Changeset 80845 in vbox for trunk/src/VBox/GuestHost/SharedClipboard

Timestamp:

Sep 17, 2019 9:05:21 AM (6 years ago)

Author:

vboxsync

svn:sync-xref-src-repo-rev:

133415

Message:

Shared Clipboard/URI: More code for transfer channel handling.

Location:

trunk/src/VBox/GuestHost/SharedClipboard

Files:

• ClipboardDataObjectImpl-win.cpp (modified) (1 diff)
• clipboard-common.cpp (modified) (8 diffs)
• clipboard-uri.cpp (modified) (15 diffs)
• clipboard-win.cpp (modified) (4 diffs)

trunk/src/VBox/GuestHost/SharedClipboard/ClipboardDataObjectImpl-win.cpp

@@ -406 +406 @@
  */
 int SharedClipboardWinDataObject::createFileGroupDescriptorFromTransfer(PSHCLURITRANSFER pTransfer,
-                                                                      bool fUnicode, HGLOBAL *phGlobal)
+                                                                        bool fUnicode, HGLOBAL *phGlobal)
 {
     AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);

trunk/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp

@@ -180 +180 @@
     RTListForEachSafe(&pSource->lstEvents, pEvIt, pEvItNext, SHCLEVENT, Node)
     {
+        RTListNodeRemove(&pEvIt->Node);
+
         SharedClipboardEventDestroy(pEvIt);
+
         RTMemFree(pEvIt);
+        pEvIt = NULL;
     }
 
@@ -199 +203 @@
 
     LogFlowFunc(("uSource=%RU16: New event: %RU16\n", pSource->uID, pSource->uEventIDNext));
-    return pSource->uEventIDNext++; /** @todo Handle rollovers? */
+
+    pSource->uEventIDNext++;
+    if (pSource->uEventIDNext == VBOX_SHARED_CLIPBOARD_MAX_EVENTS)
+        pSource->uEventIDNext = 0;
+
+    return pSource->uEventIDNext;
 }
 
@@ -235 +244 @@
 
     return 0;
+}
+
+/**
+ * Detaches a payload from an event, internal version.
+ *
+ * @param   pEvent              Event to detach payload for.
+ */
+static void sharedClipboardEventPayloadDetachInternal(PSHCLEVENT pEvent)
+{
+    AssertPtrReturnVoid(pEvent);
+
+    pEvent->pPayload = NULL;
 }
 
@@ -324 +345 @@
  * @param   uTimeoutMs          Timeout (in ms) to wait.
  * @param   ppPayload           Where to store the (allocated) event payload on success. Needs to be free'd with
- *                              SharedClipboardPayloadFree().
+ *                              SharedClipboardPayloadFree(). Optional.
  */
 int SharedClipboardEventWait(PSHCLEVENTSOURCE pSource, SHCLEVENTID uID, RTMSINTERVAL uTimeoutMs,
@@ -330 +351 @@
 {
     AssertPtrReturn(pSource, VERR_INVALID_POINTER);
+    /** ppPayload is optional. */
 
     LogFlowFuncEnter();
@@ -341 +363 @@
         if (RT_SUCCESS(rc))
         {
-            *ppPayload = pEvent->pPayload;
-
-            pEvent->pPayload = NULL;
+            if (ppPayload)
+            {
+                *ppPayload = pEvent->pPayload;
+
+                /* Make sure to detach payload here, as the caller now owns the data. */
+                sharedClipboardEventPayloadDetachInternal(pEvent);
+            }
         }
     }
@@ -402 +428 @@
     if (pEvent)
     {
-        pEvent->pPayload = NULL;
+        sharedClipboardEventPayloadDetachInternal(pEvent);
     }
 #ifdef DEBUG_andy
@@ -803 +829 @@
         RT_CASE_RET_STR(VBOX_SHARED_CLIPBOARD_HOST_MSG_READ_DATA);
         RT_CASE_RET_STR(VBOX_SHARED_CLIPBOARD_HOST_MSG_FORMATS_REPORT);
-        RT_CASE_RET_STR(VBOX_SHARED_CLIPBOARD_HOST_MSG_URI_TRANSFER_START);
+        RT_CASE_RET_STR(VBOX_SHARED_CLIPBOARD_HOST_MSG_URI_TRANSFER_STATUS);
         RT_CASE_RET_STR(VBOX_SHARED_CLIPBOARD_HOST_MSG_URI_ROOT_LIST_HDR_READ);
         RT_CASE_RET_STR(VBOX_SHARED_CLIPBOARD_HOST_MSG_URI_ROOT_LIST_HDR_WRITE);

