🚀 go-pugleaf

Hi all, I have a strange question,
the following function has been used.
void __fastcall TMainForm::Input_Symbol(AnsiString szSymbol)
{
    if (szSymbol.IsEmpty()) return;
    if (!ActiveControl->ClassNameIs("TEdit")) return;

    TEdit *edit = dynamic_cast<TEdit *>(ActiveControl);
    if (edit != NULL)
    {
        int t = edit->SelStart;
        AnsiString szText = edit->Text;
        szText.Insert(szSymbol, t + 1);
        edit->Text = szText;
        edit->SelStart = t + szSymbol.Length();
    }
}
Input_Symbol() has been used in my two project,
but one is correct and another is incorrect.
it always insert the symbol in front of cursor.
(some multi-byte characters has been used in TEdit)
the multi-byte character has been treated as one character in one project,
but in another project it has been treated as two character.
Does anyone can tell me what happened. How can i insert the appointed
symbol into cursor if there is multi-byte characters and standard character
farraginous.
Any hint?
TIA
Sky.