'===========================================================================
' Subject: PB FADING ROUTINE                 Date: Unknown Date           
' Author:  Dave Navarro, Jr.                 Code: PB                     
' Origin:  dave@powerbasic.com             Packet: GRAPHICS.ABC
'===========================================================================
$CPU 8086                 ' program works on any CPU
$OPTIMIZE SIZE            ' make smallest possible executable
$COMPILE UNIT             ' compile to a unit (PBU)
$DEBUG MAP OFF            ' turn off map file generation
$DEBUG PBDEBUG OFF        ' don't include pbdebug support in our executable
$LIB ALL        OFF       ' turn off all unused PowerBASIC libraries
$ERROR ALL      OFF       ' turn off bounds checking

DEFINT A-Z                ' default all variables to integers for maximum
                          ' speed and minimum size

%FLAGS = 0
%AX = 1
%BX = 2
%CX = 3
%DX = 4
%SI = 5
%DI = 6
%BP = 7
%DS = 8
%ES = 9

SHARED Target$

SUB FadeOut() PUBLIC
  IF LEN( Target$ ) = 0 THEN
    Target$ = STRING$( 765, 0 )
    REG %AX, &H1017
    REG %BX, 0
    REG %CX, 255
    REG %ES, STRSEG( Target$ )
    REG %DX, STRPTR( Target$ )
    CALL INTERRUPT &H10
  END IF
  FOR J% = 1 TO 32
    CALL FadeDAC( -4 )
  NEXT J%
END SUB

SUB FadeIn() PUBLIC
  IF LEN( Target$ ) = 0 THEN
    EXIT SUB
  END IF
  FOR J% = 1 TO 32
    CALL FadeDAC( 4 )
  NEXT J%
END SUB

SUB FadeDAC( Inc% ) PRIVATE
  LOCAL Buff$, N%, K%
  Buff$ = STRING$( 765, 0 )
  REG %AX, &H1017
  REG %BX, 0
  REG %CX, 255
  REG %ES, STRSEG( Buff$ )
  REG %DX, STRPTR( Buff$ )
  CALL INTERRUPT &H10
  FOR J% = 1 TO LEN( Buff$ )
    N% = ASC( MID$( Buff$, J%, 1 )) + Inc%
    IF N% < 0 THEN N% = 0
    K% = ASC( MID$( Target$, J%, 1 ))
    IF N% > K% THEN N% = K%
    MID$( Buff$, J%, 1 ) = CHR$( N% )
  NEXT J%
  REG %AX, &H1012
  REG %BX, 0
  REG %CX, 255
  REG %ES, STRSEG( Buff$ )
  REG %DX, STRPTR( Buff$ )
  CALL INTERRUPT &H10
END SUB