feat(core): add no_redirection_bitmap API on Windows

.changes/no-redirection-bitmap-api.md

@@ -0,0 +1,5 @@
+---
+'@tauri-apps/api': 'minor:feat'
+---
+
+Added `noRedirectionBitmap` option to the `Window` and `WebviewWindow` constructors on Windows.

.changes/no-redirection-bitmap-config.md

@@ -0,0 +1,6 @@
+---
+'tauri': 'minor:feat'
+'tauri-utils': 'minor:feat'
+---
+
+Added `app > windows > noRedirectionBitmap` config option to disable the window redirection bitmap on Windows.

.changes/no-redirection-bitmap.md

@@ -0,0 +1,7 @@
+---
+'tauri': 'minor:feat'
+'tauri-runtime': 'minor:feat'
+'tauri-runtime-wry': 'minor:feat'
+---
+
+Added `WindowBuilder/WebviewWindowBuilder::no_redirection_bitmap` method to disable the window redirection bitmap on Windows.

crates/tauri-cli/config.schema.json

@@ -374,7 +374,7 @@
           "type": "boolean"
         },
         "transparent": {
-          "description": "Whether the window is transparent or not.\n\n Note that on `macOS` this requires the `macos-private-api` feature flag, enabled under `tauri > macOSPrivateApi`.\n WARNING: Using private APIs on `macOS` prevents your application from being accepted to the `App Store`.",
+          "description": "Whether the window is transparent or not.\n\n Note that on `macOS` this requires the `macos-private-api` feature flag, enabled under `tauri > macOSPrivateApi`.\n WARNING: Using private APIs on `macOS` prevents your application from being accepted to the `App Store`.\n\n On Windows, using `noRedirectionBitmap` can help avoid a white flash when creating a transparent window.",
           "default": false,
           "type": "boolean"
         },
@@ -425,6 +425,11 @@
             "null"
           ]
         },
+        "noRedirectionBitmap": {
+          "description": "This sets `WS_EX_NOREDIRECTIONBITMAP`.\n\n This can avoid the white flash that may appear before the webview content is rendered\n when using a transparent window. **Windows only**.",
+          "default": false,
+          "type": "boolean"
+        },
         "theme": {
           "description": "The initial window theme. Defaults to the system theme. Only implemented on Windows and macOS 10.14+.",
           "anyOf": [

crates/tauri-runtime-wry/src/lib.rs

@@ -942,6 +942,7 @@ impl WindowBuilder for WindowBuilderWrapper {
       .content_protected(config.content_protected)
       .skip_taskbar(config.skip_taskbar)
       .theme(config.theme)
+      .no_redirection_bitmap(config.no_redirection_bitmap)
       .closable(config.closable)
       .maximizable(config.maximizable)
       .minimizable(config.minimizable)
@@ -1301,6 +1302,14 @@ impl WindowBuilder for WindowBuilderWrapper {
     self
   }
 
+  fn no_redirection_bitmap(#[allow(unused_mut)] mut self, _enable: bool) -> Self {
+    #[cfg(windows)]
+    {
+      self.inner = self.inner.with_no_redirection_bitmap(_enable);
+    }
+    self
+  }
+
   #[cfg(target_os = "android")]
   fn activity_name<S: Into<String>>(mut self, class_name: S) -> Self {
     self.inner = self.inner.with_activity_name(class_name.into());

crates/tauri-runtime/src/window.rs

@@ -363,6 +363,9 @@ pub trait WindowBuilder: WindowBuilderBase {
 
   /// Whether the window should be transparent. If this is true, writing colors
   /// with alpha values different than `1.0` will produce a transparent window.
+  ///
+  /// On Windows, using `no_redirection_bitmap` can help avoid a white flash when
+  /// creating a transparent window.
   #[cfg(any(not(target_os = "macos"), feature = "macos-private-api"))]
   #[cfg_attr(
     docsrs,
@@ -498,6 +501,13 @@ pub trait WindowBuilder: WindowBuilderBase {
   #[must_use]
   fn window_classname<S: Into<String>>(self, window_classname: S) -> Self;
 