trunk/src/VBox/GuestHost/SharedClipboard/clipboard-uri.cpp

@@ -23 +23 @@
 #include <iprt/list.h>
 #include <iprt/path.h>
+#include <iprt/rand.h>
 #include <iprt/semaphore.h>
 
@@ -1040 +1041 @@
 
 /**
- * Initializes an URI clipboard transfer struct.
- *
- * @returns VBox status code.
- * @param   enmDir              Specifies the transfer direction of this transfer.
- * @param   enmSource           Specifies the data source of the transfer.
+ * Creates an URI clipboard transfer.
+ *
+ * @returns VBox status code.
  * @param   ppTransfer          Where to return the created URI transfer struct.
  *                              Must be destroyed by SharedClipboardURITransferDestroy().
  */
-int SharedClipboardURITransferCreate(SHCLURITRANSFERDIR enmDir, SHCLSOURCE enmSource,
-                                     PSHCLURITRANSFER *ppTransfer)
+int SharedClipboardURITransferCreate(PSHCLURITRANSFER *ppTransfer)
 {
     AssertPtrReturn(ppTransfer, VERR_INVALID_POINTER);
@@ -1063 +1061 @@
     pTransfer->State.uID       = 0;
     pTransfer->State.enmStatus = SHCLURITRANSFERSTATUS_NONE;
-    pTransfer->State.enmDir    = enmDir;
-    pTransfer->State.enmSource = enmSource;
+    pTransfer->State.enmDir    = SHCLURITRANSFERDIR_UNKNOWN;
+    pTransfer->State.enmSource = SHCLSOURCE_INVALID;
 
     LogFlowFunc(("enmDir=%RU32, enmSource=%RU32\n", pTransfer->State.enmDir, pTransfer->State.enmSource));
@@ -1094 +1092 @@
     RTListInit(&pTransfer->lstRoots);
 
-    *ppTransfer = pTransfer;
-
-    if (RT_FAILURE(rc))
+    RT_ZERO(pTransfer->Events);
+
+    if (RT_SUCCESS(rc))
+    {
+        *ppTransfer = pTransfer;
+    }
+    else
     {
         if (pTransfer)
@@ -1154 +1156 @@
 }
 
