Typecasting WideString breaks array of widechar - delphi-7

Question

I use this procedure to ENUM the keys into a TNTListView (UNICODE) in Delphi 7
procedure TForm1.TntButton1Click(Sender: TObject);
var
k : HKEY;
Buffer : array of widechar;
i : Integer;
iRes : Integer;
BuffSize : DWORD;
item : TTNTListItem;
WS : WideString;
begin
if RegOpenKeyExW (HKEY_CURRENT_USER, 'Software', 0, KEY_READ, K) = ERROR_SUCCESS then begin
try
i := 0;
BuffSize := 1;
while true do begin
SetLength (Buffer, BuffSize);
iRes := RegEnumKeyW(k, I, #Buffer[0], BuffSize);
if iRes = 259 then break;
if iRes = 234 then begin
inc (BuffSize);
continue;
end;
messageboxw (0, #Buffer[0], '', 0);
item := TNTListView1.Items.Add;
item.Caption := WideString (Buffer); // BREAKS IT
{ SOLUTION }
SetLength (WS, BuffSize - 1);
CopyMemory (#WS[1], #Buffer[0], (BuffSize * 2));
{ .... }
inc (i);
BuffSize := 1;
end;
finally
RegCloseKey (k);
SetLength (Buffer, 0);
end;
end;
end;
I see that most of the listviewitems are trimmed! However if I show the Buffer in the messagebox it shows the complete string in the right length. Is this a Bug of the listview or am I missing something like a NULL CHAR (or even 2)?
Thanks for help.
EDIT: I just noticed that the Buffer get's trimmed into half when I cast it to a widestring.
EDIT2: No bug in the listview. The WideString Cast breaks the string somehow and / or doesn't detect the NULL CHAR(s).

Answer 1

You are right - casting array of WideChar to WideString halves the string length in pre-Unicode Delphi's.
Tested on Delphi 2007:
var
A: array of WideChar;
begin
SetLength(A, 4);
ShowMessage(IntToStr(Length(WideString(A)))); // 2
end;
A quick view on the above code in debugger CPU window shows that typecasting array of WideChar-> WideString does not result in any data conversion; internal WideString format stores the string size (i.e. the number of bytes) in the same place where Delphi strings or dynarrays store length. As a result typecasting halves string length.