Messages.SendStructMessage Function

Send Windows message, sending data structure.

Pascal

function SendStructMessage(Handle: HWND; Msg: UINT; WParam: WPARAM; const LParam): LRESULT;

C++

LRESULT SendStructMessage(HWND Handle, UINT Msg, WPARAM WParam, const  LParam);

File

Messages

Description

SendStructMessage calls the Windows SendMessage function and returns an LRESULT.

Handle is an HWND window handle.

Msg is the Windows message ID. This constant is exactly the same as the Windows message ID described in the Microsoft Windows SDK.

WParam is a WPARAM for the message, depending on Msg. The value is sent.

LParam is a data structure LPARAM for the message, depending on Msg. The value is sent.

Various records have been defined in the Messages unit to represent Windows messages. For instance, TWMCopy represents the message WM_COPY, TWMKeyDown represents WM_KEYDOWN, and so on.

See the Microsoft Windows SDK documentation for information on the Windows messages and their associated WPARAM and LPARAM.

C++ Examples:

Copy Code

/*
This is an example demonstrating the usage of the SendGetIntMessage,
SendStructMessage, SendGetStructMessage and SendTextMessage message
functions.
This example uses four buttons and six text edit boxes as follows:
- Button1 //SendGetIntMessage
- Button2 //SendStructMessage
- Button3 //SendGetStructMessage
- Button4 //SendTextMessage

- IntEdit //for int inputs
- StructEdit1 & StructEdit2 //for struct inputs (ints)
- GetStructEdit1 & GetStructEdit2 //for struct inputs (ints)
- TextEdit //for text input

Note: This example generates unresolved external errors with the
default NO_STRICT conditional define set.  The work around is
to use the STRICT conditional define.  This problem is addressed
in the RAID bug #267447.

This example uses three custom message structures defined in the header:
struct TMyIntMessage {
    Cardinal Msg;
    int* wparam;
    int* lparam;
    LRESULT Result;
};

struct TMyTextMessage {
    Cardinal Msg;
    int wparam;
    String lparam;
    LRESULT Result;
};

struct MStruct {
    int m_a;
    int m_b;
};

struct TMyStruct {
    Cardinal Msg;
    int wparam;
    MStruct* lparam;
    LRESULT Result;
};

Furthermore it uses 4 message handling functions described in the
header along with a message map:

MESSAGE void __fastcall UserIntHandler(TMyIntMessage &msg);
MESSAGE void __fastcall UserStructHandler(TMyStruct &msg);
MESSAGE void __fastcall UserGetStructHandler(TMyStruct &msg);
MESSAGE void __fastcall UserTextHandler(TMyTextMessage &msg);

BEGIN_MESSAGE_MAP
    MESSAGE_HANDLER(WM_INTMESSAGE, TMyIntMessage, UserIntHandler);
    MESSAGE_HANDLER(WM_GETSTRUCTMESSAGE, TMyStruct, UserGetStructHandler);
    MESSAGE_HANDLER(WM_STRUCTMESSAGE, TMyStruct, UserStructHandler);
    MESSAGE_HANDLER(WM_TEXTMESSAGE, TMyTextMessage, UserTextHandler);
END_MESSAGE_MAP(TComponent)

*/

void __fastcall TForm4::UserIntHandler(TMyIntMessage &msg){
    MessageDlg("Int message received: " + IntToStr(*msg.lparam),
            mtInformation, TMsgDlgButtons() << mbOK, 0);

