M	EQU	Byte Ptr 0[BX]
	TITLE	'DRAW - POLYLINE DRAWING ROUTINES'
; ****************************************************************************
; *                                                                          *
; *  DRAWIT : RASTER CONVERT A POLYLINE INTO THE PRINTER BITMAP BUFFER,      *
; *           CLIPPING EACH LINE SEGMENT BETWEEN THE CURRENT PLOT STRIP      *
; *                                                                          *
; ****************************************************************************
;                                                                            *
;  Revision : June 08, 1983    File "DRAW.A86"            Version 1.0        *
;                                                                            *
;                                                                            *
;***** MODE NOTES :  *********************************************************
;                                                                            *
;      1) BITMAP BUFFER EMPTY FLAG  11/3                                     *
;      2) SET EMPTY FLAG IN ADDRXY indicating Bitmap Used                    *
;      3) Rotate LINE STYLE pattern Mask : SPECIL to set bit                 *
;      4) New Pieces : Drawit, textit = Drawpl, Textit, Drawxy, Getadr       *
;      5) Special Line Style Support :                                       *
;         .Drawit Stores Line Start Point X0, Y0 for Swapping                *
;         .Clipit Returns ABOVE flag : 0=inside, 1=Y2 above, 2=Y1 above      *
;         .Drawxy Swaps Line Endpoints : Line Direction Ymax to Ymin         *
;                 Filters Y0 to TOPY and Sets Y0 inside flag for ADDRXY      *
;                 and SETBIT Rontines to start Setting Bit in BITMAP         *
;      6) Restore the Line Style Pattern After Rasterization                 *
;      7) delete Module LINETY, use rol specil,1                             *
;                                                                            *
;***** MODE NOTES :  *********************************************************
;                                                                            *
;  POLYLINE DRAWING ROUTINES                                                 *
;                                                                            *
;  Drawit (npt,x1,y1,x2,y2,...xnpt,ynpt,cindex)                              *
;                                                                            *
;  Function : For each line segment ..                                       *
;             Clip the endpoints of the line to the current plot strip and   *
;             Scan convert the line into raster pixel values mapped          *
;             into the bitmap buffer                                         *
;                                                                            *
;             Get x1, y1                                                     *
;             do i = 1, npt                                                  *
;                Get x2, y2                                                  *
;                Call Clipit                                                 *
;                Call Drawxy                                                 *
;                x1 = x2                                                     *
;                y1 = y2                                                     *
;             end;                                                           *
;                                                                            *
;  Input    : NPT - No. of Vertices in the Ployline                          *
;             XP  - Array of X-coordinates                                   *
;             YP  - Array of Y-coordinates                                   *
;             LSTPTR - Object List Buffer Pointer, where xp ans yp arrays    *
;                      are stored                                            * 
;             MPTY - Bitmap Buffer Set Indicator                             *
;                                                                            *
;  Output   : Returns Pointer to the next entry in OBJLST in <hl>            *
;                                                                            *
;  Calls    : GETXY  - Get the x,y coordinates of the next point in OBJLST   *
;             CLIPIT - Clip line to printer plot strip (ystart, yend)        *
;             DRAWXY - Raster convert vector to pixel values, maps pixel     *
;                      to bitmap address and 'sets' the bit                  *
;                                                                            *
;  Raster Variables  :                                                       *
;             X0     - Line start point coord.                               *
;             XN     - Line end point coord.                                 *
;  Line Style Support Variables                                              *
;             ABOVE  - Which Line EndPoint ABOVE Strip Flag                  *
;             SPECIL - Special Line Style Bit Pattern for the Current NDLNTY *
;             INSIDE - Line EndPoints INSIDE Strip Flag                      *
;                                                                            *
;----------------------------------------------------------------------------*
	PUBLIC	DRAWIT, SWAPY
	EXTRN	GETXY:near, CLIPIT:near, DRAWXY:near
	EXTRN	ABSHL:near, NEGHL:near, CMPDH:near, CMPS:near, SUBDH:near
        EXTRN   MIDH:near, DIDH:near, IMOD:near
	dseg
;EXTRN	BITMAP:word
	Extrn   NBIT:byte, NBYT:word, MPTY:word
	EXTRN	COLOR:byte, XMAX:word, YMAX:word
	EXTRN	XW:word, TOPY:word, BOTY:word, BOTTY:word
	EXTRN	LSTYLE:word, NDLNTY:byte, NDLNCO:byte
	EXTRN	X:word, X1:word, Y:word, Y1:word, X2:word, Y2:word
        EXTRN   DX1:word, DY:word, XDIR:word, YDIR:word
	EXTRN	X0:word, Y0:word, XN:word, YN:word
        EXTRN   doxy:byte, ABOVE:byte, INSIDE:word, SPECIL:word
	cseg
;----------------------------------------------------------------------------+
;                                                                            +
;  CALL DRAWIT                                                               +
;       <A>  = npt                                                           +
;       <HL> = current OBJLST pointer : LSTPTR                               +
;  RET                                                                       +
;                                                                            +
;        Get x1, y1                                                          +
;        do i = 1, npt                                                       +
;          Get x2, y2                                                        +
;          Call Clipit                                                       +
;          Call Drawxy                                                       +
;          x1 = x2                                                           +
;          y1 = y2                                                           +
;        end;                                                                +
;----------------------------------------------------------------------------+
DRAWIT:
	;Stack <A> = npt
	PUSH	AX

