'===========================================================================
' Subject: STARWARS SCREEN SCROLL            Date: 01-18-96 (08:17)       
' Author:  MJS                               Code: PB                     
' Origin:  Rolf@ice.prima.ruhr.de          Packet: GRAPHICS.ABC
'===========================================================================
$huge

deflng a-z

screen 9,,0,0                          ' To have some more pages

dim huge Position(0400,0:1) as integer ' Array with Positios f. virt. Screen
dim CharTable(0:255,0:13) as byte      ' ASCII-Table
dim ScrollScreen(0:400,0:79) as byte   ' Screen with Scroll-Infos

CharHeight=14

y=0
IncY=2
for z=0 to 400
 call r3d22d(320,y,z,x2,y2)          ' to get some "good" 3D's
 Position(z,0)=x2                    ' outermost right border
 Position(z,1)=y2                    ' 2D-Y-Position calculated from 3D-Pos.
 incr y,IncY
next

' Simple CharTableRead
def seg=&HA000
for a=0 to 255
 locate 1,1
 print chr$(a);
 CharPtr=0
 for y=0 to CharHeight-1
  CharTable(a,y)=peek(CharPtr)        ' read ASCII-Table
  incr CharPtr,80
 next
next

data 7
data -1,"ÚÄÄÄÄÄÄÄÄÄÄÄ¿"
data -1,"³ This is a ³"
data -1,"³  TEST !!  ³"
data -1,"³  written  ³"
data -1,"³  by  MJS  ³"
data -1,"³  in 1996  ³"
data -1,"ÀÄÄÄÄÄÄÄÄÄÄÄÙ"

read WorkLines
dim ScrollText$(WorkLines),ScrollCenter(WorkLines)
for a=1 to WorkLines
 read ScrollCenter(a),ScrollText$(a)          ' read Text to scroll
next

VisualPage=0:LastPage=1
ScrollScreenMax=CharHeight*4
ScrollLine=1
ScrollLineSub=0
ColorDiv=(ScrollScreenMax/14)

r=0
for a=1 to 15              ' set colors (black -> white)
 out &H3c8,a
 for b=1 to 3
  out &H3c9,r
 next
 incr r,4
next
for a=1 to 15
 palette a,a
next

while len(inkey$)=0
 screen 9,,LastPage,VisualPage
 line (0,0)-(639,349),0,bf                ' quicker than CLS :)
 for y=ScrollScreenMax-1 to 1 step -1
  y2=y-1
  for x=0 to 79
   ScrollScreen(y,x)=ScrollScreen(y2,x)   ' scroll 'up'
  next
 next
 h$=ScrollText$(ScrollLine)
 select case ScrollCenter(ScrollLine)     ' centering line
 case -1
  StartPos=40-(len(h$)\2)
 case else
  StartPos=ScrollCenter(ScrollLine)
 end select
 for c=1 to len(h$)                       ' read Lines of characters
  ScrollChar=asc(mid$(h$,c,1))
  ScrollScreen(0,StartPos)=CharTable(ScrollChar,ScrollLineSub)
  incr StartPos
 next
 incr ScrollLineSub
 if ScrollLineSub=CharHeight then
  ScrollLineSub=0
  incr ScrollLine
  if ScrollLine>WorkLines then ScrollLine=1
 end if
 for y=0 to ScrollScreenMax-1         ' show 'viewable' scroll-Text
  RealY=349-Position(y,1)             
  OldY=349-Position(y+1,1)
  MaxX=Position(y,0)
  WorkX=-320
  for x=0 to 79
   ScrollByte=ScrollScreen(y,x)
   if (ScrollByte>0) then
    OldX=(((MaxX*WorkX)\320)*4)+320
    for b=7 to 0 step -1
     incr WorkX
     RealX=(((MaxX*WorkX)\320)*4)+320
     if bit(ScrollByte,b) then line (OldX,OldY)-(RealX,RealY),15-(y\ColorDiv),bf
     OldX=RealX
    next
   else
    incr WorkX,8
   end if
  next
 next
 LastPage=VisualPage
 VisualPage=((VisualPage+1) and 1)    ' switch Pages
wend

end

SUB r3d22d(x1, y1, z, x2, y2)   ' calculate 3D -> 2D
' Depth=128
' x2=(x1*depth)/(z+depth)
  z2 = z + 128
  x2 = x1
  SHIFT LEFT x2, 7
  x2 = x2 \ z2
  y2 = y1
  SHIFT LEFT y2, 7
  y2 = y2 \ z2
END SUB