1 /* 2 * Copyright (c) 1996, 2017, 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 BOOL m_isDynamicLayoutSet; 181 182 AwtToolkit(); 183 ~AwtToolkit(); 184 185 BOOL Initialize(BOOL localPump); 186 BOOL Dispose(); 187 188 void SetDynamicLayout(BOOL dynamic); 189 BOOL IsDynamicLayoutSet(); 190 BOOL IsDynamicLayoutSupported(); 191 BOOL IsDynamicLayoutActive(); 192 BOOL areExtraMouseButtonsEnabled(); 193 void setExtraMouseButtonsEnabled(BOOL enable); 194 static UINT GetNumberOfButtons(); 195 196 INLINE BOOL localPump() { return m_localPump; } 197 INLINE BOOL VerifyComponents() { return FALSE; } // TODO: Use new DebugHelper class to set this flag 198 INLINE HWND GetHWnd() { return m_toolkitHWnd; } 199 200 INLINE HMODULE GetModuleHandle() { return m_dllHandle; } 201 INLINE void SetModuleHandle(HMODULE h) { m_dllHandle = h; } 202 203 INLINE static DWORD MainThread() { return GetInstance().m_mainThreadId; } 204 INLINE void VerifyActive() throw (awt_toolkit_shutdown) { 205 if (!m_isActive && m_mainThreadId != ::GetCurrentThreadId()) { 206 throw awt_toolkit_shutdown(); 207 } 208 } 209 INLINE BOOL IsDisposed() { return m_isDisposed; } 210 static UINT GetMouseKeyState(); 211 static void GetKeyboardState(PBYTE keyboardState); 212 213 static ATOM RegisterClass(); 214 static void UnregisterClass(); 215 INLINE LRESULT SendMessage(UINT msg, WPARAM wParam=0, LPARAM lParam=0) { 216 if (!m_isDisposed) { 217 return ::SendMessage(GetHWnd(), msg, wParam, lParam); 218 } else { 219 return NULL; 220 } 221 } 222 static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, 223 LPARAM lParam); 224 static LRESULT CALLBACK GetMessageFilter(int code, WPARAM wParam, 225 LPARAM lParam); 226 static LRESULT CALLBACK ForegroundIdleFilter(int code, WPARAM wParam, 227 LPARAM lParam); 228 static LRESULT CALLBACK MouseLowLevelHook(int code, WPARAM wParam, 229 LPARAM lParam); 230 231 INLINE static AwtToolkit& GetInstance() { return theInstance; } 232 INLINE void SetPeer(JNIEnv *env, jobject wToolkit) { 233 AwtToolkit &tk = AwtToolkit::GetInstance(); 234 if (tk.m_peer != NULL) { 235 env->DeleteGlobalRef(tk.m_peer); 236 } 237 tk.m_peer = (wToolkit != NULL) ? env->NewGlobalRef(wToolkit) : NULL; 238 } 239 240 INLINE jobject GetPeer() { 241 return m_peer; 242 } 243 244 // is this thread the main thread? 245 246 INLINE static BOOL IsMainThread() { 247 return GetInstance().m_mainThreadId == ::GetCurrentThreadId(); 248 } 249 250 // post a message to the message pump thread 251 252 INLINE BOOL PostMessage(UINT msg, WPARAM wp=0, LPARAM lp=0) { 253 return ::PostMessage(GetHWnd(), msg, wp, lp); 254 } 255 256 // cause the message pump thread to call the function synchronously now! 257 258 INLINE void * InvokeFunction(void*(*ftn)(void)) { 259 return (void *)SendMessage(WM_AWT_INVOKE_VOID_METHOD, (WPARAM)ftn, 0); 260 } 261 INLINE void InvokeFunction(void (*ftn)(void)) { 262 InvokeFunction((void*(*)(void))ftn); 263 } 264 INLINE void * InvokeFunction(void*(*ftn)(void *), void* param) { 265 return (void *)SendMessage(WM_AWT_INVOKE_METHOD, (WPARAM)ftn, 266 (LPARAM)param); 267 } 268 INLINE void InvokeFunction(void (*ftn)(void *), void* param) { 269 InvokeFunction((void*(*)(void*))ftn, param); 270 } 271 272 INLINE CriticalSection &GetSyncCS() { return m_Sync; } 273 274 void *SyncCall(void*(*ftn)(void *), void* param); 275 void SyncCall(void (*ftn)(void *), void *param); 276 void *SyncCall(void *(*ftn)(void)); 277 void SyncCall(void (*ftn)(void)); 278 279 // cause the message pump thread to call the function later ... 