Create a functioning form with Windows API.

program Project1;

uses

  Windows,

  Messages;

var

  WndClass: TWndClass;

  MainForm, Button1, Edit1: HWND;

  HAppInstance: integer;

  Msg: TMsg;

procedure Button1Click;

var

  EditText: array[0..255] of char;

begin

  GetWindowText(Edit1, EditText, 256);

  // Display message box

  MessageBox(MainForm,

    PChar('You typed: ' + EditText),

    'Message',

    MB_APPLMODAL OR MB_ICONINFORMATION OR MB_OK);

end;

procedure CreateControls;

var

  hControlFont: HFONT;

  lfControl: TLogFont;

begin

  // Create all controls (Edit1, Button1)

  // See the help file for a description of the style flags

  Edit1 := CreateWindowEx(WS_EX_CLIENTEDGE, // Extended style

    'EDIT', // EDIT creates an edit box

    'Edit1', // Name of window - also the text that will be in it

    WS_CHILD OR WS_VISIBLE OR ES_AUTOHSCROLL OR ES_NOHIDESEL, // style flags

    8, 16, 160, 21, // Position and size

    MainForm, // Parent window

    0, // Menu - none because it's an edit box(!)

    HAppInstance, // Application instance

    nil); // No creation data

  Button1 := CreateWindow('BUTTON', // BUTTON creates an button, obviously

    'Show Message', // Name of window - also the text that will be in it

    WS_CHILD OR WS_VISIBLE OR BS_PUSHBUTTON OR BS_TEXT, // style flags

    8, 40, 96, 25, // Position and size

    MainForm, // Parent window

    0, // Menu - none because it's a button

    HAppInstance, // Application instance

    nil); // No creation data

  // Set up the font

  { Calculate font height from point size - they are not the same thing!

    The first parameter of MulDiv is the point size. }

  lfControl.lfHeight := -MulDiv(8, GetDeviceCaps(GetDC(0), LOGPIXELSY), 96);

  lfControl.lfFaceName := 'MS Sans Serif';

  // Create the font

  hControlFont := CreateFontIndirect(lfControl);

  // Tell controls to set their fonts

  SendMessage(Edit1, WM_SETFONT, hControlFont, 1);

  SendMessage(Button1, WM_SETFONT, hControlFont, 1);

end;

function WindowProc(hwnd: HWND; uMsg: UINT; wParam: WPARAM; lParam: LPARAM):

  LRESULT; stdcall;

begin

  // This is the function Windows calls when a message is sent to the application

  case uMsg of // Check which message was sent

    WM_DESTROY: PostQuitMessage(0); // Otherwise app will continue to run

    // Handle any other messages here

    WM_ACTIVATE: SetFocus(Edit1);

    WM_COMMAND:

      begin

        Result := 0; // Default return value for this message

        if lParam = Button1 then

          case wParam of

            BN_CLICKED: Button1Click; // Button was clicked

          else Result := DefWindowProc(hwnd, uMsg, wParam, lParam);

          end; // case wNotifyCode of

      end; // case: WM_COMMAND

    // Use default message processing

    else Result := DefWindowProc(hwnd, uMsg, wParam, lParam);

  end;

end;

begin

  HAppInstance := HInstance;

  // Set up window class

  with WndClass do begin

    Style := 0;

    lpfnWndProc := @WindowProc; // See function above

    cbClsExtra := 0; // no extra class memory

    cbWndExtra := 0; // no extra window memory

    hInstance := HAppInstance; // application instance

    hIcon := 0; // use default icon

    hCursor := LoadCursor(0, IDC_ARROW); // use arrow cursor

    hbrBackground := COLOR_WINDOW; // standard window colour

    lpszMenuName := nil; // no menu resource

    lpszClassName := 'TMainForm';

  end; // with WndClass

  Windows.RegisterClass(WndClass); // Don't use Delphi's version of RegisterClass

  // Create the window

  MainForm := CreateWindow('TMainForm',

    'Delphi API Demo', // window caption

    WS_OVERLAPPEDWINDOW, // standard window style

    CW_USEDEFAULT, CW_USEDEFAULT, // default position

    320, 200, // size

    0, // no owner window

    0, // no menu

    hInstance, // application instance

    nil);

  CreateControls; // See above

  ShowWindow(MainForm, SW_SHOWNORMAL); // make window visible

  // Set up message loop

  while GetMessage(Msg, 0, 0, 0) <> BOOL(FALSE) do begin

    TranslateMessage(Msg);

    DispatchMessage(Msg);

  end;

  // I'm not sure these are actually needed

  DestroyWindow(Edit1);

  DestroyWindow(Button1);

end.