BAKGND.ASM

	.FILE	"BAKGND.ASM"
; SHELL PROGRAM - DO NOT MODIFY!
; MARK TURMELL - MAY 24, 1989
;
	.TITLE	"BACKGROUND HANDLERS"

**************************************************************************
*                                                                        *
* 	COPYRIGHT (C) 1988 WILLIAMS ELECTRONICS GAMES, INC. 		 *
* 	ALL RIGHTS RESERVED.						 *
*                                                                        *
**************************************************************************

	.OPTION	B,D,L
	.MNOLIST

*	GET THE SYSTEM STUFF
	.INCLUDE	"MPROC.EQU"		;MPROC EQUATES
	.INCLUDE	"DISP.EQU"		;DISPLAY PROCESSOR EQUATES
	.include	"gsp.inc"	;gsp assembler equates
	.include	"sys.inc"	;zunit system equates
	.include	"macros.hdr"	;macros, yeah!
	.INCLUDE	"BGNDTBL.GLO"		;BACKGROUND EQUATES

;*BACKGROUND SYSTEM STUFF
	.GLOBAL	BAKBITS,BAKMODS,BAKLST,BGND_UD1
*GLOBALS IN THIS FILE
*RAM EQUATES

	.GLOBL	FREEPAL,GETBPAL

	.BSS	BGNDPALTBL,32,1
	.BSS	MOD_POS,32,1
	.BSS	BAKBITS,10000
;	.BSS	BAK2BITS,1000
	.BSS	BAKMODS,32
;	.BSS	BAK2MODS,32
	.TEXT

*BACKGROUND UPDATER EQUATES
BLSTSTRT	.EQU	08000H
BLSTEND 	.EQU	08001H

************* LOCAL CONSTANTS FOR UPD **************
;DISP_PAD    	.SET	000300030H	  ; Y:X
DISP_PAD    	.SET	000000000H	  ; Y:X
WIDEST_BLOCK	.SET	250

;* MUST KEEP THE SIZE OF THESE STRUCTURES A MULTIPLE OF 16
MAP_ZFLAGSPAL	.SET 0
MAP_PAL		.SET 0		;SIZE 4 - PALETTE SELECT
MAP_FLAGS   	.SET 4		;SIZE 4 - BIT 0 HFLIP, BIT 1 YFLIP
MAP_Z		.SET 8		;SIZE 8
MAP_X		.SET 16		;SIZE 16
MAP_Y		.SET 32		;SIZE 16
MAP_HDR		.SET 48		;SIZE 16 - OFFSET IN LONG WORDS FROM BLOCK_HDR_TBL
				; BITS 12-15 ARE BITS 4-7 OF PAL
				; MAP_HDR SET TO 0FFFFH IF BLOCK IS NOT ALLOCATED
BLOCK_SIZE	.SET 64		;* IF CHANGED MUST GET RID OF SHIFTS BY 6

;* Offsets for a BLOCK HDR structure
MAP_SIZE	.SET	0
MAP_W		.SET	0	;SIZE 16	  ; THESE FIELDS CAN'T BE CHANGED
MAP_H		.SET	16	;SIZE 16	  ; BECAUSE THEY ARE USED AS THE
MAP_DATAPTR	.SET	32	;SIZE 32	  ;
BLOCK_HDR_SIZE	.SET 	64
;* OFFSETS FOR A BLOCK HDR STRUCTURE
;MAP_SIZE	.SET	0
;MAP_W		.SET	0	;SIZE 16	  ; THESE FIELDS CAN'T BE CHANGED
;MAP_H		.SET	16	;SIZE 16	  ; BECAUSE THEY ARE USED AS THE
;MAP_ANIMOFF	.SET 	32	;SIZE 32	  ; OIMG BLOCK HEADER
;MAP_DATAPTR	.SET	64	;SIZE 32	  ;
;BLOCK_HDR_SIZE	.SET 	96


************************************************************************
BGNDHGHT:
;PARMS	A0 - XPOS FOR WHICH HEIGHT OF BACKGROUND NEEDS TO BE DETERMINED
;RETURNS A0 -
;	MINIMUM YPOS (MAX HEIGHT) OF PRIMARY BACKGROUND WHICH OVERLAPS
;	SPECIFIED XPOS
;	A0 = 0 IF XPOS IS INVALID

;* SCAN A MODULE LIST TO FIND OUT WHICH MODULE CONTAINS BLOCKS
;* WHICH NEED TO BE CHECKED
	MMTM	SP,A1,A2,A3,A4,A7,A8,A9,A10,A11
	MOVE	A0,A1

