Bizarre problem with fopen and GetOpenFileName, please help!

[Marin]

All,

This could be an error on my part but if it is then I can't see it.
The code below was run Win2000 if that helps.

I have two functions for reading/writing data from/to a file:

--------------------------------------------
void loadUIInputData()
{
FILE* tempfile;

tempfile=fopen("appdata/uiInputData","rb");
if(tempfile!=null)
{
if(fread(&uiInputData,sizeof(uiInputData),1,tempfile)!=1)uiInputDataFileError(T("read
from"));
if(fclose(tempfile)!=0)uiInputDataFileError(T("close"));
}
}

void saveUIInputData()
{
FILE* tempfile;

tempfile=fopen("appdata/uiInputData","wb");
if(tempfile==null)uiInputDataFileError(T("create"));
else
{
if(fwrite(&uiInputData,sizeof(uiInputData),1,tempfile)!=1)uiInputDataFileError(T("write
to"));
if(fclose(tempfile)!=0)uiInputDataFileError(T("close"));
}
}
--------------------------------------------

Notice that the functions have nothing to do with any GetOpenFileName
function, they use a constant filename and the data being read/written
is simply a structure (which contains other structures - I did that so
that data would be contiguous in memory).

loadUIInputData() is called when the program starts and
saveUIInputData() is called when the program exits. If I run and close
the program it runs fine, no errors, regardless of whether the file
already exists.

I have another function which calls GetOpenFileName:

--------------------------------------------
int selectInputFile()
{
static int returnCode;
static tchar filename[_MAX_PATH+1];

inputFile.lpstrFile=filename;
returnCode=GetOpenFileName(&inputFile);
if(returnCode)SetWindowText(hwndInputFileCombobox,inputFile.lpstrFile);
return returnCode;
}
--------------------------------------------

This is triggered by clicking a "Browse" button. The name of the
selected file is put into a combobox.

Now if I run the program, click browse and select a file the call to
saveUIInputData() fails, i.e. fopen() returns null. What can be
causing this? How can showing a common dialog and setting text in a
combobox cause fopen() to fail? I'm lost as to what the problem is.
Strangely, when the file dialog closes, after selecting a file, there
is a noticable short burst of disk activity. Why? I assume
GetOpenFileName() just sets data in the referenced structure, it
doesn't actually do any disk access per se, right? If anyone has clue
let me know. I desperately need to solve this problem. :(

Many thanks,
Marin

[Ed Astle]

Maybe browsing causes the apps default drive/directory to change so that
"appdata/uiInputData" ends up being relative to where ever the browsing took
it ?

Try a getcwd() to see what the current directory is prior to fopen.

Ed.

[Joe Hagen]

"Marin" <dol...@psydolphin.net> wrote in message
news:ee1d9799.02102...@posting.google.com...

Marin,

As Ed mentioned, GetOpenFileName actually changes the current
directory.

To work around this, you'd probably have to code something like:

GetCurrentDirectory(sizeof(savedir),savedir);
GetOpenFileName(&ofn);
SetCurrentDirectory(savedir);

to ensure that the current directory is preserved.

Joe

[Cris Dunbar]

dol...@psydolphin.net (Marin) wrote in message news:<ee1d9799.02102...@posting.google.com>...

> Now if I run the program, click browse and select a file the call to
> saveUIInputData() fails, i.e. fopen() returns null. What can be
> causing this? How can showing a common dialog and setting text in a
> combobox cause fopen() to fail? I'm lost as to what the problem is.
> Strangely, when the file dialog closes, after selecting a file, there
> is a noticable short burst of disk activity. Why? I assume
> GetOpenFileName() just sets data in the referenced structure, it
> doesn't actually do any disk access per se, right? If anyone has clue
> let me know. I desperately need to solve this problem. :(
>
>
> Many thanks,
> Marin

GetOpenFilename changes current directory to the browsed-to directory
unless you specify OFN_NOCHANGEDIR in the OPENFILENAME options. Since
you're using relative pathnames, they are no longer there.