Complete VT320 emulation

[davidrg]

Despite offering a VT320 emulation option, K95 still lacks a handful of VT320 functions:

• Dynamically Redefined Character Set support #473 (optional, as VT220 doesn't have it either)
• DECRQUPSS/DECAUPSS - User-Preferred Supplemental Sets
• DECRQTSR/DECRSTS - Request/Restore Terminal State
• DECRQPSR/DECRSPS - Request/Restore Presentation State
• DECKBUM - Typewriter or Data Processing keys

DECKBUM can probably be counted as optional as it looks like it may be a little messy to implement. It looks like just adjusts the keymap slightly, though only when using some keyboard dialect other than "North American" (I guess this would be the set term vt-langauge setting in K95). DEC STD 070 seems to be a bit light on details. Or perhaps Data Processing Keys just turns deactivates NRC mode?

[j4james]

DECKBUM - Typewriter or Data Processing keys

This is actually documented in quite a lot of detail in the Keyboard Processing chapter. There's a basic explanation in section 6.7.5, but in section 6.14 they give full key mappings for every keyboard dialect, showing what changes between the different modes (typewriter keys vs data processing keys in both 8-bit and 7-bit modes).

Essentially when you're in typewriter mode on an international keyboard, you'll have direct access to the language-specific glyphs, like characters with accents, while in data processing mode you'll have access to the ASCII punctuation that is lost in typewriter mode.

And note that the byte generated for a particular glyph may vary depending on the mapping and keyboard dialect in use. For example, a small e with acute accent (é) will be 14/9 in 8-bit mode, but in 7-bit mode it will depend on the NRCS character set associated with the keyboard dialect (on an Italian keyboard it's 5/13, while on a Swiss keybard it's 5/11, and on a French keyboard it's 7/11).

You can see the which NRCS set is associated with each keyboard layout supported by the VT320 in section 6.7.6. The VT510 programmer reference has several more documented in section 8.11.