feat:Add opt‑in navigation handler for external URLs (#5531)

* add navigation handler config option

code from #5231

* Re-order branches

The branches should be reorder so that the branch that checks for
the index and assets is always taken first. Otherwise, they will
fail to load for users who forget to allow them in their custom
handlers, which will be a crappy experience and hard to debug.

* remove return

* Change behavior when handler not set

---------

Co-authored-by: not a cow <agielow@proton.me>

Author: martinmr

packages/desktop/src/config.rs

@@ -20,6 +20,10 @@ type CustomEventHandler = Box<
         ),
 >;
 
+/// A function taking a URL and returning whether the webview should navigate to it or open it in
+/// the browser. If missing in the config, all URLs will be allowed.
+type NavigationHandler = Box<dyn Fn(&str) -> bool + 'static>;
+
 /// The closing behaviour of specific application window.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 #[non_exhaustive]
@@ -70,6 +74,7 @@ pub struct Config {
     pub(crate) disable_dma_buf_on_wayland: bool,
     pub(crate) additional_windows_args: Option<String>,
     pub(crate) tray_icon_show_window_on_click: bool,
+    pub(crate) navigation_handler: Option<NavigationHandler>,
 
     #[allow(clippy::type_complexity)]
     pub(crate) on_window: Option<Box<dyn FnMut(Arc<Window>, &mut VirtualDom) + 'static>>,
@@ -124,6 +129,7 @@ impl Config {
             on_window: None,
             additional_windows_args: None,
             tray_icon_show_window_on_click: true,
+            navigation_handler: None,
         }
     }
 
@@ -350,6 +356,13 @@ impl Config {
         self.tray_icon_show_window_on_click = show;
         self
     }
+
+    /// Set a custom navigation handler for non-dioxus URLs.
+    /// Return true to allow navigation inside the webview, false to block.
+    pub fn with_navigation_handler(mut self, f: impl Fn(&str) -> bool + 'static) -> Self {
+        self.navigation_handler = Some(Box::new(f));
+        self
+    }
 }
 
 impl Default for Config {

packages/desktop/src/webview.rs

@@ -349,6 +349,7 @@ impl WebviewInstance {
             }
         };
 
+        let navigation_handler = cfg.navigation_handler.take();
         let page_loaded = AtomicBool::new(false);
 
         let mut webview = WebViewBuilder::new_with_web_context(&mut web_context)
@@ -363,15 +364,25 @@ impl WebviewInstance {
             .with_url("dioxus://index.html/")
             .with_ipc_handler(ipc_handler)
             .with_navigation_handler(move |var| {
-                // We don't want to allow any navigation
-                // We only want to serve the index file and assets
+                // Serve the index and assets.
                 if var.starts_with("dioxus://")
                     || var.starts_with("http://dioxus.")
                     || var.starts_with("https://dioxus.")
                 {
                     // After the page has loaded once, don't allow any more navigation
                     let page_loaded = page_loaded.swap(true, std::sync::atomic::Ordering::SeqCst);
-                    !page_loaded
+                    return !page_loaded;
+                }
+
+                // By default, navigation is allowed. Users can have more granular control by
+                // providing a navigation handler. If not allowed, valid URLs will be opened in the
+                // browser.
+                let allow_nav = match navigation_handler.as_ref() {
+                    Some(handler) => handler(&var),
+                    None => true,
+                };
+                if allow_nav {
+                    true
                 } else {
                     if var.starts_with("http://")
                         || var.starts_with("https://")