xxDark commented on PR #8277:
URL: https://github.com/apache/netbeans/pull/8277#issuecomment-2679959287
I think I've figured out what happens:
```C
BOOL __stdcall OpenClipboard(HWND hWndNewOwner)
{
DWORD emptyClipboard;
DWORD result = NtUserOpenClipboard(hWndNewOwner, &emptyClipboard);
if ( emptyClipboard )
ClientEmptyClipboard();
return result;
}
```
Call to `OpenClipboard` fails in the JDK, because both toolkit & EDT are
trying to access it.
`emptyClipboard` never gets set to `true` (?), so `ClientEmptyClipboard` is
never called. I think that `ClientEmptyClipboard` is a user-mode version of
`EmptyClipboard` which calls `NtUserEmptyClipboard`. In MS documentation, there
is a reference to
[WM_DESTROYCLIPBOARD](https://learn.microsoft.com/en-us/windows/desktop/dataxchg/wm-destroyclipboard)
(keep
[this](https://github.com/openjdk/jdk/blob/990d40e98da2ceb3261096eaa55550565af58fc1/src/java.desktop/windows/native/libawt/windows/awt_Toolkit.cpp#L1039)
code in mind).
`ClientEmptyClipboard` looks like this (and not called):
```C
void ClientEmptyClipboard(void)
{
struct _HANDLENODE *v0; // rbx
struct _HANDLENODE *v1; // rdi
RtlEnterCriticalSection(&gcsClipboard);
v0 = (struct _HANDLENODE *)gphn;
if ( gphn )
{
do
{
v1 = *(struct _HANDLENODE **)v0;
if ( *((_QWORD *)v0 + 3) )
DeleteClientClipboardHandle(v0);
RtlFreeHeap(pUserHeap, 0, v0);
v0 = v1;
}
while ( v1 );
}
gphn = 0LL;
if ( pfnWowEmptyClipBoard )
pfnWowEmptyClipBoard(); // Supposed to send WM_DESTROYCLIPBOARD here,
but because OpenClipboard did not succeed, the message is silently discarded (?)
RtlLeaveCriticalSection(&gcsClipboard);
}
```
So TL;DR `LostOwnership` never gets a chance to be called because
`WM_DESTROYCLIPBOARD` does not get delivered. If we follow what function native
code does: [supposed to clear current cached
contents](https://github.com/openjdk/jdk/blob/990d40e98da2ceb3261096eaa55550565af58fc1/src/java.desktop/share/classes/sun/awt/datatransfer/SunClipboard.java#L299),
but never gets a chance to do so.
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