Lazarus

Follow https://wiki.freepascal.org/Installing_Lazarus_on_macOS to install Lazarus.

After installation on macOS, the directory /Applications/Lazarus/examples contains many examples.

We need to download two files from https://sourceforge.net/projects/lazarus/files/Lazarus%20macOS%20x86-64/:

  • Lazarus-3.4-macosx-x86_64.pkg

  • fpc-src-3.2.2-20210709-macosx.dmg

fpc-src is installed in /usr/local/share/src/fpc-3.2.2. The source code of fpc can also be found at https://github.com/fpc/FPCSource

To reduce .exe file size:

  1. Select Project, Project options..., compiler options, Debugging

  2. Uncheck Generate info for the debugger (slower / increase exe size)

  3. Check Strip symbols from exectuable

  4. Note: We can create release and debug build mode instead of using the default mode.

See https://wiki.freepascal.org/Mac_Installation_FAQ to fix the following error:

ld: framework not found Cocoa

whole program optimization: https://wiki.freepascal.org/Whole_Program_Optimization#Concrete_Lazarus_IDE_example

Marcos

Samples and tutorials

TForm

See https://wiki.lazarus.freepascal.org/Form_Tutorial

To change the caption of the form, assign a string to its Caption property.

To add a hint to the form, we need to first change its property Hint and then set property ShowHint to true.

  1. How to show a second form from the main form?

  • There are two methods.

      1. The form is created automatically by the application, which is the default behavior. If we want to disable auto creation, then we can either edit *.lpr or use menu -> project options -> form, disable auto creating the form.

        Note that the above code assumes the form is created automatically.

        // unit1.pas
var
  r: Integer;
begin
  r := Form2.ShowModal;

  case r of
    1: begin ShowMessage('1'); end;
    2: begin ShowMessage('2'); end;
    3: begin ShowMessage('3'); end;
  end;
end;

// unit2.pas
// to exit form2, we can either use self.Close
// or use
//
// Self.ModalResult := 10;
//
// we can assign any integer value to Self.ModalResult
// and it will close the form immediately.

      https://lazarus-ccr.sourceforge.io/docs/lcl/forms/tmodalresult.html and https://lazarus-ccr.sourceforge.io/docs/lazutils/uitypes/tmodalresult.html and https://fossies.org/linux/lazarus/components/lazutils/uitypes.pas define some constant, e.g., mrOK, mrCancel, etc.

      If we use Self.Close or click the X to close the Form, then the returned ModalResult is mrCancel, which is 2.

      1. If the form is not created automatically, then we can use

      procedure TForm1.Button1Click(Sender: TObject);
begin
  Form2:=TForm2.Create(Nil);  //Form2 is created
  Form2.ShowModal;            //Form2 is displayed
  FreeAndNil(Form2);          //Free Form2
end;

  1. How to create a new form dynamically?

See https://wiki.lazarus.freepascal.org/Form_Tutorial#Generate_the_form_dynamically

procedure TForm1.Button1Click(Sender: TObject);
var
  MyForm: TForm;
  MyButton: TButton;
begin
  MyForm:=TForm.Create(nil);
  MyForm.SetBounds(100, 100, 220, 150);
  MyForm.Caption:='My dynamic created form';

  MyButton:=TButton.create(MyForm);
  MyButton.Caption:='Close my form';
  MyButton.SetBounds(10, 10, 200, 30);
  MyButton.Parent:=MyForm;

  MyButton.OnClick:=@MyButtonClick;

  MyForm.ShowModal;

  FreeAndNil(MyForm);
end;

Tips for manual generation of controls

See https://wiki.lazarus.freepascal.org/LCL_Tips

TButton

See

Note that we can set its tag property. Several buttons can share the same onclick event handler, we can use its tag attribute to distinguish them.

Example 1:

// from https://wiki.lazarus.freepascal.org/Lazarus_Tutorial
procedure TForm1.Button1Click(Sender: TObject);
{ Makes use of the Tag property, setting it to either 0 or 1}
begin
  if Button1.tag = 0 then
  begin
    Button1.caption := 'Press again';
    Button1.tag := 1;
  end else
  begin
    Button1.caption := 'Press';
    Button1.tag := 0;
  end;
end;

Example 2:

// from
// https://wiki.lazarus.freepascal.org/TButton
procedure TForm1.FormCreate(Sender: TObject);
var
  i:       Integer;
  aButton: TButton;
begin
  for i := 0 to 9 do begin                // create 10 Buttons
    aButton := TButton.Create(Self);      // create Button, Owner is Form1, where the button is released later
    aButton.Parent  := Self;              // determine where it is to be displayed
    aButton.Width   := aButton.Height;    // Width should correspond to the height of the buttons
    aButton.Left    := i * aButton.Width; // Distance from left
    aButton.Caption := IntToStr(i);       // Captions of the buttons (0.9)
    aButton.OnClick := @aButtonClick;     // the event handler for the button -> will be created yet
  end;
  Self.Height := aButton.Height;          // Height of the form should correspond to the height of the buttons
  Self.Width  := aButton.Width * 10;      // Width of the form to match the width of all buttons
end;

procedure TForm1.aButtonClick(Sender: TObject);
const
  Cnt: Integer = 0;
var
  i: Integer;
begin
  if (Sender is TButton) and                  // called the event handler of a button out?
     TryStrToInt(TButton(Sender).Caption, i)  // then try to convert the label in a integer
  then begin
    Cnt := Cnt + i;                           // the adding counter is incremented by the number of entrechende
    Caption:='QuickAdd: '+IntToStr(Cnt);      // write the result to the caption of the form
  end;
end;

TMemo

Support multiline texts.

It has an attributes Lines, which is of type TStringList. Lines.Count returns number of lines. If it is 0, then the text is empty. Lines.Add('a new line') to add a new line. Lines.Clear() to clear all lines.

See also https://wiki.lazarus.freepascal.org/TMemo.

Example 1:

// from https://wiki.lazarus.freepascal.org/TMemo
// assign a TStringList to a TMemo
// Note that we have to call Free to free the stringlist
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;

Example 2:

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;

TListBox

See https://wiki.lazarus.freepascal.org/TListBox.

  1. How to add an item

  2. How to get the selected item

  3. How to get multi-selected items

Dialogs

See https://wiki.lazarus.freepascal.org/Dialog_Examples.

  1. ShowMessage

  2. Application.MessageBox, we can provide several buttons, ask users to click one button, figure out which button is clicked, e.g., the yes or no button, execute some code.

  3. MessageDlg, like Application.MessageBox but we can specify which buttons to show to users. We should prefer this one.

  4. QuestionDlg: Users can customize the caption of the buttons.

  5. There are also dialogues for accepts user inputs.

TMainMenu

See https://wiki.lazarus.freepascal.org/TMainMenu

Naming convention: MenuFile, MenuFileOpen (for File -> Open), MenuHelp.