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Forums > C64 Coding > Any not allowed chars for directory (art)/directory listing?
2018-01-04 21:52
dano

Registered: Jul 2004
Posts: 131
Any not allowed chars for directory (art)/directory listing?

Maybe i was too blind, but i could not find a resource of allowed or not allowed chars with directory listings.

I am currently working a some better screen fader. For that i would need some free chars in the rom font (copied to ram), that i could overwrite with own content. Or are all (petscii) chars allowed?
 
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2018-01-05 02:25
Groepaz

Registered: Dec 2001
Posts: 8473
thing is, with some trickery (eg inserting shifted space into the filename)you can make control chars - like revers on - which then allows to admit all (not sure, but that would be my guess) the chars that cant be used in normal filenames. the real question is what exactly you want to do, what kind of "not quite exactly like BASIC LIST output" is acceptable, and how you want to deal with control chars that you cant display as control chars (think CLRSCR)
2018-01-05 17:09
dano

Registered: Jul 2004
Posts: 131
it's not about altering a directory listing but clearing the screen nicely without the chars on the screen changing their content.

i made it work with pure petscii but i will give it a go with some dithered chars. let's see what will look nicer. :)

just need some 8 chars usually not used/displayed on screen before running a demo.
2018-01-05 17:52
Groepaz

Registered: Dec 2001
Posts: 8473
that sounds like flawed thinking. obviously when you are doing a "fade from BASIC screen" effect *any* char can be there, regardless what kind of chars are allowed in a directory listing.
2018-01-06 02:40
Tao

Registered: Aug 2002
Posts: 111
If you're making a full disk demo you can just make the dirart yourself, and thus avoid the issue of having to worry about finding a subset--you just decide on a subset of your own :P
2018-01-06 02:43
Compyx

Registered: Jan 2005
Posts: 312
Quoting dano
clearing the screen nicely without the chars on the screen changing their content


That would be quite a trick. If only...
2018-01-06 09:00
ChristopherJam

Registered: Aug 2004
Posts: 777
Quote: that sounds like flawed thinking. obviously when you are doing a "fade from BASIC screen" effect *any* char can be there, regardless what kind of chars are allowed in a directory listing.

Clearly the thing to do is to analyse the screen at runtime, counting the number of occurrences of each char and using the eight that appear least often :D

Alternately, replace any commas onscreen with full stops, and any semicolons with colons, same for reverses of both - that gives you four free. Then there are the two spare spaces at 96 and 224, thats two more. Oh, and turn zeros into capital Os. Done :D
2018-01-06 10:13
soci

Registered: Sep 2003
Posts: 383
Use this replacement table for uppercase:
67 -> 64
93 -> 66
96 -> 32
106 -> 103
116 -> 101
195 -> 192
221 -> 194
224 -> 160
234 -> 231
244 -> 229

And this for lower case:
96 -> 32
106 -> 103
116 -> 101
222 -> 102
224 -> 160
230 -> 94
234 -> 231
244 -> 229

Therefore you can always get at least 8 chars to play with without changing the displayed content.
2018-01-06 12:15
Groepaz

Registered: Dec 2001
Posts: 8473
now thats interesting... are those the few cases that were "fixed" from the original thin pet/vic charset?
2018-01-06 13:09
soci

Registered: Sep 2003
Posts: 383
Yes, these are the result of the widening "fixup". The original only had the shift space as duplicate.
2018-01-07 20:22
dano

Registered: Jul 2004
Posts: 131
soci, that helps alot!
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