1 /* 2 * Copyright (c) 1996, 2016, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 /* 27 * The Toolkit class has two functions: it instantiates the AWT 28 * ToolkitPeer's native methods, and provides the DLL's core functions. 29 * 30 * There are two ways this DLL can be used: either as a dynamically- 31 * loaded Java native library from the interpreter, or by a Windows- 32 * specific app. The first manner requires that the Toolkit provide 33 * all support needed so the app can function as a first-class Windows 34 * app, while the second assumes that the app will provide that 35 * functionality. Which mode this DLL functions in is determined by 36 * which initialization paradigm is used. If the Toolkit is constructed 37 * normally, then the Toolkit will have its own pump. If it is explicitly 38 * initialized for an embedded environment (via a static method on 39 * sun.awt.windows.WToolkit), then it will rely on an external message 40 * pump. 41 * 42 * The most basic functionality needed is a Windows message pump (also 43 * known as a message loop). When an Java app is started as a console 44 * app by the interpreter, the Toolkit needs to provide that message 45 * pump if the AWT is dynamically loaded. 46 */ 47 48 #ifndef AWT_TOOLKIT_H 49 #define AWT_TOOLKIT_H 50 51 #include "awt.h" 52 #include "awtmsg.h" 53 #include "Trace.h" 54 55 #include "sun_awt_windows_WToolkit.h" 56 57 class AwtObject; 58 class AwtDialog; 59 class AwtDropTarget; 60 61 typedef VOID (CALLBACK* IDLEPROC)(VOID); 62 typedef BOOL (CALLBACK* PEEKMESSAGEPROC)(MSG&); 63 64 // Struct for _WInputMethod_enable|disableNativeIME method 65 struct EnableNativeIMEStruct { 66 jobject self; 67 jobject peer; 68 jint context; 69 jboolean useNativeCompWindow; 70 }; 71 72 /* 73 * class JNILocalFrame 74 * Push/PopLocalFrame helper 75 */ 76 class JNILocalFrame { 77 public: 78 INLINE JNILocalFrame(JNIEnv *env, int size) { 79 m_env = env; 80 int result = m_env->PushLocalFrame(size); 81 if (result < 0) { 82 DASSERT(FALSE); 83 throw std::bad_alloc(); 84 } 85 } 86 INLINE ~JNILocalFrame() { m_env->PopLocalFrame(NULL); } 87 private: 88 JNIEnv* m_env; 89 }; 90 91 /* 92 * class CriticalSection 93 * ~~~~~ ~~~~~~~~~~~~~~~~ 94 * Lightweight intra-process thread synchronization. Can only be used with 95 * other critical sections, and only within the same process. 96 */ 97 class CriticalSection { 98 public: 99 INLINE CriticalSection() { ::InitializeCriticalSection(&rep); } 100 INLINE ~CriticalSection() { ::DeleteCriticalSection(&rep); } 101 102 class Lock { 103 public: 104 INLINE Lock(const CriticalSection& cs) : critSec(cs) { 105 (const_cast<CriticalSection &>(critSec)).Enter(); 106 } 107 INLINE ~Lock() { 108 (const_cast<CriticalSection &>(critSec)).Leave(); 109 } 110 private: 111 const CriticalSection& critSec; 112 }; 113 friend class Lock; 114 115 private: 116 CRITICAL_SECTION rep; 117 118 CriticalSection(const CriticalSection&); 119 const CriticalSection& operator =(const CriticalSection&); 120 121 public: 122 virtual void Enter() { 123 ::EnterCriticalSection(&rep); 124 } 125 virtual BOOL TryEnter() { 126 return ::TryEnterCriticalSection(&rep); 127 } 128 virtual void Leave() { 129 ::LeaveCriticalSection(&rep); 130 } 131 }; 132 133 // Macros for using CriticalSection objects that help trace 134 // lock/unlock actions 135 136 /* Use THIS_FILE when it is available. */ 137 #ifndef THIS_FILE 138 #define THIS_FILE __FILE__ 139 #endif 140 141 #define CRITICAL_SECTION_ENTER(cs) { \ 142 J2dTraceLn4(J2D_TRACE_VERBOSE2, \ 143 "CS.Wait: tid, cs, file, line = 0x%x, 0x%x, %s, %d", \ 144 GetCurrentThreadId(), &(cs), THIS_FILE, __LINE__); \ 145 (cs).Enter(); \ 146 J2dTraceLn4(J2D_TRACE_VERBOSE2, \ 147 "CS.Enter: tid, cs, file, line = 0x%x, 0x%x, %s, %d", \ 148 GetCurrentThreadId(), &(cs), THIS_FILE, __LINE__); \ 149 } 150 151 #define CRITICAL_SECTION_LEAVE(cs) { \ 152 J2dTraceLn4(J2D_TRACE_VERBOSE2, \ 153 "CS.Leave: tid, cs, file, line = 0x%x, 0x%x, %s, %d", \ 154 GetCurrentThreadId(), &(cs), THIS_FILE, __LINE__); \ 155 (cs).Leave(); \ 156 J2dTraceLn4(J2D_TRACE_VERBOSE2, \ 157 "CS.Left: tid, cs, file, line = 0x%x, 0x%x, %s, %d", \ 158 GetCurrentThreadId(), &(cs), THIS_FILE, __LINE__); \ 159 } 160 161 /************************************************************************ 162 * AwtToolkit class 163 */ 164 165 class AwtToolkit { 166 public: 167 enum { 168 KB_STATE_SIZE = 256 169 }; 170 171 /* java.awt.Toolkit method ids */ 172 static jmethodID getDefaultToolkitMID; 173 static jmethodID getFontMetricsMID; 174 static jmethodID insetsMID; 175 176 /* sun.awt.windows.WToolkit ids */ 177 static jmethodID windowsSettingChangeMID; 178 static jmethodID displayChangeMID; 179 180 static jmethodID userSessionMID; 181 static jmethodID systemSleepMID; 182 183 BOOL m_isDynamicLayoutSet; 184 185 AwtToolkit(); 186 ~AwtToolkit(); 187 188 BOOL Initialize(BOOL localPump); 189 BOOL Dispose(); 190 191 void SetDynamicLayout(BOOL dynamic); 192 BOOL IsDynamicLayoutSet(); 193 BOOL IsDynamicLayoutSupported(); 194 BOOL IsDynamicLayoutActive(); 195 BOOL areExtraMouseButtonsEnabled(); 196 void setExtraMouseButtonsEnabled(BOOL enable); 197 static UINT GetNumberOfButtons(); 198 199 INLINE BOOL localPump() { return m_localPump; } 200 INLINE BOOL VerifyComponents() { return FALSE; } // TODO: Use new DebugHelper class to set this flag 201 INLINE HWND GetHWnd() { return m_toolkitHWnd; } 202 203 INLINE HMODULE GetModuleHandle() { return m_dllHandle; } 204 INLINE void SetModuleHandle(HMODULE h) { m_dllHandle = h; } 205 206 INLINE static DWORD MainThread() { return GetInstance().m_mainThreadId; } 207 INLINE void VerifyActive() throw (awt_toolkit_shutdown) { 208 if (!m_isActive && m_mainThreadId != ::GetCurrentThreadId()) { 209 throw awt_toolkit_shutdown(); 210 } 211 } 212 INLINE BOOL IsDisposed() { return m_isDisposed; } 213 static UINT GetMouseKeyState(); 214 static void GetKeyboardState(PBYTE keyboardState); 215 216 static ATOM RegisterClass(); 217 static void UnregisterClass(); 218 INLINE LRESULT SendMessage(UINT msg, WPARAM wParam=0, LPARAM lParam=0) { 219 if (!m_isDisposed) { 220 return ::SendMessage(GetHWnd(), msg, wParam, lParam); 221 } else { 222 return NULL; 223 } 224 } 225 static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, 226 LPARAM lParam); 227 static LRESULT CALLBACK GetMessageFilter(int code, WPARAM wParam, 228 LPARAM lParam); 229 static LRESULT CALLBACK ForegroundIdleFilter(int code, WPARAM wParam, 230 LPARAM lParam); 231 static LRESULT CALLBACK MouseLowLevelHook(int code, WPARAM wParam, 232 LPARAM lParam); 233 234 INLINE static AwtToolkit& GetInstance() { return theInstance; } 235 INLINE void SetPeer(JNIEnv *env, jobject wToolkit) { 236 AwtToolkit &tk = AwtToolkit::GetInstance(); 237 if (tk.m_peer != NULL) { 238 env->DeleteGlobalRef(tk.m_peer); 239 } 240 tk.m_peer = (wToolkit != NULL) ? env->NewGlobalRef(wToolkit) : NULL; 241 } 242 243 INLINE jobject GetPeer() { 244 return m_peer; 245 } 246 247 // is this thread the main thread? 