PC-98: SEDIT.EXE from NEC MS-DOS not working correctly under DosBox DOS

[yksoft1]

There seemed to be some bugs in CON driver that make the NEC editor not correctly functioning under Dosbox-X's emulated DOS.

1. Function keys are not working at all, thus the editor is not fully usable as it's using a function key-based menu system.
2. Some gibberish characters will be printed out on the screen if you push any key running SEDIT.
   

[yksoft1]

As of 2018/11/22, This problem is still not fixed and there are such logs shown.

PC-98 INT DCh unknown call AX=00FF BX=FF00 CX=000C DX=5BE8 SI=0000 DI=7A0C DS=0918 ES=0000
PC-98 INT DCh unknown call AX=00FF BX=788A CX=000D DX=7668 SI=0000 DI=7A0C DS=0918 ES=0000
PC-98 INT DCh unknown call AX=0000 BX=788A CX=000F DX=7668 SI=0000 DI=7A0C DS=0918 ES=0000

[joncampbell123]

SEDIT.EXE is using INT DCh calls not yet supported by DOSBox-X.

[yksoft1]

After recent commits of INT DCh and ANSI around 2af0db7, the gibberish characters are gone but function keys are still not responding correctly.

[joncampbell123]

SEDIT uses some INT DCh commands (0Ch and 0Dh) that have something to do with the function key row at the bottom, and the ANSI escapes returned when you press the function keys.

[joncampbell123]

It looks like INT DCh CL=0Ch copies FROM internal state TO the application, and INT DCh CL=0Dh copies FROM the application TO internal state.

[joncampbell123]

Based on what I've gotten out of looking at INT DCh CL=0Ch, it looks like SEDIT relies on changing the ANSI escape codes to map F1-F10 and CTRL F1-F10 to 0x7F 0x20+x.

For example, given the new map provided by SEDIT, pressing F1 would emit from the CON device codes 0x7F 0x21 instead of the normal 0x1B 0x53.

[joncampbell123]

It's not just the F1-F10, CTRL+F1-F10 key combinations that INT DCh re-defines, there's an array of 11 other keys in the structure that I don't know what they are yet.

[joncampbell123]

I just noticed SEDIT.EXE makes some call to disable the built-in CTRL+F6, CTRL+F7 and CTRL+F8 handling in the ANSI console.

Normally at any time you can use those to change console state in some way whenever the console is being read, but SEDIT.EXE is making an unknown call to disable those.

Interesting.

[joncampbell123]

When run in the DOSBox-X DOS environment, the log notes calls to INT DCh CL=0Ch, CL=0Dh, and CL=0Fh. Since CL=0Ch/CL=0Dh are the calls to read/write the function key mapping, CL=0Fh might be the one that controls the built-in shortcuts.

[joncampbell123]

Try the latest commit. I have yet to add code for SEDIT's re-definition of various editor keys but the function keys should work now.

EDIT: I figured out the editor keys. The 11 entries seem to match scan codes 0x36 to 0x40 inclusive.

[joncampbell123]

I just confirmed SEDIT and VZ are happy with the INT DCh update.

I just noticed that one of the scan code assignments in SEDIT is a mapping for the HELP key, which has no escape code by default in DOS, and it works in DOSBox-X.

Enjoy.