280 281 INLINE void InvokeFunctionLater(void (*ftn)(void *), void* param) { 282 if (!PostMessage(WM_AWT_INVOKE_METHOD, (WPARAM)ftn, (LPARAM)param)) { 283 JNIEnv* env = (JNIEnv *)JNU_GetEnv(jvm, JNI_VERSION_1_2); 284 JNU_ThrowInternalError(env, "Message not posted, native event queue may be full."); 285 } 286 } 287 288 // cause the message pump thread to synchronously synchronize on the handle 289 290 INLINE void WaitForSingleObject(HANDLE handle) { 291 SendMessage(WM_AWT_WAIT_FOR_SINGLE_OBJECT, 0, (LPARAM)handle); 292 } 293 294 /* 295 * Create an AwtXxxx C++ component using a given factory 296 */ 297 typedef void (*ComponentFactory)(void*, void*); 298 static void CreateComponent(void* hComponent, void* hParent, 299 ComponentFactory compFactory, BOOL isParentALocalReference=TRUE); 300 301 static void DestroyComponentHWND(HWND hwnd); 302 303 // constants used to PostQuitMessage 304 305 static const int EXIT_ENCLOSING_LOOP; 306 static const int EXIT_ALL_ENCLOSING_LOOPS; 307 308 // ... 309 310 void QuitMessageLoop(int status); 311 312 UINT MessageLoop(IDLEPROC lpIdleFunc, PEEKMESSAGEPROC lpPeekMessageFunc); 313 BOOL PumpWaitingMessages(PEEKMESSAGEPROC lpPeekMessageFunc); 314 void PumpToDestroy(class AwtComponent* p); 315 void ProcessMsg(MSG& msg); 316 BOOL PreProcessMsg(MSG& msg); 317 BOOL PreProcessMouseMsg(class AwtComponent* p, MSG& msg); 318 BOOL PreProcessKeyMsg(class AwtComponent* p, MSG& msg); 319 320 /* Checks that an free ID exists. */ 321 jboolean isFreeIDAvailable(); 322 /* Create an ID which maps to an AwtObject pointer, such as a menu. */ 323 UINT CreateCmdID(AwtObject* object); 324 325 // removes cmd id mapping 326 void RemoveCmdID(UINT id); 327 328 /* Return the AwtObject associated with its ID. */ 329 AwtObject* LookupCmdID(UINT id); 330 331 /* Return the current application icon. */ 332 HICON GetAwtIcon(); 333 HICON GetAwtIconSm(); 334 335 // Calculate a wave-like value out of the integer 'value' and 336 // the specified period. 337 // The argument 'value' is an integer 0, 1, 2, ... *infinity*. 338 // 339 // Examples: 340 // Period == 3 341 // Generated sequence: 0 1 2 1 0 ..... 342 // 343 // Period == 4 344 // Generated sequence: 0 1 2 3 2 1 0 ..... 345 static inline UINT CalculateWave(UINT value, const UINT period) { 346 if (period < 2) { 347 return 0; 348 } 349 // -2 is necessary to avoid repeating extreme values (0 and period-1) 350 value %= period * 2 -2; 351 if (value >= period) { 352 value = period * 2 -2 - value; 353 } 354 return value; 355 } 356 357 HICON GetSecurityWarningIcon(UINT index, UINT w, UINT h); 358 359 /* Turns on/off dialog modality for the system. */ 360 INLINE AwtDialog* SetModal(AwtDialog* frame) { 361 AwtDialog* previousDialog = m_pModalDialog; 362 m_pModalDialog = frame; 363 return previousDialog; 364 }; 365 INLINE void ResetModal(AwtDialog* oldFrame) { m_pModalDialog = oldFrame; }; 366 INLINE BOOL IsModal() { return (m_pModalDialog != NULL); }; 367 INLINE AwtDialog* GetModalDialog(void) { return m_pModalDialog; }; 368 369 /* Stops the current message pump (normally a modal dialog pump) */ 370 INLINE void StopMessagePump() { m_breakOnError = TRUE; } 371 372 /* Debug settings */ 373 INLINE void SetVerbose(long flag) { m_verbose = (flag != 0); } 374 INLINE void SetVerify(long flag) { m_verifyComponents = (flag != 0); } 375 INLINE void SetBreak(long flag) { m_breakOnError = (flag != 0); } 376 INLINE void SetHeapCheck(long flag); 377 378 static void SetBusy(BOOL busy); 379 380 /* Set and get the default input method Window handler. */ 381 INLINE void SetInputMethodWindow(HWND inputMethodHWnd) { m_inputMethodHWnd = inputMethodHWnd; } 382 INLINE HWND GetInputMethodWindow() { return m_inputMethodHWnd; } 383 384 static VOID CALLBACK PrimaryIdleFunc(); 385 static VOID CALLBACK SecondaryIdleFunc(); 386 static BOOL CALLBACK CommonPeekMessageFunc(MSG& msg); 387 static BOOL activateKeyboardLayout(HKL hkl); 388 389 HANDLE m_waitEvent; 390 DWORD eventNumber; 391 private: 392 HWND CreateToolkitWnd(LPCTSTR name); 393 394 BOOL m_localPump; 395 DWORD m_mainThreadId; 396 HWND m_toolkitHWnd; 397 HWND m_inputMethodHWnd; 398 BOOL m_verbose; 399 BOOL m_isActive; // set to FALSE at beginning of Dispose 400 BOOL m_isDisposed; // set to TRUE at end of Dispose 401 BOOL m_areExtraMouseButtonsEnabled; 402 403 BOOL m_vmSignalled; // set to TRUE if QUERYENDSESSION has successfully 404 // raised SIGTERM 405 406 BOOL m_verifyComponents; 407 