;	Set Current Color Index to PolyLine Color Index
	MOV	AL,Byte Ptr NDLNCO
	MOV	Byte Ptr COLOR,AL

;       Get x1, y1
	CALL	GETXY		;Returns : <DX> = x, <CX> = y,
	MOV	Word Ptr X0,DX
	MOV	Word Ptr X1,DX
	MOV	Word Ptr Y0,CX
	MOV	Word Ptr Y1,CX
;        (npt - 1) = 0 ?
DRAL01:	POP	AX
	DEC	AL			;npt = npt - 1
	JZ	DRAJ99			;DONE
	PUSH	AX
;
;        Get x2, y2
;
	CALL	GETXY		;Returns <DX> = x, <CX> = y,
	MOV	Word Ptr X2,DX
	MOV	Word Ptr XN,DX  ;Save Uncliped x2, y2 for next line segment
	MOV	Word Ptr Y2,CX
	MOV	Word Ptr YN,CX
	MOV	BX,Word Ptr LSTYLE  ;Current Line Style Bit Pattern
	MOV	Word Ptr SPECIL,BX  ;16 Bit Line Pattern for Drawxy routine
	CALL	CLIPIT		;Clip line to inside current Plot Strip
;
;        Zero = Off, if Line object lies entirely outside current Plot Strip
;
	JNZ	L@1	
	CALL	DRAWXY			;Draw line if not entirely clipped
L@1:
;        Draw to point,  x1 = x2, y1 = y2
	MOV	BX,Word Ptr XN
	MOV	Word Ptr X0,BX
	MOV	Word Ptr X1,BX		;x1 = x2
	MOV	BX,Word Ptr YN
	MOV	Word Ptr Y0,BX
	MOV	Word Ptr Y1,BX		;y1 = y2
	JMPS	DRAL01			;Draw next line segment
DRAJ99:
	RET

