source: DpiControls/Demo/UFormMain.pas

unit UFormMain;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, Forms, Controls, Graphics, Dialogs, ComCtrls, StdCtrls,
  ExtCtrls, Dpi.Controls, Dpi.Forms, UDpiFormMain;

type

  { TFormMain }

  TFormMain = class(TForm)
    ButtonNewDpiForm: TButton;
    Label1: TLabel;
    Timer1: TTimer;
    TrackBar1: TTrackBar;
    procedure ButtonNewDpiFormClick(Sender: TObject);
    procedure FormActivate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
    procedure FormShow(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure TrackBar1Change(Sender: TObject);
  private
    Initialized: Boolean;
    DpiForm: TDpiForm;
  public
    Redraw: Boolean;
  end;

var
  FormMain: TFormMain;

implementation

{$R *.lfm}

{ TFormMain }

procedure TFormMain.FormShow(Sender: TObject);
begin
  DpiScreen.Dpi := 96 * 2;
  TrackBar1.Position := DpiScreen.Dpi;
end;

procedure TFormMain.Timer1Timer(Sender: TObject);
begin
  Redraw := False;
  DpiScreen.Dpi := TrackBar1.Position;
end;

procedure TFormMain.ButtonNewDpiFormClick(Sender: TObject);
begin
  DpiApplication.CreateForm(TDpiFormMain, DpiForm);
  //DpiForm := TDpiFormMain.Create(Self);
  DpiForm.Caption := DpiForm.Name;
  DpiForm.SetBounds(100, 100, 400, 200);
  DpiForm.Show;
end;

procedure TFormMain.FormActivate(Sender: TObject);
begin
  if not Initialized then begin
    Initialized := True;
    ButtonNewDpiFormClick(nil);
  end;
end;

procedure TFormMain.FormDestroy(Sender: TObject);
begin
  FreeAndNil(DpiForm);
end;

procedure TFormMain.TrackBar1Change(Sender: TObject);
begin
  Redraw := True;
end;

end.