implement LoggerSystem on winrt

[richardeakin]

Carried over from #992.

Currently it is disabled on winrt (as in LoggerSystem::write() does nothing), since there is no EventLog. Instead it is discussed that we should try EventWrite via COM.

[lucasvickers]

I did some exploration and committed these changes to my repo.

The two most obvious logging API candidates were EventWrite and EventWriteString.

First EventWrite

The EventWrite API relies on a predefined logging event. These events are defined by EventDescriptors. If you take a look at the Remarks section of the EventDescriptors link, you'll see that we're supposed to use the Message Compiler to generate our manifest header. This is different than the prior way where we just defined the level and 0'd out the details at the time we were making the log call

In my example I keep getting ERROR_INVALID_PARAMETER (87), and I suspect it's because I have no valid EventDescriptors.

I tried digging a little deeper, and the issue is I have no app-specific provider.h file, which I believe is what we would generate when we register our provider (app?). If you take a look at this document on writing manifest based events, it says to include provider.h. I tried this, but we seem to be picking up the default file and if you inspect provider.h it has no reference to message types.

Then EventWriteString

The EventWriteString API seems far more promising (and similar to the old style of logging). We don't need any event descriptors, etc. The problem is that in evntprov.h EventWriteString is never defined due to the following check:

#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)

A quick search tells me that we need to be using the desktop version of windows for this to be true, which probably runs counter to the whole WinRT thing.

In Summary

It seems like we need to explore how to register our app as a provider (if that's the correct terminology anyway).