248 249 INLINE static BOOL IsMainThread() { 250 return GetInstance().m_mainThreadId == ::GetCurrentThreadId(); 251 } 252 253 // post a message to the message pump thread 254 255 INLINE BOOL PostMessage(UINT msg, WPARAM wp=0, LPARAM lp=0) { 256 return ::PostMessage(GetHWnd(), msg, wp, lp); 257 } 258 259 // cause the message pump thread to call the function synchronously now! 260 261 INLINE void * InvokeFunction(void*(*ftn)(void)) { 262 return (void *)SendMessage(WM_AWT_INVOKE_VOID_METHOD, (WPARAM)ftn, 0); 263 } 264 INLINE void InvokeFunction(void (*ftn)(void)) { 265 InvokeFunction((void*(*)(void))ftn); 266 } 267 INLINE void * InvokeFunction(void*(*ftn)(void *), void* param) { 268 return (void *)SendMessage(WM_AWT_INVOKE_METHOD, (WPARAM)ftn, 269 (LPARAM)param); 270 } 271 INLINE void InvokeFunction(void (*ftn)(void *), void* param) { 272 InvokeFunction((void*(*)(void*))ftn, param); 273 } 274 275 INLINE CriticalSection &GetSyncCS() { return m_Sync; } 276 277 void *SyncCall(void*(*ftn)(void *), void* param); 278 void SyncCall(void (*ftn)(void *), void *param); 279 void *SyncCall(void *(*ftn)(void)); 280 void SyncCall(void (*ftn)(void)); 281 282 // cause the message pump thread to call the function later ... 283 284 INLINE void InvokeFunctionLater(void (*ftn)(void *), void* param) { 285 if (!PostMessage(WM_AWT_INVOKE_METHOD, (WPARAM)ftn, (LPARAM)param)) { 286 JNIEnv* env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2); 287 JNU_ThrowInternalError(env, "Message not posted, native event queue may be full."); 288 } 289 } 290 291 // cause the message pump thread to synchronously synchronize on the handle 292 293 INLINE void WaitForSingleObject(HANDLE handle) { 294 SendMessage(WM_AWT_WAIT_FOR_SINGLE_OBJECT, 0, (LPARAM)handle); 295 } 296 297 /* 298 * Create an AwtXxxx C++ component using a given factory 299 */ 300 typedef void (*ComponentFactory)(void*, void*); 301 static void CreateComponent(void* hComponent, void* hParent, 302 ComponentFactory compFactory, BOOL isParentALocalReference=TRUE); 303 304 static void DestroyComponentHWND(HWND hwnd); 305 306 // constants used to PostQuitMessage 307 308 static const int EXIT_ENCLOSING_LOOP; 309 static const int EXIT_ALL_ENCLOSING_LOOPS; 310 311 // ... 312 313 void QuitMessageLoop(int status); 314 315 UINT MessageLoop(IDLEPROC lpIdleFunc, PEEKMESSAGEPROC lpPeekMessageFunc); 316 BOOL PumpWaitingMessages(PEEKMESSAGEPROC lpPeekMessageFunc); 317 void PumpToDestroy(class AwtComponent* p); 318 void ProcessMsg(MSG& msg); 319 BOOL PreProcessMsg(MSG& msg); 320 BOOL PreProcessMouseMsg(class AwtComponent* p, MSG& msg); 321 BOOL PreProcessKeyMsg(class AwtComponent* p, MSG& msg); 322 323 /* Create an ID which maps to an AwtObject pointer, such as a menu. */ 324 UINT CreateCmdID(AwtObject* object); 325 326 // removes cmd id mapping 327 void RemoveCmdID(UINT id); 328 329 /* Return the AwtObject associated with its ID. */ 330 AwtObject* LookupCmdID(UINT id); 331 332 /* Return the current application icon. */ 333 HICON GetAwtIcon(); 334 HICON GetAwtIconSm(); 335 336 // Calculate a wave-like value out of the integer 'value' and 337 // the specified period. 338 // The argument 'value' is an integer 0, 1, 2, ... *infinity*. 339 // 340 // Examples: 341 // Period == 3 342 // Generated sequence: 0 1 2 1 0 ..... 