glow.vim

A Vim plugin for previewing Markdown files using glow in a synchronized vertical split with beautiful color rendering.

This plugin is a Vimscript reimplementation of the original idea from glow.nvim, bringing the same functionality to classic Vim users with enhanced color support.

Features

• 📖 Live Preview: Real-time Markdown rendering using glow
• 🎨 Rich Colors: Custom ANSI renderer with beautiful syntax highlighting
• 🔄 Synchronized Scrolling: Preview window follows your cursor position
• ⚡ Auto-update: Preview updates on text changes
• 🪟 Split View: Clean vertical split layout
• ⌨️ Simple Commands: Easy-to-use commands and key mappings
• 🎯 Pure Vimscript: No external dependencies beyond glow

Requirements

• Vim 8.0+ or Neovim
• glow binary installed
• set termguicolors for color support

Installation

Using vim-plug

Plug 'Maxim4711/glow.vim'

Using Vundle

Plugin 'Maxim4711/glow.vim'

Using Pathogen

cd ~/.vim/bundle
git clone https://github.com/Maxim4711/glow.vim.git

Manual Installation

1. Download the plugin files
2. Copy the directories to your Vim configuration:
   • plugin/glow.vim → ~/.vim/plugin/
   • autoload/glow.vim → ~/.vim/autoload/
   • doc/glow.txt → ~/.vim/doc/

Installing Glow

macOS (Homebrew)

brew install glow

Linux (most distributions)

# Arch Linux
sudo pacman -S glow

# Ubuntu/Debian (via snap)
sudo snap install glow

# Or download from GitHub releases
curl -s https://api.github.com/repos/charmbracelet/glow/releases/latest | grep browser_download_url | cut -d '"' -f 4 | grep linux | wget -i -

Windows

Download from Glow releases

Quick Start

1. Enable colors in your .vimrc:

set termguicolors
let g:glow_use_colors = 1
let g:glow_render_colors = 1

2. Open a markdown file and toggle preview:

:edit README.md
<Leader>p

3. Enjoy beautiful colored markdown preview!

Usage

Commands

Command	Description
:GlowToggle	Toggle the preview window
:GlowOpen	Open the preview window
:GlowClose	Close the preview window
:GlowToggleSync	Toggle scroll synchronization

Default Key Mappings

Key	Command
<Leader>p	Toggle preview window
<Leader>P	Toggle scroll synchronization

Configuration

Add these options to your .vimrc:

" Basic configuration for colored preview
set termguicolors                      " Required for colors
let g:glow_use_colors = 1              " Enable ANSI colors from glow
let g:glow_render_colors = 1           " Render colors in Vim

" Optional customization
let g:glow_binary_path = 'glow'        " Path to glow binary (default: 'glow')
let g:glow_width = 100                 " Preview width in characters (default: 80)
let g:glow_style = 'dark'              " Glow style theme (default: 'auto')
let g:glow_pager = 0                   " Enable pager mode (default: 0)
let g:glow_sync_scroll = 1             " Enable scroll sync (default: 1)

" Disable default key mappings
let g:glow_disable_default_mappings = 1

Color Configuration

The plugin uses a custom ANSI renderer that creates beautiful colors for different markdown elements:

• Headers (# Header) → Bright red/pink with bold formatting
• Bold text (**bold**) → Bright green with bold formatting
• Italic text (*italic*) → Light blue with italic formatting
• Code blocks (`code`) → Yellow highlighting
• Links ([text](url)) → Purple with underline

Glow Style Options

Style	Description
'auto'	Automatically detect terminal theme (default)
'dark'	Dark theme with bright colors
'light'	Light theme
'notty'	Plain text without colors

Custom Key Mappings

If you disabled default mappings, you can create your own:

let g:glow_disable_default_mappings = 1

" Custom mappings
nnoremap <silent> <F5> :GlowToggle<CR>
nnoremap <silent> <F6> :GlowToggleSync<CR>
nnoremap <silent> <C-p> :GlowOpen<CR>

How It Works

1. Preview Generation: Captures your Markdown buffer content and passes it to the glow binary with FORCE_COLOR=1
2. ANSI Processing: Custom Vimscript ANSI renderer parses color sequences and applies them as Vim highlighting
3. Split Management: Creates and manages a vertical split window for the preview
4. Synchronization: Calculates relative scroll positions to keep source and preview in sync
5. Auto-updates: Uses Vim's autocmd system to update the preview on text changes

Color Rendering

This plugin features a custom ANSI renderer built in pure Vimscript that:

• ✅ Parses glow's ANSI color sequences without external dependencies
• ✅ Maps formatting to Vim highlight groups for optimal display
• ✅ Handles complex sequences like ;;1m that other tools struggle with
• ✅ Provides rich syntax highlighting for all markdown elements
• ✅ Works with any terminal and colorscheme

Unlike solutions that depend on external plugins like AnsiEsc, this renderer is:

• Faster: No external command execution
• More reliable: No version compatibility issues
• More customizable: Easy to modify colors and formatting
• Lighter: No additional plugin dependencies

Troubleshooting

Glow not found

Error: Glow binary not found at: glow

Solution: Install glow or set the correct path:

let g:glow_binary_path = '/path/to/glow'

No colors in preview

Solution: Enable termguicolors and color rendering:

set termguicolors
let g:glow_use_colors = 1
let g:glow_render_colors = 1

Preview not updating

• Ensure you're editing a .md file
• Check if glow is executable: :!which glow
• Try manually refreshing: :GlowClose then :GlowOpen

Scroll sync issues

• Toggle sync off and on: :GlowToggleSync
• Check that both windows are visible

Performance

The custom ANSI renderer is optimized for performance:

• Minimal overhead: Only processes visible content
• Efficient highlighting: Uses Vim's native matchadd() system
• Smart caching: Reuses highlight groups across updates
• No external calls: Everything happens within Vim

Acknowledgments

This plugin is inspired by and reimplements the functionality of glow.nvim by @ellisonleao. The original Lua implementation for Neovim provided the foundation for this Vimscript version.

Special thanks to:

• Charm for the excellent glow terminal markdown reader
• The original glow.nvim contributors for the plugin concept
• The Vim community for the inspiration to create a pure Vimscript solution

License

MIT License - see LICENSE file for details.

Contributing

Issues and pull requests are welcome! Please feel free to contribute improvements or report bugs.