Simple GUI test

[Christof Schardt]

This is a working example, maybe your questions
become obsolete by that.

--------------------------------------------------------------------------
-- winsamp.de
--------------------------------------------------------------------------
/* Compile with:
 * dmd winsamp gdi32.lib winsamp.def
 */

import std.c.windows.windows;
import std.c.stdio;

const int IDC_BTNCLICK = 101;
const int IDC_BTNDONTCLICK = 102;

extern(Windows)
int WindowProc(HWND hWnd, uint uMsg, WPARAM wParam, LPARAM lParam)
{
 switch (uMsg)
 {
     case WM_COMMAND:
     {
  switch (LOWORD(wParam))
  {
      case IDC_BTNCLICK:
   if (HIWORD(wParam) == BN_CLICKED)
    MessageBoxA(hWnd, "Hello, world!", "Greeting",
     MB_OK | MB_ICONINFORMATION);
   break;
      case IDC_BTNDONTCLICK:
   if (HIWORD(wParam) == BN_CLICKED)
   {
       MessageBoxA(hWnd, "You've been warned...", "Prepare to GP fault",
        MB_OK | MB_ICONEXCLAMATION);
       *(cast(int*) null) = 666;
   }
   break;
  }
  break;
     }

     case WM_PAINT:
     {
  static char[] text = "D Does Windows";
  PAINTSTRUCT ps;
  HDC dc = BeginPaint(hWnd, &ps);
  RECT r;
  GetClientRect(hWnd, &r);
  HFONT font = CreateFontA(80, 0, 0, 0, FW_EXTRABOLD, FALSE, FALSE,
   FALSE, ANSI_CHARSET, OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS,
   DEFAULT_QUALITY, DEFAULT_PITCH | FF_DONTCARE, "Arial");
  HGDIOBJ old = SelectObject(dc, cast(HGDIOBJ) font);
  SetTextAlign(dc, TA_CENTER | TA_BASELINE);
  TextOutA(dc, r.right / 2, r.bottom / 2, text, text.length);
  SelectObject(dc, old);
  EndPaint(hWnd, &ps);
  break;
     }
     case WM_DESTROY:
  PostQuitMessage(0);
  break;

     default:
  break;
 }
 return DefWindowProcA(hWnd, uMsg, wParam, lParam);
}

int doit()
{
 HINSTANCE hInst = GetModuleHandleA(null);
 WNDCLASS wc;
 wc.lpszClassName = "DWndClass";
 wc.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW;
 wc.lpfnWndProc = &WindowProc;
 wc.hInstance = hInst;
 wc.hIcon = LoadIconA(cast(HINSTANCE) null, IDI_APPLICATION);
 wc.hCursor = LoadCursorA(cast(HINSTANCE) null, IDC_CROSS);
 wc.hbrBackground = cast(HBRUSH) (COLOR_WINDOW + 1);
 wc.lpszMenuName = null;
 wc.cbClsExtra = wc.cbWndExtra = 0;
 RegisterClassA(&wc);

 HWND hWnd, btnClick, btnDontClick;
 hWnd = CreateWindowA("DWndClass", "Just a window", WS_THICKFRAME |
  WS_MAXIMIZEBOX | WS_MINIMIZEBOX | WS_SYSMENU | WS_VISIBLE,
  CW_USEDEFAULT, CW_USEDEFAULT, 400, 300, HWND_DESKTOP,
  cast(HMENU) null, hInst, null);
 assert(hWnd);

 btnClick = CreateWindowA("BUTTON", "Click Me", WS_CHILD | WS_VISIBLE,
  0, 0, 100, 25, hWnd, cast(HMENU) IDC_BTNCLICK, hInst, null);

 btnDontClick = CreateWindowA("BUTTON", "DON'T CLICK!", WS_CHILD | 
WS_VISIBLE,
  110, 0, 100, 25, hWnd, cast(HMENU) IDC_BTNDONTCLICK, hInst, null);

 MSG msg;
 while (GetMessageA(&msg, cast(HWND) null, 0, 0))
 {
  TranslateMessage(&msg);
  DispatchMessageA(&msg);
 }

 return 1;
}

/**********************************************************/

/* Note the similarity of this code to the console D startup
 * code in \dmd\src\phobos\dmain2.d
 * You'll also need a .def file with at least the following in it:
 * EXETYPE NT
 * SUBSYSTEM WINDOWS
 */

extern (C) void gc_init();
extern (C) void gc_term();
extern (C) void _minit();
extern (C) void _moduleCtor();
extern (C) void _moduleUnitTests();

extern (Windows)
int WinMain(HINSTANCE hInstance,
 HINSTANCE hPrevInstance,
 LPSTR lpCmdLine,
 int nCmdShow)
{
    int result;

    gc_init();   // initialize garbage collector
    _minit();   // initialize module constructor table

    try
    {
 _moduleCtor();  // call module constructors
 _moduleUnitTests(); // run unit tests (optional)

 result = doit(); // insert user code here
    }

    catch (Object o)  // catch any uncaught exceptions
    {
 MessageBoxA(null, cast(char *)o.toString(), "Error",
      MB_OK | MB_ICONEXCLAMATION);
 result = 0;  // failed
    }

    gc_term();   // run finalizers; terminate garbage collector
    return result;
}

--------------------------------------------------------------------------
-- winsamp.def
--------------------------------------------------------------------------
EXETYPE NT
SUBSYSTEM WINDOWS