May18 branch: grip position not reported for in-Editor hands

[PJBowron]

Overview

I believe there was an oversight in my changes to address #1824 - the Left/RightHandInputControl prefabs do not have 'grip position' selected as a supported feature. Additionally the CustomInputControl that governs in-Editor input doesn't update grip position/rotation in the SourcePose.

I think perhaps that a subsequent change has introduced more use of TryGetGripPosition than previously existed? It's these calls that are failing now, however, they always would have, had they been there before my change!?

Note: on device, behavior works as expected.

I've got a local fix; I'll post a PR asap.

Expected Behavior

Running in Editor, attempts to obtain grip position succeed and return the general hand position.

Actual Behavior

Attempts fail, grip position returns as 0,0,0

Steps to reproduce

1. setup an MRTK scene
2. add an object with a HandDraggable script
3. the object cannot be moved in-Editor, but can on device

Mixed Reality Toolkit Release Version

May18 branch; SHA: 01876eb

[PJBowron]

@davidkline-ms

[keveleigh]

Ah, looks like this happened in your change. CustomInputSource.cs, the script used for the hands, was updated in #1870 and #2050 to properly return the grip position from TryGetGripPosition, instead of faking it and returning the regular position in the past.

https://github.com/Microsoft/MixedRealityToolkit-Unity/pull/2050/files#diff-d55c55a745b71a905534124d85148516L176

Reverting that "fixes" it, but we should really fix the underlying issue of the fake hands having pointer position instead of grip position.

[PJBowron]

Hopefully the changes in #2133 should do the trick.
I don't really understand why I didn't see this when I made the first change... I must have had other changes that didn't make it into the submission... either way, my bad :(

[david-c-kline]

This was released in the 2017.4.0.0 release candidate