PB35 Line XOR ?

[Daniel Raymer]

Is there any way to draw a Line with XOR, so a redraw erases it? If I try to GET-PUT, I run out of memory for anything other than a little box. I'm trying to draw and move lines in real time, across the screen. I can do it great in PB-CC, but hope to do it in PB-DOS too. Thanks!

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[Michael Mattias]

If I try to GET-PUT, I run out of memory for anything other than a little box

Isn't a "line" automatically a "little" box?

If you are trying to redraw four(4) lines which make up a box, why not redraw the four lines individually instead of GET-PUT the whole box?

[Daniel Raymer]

To draw a long diagonal line then "erase" it, the only way I know is to "get" a big svreen box encompassing the endpoints, draw the line, then "put" the box back overtop the line I want to erase. I can't do that because a big box takes too much memory.

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[Emil Menzel]

Here's a snippet from a program of mine that might help.

'XorPix is Bill Sandall's 1994 PIX routine
'(in "XorGraph.BAS" in PBXtra disk)
SUB XorPix (x as integer, y as integer, colr as integer, mode as integer)
   if mode = 1 then   'if XOR mode is wanted
     out &H3CE, 3
     out &H3CF, 24
   elseif mode=2 then  'AND mode
     out &H3CE, 3
     out &H3CF, 8
   elseif mode=3 then  'OR mode
     out &H3CE, 3
     out &H3CF, 16
   end if
   pset (x,y), colr
END SUB

'By EWM & I won't swear on it
SUB XorReset
    out &H3CE,3
    out &H3CF, 32
END SUB

'this sub draws 1 ASCII text char
'(for longer strings see graphstring.bas)--NOT INCLUDED HERE
'no good in screen 1, or for non-integer sizes
SUB GraphChar (xx as integer, yy as integer, ASCcode as integer, Colour as integer, TextSize as single, XorMode as integer)
   dim isize as single, jsize as single
   dim size8 as single, TRow as integer, tempint as integer
   dim i as integer, j as integer, k as integer, l as integer
   dim ys8i as integer, tint as integer, xjk as integer
   dim xj as integer
   DIM CharTableOfs as long

   IF ASCcode<1 or ASCcode>255 THEN EXIT SUB

   DRAW "BM"+str$(xx)+","+str$(yy) 'position the graphics cursor

   if XorMode = 1 then   'if XOR mode is wanted
     out &H3CE, 3
     out &H3CF, 24
   elseif XorMode=2 then  'AND mode
     out &H3CE, 3
     out &H3CF, 8
   elseif XorMode=3 then  'OR mode
     out &H3CE, 3
     out &H3CF, 16
   end if

   CharTableOfs = &H7A6E
   DEF SEG = &HF800

   size8 = TextSize * 8 - 1

        tempint = CharTableOfs + ASCcode * 8
        isize = 0
        FOR i = 0 TO 7
          isize = isize + TextSize!
          jsize = 0
          ys8i = yy - size8 + isize
          TRow = PEEK(tempint + i)
          FOR j = 0 TO 7
            jsize = jsize + TextSize
            tint = BIT(TRow,7-j)
            xj = xx + jsize
            IF tint THEN
              FOR k = 0 TO TextSize - 1
                xjk = xj + k
                FOR l = 0 TO TextSize! - 1
                    PSET(xjk, ys8i + l), Colour
                NEXT
              NEXT
            END IF
          NEXT
        NEXT
        DEF SEG
END SUB

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[Daniel Raymer]

Thanks for your suggestion. I tried using
out &H3CE, 3
out &H3CF, 24
before a LINE call instead of PSET as in your snippet, but it didn't seem to work. Should it/can it? Or must I make my own "Line" call using a zillion PSET's?

Cheers!

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[Emil Menzel]

>Should it/can it?
I am not certain.

>Or must I make my own "Line" call using a zillion PSET's?

If one must it won't be hard. Let me know if you need help.

By the way, after I learned to use the above routine
I never missed GET/PUT. It is fast enough for my purposes, and
considerably less quirky and error-prone than GET/PUT.

P.S. (note added 04/20/06)

Here's a simple XOR-able line drawer.

'XORline by E.W. Menzel, Jr.
'based on Bill Sandall's 1994 XORPix, in PBEXTRA
'for PB-DOS
sub linedraw (x1 as single,y1 as single,x2 as single,y2 as single,colour as long,stepsize as single,XORmode as long)
   dim dx as single, dy as single, d as single
   dim ix as single, iy as single
   if stepsize <1 then stepsize =1
   dx=x2-x1
   dy=y2-y1
   d=sqr(dx^2+dy^2)

   if d<1 then exit sub 'avoid div by zero

   IF XorMode = 1 THEN   'if XOR mode is wanted
     OUT &H3CE, 3
     OUT &H3CF, 24
   ELSEIF XorMode = 2 THEN 'AND mode
     OUT &H3CE, 3
     OUT &H3CF, 8
   ELSEIF XorMode = 3 THEN 'OR mode
     OUT &H3CE, 3
     OUT &H3CF, 16
   END IF


   PSET (x1,y1),colour
   PSET (x2,y2),colour
   ix=dx/d  'increment in x at each step
   iy=dy/d  'increment in y

   for i=0 to d step stepsize
      pset (x1+i*ix, y1+i*iy),colour
   next
end sub

'demo --PB-DOS
dim x1 as single,y1 as single,x2 as single,y2 as single
dim colour as long,stepsize as single,XORmode as long
screen 12
x1=450: y1=300
x2=50: y2=180
colour=14
stepsize=5
XORmode=1
circle (x1,y1),3: circle(x2,y2),10
'draw
call linedraw(x1,y1,x2,y2,colour,stepsize,XORmode)
a$=input$(1)
'erase (if XORmode=1)
call linedraw(x1,y1,x2,y2,colour,stepsize,XORmode)

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[This message has been edited by Emil Menzel (edited April 20, 2006).]