;***	Mode Note : June 10, 1983
;	Instead of Standardize the line direction and rasterize the
;	line from x0, y0 to xn, yn, to handle the special linestyle,
;	rotate the line pattern mask, according to line direction 
;	and the delta x, delta y value to process specil linestyles.
;	if dx > dy, then :
;	 rotate the pattern mask by delta x mod 16, where
;	 delta x = x1, if line direction is from 0 to xmax, x0 --> x1
;	 delta x = xmax - x1, if line direction is from xmax to 0, x1 <-- x0
;	else if dy > dx, then :
;	 rotate the pattern mask by delta y mod 16, where
;	 delta y = y1, if line direction is from 0 to ymax, (up)
;	 delta y = ymax - y1, if line direction is from ymax to 0, (down)
swapy :
;	check dx > dy ?
	mov	al, byte ptr doxy
	or	al, al
	jnz	swapjx		; doxy = 1, dx > dy
;	doxy = 0, dy > dx, rotate pattern mask by delta y mod 16
;	compute delta y mod 16
;	check line direction, ydir = 0(down), y2 < y1, delta y = ymax - y1
;	ydir > 0(up), y1 < y2, delta y = y1
	mov	al, byte ptr ydir
	or	al, al
	jnz	swapy1 		; delta y = y1
;	rotate pattern by ymax - y1 mod 16
	mov	cx, word ptr ymax
	sub	cx, word ptr y1	; ax = delta y
	jmp	swarol
swapy1:	mov	cx, word ptr y1
	jmp	swarol
;	check line direction, xdir = 0, x2 < x1, delta x = xmax - x1
;	xdir > 0, x1 < x2, delta x = x1
swapjx:
;	IF DY = 0, (YDIR = 1), HORIZONTAL LINE, DO NOT ROTATE THE PATTERN MASK
	CMP	BYTE PTR YDIR, 1
	JZ	NOROLL
	mov	al, byte ptr xdir
	or	al, al
	jnz	swapx1
	mov	cx, word ptr xmax	; DELTA X = XMAX - X1
	sub	cx, word ptr x1
	jmp	swarol
swapx1:	mov	cx, word ptr x1
	
swarol:	and	cx, 0FH		; rotate count = delta mod 16
	rol	specil, cl	; left rotate the line style pattern mask
NOROLL:	ret

;	this replace the following section of swapy code. June 10, 1983
;----------------------------------------------------------------------------+
;        SWAPY - Standardize Line direction to always go from Ymax to Ymin   +
;                So the line Rasterization Routine can stop at bottom of     +
;                the current Plot strip                                      +
;        ABOVE - 0 = Both endpoints are either inside or below the Current   +
;                    Plot strip,                                             +
;                1 = Y2 is above the Current Plot Strip                      +
;               -1 = Y1 is above the Current Plot Strip, Direction ok        +
;----------------------------------------------------------------------------+
;SWAPY:
;	MOV	AL,Byte Ptr ABOVE	;Get Position Flag for endpoints
;        Above : 0 : no swap, both point inside strip 
;                1 : change line direction, and make line start from XN, YN
;                    Y2 = Y1, X2 = X1, Y1 = YN, X1 = XN
;               -1 : make line start from X0, Y0
;	OR	AL,AL
;	JNZ	L@2
;	RET
;L@2:
;	JS	SWAJ01			;-1 : Y1 is above Top y
;        Y2 is above Strip
;	MOV	BX,Word Ptr X1
;	MOV	Word Ptr X2,BX
;	MOV	BX,Word Ptr Y1
;	MOV	Word Ptr Y2,BX		;Change Y2 to lower point
;	MOV	BX,Word Ptr YN
;	MOV	Word Ptr Y1,BX
;	MOV	BX,Word Ptr XN		;Line was trimmed to Top y
;	MOV	Word Ptr X1,BX		;Change Y1 to the original end point
;	RET
;SWAJ01:
;	MOV	BX,Word Ptr Y0		;Y1 was clipped to Top y
;	MOV	Word Ptr Y1,BX		;Change Y1 to the Original Start point
;	MOV	BX,Word Ptr X0
;	MOV	Word Ptr X1,BX
;	RET
;*****************************************************************************
;                                                                            *
;      LINETY : GET CURRENT PATTERN FROM PATTERN WORD : LSTYLE               *
;               ROTATE NEXT BIT : ON/OFF, RETURN SET BIT FLAG ACCORDINGLY    *
;                                                                            *
;*****************************************************************************
;                                                                            *
;LINETY:
;PUSH	BX
;PUSH	CX
;MOV	BX,Word Ptr SPECIL	;Get the Pattern 
;SHL	BX,1			;Rotate out next bit 
;JNB	LSTY09			;bit not set : carry off
;INC	BX
;STC				;set bit flaga
;LSTY09:
;MOV	Word Ptr SPECIL,BX
;POP	CX
;POP	BX
;RET
; SPECIL is the Pattern Mask
;linety:
;	rol	Word Ptr specil, 1	;Rotate Out Next bit into Carry

	END