Problem with FindFirstChangeNotificationW in JwaWinBase
lazarus / 34-Windows

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JimC · 2018-08-01 11:17

I'm trying to write a directory monitor using
FindFirstChangeNotificationW and have struck a problem I can't
resolve. All the documentation states the definition as

function FindFirstChangeNotificationW(lpPathName: LPCWSTR;
bWatchSubtree: BOOL;  dwNotifyFilter: DWORD): HANDLE

however in JwaWinBase the definition is

function FindFirstChangeNotificationW(lpPathName: LPCWSTR;
bWatchSubtree: Cardinal;  dwNotifyFilter: DWORD): HANDLE

It may be something simple but I don't know how to use the Cardinal
vice boolean for bWatchSubTree, any assistance would be appreciated. 
 Using Lazarus  1.8.4, FPC 3.0.4 Windows 10 1803 Build 17134.165.
I know I'm re-inventing the wheel but I'm self taught and find
learning via experimenting\doing suits me.
Thanks
JimC

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Bart · 2018-08-01 11:33

IIRC then on Windows BOOL = LongBool, which in essence is a DWORD?

Bart

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engkin · 2018-08-01 15:31

Quote from: JimC on August 01, 2018, 01:17:59 pmI don't know how to
use the Cardinal vice boolean for bWatchSubTree
In C/C++ false is 0, which means true is any value that is *not* 0.

If you want bWatchSubTree to be false, pass 0.
If you want bWatchSubTree to be true, pass any number other than 0.

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ASerge · 2018-08-02 20:45

Quote from: JimC on August 01, 2018, 01:17:59 pmhowever in JwaWinBase
the definition is
function FindFirstChangeNotificationW(lpPathName: LPCWSTR;
bWatchSubtree: Cardinal;  dwNotifyFilter: DWORD): HANDLE
As far as I remember, in Windows 98, the bWatchSubtree parameter could
only accept values 0 or 1, i.e. BOOL(0) or BOOL(1), i.e. it turns out
that if you specify BOOL(-1), which is also True from the point of
view of BOOL, then this led to an error. Therefore, was described a
function where it is more difficult to make a mistake.