fix(android): Populate KeyEvent.text via Key::to_text()

The `text` field on `KeyEvent` was hardcoded to `None` on Android,
making it impossible for custom `NativeActivity` subclasses that
show the IME to receive functional text input using *for example* the
existing `winit-egui` crate which relies on this field being set.

Use `Key::to_text()` on press events to derive `text` from
`logical_key`, matching the convention used by the Windows and macOS
backends.

Supposedly that doesn't include all kinds of special virtual unicode
keys, but at least the basics work this way.

src/changelog/unreleased.md

@@ -51,3 +51,4 @@ changelog entry.
 - On X11, fix debug mode overflow panic in `set_timestamp`.
 - On macOS, fix crash in `set_marked_text` when native Pinyin IME sends out-of-bounds `selected_range`.
 - On Windows, fix `WM_IME_SETCONTEXT` IME UI flag masking on `lParam`.
+- On Android, populate `KeyEvent::text` and `KeyEvent::text_with_all_modifiers` via `Key::to_text()`

src/platform_impl/android/mod.rs

@@ -446,6 +446,13 @@ impl<T: 'static> EventLoop<T> {
                             &mut self.combining_accent,
                         );
 
+                        let logical_key = keycodes::to_logical(key_char, keycode);
+                        let text = if state == event::ElementState::Pressed {
+                            logical_key.to_text().map(smol_str::SmolStr::new)
+                        } else {
+                            None
+                        };
+
                         let event = event::Event::WindowEvent {
                             window_id: window::WindowId(WindowId),
                             event: event::WindowEvent::KeyboardInput {
@@ -453,10 +460,10 @@ impl<T: 'static> EventLoop<T> {
                                 event: event::KeyEvent {
                                     state,
                                     physical_key: keycodes::to_physical_key(keycode),
-                                    logical_key: keycodes::to_logical(key_char, keycode),
+                                    logical_key,
                                     location: keycodes::to_location(keycode),
                                     repeat: key.repeat_count() > 0,
-                                    text: None,
+                                    text,
                                     platform_specific: KeyEventExtra {},
                                 },
                                 is_synthetic: false,