Onscroll event for TscrollBox (in +, for Tform)

[laz_one_or2]

hip !
i mod TscrollBox ancestor(TScrollingWinControl), because many less code than if i mod only Tscrollbox.
Tform is a descendant of TScrollingWinControl, it gain the event, the more useful thing i never see .
this works for me on windows 11, fedora 44, hope for you too.

i got help from these posts :
https://forum.lazarus.freepascal.org/index.php?topic=28556.0
https://forum.lazarus.freepascal.org/index.php?topic=31550.0

In forms.pp :

Code: Pascal  [Select][+][-]

1.   { TScrollingWinControl }
2.  
3.     TScrollEvent = procedure(Sender: TObject; var ScrollPos: Integer) of object;  {onscroll}
4.  
5.  
6.   TScrollingWinControl = class(TCustomControl)
7.  
8.   strict private                {onscroll}
9.     FOnVScroll: TScrollEvent;   {onscroll}
10.     FOnHScroll: TScrollEvent;   {onscroll}
11.  
12.           published
13.  
14.         property OnVScroll: TScrollEvent read FOnVScroll write FOnVScroll; {onscroll}
15.         property OnHScroll: TScrollEvent read FOnHScroll write FOnHScroll; {onscroll}

in scrollingwincontrol.inc :

Code: Pascal  [Select][+][-]

1.        
2. procedure TScrollingWinControl.WMVScroll(var Message : TLMVScroll);
3.         begin
4.           VertScrollbar.ScrollHandler(Message);
5.            if Assigned(FOnVScroll) then
6.                   FOnVScroll(Self, FVertScrollBar.FPosition);{onscroll}
7.         end;
8.  
9.         procedure TScrollingWinControl.WMHScroll(var Message : TLMHScroll);
10.         begin
11.           //DebugLn(['TScrollingWinControl.WMHScroll ',dbgsName(Self)]);
12.           HorzScrollbar.ScrollHandler(Message);
13.           if Assigned(FOnHScroll) then
14.              FOnHScroll(Self, FHorzScrollBar.FPosition);{onscroll}
15.         end;