feat(theme): add user-configurable initial theme setting

README.md

@@ -46,6 +46,7 @@ Pre-compiled binaries are automatically downloaded for Linux and macOS (x86_64 a
       -- port = 0,              -- Optional: server port (default: random)
       -- debug = false,         -- Optional: enable debug logging
       -- sync_scroll = true,    -- Optional: sync scroll with nvim (default: true)
+      -- theme = "light/dark",  -- Optional: set theme (default: dark)
     })
   end,
   keys = {

lua/penview/init.lua

@@ -46,6 +46,7 @@ M.server_job = nil
 M.debug = false
 M.sync_scroll = true
 M.headless = false
+M.theme = "dark"
 
 function M.setup(opts)
 	opts = opts or {}
@@ -55,6 +56,13 @@ function M.setup(opts)
 	M.debug = opts.debug or false
 	M.sync_scroll = opts.sync_scroll ~= false -- default true
 
+	if opts.theme then
+		if opts.theme ~= "light" and opts.theme ~= "dark" then
+			error('[penview] \'theme\' must be "light" or "dark", got: ' .. tostring(opts.theme))
+		end
+		M.theme = opts.theme
+	end
+
 	if M.headless then
 		-- Headless mode requires a port
 		if not opts.port or opts.port == 0 then
@@ -111,10 +119,22 @@ function M.start()
 	local cmd
 	if M.headless then
 		-- Headless mode: bind to 0.0.0.0, no browser open
-		cmd = { binary, "serve", "-q", "-p", tostring(M.port), "-a", "0.0.0.0" }
+		cmd = { binary, "serve", "-q", "-p", tostring(M.port), "-a", "0.0.0.0", "--theme", M.theme }
 	else
 		-- Normal mode: --open tells server to launch browser with file path
-		cmd = { binary, "serve", "-q", "-p", tostring(M.port), "--open", path, "--browser", M.browser }
+		cmd = {
+			binary,
+			"serve",
+			"-q",
+			"-p",
+			tostring(M.port),
+			"--open",
+			path,
+			"--browser",
+			M.browser,
+			"--theme",
+			M.theme,
+		}
 	end
 
 	log("Command: " .. table.concat(cmd, " "))

rust/penview/src/main.rs

@@ -42,6 +42,10 @@ enum Args {
         /// Only used when --open is also provided.
         #[arg(short, long)]
         browser: Option<String>,
+
+        /// Initial theme for the preview page ("light" or "dark").
+        #[arg(short = 't', long, default_value_t = ("light").to_string())]
+        theme: String,
     },
     Render {
         /// The location of the Markdown file to render.
@@ -65,12 +69,13 @@ async fn main() {
             address,
             open,
             browser,
+            theme,
         } => {
             if !quiet {
                 tracing_subscriber::fmt::init();
             }
 
-            let state = state::AppState::new();
+            let state = state::AppState::new(theme);
             let app = construct_router(state);
 
             let listener = tokio::net::TcpListener::bind((address, port))
@@ -101,7 +106,7 @@ async fn main() {
             mut in_file,
             out_file,
         } => {
-            let html = render_doc(&in_file, false)
+            let html = render_doc(&in_file, false, "light")
                 .await
                 .expect("Failed to render document.");
 

rust/penview/src/page_template.rs

@@ -6,4 +6,5 @@ pub struct PageTemplate {
     pub title: String,
     pub body: String,
     pub use_websocket: bool,
+    pub theme: String,
 }

rust/penview/src/render.rs

@@ -43,7 +43,11 @@ fn generate_message_data_url(message: impl AsRef<str>, color: impl AsRef<str>) -
 ///
 /// `use_websocket` determines whether to include code for automatically updating the document with a
 /// WebSocket connection.
-pub async fn render_doc(path: impl AsRef<Path>, use_websocket: bool) -> anyhow::Result<String> {
+pub async fn render_doc(
+    path: impl AsRef<Path>,
+    use_websocket: bool,
+    theme: &str,
+) -> anyhow::Result<String> {
     let path = path.as_ref().canonicalize()?;
     let file = read_to_string(&path).await?;
     let title = path.as_os_str().to_string_lossy().to_string();
@@ -54,6 +58,7 @@ pub async fn render_doc(path: impl AsRef<Path>, use_websocket: bool) -> anyhow::
         body,
         title,
         use_websocket,
+        theme: theme.to_string(),
     };
 
