Editable text in BASIC

I need to link some text (preferably RISC OS outline fonts that can be resized) to other BASIC files. Can this be coded ideally without SWIs (poor knowledge) and then CHAINed to the other files which are all in widescreen mode (1920 × 1080). Have any of you a BASIC program to do this please?

If I understood what you were asking I could probably answer more usefully.

Fair point Chris. Is this any clearer?

1. I have a group of BASIC graphic files.
2. I need an introduction page of text. Once this first page is displayed it would be nice to link (CHAIN) all other programs in the group to run automatically so that I can make a video of it (youtube perhaps).
3. The issue is making this text page. I’m sure I’ve seen examples but can’t find them where a BASIC file displays text using a RISC OS outline font in sizes of 30-50 point. This would be easily seen on a small screen.

Maybe there is another way!

Using outline fonts from BASIC is quite straightforward, but you do need to use the Font Manager’s SWI commands. At its simplest, you need to:

1. ‘Find’ the font you want you use (say, Trinity) in the size and weight you want. This is a bit like opening a file with OPENIN – you’ll get a handle to identify the font for use
2. Paint it on to the screen using the font manager system calls
3. ‘Lose’ the font, again a bit like using CLOSE with a file

Something like the following should work (untested):

SYS "Font_FindFont",,"Trinity.Medium",192,192 TO handle%
s$="Hello world"
x%=400
y%=400
SYS "Font_Paint",handle%,s$,16,x%,y%
SYS "Font_LoseFont",handle%

You can read up more on the Font calls here: https://www.riscosopen.org/wiki/documentation/show/FontManager

Looks promising Chris but fails on the first SWI with “font not found” although it looks as though it should work according to the ‘Font calls’ link from riscosopen.

Heh. Serves me right for trying to do it without testing. I’ve tweaked it a bit – does it work now?

Yes it does. I’ve placed a MODE statement MODE 1920,1080,8 at the start of your edited version and changed the x,y parameters from 192 to 480 to increase text size to 30 point. I get a horrible red/green outline text in Trinity.Medium – could this be altered to a single colour?

I’ve not got a lot of experience of plotting fonts outside the desktop, but I think you need to set the font colours using ColourTrans. This call seems to be what you want. If you add the following line to the above code, before the Font_Paint line, it should paint as white on black:

SYS "ColourTrans_SetFontColours",handle%,&00000000,&FFFFFF00,14

“ColourTrans_SetFontColours” does it. Brilliant.

‘Armed’ with your SWI instructions I can now place the required text anywhere on the screen. I usually manage to write simpler BASIC but understanding SWIs is an issue for a non-programmer like myself.

Many thanks for your help.

I usually manage to write simpler BASIC but understanding SWIs is an issue for a non-programmer like myself.

This might sound strange, but you can help with the documentation.

Just ask questions about the bits of the PRM’s that you don’t understand and then following an explanation you do understand it becomes apparent what needs altering in the documents (maybe an example code sample or two)

Apropos of nothing useful, I recall my first Archimedes with Arthur. In an early edition of Archive there was BASIC code to demonstrate the use of outline fonts, by Adrian Look I think. I remember the astonishment and pleasure of experimenting with it after years of bitmapped system fonts. ;-)

“ColourTrans_SetFontColours” does it.

Great!

understanding SWIs is an issue for a non-programmer like myself

Some of the terminology around SWIs is confusing, and some indeed are complex to use, but in principle there’s not a whole lot of difference between calling a SWI via the SYS command in BASIC and using a PROC or a FN. If you had a call like this:

PROCmy_proc (x%,a$)

you’d call the equivalent SWI like this:

SYS "My_SWI",x%,a$

The main difference is that the parameters of a SWI call are numbered R0, R1, R2, etc, as they correspond to the ARM’s registers, and they go in a strict order. So if you want to miss out, say, R0, then you have to add commas to the SYS command (see the Font_FindFont above, which did this).

Some SWIs return information too, in which case you need the TO command, which also uses the registers in order. So if the documentation says that a SWI call returns a value in R3, then you’d use:

SYS "My_SWI",x%,a$ TO ,,,result%

The SYS command in BASIC helps you out a bit, so that in many cases you can pass it integer or string variables just like with a PROC. Quite often the value is treated as a series of bits by the call, like R2 in the Font_Paint call, in which case you need to understand something about BASIC’s bitwise arithmetic. Also, some SWIs, such as the Wimp’s ones, often work on larger chunks of data, where you need to supply pointers to those data blocks rather than values – in which case, you need to get up to speed with BASIC’s facilities for handling this.

As Steve says, though, if you’re interested in investigating more, ask away, and do point out where the existing docs aren’t helpful.