+/**
+ * Initializes an URI transfer object.
+ *
+ * @returns VBox status code.
+ * @param   pTransfer           Transfer to initialize.
+ * @param   uID                 ID to use for the transfer. Can be set to 0 if not important.
+ * @param   enmDir              Specifies the transfer direction of this transfer.
+ * @param   enmSource           Specifies the data source of the transfer.
+ */
+int SharedClipboardURITransferInit(PSHCLURITRANSFER pTransfer,
+                                   uint32_t uID, SHCLURITRANSFERDIR enmDir, SHCLSOURCE enmSource)
+{
+    pTransfer->State.uID       = uID;
+    pTransfer->State.enmDir    = enmDir;
+    pTransfer->State.enmSource = enmSource;
+
+    int rc = SharedClipboardEventSourceCreate(&pTransfer->Events, pTransfer->State.uID);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
 int SharedClipboardURITransferOpen(PSHCLURITRANSFER pTransfer)
 {
@@ -1183 +1207 @@
  * @param   hList               List handle of the list to get handle info for.
  */
-inline PSHCLURILISTHANDLEINFO sharedClipboardURITransferListGet(PSHCLURITRANSFER pTransfer,
-                                                                           SHCLLISTHANDLE hList)
+inline PSHCLURILISTHANDLEINFO sharedClipboardURITransferListGet(PSHCLURITRANSFER pTransfer, SHCLLISTHANDLE hList)
 {
     PSHCLURILISTHANDLEINFO pIt;
@@ -1330 +1353 @@
                 {
                     if (RTDirIsValid(pInfo->u.Local.hDir))
+                    {
                         RTDirClose(pInfo->u.Local.hDir);
+                        pInfo->u.Local.hDir = NIL_RTDIR;
+                    }
                     break;
                 }
@@ -1370 +1396 @@
 {
     uint64_t cbSize = 0;
-    int rc = RTFileQuerySize(pszPath, &cbSize);
+    int rc = RTFileQuerySizeByPath(pszPath, &cbSize);
     if (RT_SUCCESS(rc))
     {
@@ -2195 +2221 @@
 
 /**
+ * Returns the transfer's ID.
+ *
+ * @returns The transfer's ID.
+ * @param   pTransfer           URI clipboard transfer to return ID for.
+ */
+SHCLURITRANSFERID SharedClipboardURITransferGetID(PSHCLURITRANSFER pTransfer)
+{
+    AssertPtrReturn(pTransfer, 0);
+
+    return pTransfer->State.uID;
+}
+
+/**
  * Returns the transfer's source.
  *
@@ -2297 +2336 @@
         if (pTransfer->Thread.fStarted) /* Did the thread indicate that it started correctly? */
         {
-            pTransfer->State.enmStatus = SHCLURITRANSFERSTATUS_RUNNING;
+            pTransfer->State.enmStatus = SHCLURITRANSFERSTATUS_STARTED;
         }
         else
@@ -2352 +2391 @@
 
         pURI->cRunning    = 0;
-        pURI->cMaxRunning = 1; /* For now we only support one transfer per client at a time. */
-
-#ifdef DEBUG_andy
-        pURI->cMaxRunning = UINT32_MAX;
-#endif
+        pURI->cMaxRunning = UINT16_MAX;
+
+        RT_ZERO(pURI->bmTransferIds);
+
         SharedClipboardURICtxReset(pURI);
     }
@@ -2408 +2446 @@
 
