[LyX/master] Revert "Better identification of the focused IM segment"

[Koji Yokota]

commit 5f8fc5a634d3478c2767c828ae2d0ecda1e19b00
Author: Koji Yokota <yokota at lyx.org>
Date:   Sun Jun 14 13:28:34 2026 +0900

    Revert "Better identification of the focused IM segment"
    
    This reverts commit a2921b65c74caa5929f6169ba0369bec00281ba7.
    
    Since QInputMethodEvent::Cursor doesn't arrive on time on Linux, we adopt
    the old specification.
---
 src/frontends/qt/GuiInputMethod.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/frontends/qt/GuiInputMethod.cpp b/src/frontends/qt/GuiInputMethod.cpp
index c9e02e4441..e6b026fd97 100644
--- a/src/frontends/qt/GuiInputMethod.cpp
+++ b/src/frontends/qt/GuiInputMethod.cpp
@@ -537,7 +537,11 @@ pos_type GuiInputMethod::setTextFormat(const QInputMethodEvent::Attribute & it,
 	// NOTE: brush size is assumed to be four
 	//       if it is to be changed, change the declaration of array in
 	//       setPreeditStyle()
-	if (it.start == d->caret_rel_pos_) {
+	//       Also, the "if" below doesn't work since QInputMethodEvent::Cursor
+	//       doesn't arrive on time on Linux so d->caret_rel_pos_ can contain
+	//       old information.
+    // if (it.start == d->caret_rel_pos_) {
+	if (char_format.background().color() != QColorConstants::Black) {
 		fg = qcolorOverlay(brush[0].color(), im_fg);
 		bg = qcolorOverlay(brush[1].color(), im_bg);
 	} else {