343 // 344 // Period == 4 345 // Generated sequence: 0 1 2 3 2 1 0 ..... 346 static inline UINT CalculateWave(UINT value, const UINT period) { 347 if (period < 2) { 348 return 0; 349 } 350 // -2 is necessary to avoid repeating extreme values (0 and period-1) 351 value %= period * 2 -2; 352 if (value >= period) { 353 value = period * 2 -2 - value; 354 } 355 return value; 356 } 357 358 HICON GetSecurityWarningIcon(UINT index, UINT w, UINT h); 359 360 /* Turns on/off dialog modality for the system. */ 361 INLINE AwtDialog* SetModal(AwtDialog* frame) { 362 AwtDialog* previousDialog = m_pModalDialog; 363 m_pModalDialog = frame; 364 return previousDialog; 365 }; 366 INLINE void ResetModal(AwtDialog* oldFrame) { m_pModalDialog = oldFrame; }; 367 INLINE BOOL IsModal() { return (m_pModalDialog != NULL); }; 368 INLINE AwtDialog* GetModalDialog(void) { return m_pModalDialog; }; 369 370 /* Stops the current message pump (normally a modal dialog pump) */ 371 INLINE void StopMessagePump() { m_breakOnError = TRUE; } 372 373 /* Debug settings */ 374 INLINE void SetVerbose(long flag) { m_verbose = (flag != 0); } 375 INLINE void SetVerify(long flag) { m_verifyComponents = (flag != 0); } 376 INLINE void SetBreak(long flag) { m_breakOnError = (flag != 0); } 377 INLINE void SetHeapCheck(long flag); 378 379 static void SetBusy(BOOL busy); 380 381 /* Set and get the default input method Window handler. */ 382 INLINE void SetInputMethodWindow(HWND inputMethodHWnd) { m_inputMethodHWnd = inputMethodHWnd; } 383 INLINE HWND GetInputMethodWindow() { return m_inputMethodHWnd; } 384 385 static VOID CALLBACK PrimaryIdleFunc(); 386 static VOID CALLBACK SecondaryIdleFunc(); 387 static BOOL CALLBACK CommonPeekMessageFunc(MSG& msg); 388 static BOOL activateKeyboardLayout(HKL hkl); 389 390 HANDLE m_waitEvent; 391 volatile DWORD eventNumber; 392 volatile BOOL isInDoDragDropLoop; 393 private: 394 HWND CreateToolkitWnd(LPCTSTR name); 395 396 BOOL m_localPump; 397 DWORD m_mainThreadId; 398 HWND m_toolkitHWnd; 399 HWND m_inputMethodHWnd; 400 BOOL m_verbose; 401 BOOL m_isActive; // set to FALSE at beginning of Dispose 402 BOOL m_isDisposed; // set to TRUE at end of Dispose 403 BOOL m_areExtraMouseButtonsEnabled; 404 405 BOOL m_vmSignalled; // set to TRUE if QUERYENDSESSION has successfully 406 // raised SIGTERM 407 408 BOOL m_verifyComponents; 409 BOOL m_breakOnError; 410 411 BOOL m_breakMessageLoop; 412 UINT m_messageLoopResult; 413 414 class AwtComponent* m_lastMouseOver; 415 BOOL m_mouseDown; 416 417 HHOOK m_hGetMessageHook; 418 HHOOK m_hMouseLLHook; 419 UINT_PTR m_timer; 420 421 class AwtCmdIDList* m_cmdIDs; 422 BYTE m_lastKeyboardState[KB_STATE_SIZE]; 423 CriticalSection m_lockKB; 424 425 static AwtToolkit theInstance; 426 427 /* The current modal dialog frame (normally NULL). */ 428 AwtDialog* m_pModalDialog; 429 430 /* The WToolkit peer instance */ 431 jobject m_peer; 432 433 HMODULE m_dllHandle; /* The module handle. */ 434 435 CriticalSection m_Sync; 436 437 /* track display changes - used by palette-updating code. 438 This is a workaround for a windows bug that prevents 439 WM_PALETTECHANGED event from occurring immediately after 440 a WM_DISPLAYCHANGED event. 441 */ 442 private: 443 BOOL m_displayChanged; /* Tracks displayChanged events */ 444 // 0 means we are not embedded. 