Thumbnail Provider not working

Question

I'm trying to write a Windows Explorer thumbnail handler for our custom file type. I've got this working fine for the preview pane, but am having trouble getting it to work for the thumbnails.

Windows doesn't even seem to be trying to call the DllGetClassObject entry point.

Before I continue, note that I'm using Windows 7 and unmanaged C++.

I've registered the following values in the registry:

HKCR\CLSID\<my guid>
HKCR\CLSID\<my guid>\InprocServer32 (default value = path to my DLL)
HKCR\CLSID\<my guid>\InprocServer32\ThreadingModel (value = "Apartment")
HKCR\.<my ext>\shellex\{E357FCCD-A995-4576-B01F-234630154E96} (value = my guid)

I've also tried using the Win SDK sample, and that doesn't work. And also the sample project in this article (http://www.codemonkeycodes.com/2010/01/11/ithumbnailprovider-re-visited/), and that doesn't work.

I'm new to shell programming, so not really sure the best way of debugging this. I've tried attaching the debugger to explorer.exe, but that doesn't seem to work (breakpoints get disabled, and none of my OutputDebugStrings get displayed in the output window). Note that I tried setting the "DesktopProcess" in the registry as described in the WinSDK docs for debugging the shell, but I'm still only seeing one explorer.exe in the task manager - so that "may" be why I can't debug it??

Any help with this would be greatly appreciated!

Regards, Dan.

Answer 1

I stumbled across this since you mentioned my blog ( codemonkeycodes.com ).

What problem are you having with my sample? Did you register you DLL using regsvr32? What version of Windows 7 are you on, 32 or 64?

---

Update:

I can't say what is or isn't working for you. I just downloaded the sample from my site, followed the directions and change the function STDMETHODIMP CThumbnailProvider::GetThumbnail... to look like

{
*phbmp = NULL;
*pdwAlpha = WTSAT_UNKNOWN;

ULONG_PTR token;
GdiplusStartupInput input;
if (Ok == GdiplusStartup(&token, &input, NULL))
{
    //gcImage.LogBuffer();
    Bitmap * pBitmap = new Bitmap(188, 141);
    if( pBitmap )
    {
        Color color(0, 0, 0);
        pBitmap->GetHBITMAP(color, phbmp);
    }
}

GdiplusShutdown(token);

if( *phbmp != NULL )
    return NOERROR;

return E_NOTIMPL;
}

I registered the DLL and then created a new file with the proper extension, and tada, I had a nice black thumbnail.

I wish I could help you. Maybe you want to email me your code?