FindNextPrinterChangeNotification SafePRINTER_NOTIFY_INFO is invalid

[RikVanHaaren]

Describe the bug and how to reproduce

Having an issue with the 'FindNextPrinterChangeNotification' method within the "WinSpool". The 4th parameter, out SafePRINTER_NOTIFY_INFO pointer to a buffer that receives the printer information for the change notification, isn't set as it should be and keeps being invalid.

Below is the result of FindNextPrinterChangeNotification(hChange, out chg, default, out ppi) on the ppi: Name	Value	Type
ppi	0x0000000000000000	Vanara.PInvoke.WinSpool.SafePRINTER_NOTIFY_INFO
IsClosed	false	bool
IsInvalid	true	bool
IsNull	true	bool
handle	0x0000000000000000	System.IntPtr

What code is involved

This behavior is happening within the test StartWriteEndDocPagePrinterTest. Below is my own implementation:

SafeHPRINTER hprnt;
var printerName = "MyPrinterName";
if (!OpenPrinter(printerName, out hprnt))
{
    Console.WriteLine($"Failed to open printer {printerName}. Error: {GetLastError()}");
    return;
}

using var hChange = FindFirstPrinterChangeNotification(hprnt, PRINTER_CHANGE.PRINTER_CHANGE_ALL, PRINTER_NOTIFY_CATEGORY.PRINTER_NOTIFY_CATEGORY_2D);
while (true)
{
    var kernalStatus = Kernel32.WaitForSingleObject(hChange, 200);
    if (kernalStatus == Kernel32.WAIT_STATUS.WAIT_OBJECT_0)
    {
        SafePRINTER_NOTIFY_INFO ppi;
        PRINTER_CHANGE chg;
        bool foundPrinterNotification = FindNextPrinterChangeNotification(hChange, out chg, default, out ppi);
        if (foundPrinterNotification && !ppi.IsInvalid)
        {
            PRINTER_NOTIFY_INFO pi = ppi;
            Console.WriteLine($"{chg}: {string.Join(",", pi.aData?.Select(d => d.Field))}");
        }
    }
}

When running this program, I just request the printer to print a test page. Everything goes as expected until it hits the FindNextPrinterChangeNotification method and checks if the PPI is valid, which it is not.

Expected behavior

I expected that within the 'FindNextPrinterChangeNotification' the ppi 'SafePRINTER_NOTIFY_INFO ' should receive the printer information for the change notification.

[dahall]

See updated test in commit referenced above. You have to provide a PRINTER_NOTIFY_OPTIONS parameter value with the data you wish to see.

[RikVanHaaren]

Thanks for your addition and information, it works now!