445 DWORD m_embedderProcessID; 446 447 public: 448 BOOL HasDisplayChanged() { return m_displayChanged; } 449 void ResetDisplayChanged() { m_displayChanged = FALSE; } 450 void RegisterEmbedderProcessId(HWND); 451 BOOL IsEmbedderProcessId(const DWORD processID) const 452 { 453 return m_embedderProcessID && (processID == m_embedderProcessID); 454 } 455 456 private: 457 static JNIEnv *m_env; 458 static DWORD m_threadId; 459 public: 460 static void SetEnv(JNIEnv *env); 461 static JNIEnv* GetEnv(); 462 463 static BOOL GetScreenInsets(int screenNum, RECT * rect); 464 465 // If the DWM is active, this function uses 466 // DwmGetWindowAttribute()/DWMWA_EXTENDED_FRAME_BOUNDS. 467 // Otherwise, fall back to regular ::GetWindowRect(). 468 // See 6711576 for more details. 469 static void GetWindowRect(HWND hWnd, LPRECT lpRect); 470 471 private: 472 // The window handle of a toplevel window last seen under the mouse cursor. 473 // See MouseLowLevelHook() for details. 474 HWND m_lastWindowUnderMouse; 475 public: 476 HWND GetWindowUnderMouse() { return m_lastWindowUnderMouse; } 477 478 void InstallMouseLowLevelHook(); 479 void UninstallMouseLowLevelHook(); 480 481 482 /* AWT preloading (early Toolkit thread start) 483 */ 484 public: 485 /* Toolkit preload action class. 486 * Preload actions should be registered with 487 * AwtToolkit::getInstance().GetPreloadThread().AddAction(). 488 * AwtToolkit thread calls InitImpl method at the beghining 489 * and CleanImpl(false) before exiting for all registered actions. 490 * If an application provides own Toolkit thread 491 * (sun.awt.windows.WToolkit.embeddedInit), the thread calls Clean(true) 492 * for each action. 493 */ 494 class PreloadThread; // forward declaration 495 class PreloadAction { 496 friend class PreloadThread; 497 public: 498 PreloadAction() : initThreadId(0), pNext(NULL) {} 499 virtual ~PreloadAction() {} 500 501 protected: 502 // called by PreloadThread or as result 503 // of EnsureInited() call (on Toolkit thread!). 504 virtual void InitImpl() = 0; 505 506 // called by PreloadThread (before exiting). 507 // reInit == false: normal shutdown; 508 // reInit == true: PreloadThread is shutting down due external 509 // Toolkit thread was provided. 510 virtual void CleanImpl(bool reInit) = 0; 511 512 public: 513 // Initialized the action on the Toolkit thread if not yet initialized. 514 bool EnsureInited(); 515 516 // returns thread ID which the action was inited on (0 if not inited) 517 DWORD GetInitThreadID(); 518 519 // Allows to deinitialize action earlier. 520 // The method must be called on the Toolkit thread only. 521 // returns true on success, 522 // false if the action was inited on other thread. 523 bool Clean(); 524 525 private: 526 unsigned initThreadId; 527 // lock for Init/Clean 528 CriticalSection initLock; 529 530 // Chain support (for PreloadThread) 531 PreloadAction *pNext; // for action chain used by PreloadThread 532 void SetNext(PreloadAction *pNext) { this->pNext = pNext; } 533 PreloadAction *GetNext() { return pNext; } 534 535 // wrapper for AwtToolkit::InvokeFunction 536 static void InitWrapper(void *param); 537 538 void Init(); 539 void Clean(bool reInit); 540 541 }; 542 543 /** Toolkit preload thread class. 544 */ 545 class PreloadThread { 546 public: 547 PreloadThread(); 548 ~PreloadThread(); 549 550 // adds action & start the thread if not yet started 551 bool AddAction(PreloadAction *pAction); 552 553 // sets termination flag; returns true if the thread is running. 