Windows 编程[8] - WM_PAINT 消息

本例效果图:

---

program Project1;



uses

  Windows, Messages;



{供 WM_PAINT 消息调用的自定义过程}

procedure OnPaint(h: HWND);

const

  str = 'CodeGear Delphi 2007';

var

  DC: HDC;

  ps: PAINTSTRUCT;

  Rect: TRect;

begin

  MessageBeep(0);

  DC := BeginPaint(h, ps);

  GetClientRect(h, Rect);

  DrawText(DC, PChar(str), -1, Rect, DT_SINGLELINE or DT_CENTER or DT_VCENTER);

  EndPaint(h, ps);

end;



function WndProc(wnd: HWND; msg: UINT; wParam: Integer; lParam: Integer): Integer; stdcall;

begin

  Result := 0;

  case msg of

    WM_PAINT  : OnPaint(wnd); {在收到 WM_PAINT 消息时调用自定义的 OnPaint 过程}

    WM_DESTROY: PostQuitMessage(0);

  else

    Result := DefWindowProc(wnd, msg, wParam, lParam);

  end;

end;



function RegMyWndClass: Boolean;

var

  cls: TWndClass;

begin

  cls.style         := CS_HREDRAW or CS_VREDRAW;

  cls.lpfnWndProc   := @WndProc;

  cls.cbClsExtra    := 0;

  cls.cbWndExtra    := 0;

  cls.hInstance     := HInstance;

  cls.hIcon         := 0;

  cls.hCursor       := LoadCursor(0, IDC_ARROW);

  cls.hbrBackground := HBRUSH(COLOR_WINDOW + 1);

  cls.lpszMenuName  := nil;

  cls.lpszClassName := 'MyWnd';

  Result := RegisterClass(cls) <> 0;

end;



{程序入口}

const

  tit = 'New Form';

  ws = WS_OVERLAPPEDWINDOW;

  x = 100; y = 100; w = 300; h = 180;

var

  hWnd: THandle;

  Msg : TMsg;

begin

  RegMyWndClass;

  hWnd := CreateWindow('MyWnd', tit, ws, x, y, w, h, 0, 0, HInstance, nil);

  ShowWindow(hWnd, SW_SHOWNORMAL);

  UpdateWindow(hWnd);



  while(GetMessage(Msg, 0, 0, 0)) do

  begin

    TranslateMessage(Msg);

    DispatchMessage(Msg);

  end;

end.