Fix WindowEvent::ReceivedCharacter on web

The event was never sent to the application because of the unconditional
preventDefault()
call on keydown.

Fixes #1741

CHANGELOG.md

@@ -7,6 +7,7 @@
 - On Wayland, fix window not being resizeable when using `with_min_inner_size` in `WindowBuilder`.
 - On Unix, fix cross-compiling to wasm32 without enabling X11 or Wayland.
 - On Windows, fix use after free crash during window destruction.
+- On Web, fix `WindowEvent::ReceivedCharacter` never being send on key input.
 
 # 0.23.0 (2020-10-02)
 

src/platform_impl/web/stdweb/canvas.rs

@@ -122,7 +122,11 @@ impl Canvas {
         F: 'static + FnMut(ScanCode, Option<VirtualKeyCode>, ModifiersState),
     {
         self.on_keyboard_release = Some(self.add_user_event(move |event: KeyUpEvent| {
-            event.prevent_default();
+            let event_key = &event.key();
+            let is_key_string = event_key.len() == 1 || !event_key.is_ascii();
+            if !is_key_string {
+                event.prevent_default();
+            }
             handler(
                 event::scan_code(&event),
                 event::virtual_key_code(&event),

src/platform_impl/web/web_sys/canvas.rs

@@ -157,7 +157,11 @@ impl Canvas {
         self.on_keyboard_press = Some(self.common.add_user_event(
             "keydown",
             move |event: KeyboardEvent| {
-                event.prevent_default();
+                let event_key = &event.key();
+                let is_key_string = event_key.len() == 1 || !event_key.is_ascii();
+                if !is_key_string {
+                    event.prevent_default();
+                }
                 handler(
                     event::scan_code(&event),
                     event::virtual_key_code(&event),