add Input Method Editor support (#7325)

# Objective

- Fix #7315
- Add IME support

## Solution

- Add two new fields to `Window`, to control if IME is enabled and the candidate box position

This allows the use of dead keys which are needed in French, or the full IME experience to type using Pinyin

I also added a basic general text input example that can handle IME input.

https://user-images.githubusercontent.com/8672791/213941353-5ed73a73-5dd1-4e66-a7d6-a69b49694c52.mp4

Author: mockersf

src/lib.rs

@@ -25,9 +25,10 @@ use bevy_utils::{
     Instant,
 };
 use bevy_window::{
-    CursorEntered, CursorLeft, CursorMoved, FileDragAndDrop, ModifiesWindows, ReceivedCharacter,
-    RequestRedraw, Window, WindowBackendScaleFactorChanged, WindowCloseRequested, WindowCreated,
-    WindowFocused, WindowMoved, WindowResized, WindowScaleFactorChanged,
+    CursorEntered, CursorLeft, CursorMoved, FileDragAndDrop, Ime, ModifiesWindows,
+    ReceivedCharacter, RequestRedraw, Window, WindowBackendScaleFactorChanged,
+    WindowCloseRequested, WindowCreated, WindowFocused, WindowMoved, WindowResized,
+    WindowScaleFactorChanged,
 };
 
 use winit::{
@@ -170,6 +171,7 @@ struct InputEvents<'w> {
     mouse_button_input: EventWriter<'w, MouseButtonInput>,
     mouse_wheel_input: EventWriter<'w, MouseWheel>,
     touch_input: EventWriter<'w, TouchInput>,
+    ime_input: EventWriter<'w, Ime>,
 }
 
 #[derive(SystemParam)]
@@ -555,6 +557,25 @@ pub fn winit_runner(mut app: App) {
                             position,
                         });
                     }
+                    WindowEvent::Ime(event) => match event {
+                        event::Ime::Preedit(value, cursor) => {
+                            input_events.ime_input.send(Ime::Preedit {
+                                window: window_entity,
+                                value,
+                                cursor,
+                            });
+                        }
+                        event::Ime::Commit(value) => input_events.ime_input.send(Ime::Commit {
+                            window: window_entity,
+                            value,
+                        }),
+                        event::Ime::Enabled => input_events.ime_input.send(Ime::Enabled {
+                            window: window_entity,
+                        }),
+                        event::Ime::Disabled => input_events.ime_input.send(Ime::Disabled {
+                            window: window_entity,
+                        }),
+                    },
                     _ => {}
                 }
             }

src/system.rs

@@ -13,7 +13,7 @@ use bevy_window::{RawHandleWrapper, Window, WindowClosed, WindowCreated};
 use raw_window_handle::{HasRawDisplayHandle, HasRawWindowHandle};
 
 use winit::{
-    dpi::{LogicalSize, PhysicalPosition, PhysicalSize},
+    dpi::{LogicalPosition, LogicalSize, PhysicalPosition, PhysicalSize},
     event_loop::EventLoopWindowTarget,
 };
 
@@ -278,6 +278,17 @@ pub(crate) fn changed_window(
                 );
             }
 
+            if window.ime_enabled != previous.ime_enabled {
+                winit_window.set_ime_allowed(window.ime_enabled);
+            }
+
+            if window.ime_position != previous.ime_position {
+                winit_window.set_ime_position(LogicalPosition::new(
+                    window.ime_position.x,
+                    window.ime_position.y,
+                ));
+            }
+
             info.previous = window.clone();
         }
     }