- Implement NP (ASCII 12, Form Feed). When used with cons25, it should
clear the screen and place the cursor at the top of the screen. When
used with xterm, it should just simulate a newline.
- When we want to use xterm emulation, make teken_demo set TERM to
xterm.
Spotted by: Paul B. Mahol <onemda@gmail.com>
Because we now have cons25-style linewrapping, we must also use cons25-
style reverse linewrapping. This means that a ^H on column 0 will move
the cursor one line up.
Also fix a small regression: if the user invokes a RIS (Reset to Initial
State), we must show the cursor again.
Spotted by: Paul B. Mahol <onemda gmail com>
With cons25, there are printable characters below 0x1B. This is not the
case with ASCII, UTF-8, etc. but in this case we just have to.
Also don't set LC_CTYPE to UTF-8 when libteken is compiled without UTF-8
in the demo-application.
It turns out I was looking too much at mimicing xterm, that I didn't
take the differences of cons25 into account. There are some differences
between xterm and cons25 that are important. Create a new #define called
TEKEN_CONS25 that can be toggled to switch between cons25 and xterm
mode.
- Don't forget to redraw the cursor after processing a forward/backward
tabulation.
- Implement cons25-style (WYSE?) autowrapping. This form of autowrapping
isn't that nice. It wraps the cursor when printing something on column
80. xterm wraps when printing the first character that doesn't fit.
- In cons25, a \t shouldn't overwrite previous contents, while xterm
does.
Reported by: Garrett Cooper <yanefbsd gmail com>
The cursor is only inside the scrolling region when we are in origin
mode. In that case, it should use originreg instead of scrollreg. It is
completely valid to place the cursor outside the scrolling region.
Some time ago I started working on a library called libteken, which is
terminal emulator. It does not buffer any screen contents, but only
keeps terminal state, such as cursor position, attributes, etc. It
should implement all escape sequences that are implemented by the
cons25 terminal emulator, but also a fair amount of sequences that are
present in VT100 and xterm.
A lot of random notes, which could be of interest to users/developers:
- Even though I'm leaving the terminal type set to `cons25', users can
do experiments with placing `xterm-color' in /etc/ttys. Because we
only implement a subset of features of xterm, this may cause
artifacts. We should consider extending libteken, because in my
opinion xterm is the way to go. Some missing features:
- Keypad application mode (DECKPAM)
- Character sets (SCS)
- libteken is filled with a fair amount of assertions, but unfortunately
we cannot go into the debugger anymore if we fail them. I've done
development of this library almost entirely in userspace. In
sys/dev/syscons/teken there are two applications that can be helpful
when debugging the code:
- teken_demo: a terminal emulator that can be started from a regular
xterm that emulates a terminal using libteken. This application can
be very useful to debug any rendering issues.
- teken_stress: a stress testing application that emulates random
terminal output. libteken has literally survived multiple terabytes
of random input.
- libteken also includes support for UTF-8, but unfortunately our input
layer and font renderer don't support this. If users want to
experiment with UTF-8 support, they can enable `TEKEN_UTF8' in
teken.h. If you recompile your kernel or the teken_demo application,
you can hold some nice experiments.
- I've left PC98 the way it is right now. The PC98 platform has a custom
syscons renderer, which supports some form of localised input. Maybe
we should port PC98 to libteken by the time syscons supports UTF-8?
- I've removed the `dumb' terminal emulator. It has been broken for
years. It hasn't survived the `struct proc' -> `struct thread'
conversion.
- To prevent confusion among people that want to hack on libteken:
unlike syscons, the state machines that parse the escape sequences are
machine generated. This means that if you want to add new escape
sequences, you have to add an entry to the `sequences' file. This will
cause new entries to be added to `teken_state.h'.
- Any rendering artifacts that didn't occur prior to this commit are by
accident. They should be reported to me, so I can fix them.
Discussed on: current@, hackers@
Discussed with: philip (at 25C3)
