DrvDocumentPropertySheets problem in UI wrapper.

NTDEV
1

Hi all :slight_smile:

I finally installed printer UI wrapper which i’ve made.
but some worked, and some didn’t. As i mentioned before, every function
except DrvDocumentEvent, I just load the library “unidrvui.dll” and call
GetProcAddress function giving the corresponding function name as an
argument.

when installing, it seemed like it was working fine.
when i viewed the properties of the printer, it worked very well.
But the problem occured when

  1. using Microsoft Word,
  2. and trying to print(in every application supporting printer),
  3. and selecting the “File -> Print” menu.(also in every application
    supporting printer)
    The Error message was “0x00000000 Access violation. this cannot be read”
    I Thought it was because DrvDocumentEvent function which i’ve made, but
    there were a message following in the logfile.
    “DrvDocumentPropertySheets - Loading unidrvui.dll failed”
    (I made the program to write a logfile for every function calls, whether
    it success of not.)

And then i guessed it was because of the returning NULL pointer after
failing to load the library.

all i do in the DrvDocumentPropertySheets function is as follows.

LONG
DrvDocumentPropertySheets(
PPROPSHEETUI_INFO pPSUIInfo,
LPARAM lParam
)
{
FARPROC UIDllFunc;
LONG Value;

UIDllFunc = WrapUnidrvUI(“DrvDocumentPropertySheets”);
// WrapUnidrvUi function obtains the function pointer of the
// corresponding argument.
Value = (*UIDllFunc)(pPSUIInfo, lParam);

return (Value);
}

the strange thing is this.
DrvDocumentPropertySheets function works when trying to view the
properties of the printer. It means it loads the library successfully and
obtains the valid function pointer. I can confirm this in the logfile.
Other function calls success everytime when it gets called(fortunately).

I tested the same situation with “msplot” (NTDDK\src\print\msplot) and i
could see the DrvDocumentPropertySheets function being called from the
system in the same situation.
But the implementation of DrvDocumentPropertySheets were very complicated.
(NTDDK\src\print\msplot\plotui\docprop.c)

Why does the Loading fails only in situation which i’ve mentioned?
What do i have to do to make the library loads successfully for every
situation?

following is the module loading library and returning the function pointer

FARPROC
WrapUnidrvUI(
char *function_name // the name of the function trying to use
)
{
HINSTANCE hInstUniUI; // handling the library
FARPROC UIDllFunc; // Function pointer

MyFilePrintLine(function_name);
// MyFilePrintLine writes the string argument in the logfile.
if (hInstUniUI = LoadLibrary(_T(“UNIDRVUI.DLL”)))
{
MyFilePrintLine(“Successfully Loaded UNIDRVUI.dll”);
UIDllFunc = (FARPROC)GetProcAddress(hInstUniUI, function_name);

if (!UIDllFunc)
{
MyFilePrintLine(“Unable to GetProcAddress.\n”);
// handle the error
FreeLibrary(hInstPSUI);
UIDllFunc = NULL;
}
else
{
MyFilePrintLine(“Successfully found procedure!\n”);
}
}
else
MyFilePrintLine(“Loading UIDRVUI.dll failed\n”);

return UIDllFunc;
}

I wish i could listen for advice.
Please help me with it. I’ll be looking forward to it.

-with respect
Souneil

2

I would do a GetLastError to see why LoadLibrary fails in the first
place. Also, you should really be checking if function pointer returned
is NULL in your DrvDocumentPropertySheets function as well. This will
prevent the AV that you are seeing.

It would certainly help to know the error code when LoadLibrary fails.

  • Ashwin

This posting is provided “AS IS” with no warranties, and confers no
rights.

-----Original Message-----
From: Souneil Park [mailto:xxxxx@hanmail.net]
Sent: Wednesday, August 28, 2002 10:39 AM
To: NT Developers Interest List
Subject: [ntdev] DrvDocumentPropertySheets problem in UI wrapper.

Hi all :slight_smile:

I finally installed printer UI wrapper which i’ve made.
but some worked, and some didn’t. As i mentioned before, every function
except DrvDocumentEvent, I just load the library “unidrvui.dll” and call
GetProcAddress function giving the corresponding function name as an
argument.

when installing, it seemed like it was working fine.
when i viewed the properties of the printer, it worked very well. But
the problem occured when

  1. using Microsoft Word,
  2. and trying to print(in every application supporting printer), 3. and
    selecting the “File -> Print” menu.(also in every application supporting
    printer) The Error message was “0x00000000 Access violation. this cannot
    be read” I Thought it was because DrvDocumentEvent function which i’ve
    made, but there were a message following in the logfile.
    “DrvDocumentPropertySheets - Loading unidrvui.dll failed” (I made the
    program to write a logfile for every function calls, whether it success
    of not.)

And then i guessed it was because of the returning NULL pointer after
failing to load the library.

all i do in the DrvDocumentPropertySheets function is as follows.

LONG
DrvDocumentPropertySheets(
PPROPSHEETUI_INFO pPSUIInfo,
LPARAM lParam
)
{
FARPROC UIDllFunc;
LONG Value;

UIDllFunc = WrapUnidrvUI(“DrvDocumentPropertySheets”);
// WrapUnidrvUi function obtains the function pointer of the
// corresponding argument.
Value = (*UIDllFunc)(pPSUIInfo, lParam);

return (Value);
}

the strange thing is this.
DrvDocumentPropertySheets function works when trying to view the
properties of the printer. It means it loads the library successfully
and obtains the valid function pointer. I can confirm this in the
logfile.
Other function calls success everytime when it gets called(fortunately).

I tested the same situation with “msplot” (NTDDK\src\print\msplot) and i
could see the DrvDocumentPropertySheets function being called from the
system in the same situation. But the implementation of
DrvDocumentPropertySheets were very complicated.
(NTDDK\src\print\msplot\plotui\docprop.c)

Why does the Loading fails only in situation which i’ve mentioned? What
do i have to do to make the library loads successfully for every
situation?

following is the module loading library and returning the function
pointer

FARPROC
WrapUnidrvUI(
char *function_name // the name of the function trying to use
)
{
HINSTANCE hInstUniUI; // handling the library
FARPROC UIDllFunc; // Function pointer

MyFilePrintLine(function_name);
// MyFilePrintLine writes the string argument in the logfile.
if (hInstUniUI = LoadLibrary(_T(“UNIDRVUI.DLL”)))
{
MyFilePrintLine(“Successfully Loaded UNIDRVUI.dll”);
UIDllFunc = (FARPROC)GetProcAddress(hInstUniUI, function_name);

if (!UIDllFunc)
{
MyFilePrintLine(“Unable to GetProcAddress.\n”);
// handle the error
FreeLibrary(hInstPSUI);
UIDllFunc = NULL;
}
else
{
MyFilePrintLine(“Successfully found procedure!\n”);
}
}
else
MyFilePrintLine(“Loading UIDRVUI.dll failed\n”);

return UIDllFunc;
}

–

I wish i could listen for advice.
Please help me with it. I’ll be looking forward to it.

-with respect
Souneil

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