	CLR	A10			;INIT PACKED Y:X STARTING POSITION
	CLR	A11

	MOVE	@BAKMODS,A0,L		;* A0- PTR TO THE MODULE LIST
MODLP0:	
	MOVE	*A0+,A8,L		;LOAD MODULE PTR
	CMPI	0FFFFFFFFH,A8
	JRZ	MODX0			;END OF THE MODULE TBL
	MOVE	*A8+,A9,L		;LOAD PACKED Y:X SIZE

	MOVE	*A0+,A3,W		;X START POSITION
	ZEXT	A3,W
	CMPI	BLSTSTRT,A3
	JRNZ	NOTLSTSTRTX
	MOVE	A11,A3		
	SUBXY	A9,A3
	JRUC	GOTNEWX0
NOTLSTSTRTX:
	CMPI	BLSTEND,A3
	JRNZ	GOTNEWX0
	MOVE	A11,A3
GOTNEWX0:
	MOVE	*A0+,A4,W		;Y START POSITION
	ZEXT	A4,W
	CMPI	BLSTSTRT,A4
	JRNZ	NOTLSTSTRTY
	MOVE	A11,A4		
	SUBXY	A9,A4
	JRUC	GOTNEWY0
NOTLSTSTRTY:
	CMPI	BLSTEND,A4
	JRNZ	NOTLSTENDY
	MOVE	A11,A4
	JRUC	GOTNEWY0
NOTLSTENDY:
	SLL	16,A4
GOTNEWY0:
	MOVY	A4,A3
	MOVE	A3,A10

;	CMPXY	A10,A1
;	JRV	MODX0 	;JUMP TO EXIT LOOP IF MOD START X > X SOUGHT

	;IF MOD END X < X SOUGHT KEEP SEARCHING MOD LIST
	MOVE	A10,A11
	ADDXY	A9,A11	;A11 IS MODULE Y:X END

	MOVE	*A8+,A9,W		;LOAD # OF BLOCKS
	ADD	A9,A7		;A7 IS NEW BAKBITS PTR
	CMPXY	A11,A1
	JRNV	MODLP0		;SKIP IF AX < BX

	MOVE	A10,A0
	SRL	16,A0
	JRUC	GOTHGHT

MODX0:
	CLR	A0
GOTHGHT:
	MMFM	SP,A1,A2,A3,A4,A7,A8,A9,A10,A11
	RETS
************************************************************************

**************************** BSRCH1STXB ********************************
BSRCH1STXB:
;*** PARMS
;	A0 - X COORDINATE OF A BLOCK
;	A1 - START OF BACKGROUND BLOCK TABLE
;	A2 - END OF BLOCK TABLE
;*** RETURNS
;	A0 - ADDRESS OF FIRST BLOCK WITH X COORDINATE >= PARM
;		IF NEW X IS HIGHEST RETURNS NEXT EMPTY BLOCK
;		IF NO BLOCKS WITH >= X, RETURN 0

;* A0 = X VAL BEING SEARCHED FOR
;* A1 = BLOCK TABLE BASE + OFFSET TO X VAL
;* A14 - THRESHHOLD FOR SWITCHING FROM BINARY TO LINEAR SEARCH
;* A9 = LOW # -- # GREATEST BACKGROUND BLOCK
;* A10 = MID # -- (HIGH + LOW) >> 1
;* A2 = HIGH # -- # OF LOWEST BACKGROUND BLOCK

	MMTM	SP,A1,A2,A8,A9,A10
	CLR	A9		;* SET LOW = 0
	SUB	A1,A2
	SRL	6,A2	;* DIV BY SIZE OF BLOCK (64)
	ADDI	MAP_X,A1	;* BLOCK TBL BASE + X OFFSET
	MOVK	5,A14	;* THRESHHOLD FOR SWITCHING FROM BINARY TO LINEAR SEARCH
BSRCH:
	MOVE	A2,A10
	SUB	A9,A10	;* IF (HIGH - LOW) <= 5 FINISH WITH LINEAR SEARCH
	CMP	A14,A10
	JRLE	LSRCH

