Reverse mode in ISO mode

[mist64]

In ISO mode, reverse mode has no effect. Also, the cursor is a block that covers the character instead of inverting it.

This can be fixed by swapping the foreground and background colors both for reverse characters and for the cursor.

• At nxt3, the character is inverted (ORA #$80) in the PETSCII codepath.
• At nc3w, we currently disable the Ctrl+9 combination of having any effect in ISO mode.
• AT key5, the cursor is drawn. In ISO mode, we draw code $9F instead of inverting the character.

[mist64]

Here's some code I worked on. The cursor leaves a trail. Needs debugging.

reverse.diff.zip

It uses this magic code to swap the nibbles:
asl
adc #$80
rol
asl
adc #$80
rol

[Serentty]

If it's possible to implement reverse video with blinking this way, I think it would make sense to do this for PETSCII as well. Yes, it would mean that screen codes would no longer line up with the C64, but PETSCII text itself would still be compatible.

[mobluse]

I thought Reverse On/Off worked in PETSCII-UC, PETSCII-LC, and ISO mode, but it doesn't work in ISO mode. Try RUNning this BASIC program before and after Ctrl+O:

10 PRINT "ABCD";CHR$($12);"EFGH";CHR$($92);"IJKL"
20 PRINT "ABCD";CHR$($02);"EFGH";CHR$($02);"IJKL"

CHR$($02) for reversing only works if you have merged PR 89 for x16-rom.