XREF _custom

; write this from scratch and get it working
; then plug it into C
FUNC_CNT SET -30
FUNCDEF MACRO
_LVO\1 EQU FUNC_CNT
FUNC_CNT SET FUNC_CNT-6
  ENDM

  INCDIR "include_i_39:"
  INCDIR "extra_lvos_39:"
  INCLUDE "exec/exec_lib.i"
  INCLUDE "exec/types.i"
  INCLUDE "exec/execbase.i"
  INCLUDE "exec/libraries.i" # get the CALLLIB macro
  INCLUDE "graphics/gfxbase.i"
  INCLUDE "graphics_lvo.i"
  INCLUDE "hardware/custom.i"
  INCLUDE "hardware/dmabits.i"

START:
  BSR _takeOverSystem
  BSR _giveBackSystem
  MOVE.L #0,D0
  RTS

OpenGraphicsLibrary MACRO
    LEA GraphicsLibrary,A1
    MOVEQ #0,D0
    CALLLIB _LVOOpenLibrary
    MOVE.L D0,GraphicsBase
  ENDM

TakeOverView MACRO
    MOVE.L GraphicsBase,A6
    MOVE.L gb_ActiView(A6),OldView
    MOVEQ #0,D0
    CALLLIB _LVOLoadView
    CALLLIB _LVOWaitTOF
    CALLLIB _LVOWaitTOF
  ENDM

PreserveOldCopper MACRO
    MOVE.L $26(A6),OldCopper1
    MOVE.L $32(A6),OldCopper2
  ENDM

GetVBRPointer MACRO
    BSR getVBR
    MOVE.L D0,VBRPtr
  ENDM

PreserveOldRegisters MACRO
    LEA _custom,A6
    MOVE.W adkconr(A6),Oldadkcon
    MOVE.W intenar(A6),Oldintena
    MOVE.W dmaconr(A6),Olddmacon
  ENDM

ClearRegisters MACRO
    MOVE.W #$7FFF,D0
    BSR waitRaster
    MOVE.W D0,intena(A6)
    MOVE.W D0,dmacon(A6)
    MOVE.W D0,intreq(A6)
  ENDM

SetRegisters MACRO
    MOVE.W #$C000,intena(A6) ; enable master interrupt
    MOVE.W #$3FFF,intena(A6) ; disable every other interrupt

    MOVE.W #DMAF_SETCLR|DMAF_COPPER|DMAF_RASTER|DMAF_BLITTER,dmacon(A6)
    MOVE.W #DMAF_AUDIO|DMAF_DISK|DMAF_SPRITE,dmacon(A6)
  ENDM

_takeOverSystem:
  MOVEM.L A6,-(SP)
    CLR.W $100

    MOVE.L $4,A6
    CALLLIB _LVOForbid

    OpenGraphicsLibrary
    PreserveOldCopper

    CALLLIB _LVOOwnBlitter
    CALLLIB _LVOWaitBlit

    PreserveOldRegisters

    SetRegisters
    TakeOverView
  MOVEM.L (SP)+,A6
  RTS

waitRaster:
  MOVE.L D0,-(SP)
.loop:
    MOVE.L $DFF004,D0
    AND.L #$1FF00,D0
    CMP.L #303<<8,D0
    BNE .loop
  MOVE.L (SP)+,D0
  RTS

_giveBackSystem:
  CLR.W $100

  MOVEM.L A6,-(SP)
    LEA _custom,A6

    MOVE.W #$8000,d0
    OR.W D0,Olddmacon
    OR.W D0,Oldintena
    OR.W D0,Oldadkcon
    SUBQ #1,D0

    ;ClearRegisters

    MOVE.L OldCopper1,cop1lc(A6)
    MOVE.L OldCopper2,cop2lc(A6)
    MOVE.W #1,copjmp1(A6)

    MOVE.W Olddmacon,intena(A6)
    MOVE.W Olddmacon,dmacon(A6)
    MOVE.W Oldadkcon,adkcon(A6)

    MOVE.L OldView,A1

    MOVE.L GraphicsBase,A6
    CALLLIB _LVOLoadView
    CALLLIB _LVOWaitTOF
    CALLLIB _LVOWaitTOF

    MOVE.L $4,A6
    MOVE.L GraphicsBase,D0
    MOVE.L D0,A1
    CALLLIB _LVOCloseLibrary

    CALLLIB _LVOPermit
  MOVEM.L (SP)+,A6
  RTS

getVBR:
  MOVE.L A5,-(SP)
    MOVEQ #0,D0
    MOVE.L $4,A6
    BTST #0,AttnFlags+1(A6)
    BEQ .is68K
    LEA .get010VBR(pc),A5
    CALLLIB _LVOSupervisor
.is68K:
  MOVE.L (SP)+,A5
  RTS

.get010VBR:
  dc.l $4E7A0801 ; movec vcr,d0
  RTE

  CNOP 0,4
GraphicsLibrary dc.b 'graphics.library',0

  CNOP 0,4
GraphicsBase dc.l 1
OldView dc.l 1
OldCopper1 dc.l 1
OldCopper2 dc.l 1
VBRPtr dc.l 1
Oldadkcon dc.w 0
Oldintena dc.w 0
Olddmacon dc.w 0