	SRL	1,A10
	ADD	A9,A10		

	;* GET MID->X
	MOVE	A10,A8
	SLL	6,A8		;* MULTIPLY BY BLOCK SIZE (64)
	ADD	A1,A8
	MOVE	*A8,A8,W	;* GET X COOR OF THE BLOCK
	CMP	A0,A8
	JRLT	BLOW
	MOVE	A10,A2	;* HIGH = MID
	JRUC	BSRCH
BLOW:
	MOVE	A10,A9	;* LOW = MID
	JRUC	BSRCH
LSRCH:
	;* FINISH WITH A LINEAR SEARCH OF BLOCK TABLE FROM LOW TO HIGH
	;* ENDING WITH FIRST BLOCK X COOR THAT IS >= A0
;* A0 = X VAL BEING SEARCHED FOR
;* A9 = LOW ADDRESS -- PTS TO X OFFSET OF BLOCK
;* A2 = HIGH ADDRESS -- PTS TO X OFFSET OF BLOCK
	SLL	6,A9		;* LOW BLOCK # TO LOW BLOCK OFFSET
  	SLL	6,A2		;* HIGH BLOCK # TO HIGH BLOCK OFFSET
	ADD	A1,A9
	ADD	A1,A2
	MOVI	BLOCK_SIZE,A8
LSRCHLP:
	MOVE	*A9,A10,W	;* X COOR
	CMP	A0,A10
	JRGE	GOTB		;* IF LOW->X >= A0 GOTO FOUND
	ADD	A8,A9
	CMP	A2,A9
	JRLE	LSRCHLP
;* BLOCK NOT FOUND, RETURN 0
	CLR	A0
	JRUC BSRCHDONE
GOTB:
	;* RETURN A PTR TO THE BLOCK
	MOVE	A9,A0
	SUBI	MAP_X,A0

BSRCHDONE:
	MMFM	SP,A1,A2,A8,A9,A10
	RETS
**************************** BSRCH1STXB ********************************


*********************** BAK END *******************************
;* SCAN A MODULE LIST AND RETURN THE PACKED Y:X END POINT
;PARMS
	;A0 - MODULE LIST
;RETURNS
	;A0 - PACKED Y:X END OF WAVE
BAK_END:
	MMTM	SP,A3,A4,A8,A9,A10,A11

	CLR	A10	;CLR PACKED Y:X STARTING POSITION
	CLR	A11
WEMODLP:	
	MOVE	*A0+,A8,L		;LOAD MODULE PTR
	CMPI	0FFFFFFFFH,A8
	JRZ	WEMODX			;END OF THE MODULE TBL
	MOVE	*A8+,A9,L		;LOAD PACKED Y:X SIZE

	MOVE	*A0+,A3,W		;X START POSITION
	ZEXT	A3,W
	CMPI	BLSTSTRT,A3
	JRNZ	WENOTLASTSTARTX
	MOVE	A11,A3		
	SUBXY	A9,A3
	JRUC	WEGOTNEWX
WENOTLASTSTARTX:
	CMPI	BLSTEND,A3
	JRNZ	WEGOTNEWX
	MOVE	A11,A3
WEGOTNEWX:
	MOVE	*A0+,A4,W		;Y START POSITION
	ZEXT	A4,W
	CMPI	BLSTSTRT,A4
	JRNZ	WENOTLASTSTARTY
	MOVE	A11,A4		
	SUBXY	A9,A4
	JRUC	WEGOTNEWY
WENOTLASTSTARTY:
	CMPI	BLSTEND,A4
	JRNZ	WENOTLASTENDY
	MOVE	A11,A4
	JRUC	WEGOTNEWY
WENOTLASTENDY:
	SLL	16,A4
WEGOTNEWY:
	MOVY	A4,A3
	MOVE	A3,A10
	
	MOVE	A10,A11
	ADDXY	A9,A11	;A11 IS MODULE Y:X END
	JRUC	WEMODLP

WEMODX:
	MOVE	A11,A0
	MMFM	SP,A3,A4,A8,A9,A10,A11
	RETS
***********************************************************************

*********************** BAK START *******************************
;* SCAN A MODULE LIST AND RETURN THE PACKED Y:X STARTING POINT
;PARMS
	;A0 - MODULE LIST
;RETURNS
	;A0 - PACKED Y:X START OF WAVE
BAK_STRT:
	MMTM	SP,A3,A4,A8,A9,A11

	CLR	A11
	MOVE	*A0+,A8,L		;LOAD MODULE PTR
	CMPI	0FFFFFFFFH,A8
	JRZ	WSMODX			;END OF THE MODULE TBL
	MOVE	*A8+,A9,L		;LOAD PACKED Y:X SIZE

