Layout background colour from MODELBKCOLOR or
PAPERBKCOLOR, or undefined when the sysvar is unset.
true when resolving for model space; false for
paper space (selects the default fallback).
Packed 24-bit RGB suitable for the renderer clear colour.
readLayoutBackgroundColor — reads the sysvar then calls this
Resolves a packed RGB canvas background from an AcCmColor sysvar value, with space-specific defaults as fallback.
When the sysvar holds a concrete RGB colour (
color.RGBis defined), that value is returned directly. Otherwise the AutoCAD defaults are used: MODEL_SPACE_BACKGROUND (0x000000) for model space or PAPER_SPACE_BACKGROUND (0xffffff) for paper space.