MarkdownAssetProject

日本語版はこちら: README.ja.md

An Unreal Engine 5.5+ plugin that adds a custom Markdown asset type with a live-preview editor.

Features

• Custom Markdown Asset — UMarkdownAsset stores raw Markdown text as a first-class UObject
• Live HTML Preview — Dual-pane editor with a text editor on the left and a real-time HTML preview on the right (updates with a 0.3-second debounce for smooth editing)
• md4c Integration — Fast Markdown-to-HTML conversion powered by the embedded md4c C library
• Dark Theme — Styled HTML output with a dark background for comfortable reading
• Content Browser Integration — Create new Markdown assets directly from the context menu, with custom thumbnail previews showing the "MD" label and the first few lines of content
• Import / Export — Drag-and-drop .md / .markdown files into the Content Browser to import, reimport from source files, or export assets back to .md
• GitHub Flavored Markdown — Supports GFM extensions such as tables, task lists, and strikethrough via the MD_DIALECT_GITHUB flag
• Blueprint Support — Read/write RawMarkdownText and call GetParsedHTML(), GetRawMarkdownText(), and GetPlainText() from Blueprints
• Toolbar & Keyboard Shortcuts — Built-in formatting toolbar with keyboard shortcuts for common Markdown operations
• Undo / Redo — Full undo/redo support integrated with the Unreal Editor transaction system (Ctrl+Z / Ctrl+Y)
• Security — Raw HTML blocks and inline HTML are disabled by default to prevent XSS when rendering user-supplied Markdown
• Localization — Editor UI is fully localized for English and Japanese

Keyboard Shortcuts

Command	Shortcut
Bold	Ctrl+B
Italic	Ctrl+I
Strikethrough	Ctrl+Shift+X
Code Block	Ctrl+Shift+C
Heading 1	Ctrl+1
Heading 2	Ctrl+2
Heading 3	Ctrl+3
Bullet List	Ctrl+Shift+U
Numbered List	Ctrl+Shift+O
Blockquote	Ctrl+Shift+Q
Insert Table	—
Horizontal Rule	—

Requirements

• Unreal Engine 5.5 or later
• C++ project (the plugin includes native modules)
• WebBrowserWidget plugin (enabled automatically as a dependency)

Installation

1. Clone or copy the Plugins/MarkdownEditor directory into your project's Plugins/ folder.
2. Regenerate project files and build.
3. The plugin will be loaded automatically on editor startup.

Usage

Quick Start: See QUICKSTART.md for a step-by-step guide.

1. In the Content Browser, right-click and select Markdown > Markdown Text to create a new asset.
2. Double-click the asset to open the Markdown editor.
3. Write Markdown in the left pane — the right pane updates the HTML preview in real time.

Import / Export

• Import: Drag a .md or .markdown file into the Content Browser to create a Markdown asset.
• Reimport: Right-click an imported asset and select Reimport to reload from the original source file.
• Export: Right-click a Markdown asset and select Asset Actions > Export to save it as a .md file.

Blueprint Nodes

UMarkdownAsset exposes the following Blueprint-callable functions:

Node	Return Type	Description
GetParsedHTML	FString	Converts the Markdown text to an HTML string using md4c
GetRawMarkdownText	FString	Returns the raw Markdown text as-is
GetPlainText	FString	Returns the text content with all Markdown symbols removed

• GetPlainText is useful for displaying Markdown content in UMG Widgets or 3D text, where Markdown / HTML rendering is not available.
• GetRawMarkdownText returns the source Markdown, intended for future extensibility (e.g., custom rendering pipelines).

Project Structure

Plugins/MarkdownEditor/
├── Source/
│   ├── MarkdownAsset/            # Runtime module
│   │   ├── Public/Private/       # UMarkdownAsset class & md4c wrapper
│   │   └── ThirdParty/md4c/     # Embedded md4c parser library
│   └── MarkdownAssetEditor/      # Editor module
│       └── Public/Private/       # Asset factory, actions, and editor toolkit
└── MarkdownEditor.uplugin

Module	Load Phase	Purpose
MarkdownAsset	Runtime	Core asset class and Markdown-to-HTML conversion
MarkdownAssetEditor	Editor	Custom asset editor UI with live preview

Planned Features

Editor

• Syntax Highlighting — Color-coded Markdown syntax in the text editor
• Find & Replace — In-editor text search and replace (Ctrl+F / Ctrl+H)
• Theme Switching — Light theme and user-selectable theme options

Preview

• Mermaid Diagrams — Render flowcharts, sequence diagrams, and more via Mermaid
• Image Preview — Display referenced images in the HTML preview pane

Asset Pipeline

• PDF / HTML Export — Export Markdown assets as PDF or standalone HTML files

Platform

• Multi-platform Support — macOS and Linux compatibility

Runtime

• UMG Markdown Widget — A UMG widget for rendering Markdown directly in game UI

FAQ

Q. Does this plugin work in packaged games? A. Yes. While the Markdown Editor and live preview are editor-only features, the UMarkdownAsset and its Blueprint-callable functions (like GetParsedHTML) are part of the runtime module and work perfectly in packaged builds.

Q. Do I need an internet connection to parse Markdown? A. No. The plugin uses the lightweight md4c C library statically linked into the module. All Markdown-to-HTML conversion is done locally and instantly on your machine.

Q. How do I display the Markdown content in my game's UI? A. You have a few options:

1. Use the GetParsedHTML Blueprint node and feed the result into a WebBrowser UMG widget for fully styled text.
2. Use the GetPlainText node to strip all Markdown formatting and display it in a standard UMG Text Block.

Q. Can I edit my .md files in an external editor like VSCode? A. Yes. You can import any .md or .markdown file into the Content Browser. If you edit the original file externally, simply right-click the asset in Unreal Engine and select Reimport to update it.

Q. Is the WebBrowserWidget plugin required? A. Yes. The Engine's built-in WebBrowserWidget plugin is required to render the live HTML preview in the custom editor. This plugin will automatically enable it for you.

License

This project is licensed under the MIT License.