	MOVE	*A0+,A3,W		;X START POSITION
	ZEXT	A3,W
	CMPI	BLSTSTRT,A3
	JRNZ	WSNOTLASTSTARTX
	MOVE	A11,A3		
	SUBXY	A9,A3
	JRUC	WSGOTNEWX
WSNOTLASTSTARTX:
	CMPI	BLSTEND,A3
	JRNZ	WSGOTNEWX
	MOVE	A11,A3
WSGOTNEWX:
	MOVE	*A0+,A4,W		;Y START POSITION
	ZEXT	A4,W
	CMPI	BLSTSTRT,A4
	JRNZ	WSNOTLASTSTARTY
	MOVE	A11,A4		
	SUBXY	A9,A4
	JRUC	WSGOTNEWY
WSNOTLASTSTARTY:
	CMPI	BLSTEND,A4
	JRNZ	WSNOTLASTENDY
	MOVE	A11,A4
	JRUC	WSGOTNEWY
WSNOTLASTENDY:
	SLL	16,A4
WSGOTNEWY:
	MOVY	A4,A3
	MOVE	A3,A0

WSMODX:
	MMFM	SP,A3,A4,A8,A9,A11
	RETS
***********************************************************************

****************  U P D A T E   D I S P   L I S T **********************
;* DELETES ALL DISPLAY OBJECTS WHICH ARE NOT ON THE SCREEN
;* INSURES ALL BACKGROUND BLOCKS ON SCREEN ARE ON THE DISP LIST
BGND_UD1:		;* CALL TO UPDATE MAIN BACKGROUND
;* INPUT, WORLDTL, SCRNTL, SCRNLR, BAKLST, BAKBITS, BAKMODS
	;* THIS PROTECTS DISP_MOD AND DISP_DEL TOO!
	MMTM	SP,A0,A1,A2,A3,A4,A5,A6,A7,A8,A9,A10,A11,A12,A13,A14
	MMTM	SP,B0

	;* GET COORS OF AREA TO BE PUT ON DISPLAY LIST.
	MOVE	@WORLDTL,A3,1
	MOVE	A3,A4
	MOVE	@SCRNTL,A0,1
	ADDXY	A0,A3 		
	MOVE	@SCRNLR,A0,1
	ADDXY	A0,A4		
	MOVI	DISP_PAD,A0
	SUBXY	A0,A3		;A3 - DISP_TL
	ADDXY	A0,A4		;A4 - DISP_LR
	MOVI	BAKLST,A8	;A8 - BAKGROUND LIST
	CALLR	DISP_DEL

	;* DETERMINE WHICH MODULE
	MOVE	@BAKMODS,A0,L		;A0- PTR TO THE MODULE LIST
	MOVI	INSBOBJ,B0		;B0 - WHICH INSERT ROUTINE
	MOVI	BAKBITS,A7		;A7 - BIT TABLE FOR BLOCK BEING ON DISP LIST
	CALLR	DISP_MOD
	MMFM	SP,B0
	MMFM	SP,A0,A1,A2,A3,A4,A5,A6,A7,A8,A9,A10,A11,A12,A13,A14
	RETS

;BGND_UD2:		;* CALL TO UPDATE SECONDARY BACKGROUND
;* INPUT, BAK2TLX, BAK2TLY, SCRNTL, SCRNLR, BAK2LST, BAK2BITS, BAK2MODS
;	MMTM	SP,A0,A1,A2,A3,A4,A5,A6,A7,A8,A9,A10,A11,A12,A13,A14
;	MMTM	SP,B0
;	;* GET COORS OF AREA TO BE PUT ON DISPLAY LIST.
;	MOVE	@BAK2TLX+16,A3,W
;	MOVE	@BAK2TLY+16,A0,W
;	SLL	16,A0
;	MOVY	A0,A3
;	MOVE	A3,A4
;	MOVE	@SCRNTL,A0,L
;	ADDXY	A0,A3 		
;	MOVE	@SCRNLR,A0,L
;	ADDXY	A0,A4		
;	MOVI	DISP_PAD,A0
;	SUBXY	A0,A3		;A3 = DISP_TL
;	ADDXY	A0,A4		;A4 = DISP_LR
;	MOVI	BAK2LST,A8   		;A8 - BAKGROUND LIST
;	CALLR	DISP_DEL

;	MOVI	INSB2OBJ,B0		;B0 - WHICH INSERT ROUTINE
;	MOVE	@BAK2MODS,A0,L		;* A0- PTR TO THE MODULE LIST
;	MOVI	BAK2BITS,A7
;	CALLR	DISP_MOD
;	MMFM	SP,B0
;	MMFM	SP,A0,A1,A2,A3,A4,A5,A6,A7,A8,A9,A10,A11,A12,A13,A14
;	RETS
***********************************************************************