 /**
- * Adds a new URI transfer to an clipboard URI transfer.
- *
- * @returns VBox status code.
- * @param   pURI                URI clipboard context to add transfer to.
- * @param   pTransfer           Pointer to URI clipboard transfer to add.
- */
-int SharedClipboardURICtxTransferAdd(PSHCLURICTX pURI, PSHCLURITRANSFER pTransfer)
+ * Returns a specific URI transfer, internal version.
+ *
+ * @returns URI transfer, or NULL if not found.
+ * @param   pURI                URI clipboard context to return transfer for.
+ * @param   uID                 ID of the transfer to return.
+ */
+static PSHCLURITRANSFER sharedClipboardURICtxGetTransferInternal(PSHCLURICTX pURI, uint32_t uID)
+{
+    PSHCLURITRANSFER pTransfer;
+    RTListForEach(&pURI->List, pTransfer, SHCLURITRANSFER, Node) /** @todo Slow, but works for now. */
+    {
+        if (pTransfer->State.uID == uID)
+            return pTransfer;
+    }
+
+    return NULL;
+}
+
+/**
+ * Returns a specific URI transfer.
+ *
+ * @returns URI transfer, or NULL if not found.
+ * @param   pURI                URI clipboard context to return transfer for.
+ * @param   uID                 ID of the transfer to return.
+ */
+PSHCLURITRANSFER SharedClipboardURICtxGetTransfer(PSHCLURICTX pURI, uint32_t uID)
+{
+    return sharedClipboardURICtxGetTransferInternal(pURI, uID);
+}
+
+/**
+ * Returns the number of running URI transfers.
+ *
+ * @returns Number of running transfers.
+ * @param   pURI                URI clipboard context to return number for.
+ */
+uint32_t SharedClipboardURICtxGetRunningTransfers(PSHCLURICTX pURI)
+{
+    AssertPtrReturn(pURI, 0);
+    return pURI->cRunning;
+}
+
+/**
+ * Returns the number of total URI transfers.
+ *
+ * @returns Number of total transfers.
+ * @param   pURI                URI clipboard context to return number for.
+ */
+uint32_t SharedClipboardURICtxGetTotalTransfers(PSHCLURICTX pURI)
+{
+    AssertPtrReturn(pURI, 0);
+    return pURI->cTransfers;
+}
+
+/**
+ * Registers an URI transfer with an URI context, i.e. allocates a transfer ID.
+ *
+ * @return  VBox status code.
+ * @retval  VERR_SHCLPB_MAX_TRANSFERS_REACHED if the maximum of concurrent transfers
+ *          is reached.
+ * @param   pURI                URI clipboard context to register transfer to.
+ * @param   pTransfer           Transfer to register.
+ * @param   pidTransfer         Where to return the transfer ID on success. Optional.
+ */
+int SharedClipboardURICtxTransferRegister(PSHCLURICTX pURI, PSHCLURITRANSFER pTransfer, uint32_t *pidTransfer)
 {
     AssertPtrReturn(pURI,      VERR_INVALID_POINTER);
     AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
-
-    LogFlowFuncEnter();
-
-    if (pURI->cRunning == pURI->cMaxRunning)
+    /* pidTransfer is optional. */
+
+    /*
+     * Pick a random bit as starting point.  If it's in use, search forward
+     * for a free one, wrapping around.  We've reserved both the zero'th and
+     * max-1 IDs.
+     */
+    uint32_t idTransfer = RTRandU32Ex(1, VBOX_SHARED_CLIPBOARD_MAX_TRANSFERS - 2);
+
+    if (!ASMBitTestAndSet(&pURI->bmTransferIds[0], idTransfer))
+    { /* likely */ }
+    else if (pURI->cTransfers < VBOX_SHARED_CLIPBOARD_MAX_TRANSFERS - 2 /* First and last are not used */)
+    {
+        /* Forward search. */
+        int iHit = ASMBitNextClear(&pURI->bmTransferIds[0], VBOX_SHARED_CLIPBOARD_MAX_TRANSFERS, idTransfer);
+        if (iHit < 0)
+            iHit = ASMBitFirstClear(&pURI->bmTransferIds[0], VBOX_SHARED_CLIPBOARD_MAX_TRANSFERS);
+        AssertLogRelMsgReturn(iHit >= 0, ("Transfer count: %RU16\n", pURI->cTransfers), VERR_SHCLPB_MAX_TRANSFERS_REACHED);
+        idTransfer = iHit;
+        AssertLogRelMsgReturn(!ASMBitTestAndSet(&pURI->bmTransferIds[0], idTransfer), ("idObject=%#x\n", idTransfer), VERR_INTERNAL_ERROR_2);
+    }
+    else
+    {
+        LogFunc(("Maximum number of transfers reached (%RU16 transfers)\n", pURI->cTransfers));
         return VERR_SHCLPB_MAX_TRANSFERS_REACHED;
+    }
+
+    Log2Func(("pTransfer=%p, idTransfer=%RU32 (%RU16 transfers)\n", pTransfer, idTransfer, pURI->cTransfers));
 
