From 4891f1f0e1aebe5903daeff49bd6360b34e09eea Mon Sep 17 00:00:00 2001
From: Martin <laz.git@mfriebe.de>
Date: Wed, 11 Oct 2023 19:53:19 +0200
Subject: [PATCH] TScrollBox: fix flicker when Form.AutoSizeAll is called. Do
 not call ShowScrollBar when nothing changed.

---
 lcl/forms.pp                     |  1 +
 lcl/include/controlscrollbar.inc | 10 +++++++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/lcl/forms.pp b/lcl/forms.pp
index 984b27eed0..e64251a7ad 100644
--- a/lcl/forms.pp
+++ b/lcl/forms.pp
@@ -107,6 +107,7 @@ type
     FTracking: Boolean;
     FVisible: Boolean;
     FOldScrollInfo: TScrollInfo;
+    FOldVisible: Boolean;
     FOldScrollInfoValid: Boolean;
   protected
     FControl: TWinControl;
diff --git a/lcl/include/controlscrollbar.inc b/lcl/include/controlscrollbar.inc
index 4de12c29fb..29917ddc36 100644
--- a/lcl/include/controlscrollbar.inc
+++ b/lcl/include/controlscrollbar.inc
@@ -230,14 +230,18 @@ begin
     if (not FOldScrollInfoValid) or (not CompareMem(@ScrollInfo, @FOldScrollInfo, SizeOf(TScrollInfo))) then
     begin
       FOldScrollInfo := ScrollInfo;
-      FOldScrollInfoValid := True;
       SetScrollInfo(ControlHandle, IntfBarKind[Kind], ScrollInfo, NewVisible);
       // update policy too
       ScrollInfo.fMask := SIF_UPDATEPOLICY;
       ScrollInfo.nTrackPos := TrackToPolicyMap[FTracking];
       SetScrollInfo(ControlHandle, IntfBarKind[Kind], ScrollInfo, NewVisible);
-    end;
-    ShowScrollBar(ControlHandle, IntfBarKind[Kind], NewVisible);
+      ShowScrollBar(ControlHandle, IntfBarKind[Kind], NewVisible);
+    end
+    else
+    if (not FOldScrollInfoValid) or (FOldVisible <> NewVisible) then
+      ShowScrollBar(ControlHandle, IntfBarKind[Kind], NewVisible);
+    FOldVisible := NewVisible;
+    FOldScrollInfoValid := True;
     {$IFDEF VerboseScrollingWinControl}
     //if DebugCondition then
       DebugLn(['TControlScrollBar.UpdateScrollBar ',DbgSName(FControl),' ',DbgSName(Self),' ',dbgs(Kind),' FVisible=',FVisible,' Range=',FRange,' FPosition=',FPosition,' FPage=',FPage,' FAutoRange=',FAutoRange,' ShouldVisible=',NewVisible,' IsVisible=',IsScrollBarVisible]);