*********************** D I S P   M O D *******************************
;* SCAN A MODULE LIST TO FIND OUT WHICH MODULES CONTAIN BLOCKS
;* WHICH NEED TO BE CHECKED FOR ADDITION TO THE DISPLAY LIST.
;	B0 - WHICH INSERT ROUTINE
;	A0 - MODULE LIST
;	A3 - DISP_TL
;	A4 - DISP_LR
;	A7 - BAKBITS	;A7 - BIT TABLE FOR BLOCK BEING ON DISP LIST

;PARMS FOR DISP_ADD
;	A1 - BACKGROUND BLOCK TABLE
;	A2 - END OF BACKGROUND BLOCK TABLE
;	A5 - BACKGROUND HDR TABLE
;	A9 - MODULE START POSITION Y:X
;	A10 - PTR TO PALETTE TABLE FOR NEW BLOCK
;	    ;PASSED FROM ABOVE
;	A3 - DISP_TL
;	A4 - DISP_LR
;	A6 - WHICH BAKGROUND INSERT ROUTINE PRIMARY|SECONDARY
;	A7 - BIT TABLE FOR BLOCK BEING ON DISP LIST

;* CALLER IS RESPONSIBLE FOR PUSHING AND POPPING ALL A-REGISTERS

DISP_MOD:
	CLR	A9			;INIT Y:X STARTING POSITION
	CLR	A11			;ENDING Y:X POS
	MOVE	A7,A6			;A6 WILL POINT TO BAKBITS AFTER MOD

MODLP:	
SKDADD:
	MOVE	A6,A7
	MOVE	*A0+,A8,L		;LOAD MODULE PTR
	CMPI	0FFFFFFFFH,A8
	JRZ	MODX			;END OF THE MODULE TBL
	MOVE	*A8+,A10,L		;LOAD Y:X SIZE

	MOVE	*A0+,A14,W		;X START POSITION
	ZEXT	A14,W
	CMPI	BLSTSTRT,A14
	JRNZ	NOTLASTSTARTX
	MOVE	A11,A14		
	SUBXY	A10,A14
	JRUC	GOTNEWX
NOTLASTSTARTX:
	CMPI	BLSTEND,A14
	JRNZ	GOTNEWX
	MOVE	A11,A14
GOTNEWX:
	MOVE	*A0+,A5,W		;Y START POSITION
	ZEXT	A5,W
	CMPI	BLSTSTRT,A5
	JRNZ	NOTLASTSTARTY
	MOVE	A11,A5		
	SUBXY	A10,A5
	JRUC	GOTNEWY
NOTLASTSTARTY:
	CMPI	BLSTEND,A5
	JRNZ	NOTLASTENDY
	MOVE	A11,A5
	JRUC	GOTNEWY
NOTLASTENDY:
	SLL	16,A5
GOTNEWY:
	MOVY	A5,A14
	MOVE	A14,A9

	MOVE	A9,A11
	ADDXY	A10,A11	;A11 IS MODULE Y:X END
	MOVE	*A8+,A10,W		;LOAD # OF BLOCKS
	ADD	A10,A6		;A6 IS NEW BAKBITS PTR

; 	CMPXY	A9,A4
;	JRXLE	MODX  	;JUMP TO EXIT LOOP IF MOD START X > SCREEN END X

	CMPXY	A3,A11
	JRXLT	SKDADD		;SKIP IF MOD X END < TL X
	JRYLT	SKDADD		;SKIP IF MOD Y END < TL Y

	CMPXY	A9,A4
	JRXLT	SKDADD  ;USE THIS IF MODULES AREN'T SORTED LEFT TO RIGHT
				;JUMP TO IF MOD START X > SCREEN END X
	JRYLT	SKDADD		;SKIP IF MOD Y START > BR Y

	MOVE	*A8+,A1,L		;A1-BLOCK TABLE	
	MOVE	A10,A2
	SLL	6,A2			;EACH BLOCK IS 4 WORDS LONG
	ADD	A1,A2			;A2-BLOCK TABLE END
	MOVE	*A8+,A5,L		;A5-HDRS
	MOVE	*A8+,A10,L		;A10-PAL TBL
	SUBXY	A9,A3
	SUBXY	A9,A4
	CALLR	DISP_ADD
	ADDXY	A9,A3
	ADDXY	A9,A4
	JRUC	MODLP

