fix(windows): fix init scripts running twice

closes #2051

.changes/windows-double-init-script.md

@@ -0,0 +1,5 @@
+---
+"wry": "patch"
+---
+
+Fix initialization scripts running twice on Windows.

src/lib.rs

@@ -366,7 +366,6 @@ pub struct WebViewAttributes<'a> {
   ///
   /// ## Platform-specific
   ///
-  /// - **Windows**: scripts are injected into sub frames.
   /// - **Android:** The Android WebView does not provide an API for initialization scripts,
   /// so we prepend them to each HTML head. They are only implemented on custom protocol URLs.
   pub initialization_scripts: Vec<(String, bool)>,
@@ -695,9 +694,22 @@ impl<'a> WebViewBuilder<'a> {
   /// initialization code will be executed. It is guaranteed that code is executed before
   /// `window.onload`.
   ///
+  /// ## Example
+  /// ```no_run
+  /// # use wry::{WebViewBuilder, raw_window_handle, Rect, dpi::*};
+  /// # use winit::{window::WindowBuilder, event_loop::EventLoop};
+  /// let event_loop = EventLoop::new().unwrap();
+  /// let window = WindowBuilder::new().build(&event_loop).unwrap();
+  ///
+  /// let webview = WebViewBuilder::new()
+  ///   .with_initialization_script("console.log('Running inside main frame only')")
+  ///   .with_url("https://tauri.app")
+  ///   .build(&window)
+  ///   .unwrap();
+  /// ```
+  ///
   /// ## Platform-specific
   ///
-  /// - **Windows:** scripts are added to subframes as well.
   /// - **Android:** When [addDocumentStartJavaScript] is not supported,
   /// we prepend them to each HTML head (implementation only supported on custom protocol URLs).
   /// For remote URLs, we use [onPageStarted] which is not guaranteed to run before other scripts.
@@ -710,9 +722,20 @@ impl<'a> WebViewBuilder<'a> {
 
   /// Same as [`with_initialization_script`](Self::with_initialization_script) but with option to inject into main frame only or sub frames.
   ///
-  /// ## Platform-specific:
-  ///
-  /// - **Windows:** scripts are always added to subframes regardless of the option.
+  /// ## Example
+  /// ```no_run
+  /// # use wry::{WebViewBuilder, raw_window_handle, Rect, dpi::*};
+  /// # use winit::{window::WindowBuilder, event_loop::EventLoop};
+  /// let event_loop = EventLoop::new().unwrap();
+  /// let window = WindowBuilder::new().build(&event_loop).unwrap();
+  ///
+  /// let webview = WebViewBuilder::new()
+  ///   .with_initialization_script_for_main_only("console.log('Running inside main frame only')", true)
+  ///   .with_initialization_script_for_main_only("console.log('Running  main frame and sub frames')", false)
+  ///   .with_url("https://tauri.app")
+  ///   .build(&window)
+  ///   .unwrap();
+  /// ```
   pub fn with_initialization_script_for_main_only(self, js: &str, main_only: bool) -> Self {
     self.and_then(|mut b| {
       if !js.is_empty() {

src/webview2/mod.rs

@@ -448,9 +448,13 @@ impl InnerWebView {
       };
     }
 
-    // Initialize main frame scripts
-    for (js, for_main_only) in attributes.initialization_scripts {
-      Self::add_script_to_execute_on_document_created(&webview, js, for_main_only)?;
+    // Initialize main and subframe scripts
+    for (js, _) in attributes
+      .initialization_scripts
+      .iter()
+      .filter(|(_, for_main)| !*for_main)
+    {
+      Self::add_script_to_execute_on_document_created(&webview, js.clone())?;
     }
 
     // Enable clipboard
@@ -592,12 +596,27 @@ impl InnerWebView {
         token,
       )?;
     }
+    let scripts = attributes.initialization_scripts.clone();
+
+    webview.add_ContentLoading(
+      &ContentLoadingEventHandler::create(Box::new(move |webview, _| {
+        let Some(webview) = webview else {
+          return Ok(());
+        };
+
+        for (script, _) in scripts.iter().filter(|(_, for_main)| *for_main) {
+          Self::execute_script(&webview, script.clone(), |_| ())?;
+        }
+
+        Ok(())
+      })),
+      token,
+    )?;
 
     // Page load handler
     if let Some(on_page_load_handler) = attributes.on_page_load_handler.take() {
       let on_page_load_handler = Rc::new(on_page_load_handler);
       let on_page_load_handler_ = on_page_load_handler.clone();
-      let scripts = attributes.initialization_scripts.clone();
 
       webview.add_ContentLoading(
         &ContentLoadingEventHandler::create(Box::new(move |webview, _| {
@@ -607,12 +626,6 @@ impl InnerWebView {
 
           on_page_load_handler_(PageLoadEvent::Started, Self::url_from_webview(&webview)?);
 
-          for (script, inject_into_sub_frames) in &scripts {
-            if *inject_into_sub_frames {
-              Self::execute_script(&webview, script.clone(), |_| ())?;
-            }
-          }
-
           Ok(())
         })),
         token,
@@ -773,7 +786,6 @@ impl InnerWebView {
       String::from(
         r#"Object.defineProperty(window, 'ipc', { value: Object.freeze({ postMessage: s=> window.chrome.webview.postMessage(s) }) });"#,
       ),
-      true,
     )?;
 
     let ipc_handler = attributes.ipc_handler.take();
@@ -1186,11 +1198,7 @@ impl InnerWebView {
   }
 
   #[inline]
-  fn add_script_to_execute_on_document_created(
-    webview: &ICoreWebView2,
-    js: String,
-    _for_main_only: bool,
-  ) -> Result<()> {
+  fn add_script_to_execute_on_document_created(webview: &ICoreWebView2, js: String) -> Result<()> {
     let webview = webview.clone();
     AddScriptToExecuteOnDocumentCreatedCompletedHandler::wait_for_async_operation(
       Box::new(move |handler| unsafe {