     RTListAppend(&pURI->List, &pTransfer->Node);
 
     pURI->cTransfers++;
-    LogFlowFunc(("cTransfers=%RU32, cRunning=%RU32\n", pURI->cTransfers, pURI->cRunning));
+
+    if (pidTransfer)
+        *pidTransfer = idTransfer;
 
     return VINF_SUCCESS;
@@ -2433 +2554 @@
 
 /**
- * Removes an URI transfer from a clipboard URI transfer.
- *
- * @returns VBox status code.
- * @param   pURI                URI clipboard context to remove transfer from.
- * @param   pTransfer           Pointer to URI clipboard transfer to remove.
- */
-int SharedClipboardURICtxTransferRemove(PSHCLURICTX pURI, PSHCLURITRANSFER pTransfer)
-{
-    AssertPtrReturn(pURI,      VERR_INVALID_POINTER);
-    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
-
-    LogFlowFuncEnter();
-
-
-    int rc = SharedClipboardURITransferDestroy(pTransfer);
-    if (RT_SUCCESS(rc))
+ * Registers an URI transfer with an URI context by specifying an ID for the transfer.
+ *
+ * @return  VBox status code.
+ * @retval  VERR_ALREADY_EXISTS if a transfer with the given ID already exists.
+ * @retval  VERR_SHCLPB_MAX_TRANSFERS_REACHED if the maximum of concurrent transfers for this context has been reached.
+ * @param   pURI                URI clipboard context to register transfer to.
+ * @param   pTransfer           Transfer to register.
+ * @param   idTransfer          Transfer ID to use for registration.
+ */
+int SharedClipboardURICtxTransferRegisterByIndex(PSHCLURICTX pURI, PSHCLURITRANSFER pTransfer, uint32_t idTransfer)
+{
+    LogFlowFunc(("cTransfers=%RU16, idTransfer=%RU32\n", pURI->cTransfers, idTransfer));
+
+    if (pURI->cTransfers < VBOX_SHARED_CLIPBOARD_MAX_TRANSFERS - 2 /* First and last are not used */)
+    {
+        if (!ASMBitTestAndSet(&pURI->bmTransferIds[0], idTransfer))
+        {
+            RTListAppend(&pURI->List, &pTransfer->Node);
+
+            pURI->cTransfers++;
+            return VINF_SUCCESS;
+        }
+
+        return VERR_ALREADY_EXISTS;
+    }
+
+    LogFunc(("Maximum number of transfers reached (%RU16 transfers)\n", pURI->cTransfers));
+    return VERR_SHCLPB_MAX_TRANSFERS_REACHED;
+}
+
+/**
+ * Unregisters a transfer from an URI clipboard context.
+ *
+ * @retval  VINF_SUCCESS on success.
+ * @retval  VERR_NOT_FOUND if the transfer ID was not found.
+ * @param   pURI                URI clipboard context to unregister transfer from.
+ * @param   idTransfer          Transfer ID to unregister.
+ */
+int SharedClipboardURICtxTransferUnregister(PSHCLURICTX pURI, uint32_t idTransfer)
+{
+    int rc = VINF_SUCCESS;
+    AssertMsgStmt(ASMBitTestAndClear(&pURI->bmTransferIds, idTransfer), ("idTransfer=%#x\n", idTransfer), rc = VERR_NOT_FOUND);
+
+    PSHCLURITRANSFER pTransfer = sharedClipboardURICtxGetTransferInternal(pURI, idTransfer);
+    if (pTransfer)
     {
         RTListNodeRemove(&pTransfer->Node);
 
