feat: custom css option.

README.md

@@ -108,6 +108,7 @@ require("markdown_preview").setup({
 
   content_name = "content.md",          -- workspace content file
   index_name = "index.html",            -- workspace HTML file
+  custom_css = "",                      -- Absolute path, leave it empty for default style
   workspace_dir = nil,                  -- nil = auto (shared for takeover, per-buffer for multi)
 
   overwrite_index_on_start = true,      -- copy plugin's index.html on every start

lua/markdown_preview/init.lua

@@ -21,6 +21,7 @@ M.config = {
 
 	content_name = "content.md",
 	index_name = "index.html",
+  custom_css = "",
 
 	-- nil = per-buffer workspace (recommended); set a path to override
 	workspace_dir = nil,
@@ -110,12 +111,25 @@ local function write_index(dir)
 		error("Could not locate assets/index.html in runtimepath. Make sure the plugin ships it.")
 	end
 	local content = util.read_text(src)
+
 	-- gsub with function replacement: avoids the "%n is a capture reference"
 	-- escape problem if any substituted value contains '%'.
 	content = content:gsub("__BOTTOM_PADDING__", function() return tostring(M.config.bottom_padding) end)
 	content = content:gsub("__MERMAID_ELK__", function() return M.config.mermaid_elk and "true" or "false" end)
 	content = content:gsub("__LIVE_TOKEN__", function() return M._token or "" end)
 	content = content:gsub("__THEME__", function() return M.config.default_theme end)
+
+  -- Inline custom CSS if configured
+  if M.config.custom_css and M.config.custom_css ~= "" then
+    local css_src = vim.fn.expand(M.config.custom_css)
+    if vim.fn.filereadable(css_src) == 1 then
+      local css = util.read_text(css_src)
+      content = content:gsub("</head>", function() return  "<style>\n" .. css .. "\n</style>\n</head>" end)
+    else
+      vim.notify("Markdown Preview: custom_css not found: " .. css_src, vim.log.levels.WARN)
+    end
+  end
+
 	util.write_text(dst, content)
 	return dst
 end