winit: Re-add support for fallback renderer creation

This re-instantes the code path for a suspended renderer creation possibly failing.

Author: tronical

internal/backends/winit/lib.rs

@@ -114,7 +114,7 @@ cfg_if::cfg_if! {
 
 fn default_renderer_factory(
     shared_backend_data: &Rc<SharedBackendData>,
-) -> Box<dyn WinitCompatibleRenderer> {
+) -> Result<Box<dyn WinitCompatibleRenderer>, PlatformError> {
     cfg_if::cfg_if! {
         if #[cfg(enable_skia_renderer)] {
             renderer::skia::WinitSkiaRenderer::new_suspended(shared_backend_data)
@@ -152,17 +152,16 @@ fn try_create_window_with_fallback_renderer(
     ]
     .into_iter()
     .find_map(|renderer_factory| {
-        WinitWindowAdapter::new(
+        Some(WinitWindowAdapter::new(
             shared_backend_data.clone(),
-            renderer_factory(&shared_backend_data),
+            renderer_factory(&shared_backend_data).ok()?,
             attrs.clone(),
             None,
             #[cfg(any(enable_accesskit, muda))]
             _proxy.clone(),
             #[cfg(all(muda, target_os = "macos"))]
             muda_enable_default_menu_bar,
-        )
-        .ok()
+        ))
     })
 }
 
@@ -591,7 +590,8 @@ impl SharedBackendData {
 /// ```
 pub struct Backend {
     requested_graphics_api: Option<RequestedGraphicsAPI>,
-    renderer_factory_fn: fn(&Rc<SharedBackendData>) -> Box<dyn WinitCompatibleRenderer>,
+    renderer_factory_fn:
+        fn(&Rc<SharedBackendData>) -> Result<Box<dyn WinitCompatibleRenderer>, PlatformError>,
     event_loop_state: RefCell<Option<crate::event_loop::EventLoopState>>,
     shared_data: Rc<SharedBackendData>,
     custom_application_handler: RefCell<Option<Box<dyn crate::CustomApplicationHandler>>>,
@@ -668,26 +668,30 @@ impl i_slint_core::platform::Platform for Backend {
             attrs = hook(attrs);
         }
 
-        let adapter = WinitWindowAdapter::new(
-            self.shared_data.clone(),
-            (self.renderer_factory_fn)(&self.shared_data),
-            attrs.clone(),
-            self.requested_graphics_api.clone(),
-            #[cfg(any(enable_accesskit, muda))]
-            self.shared_data.event_loop_proxy.clone(),
-            #[cfg(all(muda, target_os = "macos"))]
-            self.muda_enable_default_menu_bar_bar,
-        )
-        .or_else(|e| {
-            try_create_window_with_fallback_renderer(
-                &self.shared_data,
-                attrs,
-                &self.shared_data.event_loop_proxy.clone(),
-                #[cfg(all(muda, target_os = "macos"))]
-                self.muda_enable_default_menu_bar_bar,
-            )
-            .ok_or_else(|| format!("Winit backend failed to find a suitable renderer: {e}"))
-        })?;
+        let adapter = (self.renderer_factory_fn)(&self.shared_data).map_or_else(
+            |e| {
+                try_create_window_with_fallback_renderer(
+                    &self.shared_data,
+                    attrs.clone(),
+                    &self.shared_data.event_loop_proxy.clone(),
+                    #[cfg(all(muda, target_os = "macos"))]
+                    self.muda_enable_default_menu_bar_bar,
+                )
+                .ok_or_else(|| format!("Winit backend failed to find a suitable renderer: {e}"))
+            },
+            |renderer| {
+                Ok(WinitWindowAdapter::new(
+                    self.shared_data.clone(),
+                    renderer,
+                    attrs.clone(),
+                    self.requested_graphics_api.clone(),
+                    #[cfg(any(enable_accesskit, muda))]
+                    self.shared_data.event_loop_proxy.clone(),
+                    #[cfg(all(muda, target_os = "macos"))]
+                    self.muda_enable_default_menu_bar_bar,
+                ))
+            },
+        )?;
         Ok(adapter)
     }
 