MODX:
	RETS
***********************************************************************

*********************** D I S P   A D D *******************************
;* THIS FUNCTION ADDS ALL MODULE BLOCKS IN THE GIVEN RANGE OF MODULE
;* RELATIVE COORS TO THE DISPLAY LIST.
;* THE BOUNDRIES ARE INCLUDED IN THE GROUP TO ADD.
DISP_ADD:
;***	PARMS:
;       B0 - WHICH BAKGROUND INSERT ROUTINE PRIMARY|SECONDARY
;	A5 - BACKGROUND HDR TABLE
;	A7 - BIT TABLE FOR BLOCK BEING ON DISP LIST
;	A9 - MODULE START POSITION Y:X
;	A10 - PTR TO PALETTE TABLE FOR NEW BLOCK
;	A1 - BACKGROUND BLOCK TABLE
;	A2 - END OF BACKGROUND BLOCK TABLE
;	A3 - DISP_TL	- RELATIVE TO THE MODULE START POS
;	A4 - DISP_LR	- " 
;*** RETURNS NOTHING

;THRASHES A1,A8,A14
	MMTM	SP,A0,A6,A7,A11

	;* FIND FIRST UNIVERSE BLOCK WITH AN X COOR >= A9
	MOVX	A3,A0
	SEXT	A0,W
	SUBI	WIDEST_BLOCK,A0
;A0 - X COORDINATE OF A BLOCK
;A1 - START OF BACKGROUND BLOCK TABLE
;A2 - END OF BLOCK TABLE
	CALLR	BSRCH1STXB
;A0 IS NOW THE ADDRESS OF A BLOCK
	JRZ	DADONE	;* NO BLOCKS WITH GTR XCOOR
	
	MOVI	BLOCK_SIZE,A6

	MOVE	A0,A8
	SUB	A1,A8	;* SUBTRACT OFF START OF TABLE
	SRL	6,A8	;* DIVIDE BY BLOCK SIZE (64)
	ADD	A7,A8	;* A8 - PTR TO BIT WHICH INDICATES BLOCK ON LIST
	SUBK	8,A8	;* AFTER INC A8, USE MOVB *A8 TO LOAD SIGN BIT
	SUB	A6,A0	;SUBTRACT BLOCK SIZE
BSCANLP0:
	INC	A8
	ADD	A6,A0	;* GET NEXT BLOCK
	;* CHECK IF THERE ARE NO MORE BGND BLOCKS
	CMP	A2,A0
	JRGE	DADONE

	;* IF BLOCK ALREADY ON DISPLAY LIST TRY AGAIN
	MOVB	*A8,A11
	JRN	BSCANLP0

	;* CHECK IF X TO BIG
	MOVE	*A0(MAP_X),A11,W
	CMPXY	A3,A11
	JRXGE	BSCAN1	   	;* JUMP IF BLOCKX >= TL X

	;* LOAD MAP HEADER
	MOVE	*A0(MAP_HDR),A14,W
	SLL	20,A14	;* ONLY WANT BOTTOM 12 BITS, TOP 4 ARE PAL BITS
	SRL	15,A14	;* LEAVES B9 << 5 == LONG WORD OFFSET
	ADD	A5,A14	;* A14 NOW PTS TO BLOCK HDR

	;* CHECK IF RIGHT END OF BLOCK HANGS ONTO SCREEN
	MOVE	*A14,A1,W	;A1 IS NOW THE WIDTH OF THE BLOCK
	ADD	A11,A1
	CMPXY	A3,A1	;* RIGHT END OF BLOCK DOESN'T HANG ON TO SCREEN
	JRXLT	BSCANLP0		;* JUMP IF BLOCK X+W < TL X

	;* IF YCOOR TO BIG TRY AGAIN
	MOVE	*A0(MAP_Y),A1,0
	SLL	16,A1
	CMPXY	A1,A4
	JRYLT BSCANLP0		;* JUMP IF BLOCK Y > BR Y

	;* IF YCOOR+HEIGHT TO SMALL TRY AGAIN
	MOVE	*A14(MAP_H),A11,0
	SLL	16,A11
	ADD	A11,A1
	CMPXY	A3,A1
	JRYLT BSCANLP0		;* JUMP IF BLOCK Y+H < TL Y

