Fix: Ensures correct IME behavior when the text input area gains or loses focus. (emilk#4896)

Fix: Ensures correct IME behavior when the text input area gains or
loses focus.

Fix: Handling `state.ime_enabled` in multiple `TextEdit`.
Fix: A symptom of characters being copied when there are multiple
TextEdits.

* Related emilk#4137
* Related emilk#4358 
* Closes emilk#4374
* Related emilk#4436
* Related emilk#4794 
* Related emilk#4908 

* Related emilk#5008

Fix Issues: When focus is moved elsewhere, you must set
`state.ime_enabled = false`, otherwise the IME will have problems when
focus returns.

Fix Issues: A symptom of characters being copied when there are multiple
TextEdits.
Deletes all current `IME events`, preventing them from being copied to
`other TextEdits`, without saving the `TextEdit ID`,

( Related Issues: Some `LINUX` seem to trigger an IME enable event on
startup. So, when we gained focus, we do `state.ime_enabled = false`. )

Author: rustbasic

crates/egui/src/widgets/text_edit/builder.rs

@@ -745,6 +745,16 @@ impl<'t> TextEdit<'t> {
             }
         }
 
+        // Ensures correct IME behavior when the text input area gains or loses focus.
+        if state.ime_enabled && (response.gained_focus() || response.lost_focus()) {
+            state.ime_enabled = false;
+            if let Some(mut ccursor_range) = state.cursor.char_range() {
+                ccursor_range.secondary.index = ccursor_range.primary.index;
+                state.cursor.set_char_range(Some(ccursor_range));
+            }
+            ui.input_mut(|i| i.events.retain(|e| !matches!(e, Event::Ime(_))));
+        }
+
         state.clone().store(ui.ctx(), id);
 
         if response.changed {