From 372fc3b29c2134708a2e67d81f6e8f81247df50b Mon Sep 17 00:00:00 2001
From: zeljan1 <zeljko@holobit.hr>
Date: Tue, 21 Jan 2025 16:18:01 +0100
Subject: [PATCH] Gtk3: safe guard against duplicate signal assignment.

---
 lcl/interfaces/gtk3/gtk3widgets.pas | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/lcl/interfaces/gtk3/gtk3widgets.pas b/lcl/interfaces/gtk3/gtk3widgets.pas
index 5c33e42c8a..f0a87d3663 100644
--- a/lcl/interfaces/gtk3/gtk3widgets.pas
+++ b/lcl/interfaces/gtk3/gtk3widgets.pas
@@ -503,6 +503,7 @@ type
   TGtk3ScrollableWin = class(TGtk3Container)
   private
     FBorderStyle: TBorderStyle;
+    FHBarInitialized, FVBarInitialized: boolean;
     function GetHScrollBarPolicy: TGtkPolicyType;
     function GetVScrollBarPolicy: TGtkPolicyType;
     procedure SetBorderStyle(AValue: TBorderStyle);
@@ -5685,14 +5686,22 @@ procedure TGtk3ScrollableWin.SetScrollBarsSignalHandlers(const
   AIsHorizontalScrollBar:boolean);
 begin
   {TODO: create real instances for scrollbars via TGtk3Widget.CreateFrom() ?}
+  if IsDesigning then
+    exit;
   FBorderStyle := bsNone;
   if AIsHorizontalScrollBar then
   begin
-    g_signal_connect_data(getHorizontalScrollbar, 'change-value',
-      TGCallback(@Gtk3RangeScrollCB), Self, nil, G_CONNECT_DEFAULT);
+    if not FHBarInitialized then
+      g_signal_connect_data(getHorizontalScrollbar, 'change-value',
+        TGCallback(@Gtk3RangeScrollCB), Self, nil, G_CONNECT_DEFAULT);
+    FHBarInitialized := True;
   end else
-    g_signal_connect_data(getVerticalScrollbar, 'change-value',
-      TGCallback(@Gtk3RangeScrollCB), Self, nil, G_CONNECT_DEFAULT);
+  begin
+    if not FVBarInitialized then
+      g_signal_connect_data(getVerticalScrollbar, 'change-value',
+        TGCallback(@Gtk3RangeScrollCB), Self, nil, G_CONNECT_DEFAULT);
+    FVBarInitialized := True;
+  end;
 end;
 
 {$IFDEF GTK3DEBUGSIZE}