    *msg.lparam = *msg.lparam + 50;
}
void __fastcall TForm4::UserStructHandler(TMyStruct &msg){
    MessageDlg("Struct received: " + IntToStr(msg.lparam->m_a) +
                " " + IntToStr(msg.lparam->m_b),
            mtInformation, TMsgDlgButtons() << mbOK, 0);
}
void __fastcall TForm4::UserGetStructHandler(TMyStruct &msg){
    MessageDlg("Struct received: " + IntToStr(msg.lparam->m_a) +
            "" + IntToStr(msg.lparam->m_b),
            mtInformation, TMsgDlgButtons() << mbOK, 0);
    msg.lparam->m_a = msg.lparam->m_a + 50;
    msg.lparam->m_b = msg.lparam->m_b + 50;
}
void __fastcall TForm4::UserTextHandler(TMyTextMessage &msg){
    MessageDlg("Text received: " + msg.lparam,
            mtInformation, TMsgDlgButtons() << mbOK, 0);
}
void __fastcall TForm4::Button1Click(TObject *Sender)
{
    int wparam = 0;
    int lparam = StrToIntDef(IntEdit->Text,0);
    int lbase = lparam;

    SendGetIntMessage(Handle,WM_INTMESSAGE,wparam,lparam);

    if (lbase != lparam)
    {
        MessageDlg("Value modified by handler function: " +
                    IntToStr(lparam),
                    mtInformation, TMsgDlgButtons() << mbOK, 0);
        IntEdit->Text = IntToStr(lparam);
    }

}
//---------------------------------------------------------------------------

void __fastcall TForm4::Button2Click(TObject *Sender){
    int wparam = 0;
    String lparam = TextEdit->Text;

    SendTextMessage(Handle,WM_TEXTMESSAGE,wparam,lparam);
}
//---------------------------------------------------------------------------

void __fastcall TForm4::Button3Click(TObject *Sender)
{
    int wparam = 0;
    MStruct lparam;

    lparam.m_a = StrToIntDef(StructEdit1->Text,0);
    lparam.m_b = StrToIntDef(StructEdit2->Text,0);

    SendStructMessage(Handle, WM_STRUCTMESSAGE, wparam, &lparam);
}
//---------------------------------------------------------------------------

void __fastcall TForm4::Button4Click(TObject *Sender)
{
    int wparam = 0;
    MStruct lparam, lbase;

    lparam.m_a = StrToIntDef(GetStructEdit1->Text,0);
    lparam.m_b = StrToIntDef(GetStructEdit2->Text,0);

    lbase = lparam;

    SendStructMessage(Handle, WM_GETSTRUCTMESSAGE, wparam, &lparam);

    if (lbase.m_a != lparam.m_a) {
        MessageDlg("Struct modified by handler function: " +
                    IntToStr(lparam.m_a) + " " + IntToStr(lparam.m_b),
                    mtInformation, TMsgDlgButtons() << mbOK, 0);
        GetStructEdit1->Text = IntToStr(lparam.m_a);
        GetStructEdit2->Text = IntToStr(lparam.m_b);
    }
}
//---------------------------------------------------------------------------

Delphi Examples:

Copy Code

{
This is an example demonstrating the usage of the SendGetIntMessage,
SendStructMessage, SendGetStructMessage and SendTextMessage message
functions.
This example uses four buttons and six text edit boxes as follows:
- Button1 //SendGetIntMessage
- Button2 //SendStructMessage
- Button3 //SendGetStructMessage
- Button4 //SendTextMessage

- IntEdit //for int inputs
- StructEdit1 & StructEdit2 //for struct inputs (ints)
- GetStructEdit1 & GetStructEdit2 //for struct inputs (ints)
- TextEdit //for text input
}


const
  WM_INTMSG = WM_USER + 100;
  WM_STRUCTMSG = WM_USER + 101;
  WM_GETSTRUCTMSG = WM_USER + 102;
  WM_TEXTMSG = WM_USER + 103;


type
  TMyIntMessage = packed record
    Msg: Cardinal;
    WParam: ^Integer;
    LParam: ^Integer;
    Result: LRESULT;
  end;

  TMyTextMessage = packed record
    Msg: Cardinal;
    WParam: Integer;
    LParam: String;
    Result: LRESULT;
  end;

  MStruct = packed record
    m_a : Integer;
    m_b : Integer;
  end;

  TMyStruct = packed record
    Msg : Cardinal;
    WParam : Integer;
    LParam : ^MStruct;
    Result : LRESULT;
  end;

