Optional
The layers: each a grid child rooted in a Layer, as in a sheet's layers.
Layer
layers
The sheets whose surfaces get the layers. Omitted, every sheet's do.
The surfaces the layers are rendered on. A layer on more than one reads which it is on with useGridSurface.
'cells' Copy
'cells'
The layers: each a grid child rooted in a
Layer, as in a sheet'slayers.