-        RTMemFree(pTransfer);
-        pTransfer = NULL;
-    }
-
-    LogFlowFuncLeaveRC(rc);
-    return rc;
-}
-
-/**
- * Returns a specific URI transfer, internal version.
- *
- * @returns URI transfer, or NULL if not found.
- * @param   pURI                URI clipboard context to return transfer for.
- * @param   uIdx                Index of the transfer to return.
- */
-static PSHCLURITRANSFER sharedClipboardURICtxGetTransferInternal(PSHCLURICTX pURI, uint32_t uIdx)
-{
-    AssertReturn(uIdx == 0, NULL); /* Only one transfer allowed at the moment. */
-    return RTListGetFirst(&pURI->List, SHCLURITRANSFER, Node);
-}
-
-/**
- * Returns a specific URI transfer.
- *
- * @returns URI transfer, or NULL if not found.
- * @param   pURI                URI clipboard context to return transfer for.
- * @param   uIdx                Index of the transfer to return.
- */
-PSHCLURITRANSFER SharedClipboardURICtxGetTransfer(PSHCLURICTX pURI, uint32_t uIdx)
-{
-    return sharedClipboardURICtxGetTransferInternal(pURI, uIdx);
-}
-
-/**
- * Returns the number of running URI transfers.
- *
- * @returns Number of running transfers.
- * @param   pURI                URI clipboard context to return number for.
- */
-uint32_t SharedClipboardURICtxGetRunningTransfers(PSHCLURICTX pURI)
-{
-    AssertPtrReturn(pURI, 0);
-    return pURI->cRunning;
-}
-
-/**
- * Returns the number of total URI transfers.
- *
- * @returns Number of total transfers.
- * @param   pURI                URI clipboard context to return number for.
- */
-uint32_t SharedClipboardURICtxGetTotalTransfers(PSHCLURICTX pURI)
-{
-    AssertPtrReturn(pURI, 0);
-    return pURI->cTransfers;
+        Assert(pURI->cTransfers);
+        pURI->cTransfers--;
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    LogFlowFunc(("idTransfer=%RU32, rc=%Rrc\n", idTransfer, rc));
+    return rc;
 }
 
@@ -2525 +2628 @@
     RTListForEachSafe(&pURI->List, pTransfer, pTransferNext, SHCLURITRANSFER, Node)
     {
-        if (SharedClipboardURITransferGetStatus(pTransfer) != SHCLURITRANSFERSTATUS_RUNNING)
+        if (SharedClipboardURITransferGetStatus(pTransfer) != SHCLURITRANSFERSTATUS_STARTED)
         {
             SharedClipboardURITransferDestroy(pTransfer);
@@ -2841 +2944 @@
 }
 
+/**
+ * Translates a Shared Clipboard transfer status (SHCLURITRANSFERSTATUS_XXX) into a string.
+ *
+ * @returns Transfer status string name.
+ * @param   uStatus             The transfer status to translate.
+ */
+const char *VBoxClipboardTransferStatusToStr(uint32_t uStatus)
+{
+    switch (uStatus)
+    {
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_NONE);
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_READY);
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_STARTED);
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_STOPPED);
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_CANCELED);
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_KILLED);
+        RT_CASE_RET_STR(SHCLURITRANSFERSTATUS_ERROR);
+    }
+    return "Unknown";
+}

trunk/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp

@@ -106 +106 @@
         const DWORD dwLastErr = GetLastError();
         if (dwLastErr == ERROR_CLIPBOARD_NOT_OPEN)
-            rc = VERR_INVALID_STATE;
+        {
+            rc = VINF_SUCCESS; /* Not important, so just report success instead. */
+        }
         else
+        {
             rc = RTErrConvertFromWin32(dwLastErr);
-
-        LogFunc(("Failed with %Rrc (0x%x)\n", rc, dwLastErr));
+            LogFunc(("Failed with %Rrc (0x%x)\n", rc, dwLastErr));
+        }
     }
     else
@@ -147 +150 @@
 