  TForm4 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    IntEdit: TEdit;
    StructEdit1: TEdit;
    GetStructEdit1: TEdit;
    TextEdit: TEdit;
    StructEdit2: TEdit;
    GetStructEdit2: TEdit;
    procedure Button1Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    procedure UserIntHandler(var msg: TMyIntMessage); message WM_INTMSG;

    procedure UserStructHandler(var msg: TMyStruct); message WM_STRUCTMSG;

    procedure UserGetStructHandler(var msg: TMyStruct); message WM_GETSTRUCTMSG;

    procedure UserTextHandler(var msg: TMyTextMessage); message WM_TEXTMSG;

  end;

var
  Form4: TForm4;

implementation

{$R *.dfm}

{ TForm4 }

procedure TForm4.Button1Click(Sender: TObject);
var
  wparam : Integer;
  lparam, lbase : Integer;
begin
  //SendGetIntMessage
  wparam := 0;

  lparam := StrToIntDef(IntEdit.Text,0);
  lbase := lparam;

  SendGetIntMessage(Handle, WM_INTMSG, wparam, lparam);

  if lbase <> lparam then
  begin
  MessageDlg('Value modified by handler function: ' + IntToStr(lparam),
              mtInformation, [mbOK], 0);
  IntEdit.Text := IntToStr(lparam);
  end;
end;

procedure TForm4.Button2Click(Sender: TObject);
var
  wparam : Integer;
  lparam : MStruct;
begin
  //SendStructMessage
  wparam := 0;

  lparam.m_a := StrToIntDef(StructEdit1.Text,0);
  lparam.m_b := StrToIntDef(StructEdit2.Text,0);

  SendStructMessage(Handle, WM_STRUCTMSG, wparam, lparam);
end;

procedure TForm4.Button3Click(Sender: TObject);
var
  wparam : Integer;
  lparam, lbase : MStruct;
begin
  //SendGetStructMessage
  wparam := 0;

  lparam.m_a := StrToIntDef(GetStructEdit1.Text,0);
  lparam.m_b := StrToIntDef(GetStructEdit2.Text,0);

  lbase := lparam;

  SendGetStructMessage(Handle, WM_GETSTRUCTMSG, wparam, lparam);

  if lbase.m_a <> lparam.m_a then
  begin
  MessageDlg('Struct modified by handler function: ' +
              IntToStr(lparam.m_a) + ' ' + IntToStr(lparam.m_b),
              mtInformation, [mbOK], 0);
  GetStructEdit1.Text := IntToStr(lparam.m_a);
  GetStructEdit2.Text := IntToStr(lparam.m_b);
  end;

end;

procedure TForm4.Button4Click(Sender: TObject);
var
  wparam : Integer;
  lparam : UnicodeString;
begin
  //SendTextMessage
  wparam := 0;

  lparam := TextEdit.Text;

  SendTextMessage(Handle, WM_TEXTMSG, wparam, lparam);

end;

procedure TForm4.UserGetStructHandler(var msg: TMyStruct);
begin
  MessageDlg('Struct msg received: ' + IntToStr(msg.LParam^.m_a) +
           ' '  + IntToStr(msg.LParam^.m_b), mtInformation, [mbOK], 0);
  msg.LParam^.m_a := msg.LParam^.m_a + 50;
  msg.LParam^.m_b := msg.LParam^.m_b + 50;
end;

procedure TForm4.UserIntHandler(var msg: TMyIntMessage);
begin
  MessageDlg('Int msg received: ' + IntToStr(msg.LParam^),
              mtInformation, [mbOK], 0);

  msg.LParam^ := msg.LParam^ + 50;
end;

procedure TForm4.UserStructHandler(var msg: TMyStruct);
begin
  MessageDlg('Struct msg received: ' + IntToStr(msg.LParam^.m_a) +
           ' '  + IntToStr(msg.LParam^.m_b), mtInformation, [mbOK], 0);
end;

procedure TForm4.UserTextHandler(var msg: TMyTextMessage);
begin
  MessageDlg('Text msg received: ' + msg.LParam,
              mtInformation, [mbOK], 0);
end;