Create custom message box (yes / no) in Inno Setup

Question

How to create custom message box similar to this code: Hide X button (close) at message box in Inno Setup (for a message box with one button) but with two buttons, Yes/No, with the possibility of different actions for each election.

Answer 1

Just add the second TButton:

function MyYesNoMessageBox: Integer;
var
  Form: TSetupForm;
  YesButton, NoButton: TNewButton;
  MesssageLabel: TLabel;
begin
  Form := CreateCustomForm;
  Form.BorderStyle := bsDialog;
  Form.Position := poOwnerFormCenter;
  Form.ClientWidth := ScaleX(400);
  Form.ClientHeight := ScaleY(130);
  Form.Caption := 'Caption';

  MesssageLabel := TLabel.Create(Form);
  MesssageLabel.Parent := Form;
  MesssageLabel.Left := ScaleX(16);
  MesssageLabel.Top := ScaleX(16);
  MesssageLabel.Width := Form.ClientWidth - 2*ScaleX(16);
  MesssageLabel.Height := ScaleY(32);
  MesssageLabel.AutoSize := False;
  MesssageLabel.WordWrap := True;
  MesssageLabel.Caption := 'Lorem ipsum dolor sit amet, ...';

  YesButton := TNewButton.Create(Form);
  YesButton.Parent := Form;
  YesButton.Width := ScaleX(80);
  YesButton.Height := ScaleY(24);
  YesButton.Left := Form.ClientWidth - 2 * (YesButton.Width + ScaleX(8));
  YesButton.Top := Form.ClientHeight - YesButton.Height - ScaleY(8);
  YesButton.Caption := '&Yes';
  YesButton.ModalResult := mrYes;

  NoButton := TNewButton.Create(Form);
  NoButton.Parent := Form;
  NoButton.Width := YesButton.Width;
  NoButton.Height := YesButton.Height;
  NoButton.Left := YesButton.Left + YesButton.Width + ScaleX(8);
  NoButton.Top := YesButton.Top;
  NoButton.Caption := '&No';
  NoButton.ModalResult := mrNo;

  Result := Form.ShowModal;
end;

And test return code of Form.ShowModal (or check Form.ModalResult):

if MyYesNoMessageBox = mrYes then
begin
  MsgBox('Yes selected', mbInformation, MB_OK);
end
  else
begin
  MsgBox('No selected', mbInformation, MB_OK);
end;