Make raw_window_handle field in Window and ExtractedWindow an Option. (#6114)

# Objective

- Trying to make it possible to do write tests that don't require a raw window handle.
- Fixes https://github.com/bevyengine/bevy/issues/6106.

## Solution

- Make the interface and type changes.  Avoid accessing `None`.
---

## Changelog

- Converted `raw_window_handle` field in both `Window` and `ExtractedWindow` to `Option<RawWindowHandleWrapper>`.
- Revised accessor function `Window::raw_window_handle()` to return `Option<RawWindowHandleWrapper>`.
- Skip conditions in loops that would require a raw window handle (to create a `Surface`, for example).

## Migration Guide

`Window::raw_window_handle()` now returns `Option<RawWindowHandleWrapper>`.


Co-authored-by: targrub <62773321+targrub@users.noreply.github.com>

crates/bevy_render/src/lib.rs

@@ -144,14 +144,21 @@ impl Plugin for RenderPlugin {
             .register_type::<Color>();
 
         if let Some(backends) = options.backends {
+            let windows = app.world.resource_mut::<bevy_window::Windows>();
             let instance = wgpu::Instance::new(backends);
             let surface = {
-                let windows = app.world.resource_mut::<bevy_window::Windows>();
+                if let Some(window) = windows.get_primary() {
-                let raw_handle = windows.get_primary().map(|window| unsafe {
+                    if let Some(raw_window_handle) = window.raw_window_handle() {
-                    let handle = window.raw_window_handle().get_handle();
+                        unsafe {
-                    instance.create_surface(&handle)
+                            let handle = raw_window_handle.get_handle();
-                });
+                            Some(instance.create_surface(&handle))
-                raw_handle
+                        }
+                    } else {
+                        None
+                    }
+                } else {
+                    None
+                }
             };
             let request_adapter_options = wgpu::RequestAdapterOptions {
                 power_preference: options.power_preference,

crates/bevy_render/src/view/window.rs

@@ -38,7 +38,7 @@ impl Plugin for WindowRenderPlugin {
 
 pub struct ExtractedWindow {
     pub id: WindowId,
-    pub handle: RawWindowHandleWrapper,
+    pub raw_window_handle: Option<RawWindowHandleWrapper>,
     pub physical_width: u32,
     pub physical_height: u32,
     pub present_mode: PresentMode,
@@ -83,7 +83,7 @@ fn extract_windows(
                 .entry(window.id())
                 .or_insert(ExtractedWindow {
                     id: window.id(),
-                    handle: window.raw_window_handle(),
+                    raw_window_handle: window.raw_window_handle(),
                     physical_width: new_width,
                     physical_height: new_height,
                     present_mode: window.present_mode(),
@@ -161,14 +161,20 @@ pub fn prepare_windows(
     render_instance: Res<RenderInstance>,
     render_adapter: Res<RenderAdapter>,
 ) {
-    let window_surfaces = window_surfaces.deref_mut();
+    for window in windows
-    for window in windows.windows.values_mut() {
+        .windows
+        .values_mut()
+        // value of raw_winndow_handle only None if synthetic test
+        .filter(|x| x.raw_window_handle.is_some())
+    {
+        let window_surfaces = window_surfaces.deref_mut();
         let surface = window_surfaces
             .surfaces
             .entry(window.id)
             .or_insert_with(|| unsafe {
                 // NOTE: On some OSes this MUST be called from the main thread.
-                render_instance.create_surface(&window.handle.get_handle())
+                render_instance
+                    .create_surface(&window.raw_window_handle.as_ref().unwrap().get_handle())
             });
 