+  /// This sets `WS_EX_NOREDIRECTIONBITMAP`.
+  ///
+  /// This can avoid the white flash that may appear before the webview content is rendered
+  /// when using a transparent window. **Windows only**.
+  #[must_use]
+  fn no_redirection_bitmap(self, enable: bool) -> Self;
+
   /// The name of the activity to create for this webview window.
   #[cfg(target_os = "android")]
   fn activity_name<S: Into<String>>(self, class_name: S) -> Self;

crates/tauri-schema-generator/schemas/config.schema.json

@@ -374,7 +374,7 @@
           "type": "boolean"
         },
         "transparent": {
-          "description": "Whether the window is transparent or not.\n\n Note that on `macOS` this requires the `macos-private-api` feature flag, enabled under `tauri > macOSPrivateApi`.\n WARNING: Using private APIs on `macOS` prevents your application from being accepted to the `App Store`.",
+          "description": "Whether the window is transparent or not.\n\n Note that on `macOS` this requires the `macos-private-api` feature flag, enabled under `tauri > macOSPrivateApi`.\n WARNING: Using private APIs on `macOS` prevents your application from being accepted to the `App Store`.\n\n On Windows, using `noRedirectionBitmap` can help avoid a white flash when creating a transparent window.",
           "default": false,
           "type": "boolean"
         },
@@ -425,6 +425,11 @@
             "null"
           ]
         },
+        "noRedirectionBitmap": {
+          "description": "This sets `WS_EX_NOREDIRECTIONBITMAP`.\n\n This can avoid the white flash that may appear before the webview content is rendered\n when using a transparent window. **Windows only**.",
+          "default": false,
+          "type": "boolean"
+        },
         "theme": {
           "description": "The initial window theme. Defaults to the system theme. Only implemented on Windows and macOS 10.14+.",
           "anyOf": [

crates/tauri-utils/src/config.rs

@@ -2021,6 +2021,8 @@ pub struct WindowConfig {
   ///
   /// Note that on `macOS` this requires the `macos-private-api` feature flag, enabled under `tauri > macOSPrivateApi`.
   /// WARNING: Using private APIs on `macOS` prevents your application from being accepted to the `App Store`.
+  ///
+  /// On Windows, using `noRedirectionBitmap` can help avoid a white flash when creating a transparent window.
   #[serde(default)]
   pub transparent: bool,
   /// Whether the window is maximized or not.
@@ -2053,6 +2055,12 @@ pub struct WindowConfig {
   pub skip_taskbar: bool,
   /// The name of the window class created on Windows to create the window. **Windows only**.
   pub window_classname: Option<String>,
+  /// This sets `WS_EX_NOREDIRECTIONBITMAP`.
+  ///
+  /// This can avoid the white flash that may appear before the webview content is rendered
+  /// when using a transparent window. **Windows only**.
+  #[serde(default, alias = "no-redirection-bitmap")]
+  pub no_redirection_bitmap: bool,
   /// The initial window theme. Defaults to the system theme. Only implemented on Windows and macOS 10.14+.
   pub theme: Option<crate::Theme>,
   /// The style of the macOS title bar.
@@ -2327,6 +2335,7 @@ impl Default for WindowConfig {
       content_protected: false,
       skip_taskbar: false,
       window_classname: None,
+      no_redirection_bitmap: false,
       theme: None,
       title_bar_style: Default::default(),
       traffic_light_position: None,
@@ -3873,6 +3882,7 @@ mod build {
       let content_protected = self.content_protected;
       let skip_taskbar = self.skip_taskbar;
       let window_classname = opt_str_lit(self.window_classname.as_ref());
+      let no_redirection_bitmap = self.no_redirection_bitmap;
       let theme = opt_lit(self.theme.as_ref());
       let title_bar_style = &self.title_bar_style;
       let traffic_light_position = opt_lit(self.traffic_light_position.as_ref());
@@ -3938,6 +3948,7 @@ mod build {
         content_protected,
         skip_taskbar,
         window_classname,
+        no_redirection_bitmap,
         theme,
         title_bar_style,
         traffic_light_position,

