Video Manager (VMAN)

This section describes how the Video Manager (VMAN) component fits into 
the GRADD model. 

When VMAN is initialized, a series of components are loaded and 
initialized.  These components include SOFTDRAW and the GRADDs required 
for the available graphics adapters (each graphics adapter may require 
more than one GRADD). 

The GRADD model supports multiple GRADDs. If a developer wants to extend 
the GRADD model or to filter out operations, a filter GRADD can be placed 
between VMAN and the primary GRADD running the hardware. This form of 
linking GRADDs is called chaining and provides a way of modifying a 
GRADD's behavior without rewriting and recompiling the GRADD.  "Adding 
Extensions" in Graphics Adapter Device Drivers discusses the specifics 
involved when extending the GRADD architecture.