         let swap_chain_descriptor = wgpu::SurfaceConfiguration {

crates/bevy_window/src/window.rs

@@ -187,6 +187,59 @@ impl WindowResizeConstraints {
 ///     }
 /// }
 /// ```
+/// To test code that uses `Window`s, one can test it with varying `Window` parameters by
+/// creating `WindowResizeConstraints` or `WindowDescriptor` structures.
+/// values by setting
+///
+/// ```
+/// # use bevy_utils::default;
+/// # use bevy_window::{Window, WindowCommand, WindowDescriptor, WindowId, WindowResizeConstraints};
+/// # fn compute_window_area(w: &Window) -> f32 {
+/// #   w.width() * w.height()
+/// # }
+/// # fn grow_window_to_text_size(_window: &mut Window, _text: &str) {}
+/// # fn set_new_title(window: &mut Window, text: String) { window.set_title(text); }
+/// # fn a_window_resize_test() {
+/// let resize_constraints = WindowResizeConstraints {
+///                             min_width: 400.0,
+///                             min_height: 300.0,
+///                             max_width: 1280.0,
+///                             max_height: 1024.0,
+/// };
+/// let window_descriptor = WindowDescriptor {
+///     width: 800.0,
+///     height: 600.0,
+///     resizable: true,
+///     resize_constraints,
+///     ..default()
+/// };
+/// let mut window = Window::new(
+///    WindowId::new(),
+///    &window_descriptor,
+///    100, // physical_width
+///    100, // physical_height
+///    1.0, // scale_factor
+///    None, None);
+///
+/// let area = compute_window_area(&window);
+/// assert_eq!(area, 100.0 * 100.0);
+///
+/// grow_window_to_text_size(&mut window, "very long text that does not wrap");
+/// assert_eq!(window.physical_width(), window.requested_width() as u32);
+/// grow_window_to_text_size(&mut window, "very long text that does wrap, creating a maximum width window");
+/// assert_eq!(window.physical_width(), window.requested_width() as u32);
+///
+/// set_new_title(&mut window, "new title".to_string());
+/// let mut found_command = false;
+/// for command in window.drain_commands() {
+///     if command == (WindowCommand::SetTitle{ title: "new title".to_string() }) {
+///         found_command = true;
+///         break;
+///     }
+/// }
+/// assert_eq!(found_command, true);
+/// }
+/// ```
 #[derive(Debug)]
 pub struct Window {
     id: WindowId,
@@ -206,7 +259,7 @@ pub struct Window {
     cursor_visible: bool,
     cursor_locked: bool,
     physical_cursor_position: Option<DVec2>,
-    raw_window_handle: RawWindowHandleWrapper,
+    raw_window_handle: Option<RawWindowHandleWrapper>,
     focused: bool,
     mode: WindowMode,
     canvas: Option<String>,
@@ -217,7 +270,7 @@ pub struct Window {
 ///
 /// Bevy apps don't interact with this `enum` directly. Instead, they should use the methods on [`Window`].
 /// This `enum` is meant for authors of windowing plugins. See the documentation on [`crate::WindowPlugin`] for more information.
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 #[cfg_attr(feature = "serialize", derive(serde::Serialize, serde::Deserialize))]
 pub enum WindowCommand {
     /// Set the window's [`WindowMode`].
@@ -315,7 +368,7 @@ impl Window {
         physical_height: u32,
         scale_factor: f64,
         position: Option<IVec2>,
-        raw_window_handle: RawWindowHandle,
+        raw_window_handle: Option<RawWindowHandle>,
     ) -> Self {
         Window {
             id,
@@ -335,7 +388,7 @@ impl Window {
             cursor_locked: window_descriptor.cursor_locked,
             cursor_icon: CursorIcon::Default,
             physical_cursor_position: None,
-            raw_window_handle: RawWindowHandleWrapper::new(raw_window_handle),
+            raw_window_handle: raw_window_handle.map(RawWindowHandleWrapper::new),
             focused: true,
             mode: window_descriptor.mode,
             canvas: window_descriptor.canvas.clone(),
@@ -719,9 +772,11 @@ impl Window {
     pub fn is_focused(&self) -> bool {
         self.focused
     }
-    /// Get the [`RawWindowHandleWrapper`] corresponding to this window
+    /// Get the [`RawWindowHandleWrapper`] corresponding to this window if set.
-    pub fn raw_window_handle(&self) -> RawWindowHandleWrapper {
+    ///
-        self.raw_window_handle.clone()
+    /// During normal use, this can be safely unwrapped; the value should only be [`None`] when synthetically constructed for tests.
+    pub fn raw_window_handle(&self) -> Option<RawWindowHandleWrapper> {
+        self.raw_window_handle.as_ref().cloned()
     }
 
     /// The "html canvas" element selector.

crates/bevy_winit/src/winit_windows.rs

@@ -201,7 +201,7 @@ impl WinitWindows {
             inner_size.height,
             scale_factor,
             position,
-            raw_window_handle,
+            Some(raw_window_handle),
         )
     }