Hi!

I would like to know how to make characters inverted in Basic > screen 0.

Example:

With the color setting 15,4,4 you get white characters on an blue screen,
I would like to know how some characters can turn blue with a white background.

I know it can be done, but I don't remember how...

Anybody??

Redefine, xor 255.

Mafcase: redefining is an option, but when redefining the letter A, all As become blue/white. It might be better to use screen 1 instead - you can change colors for every 8 characters.

Copy the ASCII chars 0-127 into 128-255 and XOR this second set. Then you will have a "normal set" and an "inverted set" to be used at the same time in SCREEN 0. I think that this is the best solution, at least for MSX1, SCREEN 0.

To "invert" parts of the screen, it will be enough to XOR 80h the requiered positions in the VRAM NAME TABLE. Easy enough?

Because "Redefine, xor 255." does not help everyone...

To invert ALL characters:

FORI=BASE(2)TOBASE(2)+2047:VPOKEI,VPEEK(I)XOR255:NEXT

To invert 7bit ASCII characters to characters 128-255

FORI=BASE(2)TOBASE(2)+1023:VPOKEI+1024,VPEEK(I)XOR255:NEXT

Here is another method for inverting all characters, but this works only in MSX2 and up.

WIDTH80:FORI=BASE(1)TOBASE(1)+240:VPOKEI,255:NEXT:VDP(13)=PEEK(&HF3E9)+PEEK(&HF3EA)*16:VDP(14)=16

Instead of using VPEEKs, you can always grab the data from the font characters present in ROM, that you can easily read with PEEK, that I guess would be slightly faster.

How about the trick dvik & joyrex used in the end part of the 'MSX Unleashed' demo?

AFAIK there should be some VDP register to do that!
It should be a feature of scr0 at 80 columns,
look at the blinking registers, maybe they do what you
need

Not many registers for good 'n old TMS9918!

Quote:

Instead of using VPEEKs, you can always grab the data from the font characters present in ROM, that you can easily read with PEEK, that I guess would be slightly faster.

Instead of using BASIC , you can always use assembler, that would be quite a lot faster. In theory you are anyway right...

FA=PEEK(&HF920)+PEEK(&HF921)*256:FORI=0TO1023:VPOKEI+BASE(2),PEEK(FA+I)XOR255:NEXT

Quote:

AFAIK there should be some VDP register to do that! It should be a feature of scr0 at 80 columns, look at the blinking registers, maybe they do what you need

That was the 3rd example...

And if you combine the "redefine characters 128-255 to the inverted forms of 0-127" with the VDP(13)/VDP(14) trick you'll have 4 color combinations to play with:

- ForegroundColor 1 / BackgroundColor 1
- BackgroundColor 1 / ForegroundColor 1
- ForegroundColor 2 / BackgroundColor 2
- BackgroundColor 2 / ForegroundColor 2

(Combining e.g. ForegroundColor 1 and BackgroundColor 2 is not an option unfortunately)

why not? there's always the palette

and you don't have 4 color combinations then, just 4 simultaneous colors.

Theoretically, some interesting colour effects could be implemented too in MSX(1) using dirty out-of-blank VDP register manipulations. Main issue here will be timing, of course. But the bonus part of the UNLEASHED demo showed how this could be done. Again, a notorious separation between one colour and other would be a good idea.

(snip)

Quote:

why not? there's always the palette and you don't have 4 color combinations then, just 4 simultaneous colors.

Then, dear Beefmaster, enlighten me:
Assuming

    color 1,2,2
    vdp(13)=&h34

how would I get one single character on the screen with foreground color 1 and backdrop color 4, hm?