File association and thumbnail preview in Windows 10

Question

I have created an application and associated on registry a file extension on Windows 10, so when you double click a file associated with my extension, it opens my app with the file as parameter.

Now, I want the files associated to my application to behave in Windows 10 just like images - I mean, having a thumbnail preview, so when the user selects "large icons", he would be able to see a preview of the file.

I wonder how can I do it. What kind of metadata my file should have so Windows would recognize it and show a preview. Of course, I don't want just large icons, I want a file preview just like image files.

It isn't hard for me to generate a preview bitmap and integrate it to the file format I created (or even to change the file format completely, since I didn't publish anything yet), but how would windows recognize it? Is this even possible?

Thanks in advance

Answer 1

After some research, I found a sample code that does exactly what I need. It creates a thumbnail provider, which have access to the file's contents (binary), and then I can use it to generate the thumbnail of the file.

The sample that creates a IThumbnailProvider can be found here: https://code.msdn.microsoft.com/windowsapps/CppShellExtThumbnailHandler-32399b35/view/SourceCode#content

The project should generate a dll, that we should register on Windows. It might be done using the following lines:

system32/regsvr32 ThumbnailProviderx64.dll
syswow64/regsvr32 ThumbnailProviderx86.dll

unregistering is like this:

system32/regsvr32 /u ThumbnailProviderx64.dll
syswow64/regsvr32 /u ThumbnailProviderx86.dll

Another nice sample could be found at: http://www.codemonkeycodes.com/2010/01/11/ithumbnailprovider-re-visited/