	MOVE	A0,A7
	CALLR	ADDBLOCK	;THRASHES A1,A14
	JRNC BSCANLP0
	JRUC	DADONE		;* WAS UNABLE TO ADD BLOCK - NO BLOCKS LEFT

BSCAN1:
	DEC	A8		;* BIT PTR FOR BLOCK ON DISP LIST
	SUB	A6,A0		;SUBTRACT OFF BLOCK SIZE
BSCANLP1:
	INC	A8
	ADD	A6,A0	;GET NEXT BLOCK
	;* CHECK IF THERE ARE NO MORE BGND BLOCKS
	CMP	A2,A0
	JRGE	DADONE

	;* IF BLOCK ALREADY ON DISPLAY LIST TRY AGAIN
	MOVB	*A8,A11
	JRN	BSCANLP1

	;* IF YCOOR TO BIG TRY AGAIN
	MOVE	*A0(MAP_Y),A1,W
	SLL	16,A1
	CMPXY	A1,A4
	JRYLT BSCANLP1		;* JUMP IF BLOCK Y > BR Y

	;* IF YCOOR+HEIGHT TO SMALL TRY AGAIN
	MOVE	*A0(MAP_HDR),A14,W
	SLL	20,A14	;* ONLY WANT BOTTOM 12 BITS, TOP 4 ARE PAL BITS
	SRL	15,A14	;* LEAVES B9 << 5 == LONG WORD OFFSET
	ADD	A5,A14	;* B9 NOW PTS TO BLOCK HDR
	MOVE	*A14(MAP_H),A11,W
	SLL	16,A11
	ADD	A11,A1
	CMPXY	A3,A1
	JRYLT BSCANLP1		;* JUMP IF BLOCK Y+H < TL Y

	;* IF XCOOR TO BIG QUIT
	MOVE	*A0(MAP_X),A1,W
	CMPXY	A1,A4
	JRXLT DADONE	;* JUMP IF BLOCK X > BR X

	MOVE	A0,A7
	CALLR	ADDBLOCK
	JRNC	BSCANLP1

DADONE:
	MMFM	SP,A0,A6,A7,A11
	RETS
***********************************************************************

***********************************************************************
ADDBLOCK:
;* PARMS
; B0 - WHICH INS ROUTINE
; A5 - BASE OF BACKGROUND BLOCK HDR
; A7 - PTR TO BACKGROUND BLOCK
; A8 - PTR TO BIT MAP FOR BLOCK ON DISP LIST
; A9 - MODULE START POSITION Y:X
; A10 - PTR TO PALETTE TABLE FOR NEW BLOCK

;* RETURNS CARRY SET IF GETOBJ FAILS...
	;* ALSO DESTROYS A1,A14 BUT THEY ARE USED AS TEMPS IN DISP_ADD
	MMTM	SP,A0,A2,A3,A4

	CALLA	GETOBJ
	JRZ  	ADDX

	;* SET BIT IN BITMAP FOR BLOCK ON LIST
	MOVB	*A8,A14
	ORI	080H,A14
	MOVB	A14,*A8
	MOVE	A8,*A0(OPLINK),L ;SET OPLINK TO BE A PTR TO THE DISP LIST BIT
	
	MOVE	*A7(MAP_X),A1,L	;A1 YPOS:XPOS OF BLOCK FROM MOD BASE
	ADDXY	A9,A1		;ADD IN MODULE BASE POSITION
	MOVE	A1,*A0(OXPOS),W
	SRL	16,A1
	MOVE	A1,*A0(OYPOS),W
	MOVE	*A7,A4,W	;A4 - MAP_Z,8:MAP_FLAGS,4:MAP_PAL,4
	MOVE	A4,A3
	ZEXT	A3
	SRL	8,A3
**	SLL	24,A3
**	SRL	8,A3
	MOVE	A3,*A0(OZPOS),W

	MOVE	*A7(MAP_HDR),A1,W
	MOVX	A1,A14
	SLL	16,A14
	SRL	28,A14
	SLL	4,A14		;* BITS 12-15 ARE BITS 4-7 OF PAL INDEX
	
	SLL	20,A1		;* BITS 0-11 ARE HDR PTR;
	SRL	15,A1		;* A1-LONG WORD OFFSET INTO BLOCK HDR TBL
	ADD	A5,A1		;* A1 - PTR TO OIMG HDR - INPUT TO GSAGOF

	;A4 - MAP_Z,8:MAP_FLAGS,4:MAP_PAL,4
	MOVE	A4,A3
	SLL	28,A4		;* LAST FOUR BITS FOR PAL
	SRL	28,A4
	ADD	A14,A4	
	SLL	5,A4   		;* A4 IS LWORD PTR FROM PAL TBL
	ADD	A10,A4		;* ADD IN PAL TBL
	MOVE	A0,A2		;SAVE A0
	MOVE	*A4,A0,L	;* GET PALETTE
	CALLA	GETBPAL
	JRNZ	BSETPAL
	CLR	A0
BSETPAL:
	MOVE	A0,*A2(OPAL),W
	MOVE	A2,A0		;RESTORE A0

