C/C++ Users Group Library 1996 July

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Assembly Source File | 1988-03-28 | 18.0 KB | 518 lines

page 80,132 page ; ; EGA Graphic Primitive for Turbo Pascal 3.01A, Version 01MAR86. ; (C) 1986 by Kent Cedola, 2015 Meadow Lake Ct., Norfolk, VA, 23518 ; ; The algorithm for drawing a circle (below) was from an article in ; Dr. Dobb's Journal, December 1983, pp. 19 by Michael T. Enright. ; ; I converted it from BASIC source (from above) to assembler for high ; speed plotting and added color/shading fill and clipping code. ; radius equ 4 xcoor1 equ -2 ; X coordinate (left half) xcoor2 equ -4 ; X coordinate (right half) ycoor1 equ -6 ; Location of Y graphic row, contains ycoor2 equ -8 ; ... row byte offset. xc equ -10 yc equ -12 xd equ -14 ; Long integer (32 bits) yd equ -18 ; Long integer (32 bits) zx equ -22 ; Long integer (32 bits) zy equ -26 ; Long integer (32 bits) tx equ -30 ; Long integer (32 bits) ty equ -34 ; Long integer (32 bits) tb equ -38 ; Long integer (32 bits) er equ -42 ; Long integer (32 bits) atx equ -46 ; Long integer (32 bits) aty equ -50 ; Long integer (32 bits) atb equ -54 ; Long integer (32 bits) xf1 equ -58 xf2 equ -60 yf1 equ -62 yf2 equ -64 needed equ 68 ; Amount of temporary space needed dgroup group _data _data segment word public 'data' assume ds:dgroup extrn _gdtype:byte extrn _gdmaxcol:word,_gdmaxrow:word extrn _gdcolor:byte,_gdmerge:byte,_gdaspc1:word,_gdaspc2:word extrn _gdcur_x:word,_gdcur_y:word extrn _gdwd_x1:word,_gdwd_x2:word,_gdwd_x3:word extrn _gdwd_y1:word,_gdwd_y2:word,_gdwd_y3:word extrn _gdvw_x1:word,_gdvw_x2:word,_gdvw_x3:word extrn _gdvw_y1:word,_gdvw_y2:word,_gdvw_y3:word extrn _gdshade:word extrn _gdc_flg:byte,_gds_flg:byte,_gdw_flg:byte _data ends _text segment byte public 'code' assume cs:_text,ds:dgroup public _gpball _gpball proc near push bp mov bp,sp sub sp,needed ; Reserve space for temp. variables push si push di mov _GDC_FLG,2 ; Set clipping flag ; Compute AE = R (save in BX for later) mov ax,[bp+radius] ; Load user specified radius or ax,ax ; If radius is zero, make it 1 jnz notzero ; inc ax ; notzero: mov bx,ax ; Copy to BX (AX used later) mov ax,_GDCUR_X sub ax,bx cmp ax,_GDVW_X2 jbe next1 jmp theend next1: mov [bp+xc],ax add ax,bx add ax,bx cmp ax,_GDVW_X1 jae next2 jmp theend next2: ; Compute BE = (R * _GDASPC1 / _GDASPC2) (save in DX for later) mov ax,bx ; Start with R (AE above) mul _GDASPC1 ; Compute the real Y radius from the div _GDASPC2 ; the defined screen aspects mov dx,ax ; Copy to DX (temp save area) ; Compute the Y coordinate graphic row offset. mov cx,_GDCUR_Y ; Compute the upper and lower row for sub cx,ax ; line clipping logic cmp cx,_GDVW_Y2 ; jbe next3 jmp theend next3: mov [bp+yc],cx mov [bp+yf1],cx ; ... add cx,ax ; ... add cx,ax ; ... cmp cx,_GDVW_Y1 jae next4 jmp theend next4: mov [bp+yf2],cx ; ... mov _GDC_FLG,0 ; Clear clipping flag shl ax,1 ; Compute the graphic segment offset shl ax,1 ; for the Y radius length add ax,dx ; ... mov si,ax ; Copy to SI (temp save area) mov ax,_GDCUR_Y ; Compute the graphic segment offset shl ax,1 ; for the current row shl ax,1 ; ... = A000 + (80 * Y) / 16; add ax,_GDCUR_Y ; ... add ax,0A000h ; ... sub ax,si ; Init the top and bottow y coordinates mov [bp+ycoor1],ax ; ... add ax,si ; ... add ax,si ; ... mov [bp+ycoor2],ax ; ... ; Compute the X coordinate graphic bit offset. mov ax,_GDCUR_X ; Compute the column byte offset mov [bp+xf1],ax ; Save the left and right column numbers mov [bp+xf2],ax ; for clipping logic ; Compute XD = BE * BE mov cx,dx ; Save BE for later (in CX) mov ax,dx ; Must use AX for multiply mul dx ; BE * BE (AX * DX) mov [bp+xd],ax ; Save XD mov [bp+xd-2],dx ; ... ; Compute DX = 2 * BE * BE (or XD * 2) shl ax,1 ; Long shift left for multiply rcl dx,1 ; ... mov [bp+zx],ax ; Save DX mov [bp+zx-2],dx ; ... ; Compute DY = 2 * AE * AE mov ax,bx ; Move current AE to AX mul bx ; ... (AE * AE) push dx ; Save the value (AE * AE) for later push ax ; ... shl ax,1 ; Compute AE * AE * 2 (shift left) rcl dx,1 ; ... mov [bp+zy],ax ; Save DY mov [bp+zy-2],dx ; ... ; Compute YD = (2 * BE - 1) * AE * AE pop ax shl cx,1 ; Compute BE * 2 dec cx ; Compute BE * 2 - 1 mul cx ; Compute (BE * 2 - 1) * AE mov [bp+yd],ax ; Save what we have so far mov [bp+yd-2],dx ; ... pop ax ; Compute (BE * 2 - 1) * AE * AE mul cx ; ... add [bp+yd-2],ax ; ... ; Compute ER = 0 xor ax,ax ; Clear AX to clear ER mov [bp+er],ax ; ... mov [bp+er-2],ax ; ... ; Setup the EGA to perform graphics mov dx,03CEh ; Load EGA graphic controller port addr. mov ah,_GDMERGE ; Load current merge setting mov al,3 ; Merge register is number three out dx,ax ; Set the EGA's merge register mov ax,0205h ; Load write mode number two out dx,ax ; Set the EGA's mode register mov al,8 ; Load the mask register number out dx,al ; Just postion EGA's controller to it call plotpnts ; Plot the first set of points next_x: mov cx,-1 mov ax,[bp+er] ; Compute TX = ER + XD mov dx,[bp+er-2] ; ... add ax,[bp+xd] ; ... adc dx,[bp+xd-2] ; ... mov [bp+tx],ax ; ... mov [bp+tx-2],dx ; ... jns abs_tx ; Compute ATX = abs(TX), if needed xor ax,cx xor dx,cx inc ax jnc abs_tx inc dx abs_tx: mov [bp+atx],ax ; ... mov [bp+atx-2],dx ; ... mov ax,[bp+er] ; Compute TY = ER - YD mov dx,[bp+er-2] ; ... sub ax,[bp+yd] ; ... sbb dx,[bp+yd-2] ; ... mov [bp+ty],ax ; ... mov [bp+ty-2],dx ; ... jns abs_ty ; Compute ATY = abs(TY), if needed xor ax,cx ; ... xor dx,cx ; ... inc ax ; ... jnc abs_ty ; ... inc dx ; ... abs_ty: mov [bp+aty],ax ; ... mov [bp+aty-2],dx ; ... mov ax,[bp+tx] ; Compute TB = ER + XD - YD mov dx,[bp+tx-2] ; ... (or TB = TX - YD) sub ax,[bp+yd] ; ... sbb dx,[bp+yd-2] ; ... mov [bp+tb],ax ; ... mov [bp+tb-2],dx ; ... jns abs_tb ; Compute ATB = abs(TB), if needed xor ax,cx ; ... xor dx,cx ; ... inc ax ; ... jnc abs_tb ; ... inc dx ; ... abs_tb: mov [bp+atb],ax ; ... mov [bp+atb-2],dx ; ... cond1: mov ax,[bp+atx] ; Load absolute value of TX mov dx,[bp+atx-2] ; ... cmp dx,[bp+aty-2] ; if (abs(TX) < abs(TY) ja cond2 ; ... jb cond1a ; ... cmp ax,[bp+aty] ; ... jae cond2 ; ... cond1a: cmp dx,[bp+atb-2] ; and (abs(TX) < abs(TB)) ja cond2 ; ... jb cond1b ; ... cmp ax,[bp+atb] ; ... jae cond2 ; ... cond1b: ; Compute XF1 = XF1 - 1 dec word ptr [bp+xf1] ; Compute XF2 = XF2 + 1 inc word ptr [bp+xf2] mov ax,[bp+tx] ; ER = TX mov dx,[bp+tx-2] ; ... mov [bp+er],ax ; ... mov [bp+er-2],dx ; ... mov ax,[bp+zx] ; XD = XD + DX mov dx,[bp+zx-2] ; ... add [bp+xd],ax ; ... adc [bp+xd-2],dx ; ... jmp until cond2: mov ax,[bp+aty] ; Load absolute value of TY mov dx,[bp+aty-2] ; ... cmp dx,[bp+atx-2] ; if (abs(TY) < abs(TX) ja cond3 ; ... jb cond2a ; ... cmp ax,[bp+atx] ; ... jae cond3 ; ... cond2a: cmp dx,[bp+atb-2] ; and (abs(TY) < abs(TB)) ja cond3 ; ... jb cond2b ; ... cmp ax,[bp+atb] ; ... jae cond3 ; ... cond2b: ; Compute YF1 = YF1 - 1 add word ptr [bp+ycoor1],5 inc word ptr [bp+yf1] ; Compute YF2 = YF2 + 1 sub word ptr [bp+ycoor2],5 dec word ptr [bp+yf2] mov ax,[bp+ty] ; ER = TY mov dx,[bp+ty-2] ; ... mov [bp+er],ax ; ... mov [bp+er-2],dx ; ... mov ax,[bp+zy] ; YD = YD - DY mov dx,[bp+zy-2] ; ... sub [bp+yd],ax ; ... sbb [bp+yd-2],dx ; ... jmp until cond3: ; Compute XF1 = XF1 - 1 dec word ptr [bp+xf1] ; Compute XF2 = XF2 + 1 inc word ptr [bp+xf2] ; Compute YF1 = YF1 + 1 add word ptr [bp+ycoor1],5 inc word ptr [bp+yf1] ; Compute YF2 = YF2 - 1 sub word ptr [bp+ycoor2],5 dec word ptr [bp+yf2] mov ax,[bp+tb] ; ER = TB mov dx,[bp+tb-2] ; ... mov [bp+er],ax ; ... mov [bp+er-2],dx ; ... mov ax,[bp+zx] ; XD = XD + DX mov dx,[bp+zx-2] ; ... add [bp+xd],ax ; ... adc [bp+xd-2],dx ; ... mov ax,[bp+zy] ; YD = YD - DY mov dx,[bp+zy-2] ; ... sub [bp+yd],ax ; ... sbb [bp+yd-2],dx ; ... until: call plotpnts ; Plot the next set of points mov ax,[bp+ycoor1] ; When the two y coordinates are equal cmp ax,[bp+ycoor2] ; ... we are done. je done ; ... (all done condition) jmp next_x ; ... (do the next row condition) done: mov dx,03CFh mov al,0FFh ; Reset EGA back to standard mode out dx,al ; ... dec dx ; ... mov ax,0005h ; ... out dx,ax ; ... mov al,03h ; ... out dx,ax ; ... jmp theend ; Restore the callers parameter frame plotpnts: mov ax,[bp+xf1] ; Load left x coordinate mov di,_GDVW_X2 ; Load X2 coordinate of viewport (speed) cmp ax,di ; Are we out of the viewport? ja plotret ; Yes, skip this plot mov cx,[bp+xf2] ; Load right x coordinate mov si,_GDVW_X1 ; Load X1 coordinate of viewport (speed) cmp cx,si ; Are we out of the viewport? jb plotret ; Yes, skip this plot cmp ax,si ; Clip x1 to stay in viewport jae plot01 ; Already in the viewport, continue mov ax,si ; Lets clip it plot01: cmp cx,di ; Clip x2 to stay in viewport jbe plot02 ; Already in the viewport, continue mov cx,di ; Lets clip it plot02: sub cx,ax ; Compute delta X + 1 inc cx ; ... push ax ; Save starting x coordinate for later push cx ; Save counter for later mov cx,ax ; Compute starting bit shr ax,1 ; shr ax,1 ; shr ax,1 ; mov di,ax ; and cl,7 ; mov al,080h ; ror al,cl ; mov dx,03CFh ; pop cx ; Restore counter (width of line) pop bx mov si,[bp+yf1] cmp si,_GDVW_Y1 jb plot03 cmp si,_GDVW_Y2 ja plot03 mov es,[bp+ycoor1] push ax push bx push cx push di call plotline pop di pop cx pop bx pop ax plot03: mov si,[bp+yf2] cmp si,_GDVW_Y1 jb plotret cmp si,_GDVW_Y2 ja plotret mov es,[bp+ycoor2] call plotline plotret: ret plotline: cmp _GDS_FLG,0 jne shading color: mov ah,_GDCOLOR color01: out dx,al mov bh,es:[di] mov es:[di],ah ror al,1 jnc color04 color02: inc di cmp cx,8 jb color04 mov al,0FFh out dx,al color03: mov es:[di],ah inc di sub cx,8 cmp cx,8 jae color03 mov al,080h inc cx color04: loop color01 ret ; al = bit ; bx = starting offset ; cx = width ; dx = port ; di = byte ; es = segment shading: mov si,_GDSHADE mov bx,[si] inc si inc si push cx xor bh,bh mov cx,bx jmp short shade02 shade01: push cx mov cx,bx sub si,bx shade02: out dx,al mov ah,es:[di] mov ah,[si] mov es:[di],ah ror al,1 adc di,0 inc si loop shade02 pop cx loop shade01 ret theend: pop di pop si mov sp,bp ; Restore the stack pop bp ret _gpball endp _text ends end