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type

{$IFDEF WIN32}

WParameter = LongInt;

{$ELSE}

WParameter = Word;

{$ENDIF}

LParameter = LongInt;

{Declare a variable to hold the window procedure we are replacing}

var

OldWindowProc : Pointer;

function NewWindowProc(WindowHandle : hWnd;

TheMessage : WParameter;

ParamW : WParameter;

ParamL : LParameter) : LongInt

{$IFDEF WIN32} stdcall; {$ELSE} ; export; {$ENDIF}

var

TheRangeMin : integer;

TheRangeMax : integer;

TheRange : integer;

begin

if TheMessage = WM_VSCROLL then begin

{Get the min and max range of the horizontal scroll box}

GetScrollRange(WindowHandle,

SB_HORZ,

TheRangeMin,

TheRangeMax);

{Get the vertical scroll box position}

TheRange := GetScrollPos(WindowHandle,

SB_VERT);

{Make sure we wont exceed the range}

if TheRange < TheRangeMin then

TheRange := TheRangeMin else

if TheRange > TheRangeMax then

TheRange := TheRangeMax;

{Set the horizontal scroll bar}

SetScrollPos(WindowHandle,

SB_HORZ,

TheRange,

true);

end;

if TheMessage = WM_HSCROLL then begin

{Get the min and max range of the horizontal scroll box}

GetScrollRange(WindowHandle,

SB_VERT,

TheRangeMin,

TheRangeMax);

{Get the horizontal scroll box position}

TheRange := GetScrollPos(WindowHandle,

SB_HORZ);

{Make sure we wont exceed the range}

if TheRange < TheRangeMin then

TheRange := TheRangeMin else

if TheRange > TheRangeMax then

TheRange := TheRangeMax;

{Set the vertical scroll bar}

SetScrollPos(WindowHandle,

SB_VERT,

TheRange,

true);

end;

{ Call the old Window procedure to }

{ allow processing of the message. }

NewWindowProc := CallWindowProc(OldWindowProc,

WindowHandle,

TheMessage,

ParamW,

ParamL);

end;

procedure TForm1.FormCreate(Sender: TObject);

begin

{ Set the new window procedure for the control }

{ and remember the old window procedure. }

OldWindowProc := Pointer(SetWindowLong(ScrollBox1.Handle,

GWL_WNDPROC,

LongInt(@NewWindowProc)));

end;

procedure TForm1.FormDestroy(Sender: TObject);

begin

{ Set the window procedure back }

{ to the old window procedure. }

SetWindowLong(ScrollBox1.Handle,

GWL_WNDPROC,

LongInt(OldWindowProc));

end;