feature request: include layer name in PerspectiveRenderEventDetail custom event

[xgui3783]

Currently, as of 3011c56, PerspectiveRenderEventDetail has the following interface:

export interface PerspectiveRenderEventDetail {
  /** Value of -1 indicates that there are no visible segmentation layers */
  meshesLoaded: number,
  /** Value of -1 indicates that there are no visible segmentation layers */
  meshFragmentsLoaded: number,
  lastLoadedMeshId?: string
}

It would be lovely to include an additional piece of information regarding from which layer the mesh loaded from. lastLoadedMeshId currently outputs the label index, but this falls short if there exist several segmentation layer, which is the case for big brain cyto map, as well as julich-brain v18.

For example, for big brain cyto, v1, v2 and interpolated maps are independent segmentation layers. On call to setMeshestoLoad for all three layers result in the emitted perspective events:

  12,0
  14,0
  13,0
  5,0
  15,0
  18,0
  3,0
  23,0
  21,0
  22,0
  25,0
  7,0
  2,0
3 1,0

edit: it would be ideal to have something like

interpolated:12,0
interpolated:14,0
interpolated:13,0
interpolated:5,0
interpolated:15,0
interpolated:18,0
interpolated:3,0
interpolated:23,0
interpolated:21,0
interpolated:22,0
interpolated:25,0
interpolated:7,0
interpolated:2,0
interpolated:1,0
v1:1,0
v2:1,0

or perhaps in a separate key layer, which would be ideal