Nvim Knap: Real-time PDF Preview for Markdown and LaTeX

The Problem

When writing LaTeX documents in Neovim, I’ve been using vimtex which offers a complete suite of tools: syntax highlighting, snippets, compilation, and live PDF preview with Zathura (or anyother of my choice).

However, when writing Markdown files that I need to convert to PDF using Pandoc, I couldn’t find a similar seamless workflow. I was using plugins like markdown-preview.nvim and render-markdown.nvim, but still missed the automatic save-and-preview functionality for the generated PDFs.

Enter Knap

I discovered the Knap plugin (Kevin’s Neovim Auto-Previewer), which provides a flexible way to monitor specific file types and execute custom commands for compilation and preview.

The Solution

Here’s my Knap configuration using lazy.nvim:

return {
  {
    "frabjous/knap",
    lazy = false,
    config = function()
      -- Configure KNAP settings
      vim.g.knap_settings = {
        mdoutputext = "pdf",
        mdtopdf = "pandoc -o %outputfile% --pdf-engine=xelatex",
        mdtopdfviewerlaunch = "zathura %outputfile%",
        mdtopdfviewerrefresh = "none",
        mdtopdfbufferasstdin = true,
      }

      -- Set up keymappings for all markdown files
      vim.api.nvim_create_autocmd("FileType", {
        pattern = { "markdown", "pandoc", "md" },
        callback = function()
          vim.keymap.set("n", "<lejder>kt", function()
            require("knap").toggle_autopreviewing()
          end, { buffer = true, desc = "KNAP toggle auto-preview" })
        end,
      })
    end,
  },
}

How It Works

With this setup:

Knap is configured to output PDF files from Markdown using Pandoc with XeLaTeX as the PDF engine
It uses Zathura as the PDF viewer
When editing Markdown files, I can press <leader>kt to toggle automatic previewing
After toggling it on, every time I save my Markdown file, Knap automatically runs Pandoc to generate a PDF and refreshes the viewer

How It looks

So, yay!