     Ok(template.render().unwrap())

rust/penview/src/routes/index.rs

@@ -1,19 +1,29 @@
 use std::path::PathBuf;
 
-use axum::{extract::Query, response::Html};
+use axum::{
+    extract::{Query, State},
+    response::Html,
+};
 use resolve_path::PathResolveExt;
 use serde::Deserialize;
 use tracing::info;
 
-use crate::render::render_doc;
+use crate::{render::render_doc, state::AppState};
 
 #[derive(Debug, Deserialize)]
 pub struct IndexParams {
     path: PathBuf,
 }
 
-pub async fn index(Query(IndexParams { path }): Query<IndexParams>) -> Html<String> {
+pub async fn index(
+    Query(IndexParams { path }): Query<IndexParams>,
+    State(state): State<AppState>,
+) -> Html<String> {
     info!("Rendering document {}", path.to_string_lossy());
 
-    Html(render_doc(path.resolve(), true).await.unwrap())
+    Html(
+        render_doc(path.resolve(), true, &state.theme)
+            .await
+            .unwrap(),
+    )
 }

rust/penview/src/state.rs

@@ -8,12 +8,14 @@ use tokio::sync::{Mutex, broadcast};
 #[derive(Clone)]
 pub struct AppState {
     pub channels: Arc<Mutex<HashMap<PathBuf, broadcast::Sender<String>>>>,
+    pub theme: String,
 }
 
 impl AppState {
-    pub fn new() -> Self {
+    pub fn new(theme: String) -> Self {
         Self {
             channels: Arc::new(Mutex::new(HashMap::new())),
+            theme,
         }
     }
 

rust/penview/templates/page.html

@@ -1,11 +1,11 @@
 <!DOCTYPE html>
-<html lang="en">
+<html lang="en" {% if theme == "dark" %}data-theme="dark"{% endif %}>
 
 <head>
   <meta charset="utf-8">
   <title>{{ title }}</title>
-  <link id="theme-light" rel="stylesheet" href="https://cdn.jsdelivr.net/npm/github-markdown-css/github-markdown-light.css">
-  <link id="theme-dark" rel="stylesheet" href="https://cdn.jsdelivr.net/npm/github-markdown-css/github-markdown-dark.css" disabled>
+  <link id="theme-light" rel="stylesheet" href="https://cdn.jsdelivr.net/npm/github-markdown-css/github-markdown-light.css" {% if theme == "dark" %}disabled{% endif %}>
+  <link id="theme-dark" rel="stylesheet" href="https://cdn.jsdelivr.net/npm/github-markdown-css/github-markdown-dark.css" {% if theme != "dark" %}disabled{% endif %}>
   <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.16.10/dist/katex.min.css"
     integrity="sha384-wcIxkf4k558AjM3Yz3BBFQUbk/zgIYC2R0QpeeYb+TwlBVMrlgLqwRjRtGZiK7ww" crossorigin="anonymous">
   <script src="https://code.jquery.com/jquery-3.7.1.slim.min.js" crossorigin="anonymous"></script>
@@ -246,8 +246,8 @@
         window.mermaidRender?.();
       }
 
-      // Load saved preference or default to light
-      const saved = localStorage.getItem('penview-theme') || 'light';
+      // Load saved preference or use server-configured default
+      const saved = localStorage.getItem('penview-theme') || '{{ theme }}';
       setTheme(saved);
 
       toggle.addEventListener('click', function() {