-run.ps1

  Pass files to open:

   pwsh -ExecutionPolicy Bypass -File .\scripts\dev-run.ps1 -- "C:\\Docs\\README.md" "C:\\Notes\\todo.txt"

• Package for Microsoft Store (.msixbundle):

   pwsh -ExecutionPolicy Bypass -File .\scripts\package-store.ps1 -PfxPath .\certs\ViewMD.pfx

  You will be prompted for the PFX password (used only for local/sideload testing; the Store re-signs). Artifacts: ViewMD.msix (x64), ViewMD-arm64.msix, ViewMD.msixbundle.

• Install locally (sideload):

   pwsh -ExecutionPolicy Bypass -File .\scripts\install-local.ps1

  If you see 0x800B010A, see docs/LOCAL-SIDELOAD.md.