GRADD Model Components

This chapter describes the individual components of the Graphics ADapter 
Device (GRADD) driver model used for developing device drivers. 

The GRADD model is composed of several components that coordinate the 
communication among each graphic subsystem and the available graphics 
hardware. The components include the following: 

 Video Manager (VMAN) 
                     The VMAN component binds the GRADD model components 
                     together.  VMAN synchronizes the communication 
                     between translation layers and a GRADD and also 
                     manages the graphics pointer. 

                     When an operating system service requests a graphics 
                     operation, the associated translation layer sends one 
                     of the defined Video Manager Interface (VMI) commands 
                     to VMAN.  On receiving a VMI command, VMAN either 
                     handles the request or sends it down to the 
                     appropriate GRADD.  For more information about VMAN, 
                     refer to Video Manager (VMAN). 

 Translation Layers 
                     A translation layer exists for each graphics engine 
                     in OS/2 Warp.  The translation layer converts the 
                     function calls made by the graphics engine to the VMI 
                     protocol required by VMAN.  For more information 
                     about transition layers, refer to Translation Layers. 
                     

 SOFTDRAW 
                     SOFTDRAW is the default for any simulated graphics 
                     functions for nonaccelerated graphics operations. 

                     Acting as a graphics library, SOFTDRAW exports the 
                     base drawing functions (SDBitBlt and SDLine) used by 
                     VMAN to simulate graphics operations. SOFTDRAW 
                     provides a generic graphics library. Given a pointer 
                     to a linear address (a VRAM bit map or system-memory 
                     bit map), SOFTDRAW can draw the bits directly into 
                     the bit map. 

 Graphics Adapter Device Driver 
                     The GRADDs represent the available video hardware. 
                      They execute the requested operation or returns it 
                     for simulation. 

                     When a GRADD receives a GHI function call from VMAN 
                     that is not mandatory, the GRADD has the option of 
                     performing the requested operation or returning the 
                     request to VMAN with a return code of RC_SIMULATE. 
                     The RC_SIMULATE return code informs VMAN that the 
                     operation needs to be simulated in software.  For 
                     more information about GRADDs, refer to Graphics 
                     Adapter Device Driver (GRADD). 
 

 The following figure graphically illustrates the components of the GRADD 
 model.