终于懂了：Delphi消息的Result完全是生造出来的，不是Windows消息自带的（Delphi对Windows编程体系的改造越大，学习收获就越大）

#include <afx.h>

void Cxe111Dlg::OnBnClickedButton1()
{
    CString m_Str;
    int ddd = sizeof(MSG);
    m_Str.Format(_T("%d"), ddd);
    AfxMessageBox(m_Str);
}

void Cxe111Dlg::OnBnClickedButton1()
{
    CString m_Str;
    int ddd = sizeof(WM_SIZE);
    m_Str.Format(_T("%d"), ddd);
    AfxMessageBox(m_Str);
}

void Cxe111Dlg::OnBnClickedButton1()
{
    CString m_Str;
    int ddd = sizeof(WM_CHAR);
    m_Str.Format(_T("%d"), ddd);
    AfxMessageBox(m_Str);
}

  PMsg = ^TMsg;
  tagMSG = packed record
    hwnd: HWND;
    message: UINT;
    wParam: WPARAM;
    lParam: LPARAM;
    time: DWORD;
    pt: TPoint;
  end;

  TMsg = tagMSG;
  MSG = tagMSG;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ShowMessage(IntToStr(sizeof(tagMSG)));
end;

  PMessage = ^TMessage;
  TMessage = packed record
    Msg: Cardinal;
    case Integer of
      0: (
        WParam: Longint;
        LParam: Longint;
        Result: Longint);
      1: (
        WParamLo: Word;
        WParamHi: Word;
        LParamLo: Word;
        LParamHi: Word;
        ResultLo: Word;
        ResultHi: Word);
  end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ShowMessage(IntToStr(sizeof(TMessage)));
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ShowMessage(IntToStr(sizeof(WM_CHAR)));
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ShowMessage(IntToStr(sizeof(WM_SIZE)));
end;

  TWMSize = packed record
    Msg: Cardinal;
    SizeType: Longint; { SIZE_MAXIMIZED, SIZE_MINIMIZED, SIZE_RESTORED,
                         SIZE_MAXHIDE, SIZE_MAXSHOW }
    Width: Word;
    Height: Word;
    Result: Longint;
  end;

  TWMKey = packed record
    Msg: Cardinal;
    CharCode: Word;
    Unused: Word;
    KeyData: Longint;
    Result: Longint;
  end;

  TWMChar = TWMKey;

  TWMPaint = packed record
    Msg: Cardinal;
    DC: HDC;
    Unused: Longint;
    Result: Longint;
  end;

  TWMCommand = packed record
    Msg: Cardinal;
    ItemID: Word;
    NotifyCode: Word;
    Ctl: HWND;
    Result: Longint;
  end;

  TWMNotify = packed record
    Msg: Cardinal;
    IDCtrl: Longint;
    NMHdr: PNMHdr;
    Result: Longint;
  end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  ShowMessage(IntToStr(sizeof(TWMSize)));
  ShowMessage(IntToStr(sizeof(TWMChar)));
  ShowMessage(IntToStr(sizeof(TWMPaint)));
  ShowMessage(IntToStr(sizeof(TWMCommand)));
  ShowMessage(IntToStr(sizeof(TWMNotify)));
end;