Make Application and Sandbox return a Result

src/error.rs

@@ -0,0 +1,34 @@
+use iced_futures::futures;
+
+/// An error that occurred while running an application.
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    /// The futures executor could not be created.
+    #[error("the futures executor could not be created")]
+    ExecutorCreationFailed(futures::io::Error),
+
+    /// The application window could not be created.
+    #[error("the application window could not be created")]
+    WindowCreationFailed(Box<dyn std::error::Error>),
+
+    /// A suitable graphics adapter or device could not be found.
+    #[error("a suitable graphics adapter or device could not be found")]
+    GraphicsAdapterNotFound,
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+impl From<iced_winit::Error> for Error {
+    fn from(error: iced_winit::Error) -> Error {
+        match error {
+            iced_winit::Error::ExecutorCreationFailed(error) => {
+                Error::ExecutorCreationFailed(error)
+            }
+            iced_winit::Error::WindowCreationFailed(error) => {
+                Error::WindowCreationFailed(Box::new(error))
+            }
+            iced_winit::Error::GraphicsAdapterNotFound => {
+                Error::GraphicsAdapterNotFound
+            }
+        }
+    }
+}