Getting layer information

Hi,



I'm creating a filter plug-in.

By getting ReadLayerDesc, I can get some layer information such as layer name, but I need other properties:



- layer opacity (not the per-pixel transparency but of the layer itself)

- whether the layer is visible

- whether the layer is the current target (or which layer is current)



Does anyone know how?

I appreciate any comments.
Getting layer information
I see these flags in ReadChannelDesc



Boolean target; // Is this a target channel.

Boolean shown; // Is this channel shown?