TMemo

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A TMemo is a control with multiple lines of editable text. It is available from the Standard tab of the Component Palette.

Usage

To use a TMemo on a form, you can simply select it on the Standard component pallet and place it by clicking on the form. In this text box, you can now edit a multiline text at run time.

For example, have you added a TMemo Memo1 to your form Form1, you can use Memo1.Text:='this is a singleline text'; to assign a String.

Also you can use anywhere in the source code the stored text of Memo1 with myString:=Memo1.Text;.

It is also possible to assign a multiline text with Memo1.Text:='This'+LineEnding+'is'+LineEnding+'a'+LineEnding+'multiline'+LineEnding+'text'; .

Assignment of a TStrings or TStringList

Common, to assign a text to a TMemo is the use of a TStringList or its parent TStrings. The following example shows this (in the event handler of an inserted TButton Button1 in a form Form1 and a TMemo Memo1 on it):

procedure TForm1.Button1Click(Sender: TObject);
var
  myStringList: TStringList;
begin
  myStringList:=TStringList.Create;               //Create my StringList
  myStringList.Add('This is the first line.');    //add a line
  myStringList.Add('This is the second line.');
  myStringList.Add('This is the third line.');
  myStringList.Add('etc.');
  Memo1.Lines.Assign(myStringList);               //assign text content
  myStringList.Free;                              //free my StringList
end;

Insert lines directly

You can add directly the contents of the memo for example:

procedure TForm1.Button1Click(Sender: TObject);
begin
  Memo1.Lines.Clear;                              //delete all lines of Memo1
  Memo1.Lines.Add('This is the first line.');     //add a line
  Memo1.Lines.Add('This is the second line.');
  Memo1.Lines.Add('This is the third line.');
  Memo1.Lines.Add('etc.');
end;

Read a line

If you want to know what is in a particular line, you can check it directly with myString:=Memo1.Lines[Index];. Note, the index of TMemo.Lines is zero based, i.e. the first line would be: myString:=Memo1.Lines[0];

The preceding example add yet a TButton Button2, you can display the third line as follows:

procedure TForm1.Button2Click(Sender: TObject);
begin
  ShowMessage(Memo1.Lines[2]);
end;

Selected text

You can mark text parts at run time by holding the left mouse button or press and hold the [Shift] key and select the text with the mouse or keyboard. This text (String) you can display like this:

procedure TForm1.Button2Click(Sender: TObject);
begin
  ShowMessage(Memo1.SelText); 
end;

Search text

Contrary to the previous example, you can also looking for a text (String) in a TMemo and return the place where it is: Position:=Memo1.SelStart;

The following example shows how you can search and search further for a text in a memo:

• Create a new application with a TEdit Edit1, a TMemo Memo1 and two TButton Button1 and Button2.
• Complete the uses clause to LCLProc and strutils.
• In the event handler OnClick of Button1 fill the memo with any text, as in the example Insert lines directly.
• In the source text editor add following function (based on the example from the German Lazarusforum):

// FindInMemo: Returns the position where the string to search was found
function FindInMemo(AMemo: TMemo; AString: String; StartPos: Integer): Integer;
begin
  Result := PosEx(AString, AMemo.Text, StartPos);
  if Result > 0 then
  begin
    AMemo.SelStart := UTF8Length(PChar(AMemo.Text), Result - 1);
    AMemo.SelLength := Length(AString);
    AMemo.SetFocus;
  end;
end;

• Now, add following code in the event handler OnClick from Button2:

procedure TForm1.Button2Click(Sender: TObject);
const
  SearchStr: String = '';                     // The string to search for
  SearchStart: Integer = 0;                   // Last position of the string to search for
begin
  if SearchStr <> Edit1.Text then begin       // Falls sich der zu suchende String geändert hat
    SearchStart := 0;
    SearchStr := Edit1.Text;
  end;
  SearchStart := FindInMemo(Memo1, SearchStr, SearchStart + 1);

  if SearchStart > 0 then
    Caption := 'Found at position['+IntToStr(SearchStart)+']!'
  else
    Caption := 'No further finds!';
end;

• Now at run time, you can fill the memo with a text with Button1, paste the text to be searched in Edit1 and looking or keep looking for these in memo with Button2.

EM_SCROLLCARET

Messages like EM_SCROLLCARET as used in windows are not available in Lazarus and thus need a workaround...

Save and load

You can quite easily save and load the contents of a memo by using the methods SaveToFile and LoadFromFile of the class TStrings.

The following example shows you how:

• Create a new application with a TMemo Memo1 and three TButton Button1, Button2 and Button3.
• Additionally put a TSaveDialog and a TOpenDialog from the component palette Dialogs on the form.
• Change Caption of Button1 to "Fill memo".
• In the event handler OnClick of Button1 fill the memo with any text, as in the example Insert lines directly.
• Change Caption of Button2 to "Save memo".
• Change Caption of Button3 to "Load memo".
• now modify the event handler OnClick of the buttons:

procedure TForm1.Button2Click(Sender: TObject);
begin
  if SaveDialog1.Execute then
    Memo1.Lines.SaveToFile(SaveDialog1.FileName);
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
  if OpenDialog1.Execute then
    Memo1.Lines.LoadFromFile(OpenDialog1.FileName);
end;

See also

• TMemo doc
• TRichMemo - Like Delphi TRichEdit component: formatted text (color, size, etc.)
• TListBox - A scrollable list of strings