BOOL m_breakOnError; 408 409 BOOL m_breakMessageLoop; 410 UINT m_messageLoopResult; 411 412 class AwtComponent* m_lastMouseOver; 413 BOOL m_mouseDown; 414 415 HHOOK m_hGetMessageHook; 416 HHOOK m_hMouseLLHook; 417 UINT_PTR m_timer; 418 419 class AwtCmdIDList* m_cmdIDs; 420 BYTE m_lastKeyboardState[KB_STATE_SIZE]; 421 CriticalSection m_lockKB; 422 423 static AwtToolkit theInstance; 424 425 /* The current modal dialog frame (normally NULL). */ 426 AwtDialog* m_pModalDialog; 427 428 /* The WToolkit peer instance */ 429 jobject m_peer; 430 431 HMODULE m_dllHandle; /* The module handle. */ 432 433 CriticalSection m_Sync; 434 435 /* track display changes - used by palette-updating code. 436 This is a workaround for a windows bug that prevents 437 WM_PALETTECHANGED event from occurring immediately after 438 a WM_DISPLAYCHANGED event. 439 */ 440 private: 441 BOOL m_displayChanged; /* Tracks displayChanged events */ 442 // 0 means we are not embedded. 443 DWORD m_embedderProcessID; 444 445 public: 446 BOOL HasDisplayChanged() { return m_displayChanged; } 447 void ResetDisplayChanged() { m_displayChanged = FALSE; } 448 void RegisterEmbedderProcessId(HWND); 449 BOOL IsEmbedderProcessId(const DWORD processID) const 450 { 451 return m_embedderProcessID && (processID == m_embedderProcessID); 452 } 453 454 private: 455 static JNIEnv *m_env; 456 static DWORD m_threadId; 457 public: 458 static void SetEnv(JNIEnv *env); 459 static JNIEnv* GetEnv(); 460 461 static BOOL GetScreenInsets(int screenNum, RECT * rect); 462 463 // If the DWM is active, this function uses 464 // DwmGetWindowAttribute()/DWMWA_EXTENDED_FRAME_BOUNDS. 465 // Otherwise, fall back to regular ::GetWindowRect(). 466 // See 6711576 for more details. 467 static void GetWindowRect(HWND hWnd, LPRECT lpRect); 468 469 private: 470 // The window handle of a toplevel window last seen under the mouse cursor. 471 // See MouseLowLevelHook() for details. 472 HWND m_lastWindowUnderMouse; 473 public: 474 HWND GetWindowUnderMouse() { return m_lastWindowUnderMouse; } 475 476 void InstallMouseLowLevelHook(); 477 void UninstallMouseLowLevelHook(); 478 479 480 /* AWT preloading (early Toolkit thread start) 481 */ 482 public: 483 /* Toolkit preload action class. 484 * Preload actions should be registered with 485 * AwtToolkit::getInstance().GetPreloadThread().AddAction(). 486 * AwtToolkit thread calls InitImpl method at the beghining 487 * and CleanImpl(false) before exiting for all registered actions. 488 * If an application provides own Toolkit thread 489 * (sun.awt.windows.WToolkit.embeddedInit), the thread calls Clean(true) 490 * for each action. 491 */ 492 class PreloadThread; // forward declaration 493 class PreloadAction { 494 friend class PreloadThread; 495 public: 496 PreloadAction() : initThreadId(0), pNext(NULL) {} 497 virtual ~PreloadAction() {} 498 499 protected: 500 // called by PreloadThread or as result 501 // of EnsureInited() call (on Toolkit thread!). 502 virtual void InitImpl() = 0; 503 504 // called by PreloadThread (before exiting). 505 // reInit == false: normal shutdown; 506 // reInit == true: PreloadThread is shutting down due external 507 // Toolkit thread was provided. 508 virtual void CleanImpl(bool reInit) = 0; 509 510 public: 511 // Initialized the action on the Toolkit thread if not yet initialized. 512 bool EnsureInited(); 513 514 // returns thread ID which the action was inited on (0 if not inited) 515 DWORD GetInitThreadID(); 516 517 // Allows to deinitialize action earlier. 518 // The method must be called on the Toolkit thread only. 519 // returns true on success, 520 // false if the action was inited on other thread. 521 bool Clean(); 522 523 private: 524 unsigned initThreadId; 525 // lock for Init/Clean 526 CriticalSection initLock; 527 528 // Chain support (for PreloadThread) 529 PreloadAction *pNext; // for action chain used by PreloadThread 530 void SetNext(PreloadAction *pNext) { this->pNext = pNext; } 531 PreloadAction *GetNext() { return pNext; } 532 533 // wrapper for AwtToolkit::InvokeFunction 534 static void InitWrapper(void *param); 535 536 void Init(); 537 void Clean(bool reInit); 538 539 }; 540 541 /** Toolkit preload thread class. 