	MOVI	08002H,A4	;08000H DMA GO, 2
	SRL	4,A3	;* REMOVE PALETTE BITS
	SLL	30,A3		
	JRC	SKIP0	;* CARRY BIT IS THE TRANSPARENCY BIT
	ADDK	1,A4
SKIP0:
	SRL	26,A3	;* LINE UP FLIP H,V BITS
	ADD	A3,A4	;A4 - FLAGS FOR GSAGOF
	MOVE	A1,*A0(OIMG),L
*A1=DATA BLOCK POINTER
*A4=OBJECT FLAGS
	calla	BKGSAGOF	;USES ISAG-020H FOR ISAG
;	CALLA	GSAGOF
*A2=RETURNED WITH NEW OSIZE
*A3=RETURNED WITH NEW SAG
*A4=RETURNED WITH NEW OFFSET:OFLAGS
	MOVE	A0,A1
	ADDI	OSIZE+020H,A1
	MMTM	A1,A2,A3,A4		;STUFF OSIZE,OSAG,OFFSET,OFLAGS

	CALL	B0
	CLRC
	MMFM	SP,A0,A2,A3,A4
	RETS
ADDX: ;FAILURE TO GET OBJECT
	SETC
	MMFM	SP,A0,A2,A3,A4
	RETS
**********************************************************************


************************ D I S P   D E L *****************************
;* THIS FUNCTION DELETES ALL OBJS OUTSIDE THE GIVEN RANGE
;* OF COORS FROM THE DISPLAY LIST.
;* THE BOUNDRIES ARE NOT INCLUDED IN THE GROUP TO DELETE.
DISP_DEL:
;***	PARMS:
;	A8 - BAK LIST	
;	A3 - DISP_TL
;	A4 - DISP_LR
;*** RETURNS NOTHING

;THRASHES A0,A6,A7,A8,A9	;ALL OF WHICH ARE PUSHED BY CALLER

DEL_LOOP:
	MOVE	A8,A9	   	; PTR TO PREV IN A9
	MOVE	*A9,A8,L   	; PTR TO NEXT IN A8
	JRZ	DEL_DONE	   	; QUIT IF AT END OF LIST

	;IF X > XMAX CONTINUE
	MOVE	*A8(OXPOS),A7,W
	CMPXY	A7,A4
	JRXLT	DEL_IT		;* JUMP IF BR X < BLOCK X

	;IF Y > YMAX CONTINUE
	MOVE	*A8(OYPOS),A0,W
	SLL	16,A0
	CMPXY	A0,A4
	JRYLT	DEL_IT		;* JUMP IF BR Y < BLOCK Y

	MOVE *A8(OIMG),A1,L
	;IF X+WIDTH < XMIN CONTINUE
	MOVE	*A1,A6,W		;A6 BLOCK WIDTH
	ADD	A6,A7
	CMPXY	A3,A7
	JRXLT	DEL_IT		;* JUMP IF TL X > BLOCK X+W

	;IF Y+HEIGHT < YMIN CONTINUE
	MOVE	*A1(MAP_H),A7,0		;A7 BLOCK HEIGHT
	SLL	16,A7
	ADD	A7,A0
	CMPXY	A3,A0
	JRYLT	DEL_IT		;* JUMP IF TL Y > BLOCK Y+H

	JRUC	DEL_LOOP

DEL_IT:	;* DELETE THE OBJ
    ;* FREE THE PALETTE
	MOVE	*A8(OPAL),A0,W
	JRZ	NOFREEP
	CALLA	FREEPAL
NOFREEP:

	;* UNSET THE ON DISPLAY LIST BIT
	MOVE	*A8(OPLINK),A0,L
	MOVB	*A0,A7
	ANDI	07FH,A7
	MOVB	A7,*A0
		
	MOVE	*A8,*A9,L  	; PUT NEXT LINK IN PREV OBJ
	MOVE	@OFREE,A0,L				
	MOVE	A0,*A8,L
	MOVE	A8,@OFREE,L	; RETURN DELETED BLOCK TO FREE STACK
	MOVE	A9,A8		;A1- POINTS TO LAST OBJ
	JRUC	DEL_LOOP

DEL_DONE:
	RETS

	.END