From 385daeb354fe10dc0bf968c760b9be7437684d49 Mon Sep 17 00:00:00 2001
From: rustbasic <127506429+rustbasic@users.noreply.github.com>
Date: Fri, 8 Mar 2024 18:00:28 +0900
Subject: [PATCH] Fix IME bug where currently typed characters got copied

* Closes #3730

Fix IME: Currently typed characters get copied when switching TextEdit
fields
---
 crates/egui/src/widgets/text_edit/builder.rs | 11 ++++++++---
 crates/egui/src/widgets/text_edit/state.rs   |  4 ++++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/crates/egui/src/widgets/text_edit/builder.rs b/crates/egui/src/widgets/text_edit/builder.rs
index 22a5623f..12077b93 100644
--- a/crates/egui/src/widgets/text_edit/builder.rs
+++ b/crates/egui/src/widgets/text_edit/builder.rs
@@ -940,6 +940,7 @@ fn events(
                     if !text_mark.is_empty() {
                         text.insert_text_at(&mut ccursor, text_mark, char_limit);
                     }
+                    state.ime_cursor_range = cursor_range;
                     Some(CCursorRange::two(start_cursor, ccursor))
                 } else {
                     None
@@ -947,12 +948,16 @@ fn events(
             }
 
             Event::CompositionEnd(prediction) => {
-                // CompositionEnd only characters may be typed into TextEdit without trigger CompositionStart first, so do not check `state.has_ime = true` in the following statement.
+                // CompositionEnd only characters may be typed into TextEdit without trigger CompositionStart first,
+                // so do not check `state.has_ime = true` in the following statement.
                 if prediction != "\n" && prediction != "\r" {
                     state.has_ime = false;
-                    let mut ccursor = text.delete_selected(&cursor_range);
-                    if !prediction.is_empty() {
+                    let mut ccursor;
+                    if !prediction.is_empty() && cursor_range == state.ime_cursor_range {
+                        ccursor = text.delete_selected(&cursor_range);
                         text.insert_text_at(&mut ccursor, prediction, char_limit);
+                    } else {
+                        ccursor = cursor_range.primary.ccursor;
                     }
                     Some(CCursorRange::one(ccursor))
                 } else {
diff --git a/crates/egui/src/widgets/text_edit/state.rs b/crates/egui/src/widgets/text_edit/state.rs
index 81968828..8901fd56 100644
--- a/crates/egui/src/widgets/text_edit/state.rs
+++ b/crates/egui/src/widgets/text_edit/state.rs
@@ -44,6 +44,10 @@ pub struct TextEditState {
     #[cfg_attr(feature = "serde", serde(skip))]
     pub(crate) has_ime: bool,
 
+    // cursor range for IME candidate.
+    #[cfg_attr(feature = "serde", serde(skip))]
+    pub(crate) ime_cursor_range: CursorRange,
+
     // Visual offset when editing singleline text bigger than the width.
     #[cfg_attr(feature = "serde", serde(skip))]
     pub(crate) singleline_offset: f32,