SB BBC @ GBR
Oldie hints/tips #091-092
Hints and tips from the archives of Wakefield BBC Micro User Group...

91. Shadow printing
    ~~~~~~~~~~~~~~~
Text printing on the screen looks far bolder and nicer if it appears to cast
a slight shadow. This is used to good effect in the titles to a number of
commercial programs. Here is a very useful procedure to produce this in any
mode with 4 or more colours; ie Modes 1,2 and 5. You must specify the two
colours to be used, and these must not be the same as the current background
colour. In the example below, colours 1 and 2 are used, and you can alter the
MODE statement to either 1 or 5 to see how the function automatically adjusts
to cater for the different graphic resolution. If you are sticking to just
one mode, then you can simplify the function by getting rid of line 110,
removing all references to A%, mode% and fact%, and substituting 32 or 64 for
the variable fact% in lines 130 and 140. (The expression fact%DIV32 will of
course also simplify to just 1 or 2.) If you do not want to have to specify
the colours in the FN brackets, then you can omit them, remove all reference
to c1% and c2% in the program, and merely substitute the required numbers in
line 130 and 140. This will simplify the procedure even further, at the
expense of versatility.

A very pleasing effect can be produced by running the program below in Mode
2, after adding :COLOUR132:CLS: immediately after the MODE statement in line
10. You can alter the position of the shadow by trying different combinations
of +4, 0 and -4 in place of the two -4's in line 130. Ie the shadow can fall
above, below, to the right, left or centre of the text.

Do remember that the Function is only for Modes 1,2 and 5; it simply won't
work in the others.

 10 MODE2:PRINTTAB(0,9)"WAKEFIELD "FNshad(1,2,"BBC")" MICROS"
 30 END
 40 :
100 DEFFNshad(c1%,c2%,text$):LOCALA%,mode%,fact%,v%,p%
110 A%=&87:mode%=(USR(&FFF4)AND&FF0000)DIV&10000
120 p%=POS:v%=VPOS:IFmode%=1THENfact%=32ELSEfact%=64
130 VDU5:GCOL0,c2%:MOVEp%*fact%-4*(fact%DIV32),((32-v%)*32-1)-4
140 PRINTtext$:GCOL0,c1%:MOVEp%*fact%,(32-v%)*32-1:PRINTtext$
150 VDU4,31,p%+LEN(text$),v%:=""

92. Graphics demo
~~~~~~~~~~~~~~~~~
This is a short demonstration of an interesting undocumented feature of the
BBC Operating System on the BBC B, B+, Master, Arc etc.. It's a weird graphic
effect that is easier to demonstrate than describe, so get typing!

Make sure you type it in very carefully, and save it before you run it. If
you make any mistakes, the machine might 'hang up'.

10 REPEAT:READ A$:A%=EVAL("&"+A$):CALL 65518:UNTIL A%=&15
20 DATA 16,7,1F,C,C,88,83,41,70,72,69,6C,86,46,6F,6F,6C,1E,15

73 Rick G4BLT @ GB7WRG