internal/backends/winit/renderer/femtovg.rs

@@ -28,8 +28,8 @@ pub struct GlutinFemtoVGRenderer {
 impl GlutinFemtoVGRenderer {
     pub fn new_suspended(
         _shared_backend_data: &Rc<crate::SharedBackendData>,
-    ) -> Box<dyn WinitCompatibleRenderer> {
-        Box::new(Self { renderer: FemtoVGRenderer::new_suspended() })
+    ) -> Result<Box<dyn WinitCompatibleRenderer>, PlatformError> {
+        Ok(Box::new(Self { renderer: FemtoVGRenderer::new_suspended() }))
     }
 }
 
@@ -94,11 +94,11 @@ pub struct WGPUFemtoVGRenderer {
 impl WGPUFemtoVGRenderer {
     pub fn new_suspended(
         _shared_backend_data: &Rc<crate::SharedBackendData>,
-    ) -> Box<dyn WinitCompatibleRenderer> {
-        Box::new(Self {
+    ) -> Result<Box<dyn WinitCompatibleRenderer>, PlatformError> {
+        Ok(Box::new(Self {
             renderer: FemtoVGRenderer::<i_slint_renderer_femtovg::wgpu::WGPUBackend>::new_suspended(
             ),
-        })
+        }))
     }
 }
 

internal/backends/winit/renderer/skia.rs

@@ -16,8 +16,8 @@ pub struct WinitSkiaRenderer {
 impl WinitSkiaRenderer {
     pub fn new_suspended(
         shared_backend_data: &Rc<crate::SharedBackendData>,
-    ) -> Box<dyn super::WinitCompatibleRenderer> {
-        Box::new(Self { renderer: SkiaRenderer::default(&shared_backend_data.skia_context) })
+    ) -> Result<Box<dyn super::WinitCompatibleRenderer>, PlatformError> {
+        Ok(Box::new(Self { renderer: SkiaRenderer::default(&shared_backend_data.skia_context) }))
     }
 
     #[cfg(not(target_os = "android"))]

internal/backends/winit/renderer/sw.rs

@@ -72,12 +72,12 @@ impl TargetPixel for SoftBufferPixel {
 impl WinitSoftwareRenderer {
     pub fn new_suspended(
         _shared_backend_data: &Rc<crate::SharedBackendData>,
-    ) -> Box<dyn WinitCompatibleRenderer> {
-        Box::new(Self {
+    ) -> Result<Box<dyn WinitCompatibleRenderer>, PlatformError> {
+        Ok(Box::new(Self {
             renderer: SoftwareRenderer::new(),
             _context: RefCell::new(None),
             surface: RefCell::new(None),
-        })
+        }))
     }
 }
 

internal/backends/winit/winitwindowadapter.rs

@@ -385,7 +385,7 @@ impl WinitWindowAdapter {
         requested_graphics_api: Option<RequestedGraphicsAPI>,
         #[cfg(any(enable_accesskit, muda))] proxy: EventLoopProxy<SlintEvent>,
         #[cfg(all(muda, target_os = "macos"))] muda_enable_default_menu_bar: bool,
-    ) -> Result<Rc<Self>, PlatformError> {
+    ) -> Rc<Self> {
         let self_rc = Rc::new_cyclic(|self_weak| Self {
             shared_backend_data: shared_backend_data.clone(),
             window: OnceCell::from(corelib::api::Window::new(self_weak.clone() as _)),
@@ -428,7 +428,7 @@ impl WinitWindowAdapter {
 
         self_rc.shared_backend_data.register_inactive_window((self_rc.clone()) as _);
 
-        Ok(self_rc)
+        self_rc
     }
 
     fn renderer(&self) -> &dyn WinitCompatibleRenderer {