* This is a leftover from before the interface was hoisted out, and most
windows were still calling directly to CaptureContext instead of via
the public ICaptureContext interface
* Any work that might use Qt needs to happen on the UI thread, so when
running a python script on the python thread we need to invoke across.
We wrap the main ICaptureContext interface to block invoke onto the UI
for any function calls that aren't just returning internal data.