Topic       : The GFA-Basic Compendium
Author      : GFA Systemtechnik GmbH
Version     : GFABasic.HYP v2.98 (12/31/2023)
Subject     : Documentation/Programming
Nodes       : 899
Index Size  : 28056
HCP-Version : 3
Compiled on : Atari
@charset    : atarist
@lang       : 
@default    : Document not found
@help       : Help
@options    : +g -i -s +z
@width      : 75
@hostname   : STRNGSRV
@hostname   : CAB     
@hostname   : HIGHWIRE
@hostname   : THING   
View Ref-FileThis information was provided by Ingo Schmidt (from a book).

Starting address of a memory block which GEM installs to manage the VDI
parameters. This list isn't valid for the Mega-TOS or Blitter-TOS. GFA V3.0
gives confused values here. However, in the standard ROM-TOS the parameter
block for the virtual workstation is at address &H578C. That block also is 308
bytes long and has the same structure as VDIBASE. The VDIBASE is a copy of that
parameter block. So in V3.0 you can use the hardware address instead of
VDIBASE.

Offset  Size  Description
   0    word  current text rotation (0, 900, 1800, 2700)
   2    word  clipping flag (0=on, 1=off)
   4    long  address of current font header
   8    word  DDA_INC (?)
   10   word  multi-fill flag
   12   word  number of scan lines of current fill pattern
   14   long  start address of fill pattern
   18   word  points/absolute mode (?)
   20   long  SCRTCHP (buffer pointer, current boot sector ??)
   24   word  SCRPT2 (minus offset to LPEEK(VDIBASE+20) ??)
              Gives the start of the eventually executable part of the boot
              sector -> from LPEEK(VDIBASE+20)-DPEEK(VDIBASE+24) these are the
              last 490 bytes of the boot sector ??
   26   word  current text style
   28   word  T_SCLSTS (=0 ??)
   30   word  current polygon fill color
   32   word  current fill pattern -> DEFFILL color,DPEEK(VDIBASE+32)-1,style
   34   word  boundary flag
   36   word  current fill style
   38   word  current text alignment (0=left, 1=centered, 2=right)
   40   word  VDI handle of current workstation (GFA-BasicGFA-Basic is the best BASIC for the Atari!
)
   42   word  current line start form
   44   word  current line color
   46   word  current line end form
   48   word  current line style
   50   word  current line width
   52   long  pointer to next VDI-(GDOS) font
   56   word  current polymarker color
   58   word  current polymarker height
   60   word  current polymarker type
   62   word  relative polymarker height
   64   long  pointer to next virtual workstation parameter block
   68   word  number of available GEM/VDI fonts
   70   word  index of current GEM/VDI font
   72   byte  copy of current font header (88 bytes)
   160  word  ?
   162  word  current text color
   164  word  current user line style
   166  word  plane 1 of user fill pattern [mono]  (16 words)
   198  word  plane 2 of user fill pattern [color] (16 words)
   230  word  plane 3 of user fill pattern [color] (16 words)
   262  word  plane 4 of user fill pattern [mono]  (16 words)
   294  word  current vertical text alignment
              0=baseline, 1=halfline, 2=ascentline,
              3=bottomline, 4=descentline, 5=topline
   296  word  current graphics mode -> GRAPHMODE DPEEK(VDIBASE+296)-1
   298  word  current coordinate system
              Normalized Device Coordinates (NDC)=0
              Raster Coordinates (RC)=2 -> standard
   300  word  x1, y1, x2, y2 of current clipping box (4 words)

This system variable should be avoided. This table is actually stored outside
the programs memory space. Messing around with this table can lead to
unpredictable results.