eframe error handling (#2433)

* eframe::run_native: return errors instead of crashing

* Detect and handle glutin errors

* egui_demo_app: silence wgpu log spam

* Add trace logs for why eframe is shutting down

* Fix: only save App state once on Mac

* Handle Winit failure

* Log where we load app state from

* Don't panic on zero-sized window

* Clamp loaded window size to not be too tiny to see

* Simplify code: more shared code in window_builder

* Improve code readability

* Fix wasm32 build

* fix android

* Update changelog

examples/custom_font_style/src/main.rs

@@ -58,14 +58,14 @@ impl eframe::App for MyApp {
     }
 }
 
-fn main() {
+fn main() -> Result<(), eframe::EframeError> {
     let options = eframe::NativeOptions::default();
 
     eframe::run_native(
         "egui example: global font style",
         options,
         Box::new(|cc| Box::new(MyApp::new(cc))),
-    );
+    )
 }
 
 pub const LOREM_IPSUM: &str = "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.";