542 */ 543 class PreloadThread { 544 public: 545 PreloadThread(); 546 ~PreloadThread(); 547 548 // adds action & start the thread if not yet started 549 bool AddAction(PreloadAction *pAction); 550 551 // sets termination flag; returns true if the thread is running. 552 // wrongThread specifies cause of the termination: 553 // false means termination on the application shutdown; 554 // wrongThread is used as reInit parameter for action cleanup. 555 bool Terminate(bool wrongThread); 556 bool InvokeAndTerminate(void(_cdecl *fn)(void *), void *param); 557 558 // waits for the the thread completion; 559 // use the method after Terminate() only if Terminate() returned true 560 INLINE void Wait4Finish() { 561 ::WaitForSingleObject(hFinished, INFINITE); 562 } 563 564 INLINE unsigned GetThreadId() { 565 CriticalSection::Lock lock(threadLock); 566 return threadId; 567 } 568 INLINE bool IsWrongThread() { 569 CriticalSection::Lock lock(threadLock); 570 return wrongThread; 571 } 572 // returns true if the current thread is "preload" thread 573 bool OnPreloadThread(); 574 575 private: 576 // data access lock 577 CriticalSection threadLock; 578 579 // the thread status 580 enum Status { 581 None = -1, // initial 582 Preloading = 0, // preloading in progress 583 RunningToolkit, // Running as Toolkit thread 584 Cleaning, // exited from Toolkit thread proc, cleaning 585 Finished // 586 } status; 587 588 // "wrong thread" flag 589 bool wrongThread; 590 591 // thread proc (calls (this)param->ThreadProc()) 592 static unsigned WINAPI StaticThreadProc(void *param); 593 unsigned ThreadProc(); 594 595 INLINE void AwakeThread() { 596 ::SetEvent(hAwake); 597 } 598 599 // if threadId != 0 -> we are running 600 unsigned threadId; 601 // ThreadProc sets the event on exit 602 HANDLE hFinished; 603 // ThreadProc waits on the event for NewAction/Terminate/InvokeAndTerminate 604 HANDLE hAwake; 605 606 // function/param to invoke (InvokeAndTerminate) 607 // if execFunc == NULL => just terminate 608 void(_cdecl *execFunc)(void *); 609 void *execParam; 610 611 // action chain 612 PreloadAction *pActionChain; 613 PreloadAction *pLastProcessedAction; 614 615 // returns next action in the list (NULL if no more actions) 616 PreloadAction* GetNextAction(); 617 618 }; 619 620 INLINE PreloadThread& GetPreloadThread() { return preloadThread; } 621 622 private: 623 PreloadThread preloadThread; 624 625 }; 626 627 628 /* creates an instance of T and assigns it to the argument, but only if 629 the argument is initially NULL. Supposed to be thread-safe. 630 returns the new value of the argument. I'm not using volatile here 631 as InterlockedCompareExchange ensures volatile semantics 632 and acquire/release. 633 The function is useful when used with static POD NULL-initialized 634 pointers, as they are guaranteed to be NULL before any dynamic 635 initialization takes place. This function turns such a pointer 636 into a thread-safe singleton, working regardless of dynamic 637 initialization order. Destruction problem is not solved, 638 we don't need it here. 639 */ 640 641 template<typename T> inline T* SafeCreate(T* &pArg) { 642 /* this implementation has no locks, it just destroys the object if it 643 fails to be the first to init. another way would be using a special 644 flag pointer value to mark the pointer as "being initialized". */ 645 T* pTemp = (T*)InterlockedCompareExchangePointer((void**)&pArg, NULL, NULL); 646 if (pTemp != NULL) return pTemp; 647 T* pNew = new T; 648 pTemp = (T*)InterlockedCompareExchangePointer((void**)&pArg, pNew, NULL); 649 if (pTemp != NULL) { 650 // we failed it - another thread has already initialized pArg 651 delete pNew; 652 return pTemp; 653 } else { 654 return pNew; 655 } 656 } 657 658 #endif /* AWT_TOOLKIT_H */