[LyX/master] Allow negative offset in GuiLine (#13102)

[Juergen Spitzmueller]

commit 2244ac3dee416235b49e671b67d63d2ca1f4dcb6
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Wed Sep 25 09:53:00 2024 +0200

    Allow negative offset in GuiLine (#13102)
---
 src/frontends/qt/GuiLine.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/frontends/qt/GuiLine.cpp b/src/frontends/qt/GuiLine.cpp
index 2a8b9de2bc..8587a5d6eb 100644
--- a/src/frontends/qt/GuiLine.cpp
+++ b/src/frontends/qt/GuiLine.cpp
@@ -56,7 +56,10 @@ GuiLine::GuiLine(QWidget * parent) : InsetParamsWidget(parent)
 	addCheckedWidget(WidthLE, WidthValueL);
 	addCheckedWidget(HeightLE, HeightValueL);
 
-	OffsetLE->setValidator(unsignedGlueLengthValidator(OffsetLE));
+	// Set up a signed glue length validator
+	LengthValidator * v = new LengthValidator(OffsetLE);
+	v->setBottom(GlueLength());
+	OffsetLE->setValidator(v);
 	WidthLE->setValidator(unsignedGlueLengthValidator(WidthLE));
 	HeightLE->setValidator(unsignedGlueLengthValidator(HeightLE));