Windows 編程[8] – WM_PAINT 訊息

本例:

program Project1;uses  Windows, Messages;{供 WM_PAINT 訊息調用的自訂過程}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 訊息時調用自訂的 OnPaint 過程}    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;{程式入口}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.