Introduce error handling in the FemtoVG and Skia renderers

Avoid unwrap() and expect() and instead propagate errors all the way
down to run_event_loop(), show(), and hide() in the Slint AIP.

api/cpp/platform.rs

@@ -53,8 +53,9 @@ impl WindowAdapterSealed for CppWindowAdapter {
         unsafe { (self.show)(self.user_data) };
         Ok(())
     }
-    fn hide(&self) {
+    fn hide(&self) -> Result<(), PlatformError> {
         unsafe { (self.hide)(self.user_data) }
+        Ok(())
     }
 
     fn request_redraw(&self) {
@@ -230,7 +231,7 @@ pub unsafe extern "C" fn slint_skia_renderer_show_win32(
         RawWindowHandle::Win32(init_raw!(raw_window_handle::Win32WindowHandle { hwnd, hinstance })),
         RawDisplayHandle::Windows(raw_window_handle::WindowsDisplayHandle::empty()),
     );
-    r.show(handle, PhysicalSize { width: size.width, height: size.height })
+    r.show(handle, PhysicalSize { width: size.width, height: size.height }).unwrap()
 }
 
 #[no_mangle]
@@ -248,7 +249,7 @@ pub unsafe extern "C" fn slint_skia_renderer_show_x11(
         RawWindowHandle::Xcb(init_raw!(XcbWindowHandle { window, visual_id })),
         RawDisplayHandle::Xcb(init_raw!(XcbDisplayHandle { connection, screen })),
     );
-    r.show(handle, PhysicalSize { width: size.width, height: size.height })
+    r.show(handle, PhysicalSize { width: size.width, height: size.height }).unwrap();
 }
 
 #[no_mangle]
@@ -265,7 +266,7 @@ pub unsafe extern "C" fn slint_skia_renderer_show_wayland(
         RawWindowHandle::Wayland(init_raw!(WaylandWindowHandle { surface })),
         RawDisplayHandle::Wayland(init_raw!(WaylandDisplayHandle { display })),
     );
-    r.show(handle, PhysicalSize { width: size.width, height: size.height })
+    r.show(handle, PhysicalSize { width: size.width, height: size.height }).unwrap();
 }
 
 #[no_mangle]
@@ -282,25 +283,25 @@ pub unsafe extern "C" fn slint_skia_renderer_show_appkit(
         RawWindowHandle::AppKit(init_raw!(AppKitWindowHandle { ns_view, ns_window })),
         RawDisplayHandle::AppKit(AppKitDisplayHandle::empty()),
     );
-    r.show(handle, PhysicalSize { width: size.width, height: size.height })
+    r.show(handle, PhysicalSize { width: size.width, height: size.height }).unwrap();
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn slint_skia_renderer_hide(r: SkiaRendererOpaque) {
     let r = &*(r as *const SkiaRenderer);
-    r.hide()
+    r.hide().unwrap()
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn slint_skia_renderer_resize(r: SkiaRendererOpaque, size: IntSize) {
     let r = &*(r as *const SkiaRenderer);
-    r.resize_event(PhysicalSize { width: size.width, height: size.height });
+    r.resize_event(PhysicalSize { width: size.width, height: size.height }).unwrap();
 }
 
 #[no_mangle]
 pub unsafe extern "C" fn slint_skia_renderer_render(r: SkiaRendererOpaque, size: IntSize) {
     let r = &*(r as *const SkiaRenderer);
-    r.render(PhysicalSize { width: size.width, height: size.height });
+    r.render(PhysicalSize { width: size.width, height: size.height }).unwrap();
 }
 
 #[no_mangle]

api/node/native/lib.rs

@@ -498,7 +498,7 @@ declare_types! {
             let this = cx.this();
             let window = cx.borrow(&this, |x| x.0.as_ref().cloned());
             let window_adapter = window.ok_or(()).or_else(|()| cx.throw_error("Invalid type"))?;
-            window_adapter.hide();
+            window_adapter.hide().unwrap();
             Ok(JsUndefined::new().as_value(&mut cx))
         }
 

api/rs/slint/docs.rs

@@ -110,7 +110,7 @@ pub mod generated_code {
 
         /// Marks the window of this component to be hidden on the screen. This de-registers
         /// the window from the windowing system and it will not receive any further events.
-        fn hide(&self) {
+        fn hide(&self) -> Result<(), crate::PlatformError> {
             unimplemented!();
         }
 

api/wasm-interpreter/src/lib.rs

@@ -191,8 +191,8 @@ impl WrappedInstance {
     }
     /// Hides this instance and prevents further updates of the canvas element.
     #[wasm_bindgen]
-    pub fn hide(&self) {
-        self.0.hide();
+    pub fn hide(&self) -> Result<(), JsValue> {
+        self.0.hide().map_err(|e| -> JsValue { format!("{e}").into() })
     }
 
     /// THIS FUNCTION IS NOT PART THE PUBLIC API!

examples/todo/rust/main.rs

@@ -48,7 +48,7 @@ pub fn main() {
     let weak_window = main_window.as_weak();
     main_window.on_popup_confirmed(move || {
         let window = weak_window.unwrap();
-        window.hide();
+        window.hide().unwrap();
     });
 
     {

internal/backends/qt/qt_window.rs

@@ -1498,7 +1498,7 @@ impl WindowAdapterSealed for QtWindow {
         Ok(())
     }
 
-    fn hide(&self) {
+    fn hide(&self) -> Result<(), i_slint_core::platform::PlatformError> {
         self.rendering_metrics_collector.take();
         let widget_ptr = self.widget_ptr();
         cpp! {unsafe [widget_ptr as "QWidget*"] {
@@ -1507,6 +1507,7 @@ impl WindowAdapterSealed for QtWindow {
             // visible windows, and ends the application if needed
             QEventLoopLocker();
         }};
+        Ok(())
     }
 
     fn request_redraw(&self) {
@@ -1930,9 +1931,10 @@ impl Renderer for QtWindow {
         &self,
         component: ComponentRef,
         _items: &mut dyn Iterator<Item = Pin<i_slint_core::items::ItemRef<'_>>>,
-    ) {
+    ) -> Result<(), i_slint_core::platform::PlatformError> {
         // Invalidate caches:
         self.cache.component_destroyed(component);
+        Ok(())
     }
 }
 

internal/backends/testing/lib.rs

@@ -60,8 +60,9 @@ impl WindowAdapterSealed for TestingWindow {
         Ok(())
     }
 
-    fn hide(&self) {
+    fn hide(&self) -> Result<(), i_slint_core::platform::PlatformError> {
         self.shown.set(false);
+        Ok(())
     }
 
     fn renderer(&self) -> &dyn Renderer {