Blender Git Loki

Fix T76595: No Indication of Active Keyframe in Graph Editor

Currently there is a panel that says "Active Keyframe" for numerically editing one keyframe's values, but in the code there is no concept of the "active keyframe."

This patch adds an "active keyframe index" to each FCurve, and displays it with a theme color for the active vertex (which didn't exist before) if the FCurve is active.

{F8536092}

The active keyframe is not currently set for select operations other than basic click-select, which mirrors the behavior in the 3D view.

Differential Revision: https://developer.blender.org/D7737