crates/tauri/src/test/mock_runtime.rs

@@ -464,6 +464,10 @@ impl WindowBuilder for MockWindowBuilder {
     self
   }
 
+  fn no_redirection_bitmap(self, enable: bool) -> Self {
+    self
+  }
+
   fn shadow(self, enable: bool) -> Self {
     self
   }

crates/tauri/src/webview/webview_window.rs

@@ -599,6 +599,16 @@ impl<'a, R: Runtime, M: Manager<R>> WebviewWindowBuilder<'a, R, M> {
     self
   }
 
+  /// This sets `WS_EX_NOREDIRECTIONBITMAP`.
+  ///
+  /// This can avoid the white flash that may appear before the webview content is rendered
+  /// when using a transparent window. **Windows only**.
+  #[must_use]
+  pub fn no_redirection_bitmap(mut self, enable: bool) -> Self {
+    self.window_builder = self.window_builder.no_redirection_bitmap(enable);
+    self
+  }
+
   /// Sets whether or not the window has shadow.
   ///
   /// ## Platform-specific
@@ -1072,6 +1082,9 @@ impl<R: Runtime, M: Manager<R>> WebviewWindowBuilder<'_, R, M> {
 
   /// Whether the window should be transparent. If this is true, writing colors
   /// with alpha values different than `1.0` will produce a transparent window.
+  ///
+  /// On Windows, using `no_redirection_bitmap` can help avoid a white flash when
+  /// creating a transparent window.
   #[cfg(any(not(target_os = "macos"), feature = "macos-private-api"))]
   #[cfg_attr(
     docsrs,

crates/tauri/src/window/mod.rs

@@ -611,6 +611,16 @@ impl<'a, R: Runtime, M: Manager<R>> WindowBuilder<'a, R, M> {
     self
   }
 
+  /// This sets `WS_EX_NOREDIRECTIONBITMAP`.
+  ///
+  /// This can avoid the white flash that may appear before the webview content is rendered
+  /// when using a transparent window. **Windows only**.
+  #[must_use]
+  pub fn no_redirection_bitmap(mut self, enable: bool) -> Self {
+    self.window_builder = self.window_builder.no_redirection_bitmap(enable);
+    self
+  }
+
   /// Sets whether or not the window has shadow.
   ///
   /// ## Platform-specific
@@ -906,6 +916,9 @@ impl<'a, R: Runtime, M: Manager<R>> WindowBuilder<'a, R, M> {
 
   /// Whether the window should be transparent. If this is true, writing colors
   /// with alpha values different than `1.0` will produce a transparent window.
+  ///
+  /// On Windows, using `no_redirection_bitmap` can help avoid a white flash when
+  /// creating a transparent window.
   #[cfg(any(not(target_os = "macos"), feature = "macos-private-api"))]
   #[cfg_attr(
     docsrs,

packages/api/src/window.ts

@@ -2362,6 +2362,8 @@ interface WindowOptions {
    * Whether the window is transparent or not.
    * Note that on `macOS` this requires the `macos-private-api` feature flag, enabled under `tauri.conf.json > app > macOSPrivateApi`.
    * WARNING: Using private APIs on `macOS` prevents your application from being accepted to the `App Store`.
+   *
+   * On Windows, using `noRedirectionBitmap` can help avoid a white flash when creating a transparent window.
    */
   transparent?: boolean
   /** Whether the window should be maximized upon creation or not. */
@@ -2378,6 +2380,13 @@ interface WindowOptions {
   contentProtected?: boolean
   /** Whether or not the window icon should be added to the taskbar. */
   skipTaskbar?: boolean
+  /**
+   * This sets `WS_EX_NOREDIRECTIONBITMAP`.
+   *
+   * This can avoid the white flash that may appear before the webview content is rendered
+   * when using a transparent window. **Windows only**.
+   */
+  noRedirectionBitmap?: boolean
   /**
    *  Whether or not the window has shadow.
    *