 /**
+ * Initializes a Shared Clipboard Windows context.
+ *
+ * @returns VBox status code.
+ * @param   pWinCtx             Shared Clipboard Windows context to initialize.
+ */
+int SharedClipboardWinCtxInit(PSHCLWINCTX pWinCtx)
+{
+    int rc = RTCritSectInit(&pWinCtx->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        /* Check that new Clipboard API is available. */
+        rc = SharedClipboardWinCheckAndInitNewAPI(&pWinCtx->newAPI);
+        if (RT_SUCCESS(rc))
+        {
+            pWinCtx->hWnd                 = NULL;
+            pWinCtx->hWndClipboardOwnerUs = NULL;
+            pWinCtx->hWndNextInChain      = NULL;
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a Shared Clipboard Windows context.
+ *
+ * @param   pWinCtx             Shared Clipboard Windows context to destroy.
+ */
+void SharedClipboardWinCtxDestroy(PSHCLWINCTX pWinCtx)
+{
+    if (!pWinCtx)
+        return;
+
+    if (RTCritSectIsInitialized(&pWinCtx->CritSect))
+    {
+        int rc2 = RTCritSectDelete(&pWinCtx->CritSect);
+        AssertRC(rc2);
+    }
+}
+
+/**
  * Checks and initializes function pointer which are required for using
  * the new clipboard API.
@@ -299 +344 @@
  */
 LRESULT SharedClipboardWinChainPassToNext(PSHCLWINCTX pWinCtx,
-                                        UINT msg, WPARAM wParam, LPARAM lParam)
+                                          UINT msg, WPARAM wParam, LPARAM lParam)
 {
     LogFlowFuncEnter();
@@ -874 +919 @@
                  *        where another application could own the clipboard (open), and thus the call to
                  *        OleSetClipboard() will fail. Needs (better) fixing. */
+                HRESULT hr = S_OK;
+
                 for (unsigned uTries = 0; uTries < 3; uTries++)
                 {
-                    HRESULT hr = OleSetClipboard(pWinURITransferCtx->pDataObj);
-                    if (SUCCEEDED(hr))
+                    /* Make sure to enter the critical section before setting the clipboard data, as otherwise WM_CLIPBOARDUPDATE
+                     * might get called *before* we had the opportunity to set pWinCtx->hWndClipboardOwnerUs below. */
+                    rc = RTCritSectEnter(&pWinCtx->CritSect);
+                    if (RT_SUCCESS(rc))
                     {
-                        /*
-                         * Calling OleSetClipboard() changed the clipboard owner, which in turn will let us receive
-                         * a WM_CLIPBOARDUPDATE message. To not confuse ourselves with our own clipboard owner changes,
-                         * save a new window handle and deal with it in WM_CLIPBOARDUPDATE.
-                         */
-                        pWinCtx->hWndClipboardOwnerUs = GetClipboardOwner();
-                        break;
+                        hr = OleSetClipboard(pWinURITransferCtx->pDataObj);
+                        if (SUCCEEDED(hr))
+                        {
+                            Assert(OleIsCurrentClipboard(pWinURITransferCtx->pDataObj) == S_OK); /* Sanity. */
+
+                            /*
+                             * Calling OleSetClipboard() changed the clipboard owner, which in turn will let us receive
+                             * a WM_CLIPBOARDUPDATE message. To not confuse ourselves with our own clipboard owner changes,
+                             * save a new window handle and deal with it in WM_CLIPBOARDUPDATE.
+                             */
+                            pWinCtx->hWndClipboardOwnerUs = GetClipboardOwner();
+
+                            rc = RTCritSectLeave(&pWinCtx->CritSect);
+                            AssertRC(rc);
+                            break;
+                        }
                     }
-                    else
-                    {
-                        rc = VERR_ACCESS_DENIED; /** @todo Fudge; fix this. */
-                        LogRel(("Shared Clipboard: Failed with %Rhrc when setting data object to clipboard\n", hr));
-                        RTThreadSleep(100); /* Wait a bit. */
-                    }
+
+                    rc = RTCritSectLeave(&pWinCtx->CritSect);
+                    AssertRCBreak(rc);
+
+                    LogFlowFunc(("Failed with %Rhrc (try %u/3)\n", hr, uTries + 1));
+                    RTThreadSleep(500); /* Wait a bit. */
+                }
+
+                if (FAILED(hr))
+                {
+                    rc = VERR_ACCESS_DENIED; /** @todo Fudge; fix this. */
+                    LogRel(("Shared Clipboard: Failed with %Rhrc when setting data object to clipboard\n", hr));
                 }
             }