554 // wrongThread specifies cause of the termination: 555 // false means termination on the application shutdown; 556 // wrongThread is used as reInit parameter for action cleanup. 557 bool Terminate(bool wrongThread); 558 bool InvokeAndTerminate(void(_cdecl *fn)(void *), void *param); 559 560 // waits for the thread completion; 561 // use the method after Terminate() only if Terminate() returned true 562 INLINE void Wait4Finish() { 563 ::WaitForSingleObject(hFinished, INFINITE); 564 } 565 566 INLINE unsigned GetThreadId() { 567 CriticalSection::Lock lock(threadLock); 568 return threadId; 569 } 570 INLINE bool IsWrongThread() { 571 CriticalSection::Lock lock(threadLock); 572 return wrongThread; 573 } 574 // returns true if the current thread is "preload" thread 575 bool OnPreloadThread(); 576 577 private: 578 // data access lock 579 CriticalSection threadLock; 580 581 // the thread status 582 enum Status { 583 None = -1, // initial 584 Preloading = 0, // preloading in progress 585 RunningToolkit, // Running as Toolkit thread 586 Cleaning, // exited from Toolkit thread proc, cleaning 587 Finished // 588 } status; 589 590 // "wrong thread" flag 591 bool wrongThread; 592 593 // thread proc (calls (this)param->ThreadProc()) 594 static unsigned WINAPI StaticThreadProc(void *param); 595 unsigned ThreadProc(); 596 597 INLINE void AwakeThread() { 598 ::SetEvent(hAwake); 599 } 600 601 // if threadId != 0 -> we are running 602 unsigned threadId; 603 // ThreadProc sets the event on exit 604 HANDLE hFinished; 605 // ThreadProc waits on the event for NewAction/Terminate/InvokeAndTerminate 606 HANDLE hAwake; 607 608 // function/param to invoke (InvokeAndTerminate) 609 // if execFunc == NULL => just terminate 610 void(_cdecl *execFunc)(void *); 611 void *execParam; 612 613 // action chain 614 PreloadAction *pActionChain; 615 PreloadAction *pLastProcessedAction; 616 617 // returns next action in the list (NULL if no more actions) 618 PreloadAction* GetNextAction(); 619 620 }; 621 622 INLINE PreloadThread& GetPreloadThread() { return preloadThread; } 623 624 private: 625 PreloadThread preloadThread; 626 627 }; 628 629 630 /* creates an instance of T and assigns it to the argument, but only if 631 the argument is initially NULL. Supposed to be thread-safe. 632 returns the new value of the argument. I'm not using volatile here 633 as InterlockedCompareExchange ensures volatile semantics 634 and acquire/release. 635 The function is useful when used with static POD NULL-initialized 636 pointers, as they are guaranteed to be NULL before any dynamic 637 initialization takes place. This function turns such a pointer 638 into a thread-safe singleton, working regardless of dynamic 639 initialization order. Destruction problem is not solved, 640 we don't need it here. 641 */ 642 643 template<typename T> inline T* SafeCreate(T* &pArg) { 644 /* this implementation has no locks, it just destroys the object if it 645 fails to be the first to init. another way would be using a special 646 flag pointer value to mark the pointer as "being initialized". */ 647 T* pTemp = (T*)InterlockedCompareExchangePointer((void**)&pArg, NULL, NULL); 648 if (pTemp != NULL) return pTemp; 649 T* pNew = new T; 650 pTemp = (T*)InterlockedCompareExchangePointer((void**)&pArg, pNew, NULL); 651 if (pTemp != NULL) { 652 // we failed it - another thread has already initialized pArg 653 delete pNew; 654 return pTemp; 655 } else { 656 return pNew; 657 } 658 } 659 660 #endif /* AWT_TOOLKIT_H */