I found something in a Microsoft development forum that addresses this topic. The question was about a way to provide a custom thumbnail image, to which Microsoft's Leonardo Blanco responded with this:
We do no[t] plan to provide a means for an app to create a
custom alternative thumbnail representation, but we will
provide an API to opt out of the normal thumbnail image
altogether ....
It looks like those plans might have changed in the meantime, judging from the existence in MSDN of the functions DwmSetIconicLivePreviewBitmap
and DwmSetIconicThumbnail
for Windows 7. Right now those entries don't really contain any explanations, but their names look promising.
Someone pointed out that the thumbnail for Windows Media Player shows moving video even while the window is minimized. Blanco's explanation:
WMP uses a new video pipeline that talks directly to the
[Desktop Window Manager] to achieve a smoother playback
experience. This pipeline relies on [DirectX] and doesn't
depend on window visibility information, so the thumbnail
can be kept alive even though the window is minimized, as
long as the app continues to submit frames. You may notice,
however, that the UI around the video isn't live anymore
(this is tricky to observe because the UI around the video
doesn't usually update). For a bit more info on this method,
see the DwmSetPresentParameters
API.
I'm afraid I can't find anything more about this. Documentation for DWM functions is sparse.
Given the nature of your application, maybe it's worth considering a gadget to live on the Windows Sidebar.