This section describes the functions that must be supported by the display driver for the primary screen. Although these functions are not required for hardcopy drivers, hardcopy drivers should provide a default routine to handle the functions described in this section, and at FillLogicalDeviceBlock time, put a pointer to the default routine in the relevant entries in the dispatch table. The default routine will post a warning PMERR_DEV_FUNC_NOT_INSTALLED and return BOOLEAN TRUE.

Descriptions of these mandatory functions for display drivers are provided. The functions are grouped according to the conditional include sections of the header file, as follows:

• AVIO functions (INCL_AVIOP, INCL_GRE_DEVMISC1)
  
• Bit-map functions (INCL_GRE_BITMAPS)
  
• Device functions 2 (INCL_GRE_DEVMISC2)
  
• Device functions 3 (INCL_GRE_DEVMISC3)
  
• Miscellaneous screen functions (INCL_GRE_PICK, INCL_WINPOINTERS)

Each description shows what the handling routine is expected to do, the parameters passed to the routine, and the values that the routine returns.