Poking Technology's video: Hjalfi writes a vi for CP M

In which yr hmbl svt decides that there aren't enough shabby vi clones around, and writes one from scratch in a single sitting (not counting a dinner break). This is part of my cpmish project, which is an open source CP/M distribution --- the seminal 1977 8080/Z80 operating system which inspired MS-DOS. http://cowlark.com/cpmish This was a marathon. My original plan turned out to simply be not fast enough: I'm using the Amsterdam Compiler Kit (http://tack.sourceforge.net/) compiler, because it's the only one which will generate 8080 machine code, but the code quality isn't good and is very slow. So partway in I had to redo the entire display layer when I realised that I couldn't do screen updates fast enough. (It would totally have worked had I written it in raw machine code...) I also took several other wrong turns later, all of which wasted time. But I did eventually produce an adequate, working text editor, supporting most of the basic vi editing commands I use. - 00:01:30 Boilerplate - 00:05:30 First, broken version of the refresh code - 00:58:35 Start work on the editor - 01:36:00 Initial text rendering works; start work on command loop - 01:36:30 Realise that I need direct BIOS access and I add support to the ACK - 01:54:40 Continue on the command loop and cursor movement - 02:39:00 Realisation that the screen refresh code won't work - 02:44:00 Start ripping out the refresh code - 03:07:00 First redraw with the new refresh code - 03:22:00 Horizontal cursor movement works - 03:48:30 Vertical movement works, slowly - 03:56:57 Dinner break, decision to drastically simplify editor model - 04:28:05 Cursor movement with the new model works - 04:51:10 Cursor movement with the new model works _quickly_ - 05:00:00 Insert mode works - 05:21:30 Motion by words works - 05:37:45 Repetition count works - 05:49:40 Inserting newlines works - 06:30:00 Scrolling works, up to a point - 07:17:30 Lots of commands work, start thinking about batching redraws - 07:34:45 Notice a hanging problem with scrolling over big lines - 07:39:30 Tea break, remove all the batching redraw stuff - 08:07:08 Finally figure out the horrible scrolling bug - 08:53:15 Saving documents works - 09:09:07 Simple colon commands work Right now it's a shade under 10kB, allowing files of up to 49kB on a Kaypro II; that's not bad. If I were to recompile it with sdcc it'd be both faster and about half the size but sdcc's CP/M support is very poor and I keep running into code generation bugs, so I'm sticking with the ACK for now. (Maybe when z88dk reaches Debian...) The main missing features are search and a yank buffer. Neither would be hard to add, although I don't think this will ever get regular expressions, and the yank buffer is most easily implemented by keeping the buffer on disk; that'd be slow, though. Since doing the video above I've done some polishing, bugfixing, and a few more features. Terminal support is now factored out into a standalone library, making it easy to support multiple terminal types, and for the Kaypro II and NC200 it supports the erase-until-end-of-line control code, making redraws a lot faster. The code is BSD-2 clause licensed, meaning you can pretty much do with it what you like! https://github.com/davidgiven/cpmish/blob/master/cpmtools/qe.c