DrawScript at London user group / Mon 16th July 2018

The next meeting of the RISC OS User Group Of London will be:

DrawScript, presented by David Lane

Monday 16th July 2018, 7.45pm

The Blue-Eyed Maid (upstairs in the restaurant)
173 Borough High Street
London, SE1 1HR

http://www.rougol.jellybaby.net/

DrawScript is a programming (or script) language for producing line-drawings in Draw format. The language used is BASIC extended with extra graphics commands. DrawScript is capable of producing much more elaborate drawings than could be created manually only using a mouse, as shown by the examples in the DrawScript gallery.

http://drawscript.jettons.co.uk/drawscriptold/index.html

David will describe in more detail what DrawScript is and what it does, demonstrating some simple examples that come with the software as well as some of his own programs. Uses of DrawScript will be given and some bugs discussed. DrawScript and BASIC programs that relate to one of the many proofs of the rectangular tiling theorem will be demonstrated.

No preparation or knowledge of DrawScript is necessary as all will be explained. If, however, you have the program you are encouraged to experiment and suggest your own uses.

A question from David: Can you get DrawScript to produce more than one Draw file from one program?

More info here – http://rougol.jellybaby.net/meetings/index.html

ROUGOL’s venue is easy to reach by public transport from in and around London and the south east:
- 2 minutes walk from Borough tube station
- 5 minutes walk from London Bridge station
- 10 minutes from Waterloo (two stops eastbound on the Jubilee line to London Bridge)
- 20 minutes from Euston and Kings Cross/St Pancras (southbound on the Bank branch of the Northern Line to Borough)

ROUGOL meetings take over the pub’s upstairs restaurant for the evening. Entry is free, food & drink plentiful (but not free!).

I hope to be there. With luck I may have been playing with DrawScript by then…I wonder whether there will be interesting ways to combine using it with using my various drawfile editing programs (one of which I’m upgrading at the moment)…

I’ve been playing with DrawScript a bit…

If anyone wants a look at the (horribly uncommented & with meaningless variable names) little script I’ve written, be my guest – it’s at http://clive.semmens.org.uk/RISCOS/PrimeSpiral – just set its type to b9b and (assuming you’ve got DrawScript) run it…

A little question – I couldn’t see how to stop a path being filled. The final white spiral on top of everything is made of 2,500 separate short lines, because when it was a single line it had a black fill, that being the last fill colour I’d used. How do you get rid of a fill colour?? My manky workaround wouldn’t work with curved lines.

DrawFile uses -1 to mean ‘no colour’, so set fill colour to -1.

I tried that. I know what Drawfile does – I’ve written apps that generate drawfiles myself. But no, didn’t work – it fills white, presumably only taking notice of the top three bytes for fill colour…

But… d’uh …your post makes me look at my program again, and it’s a different error that’s the cause of the trouble, and indeed putting Fill(-1) does work.

Stupidity: to shorten the data in my palette, I was only putting the top three bytes in, and then shifting them left a byte at the point of use…which oddly enough does turn -1 into &FFFFFF00, which is white…

Now working without the manky workaround.

The words ‘quart’ and ‘pint-pot’ come to mind.

8~) Something like that. Since I’m only using 16 different colours, I put all the palette into an array like this:

c%()=0,&C0C0C0,&FFFF80,&A0A000,&FF80FF,&800080,&C0FFFF,&A0B0,&806000,&FF00FF,&D0FF,&FF,&686868,&747474,&808080,&8C8C8C,-1

which is fine – except that -1 shifted left a byte is a bit sad and sorry but I’m not ashamed. Well, not much.

(DrawScript is basically BASIC with a some nice procedures that don’t need to appear in the script.)

Hello Clive. I will show your Primespiral tonight at ROUGOL.