Gets the layer plane (level) of the frame buffer.
Zero is the default frame buffer.
Positive layer planes correspond to frame buffers that overlay the default
buffer, and negative layer planes correspond to frame buffers that underlie
the default frame buffer.
Gets the layer plane (level) of the frame buffer. Zero is the default frame buffer. Positive layer planes correspond to frame buffers that overlay the default buffer, and negative layer planes correspond to frame buffers that underlie the default frame buffer.