Non-x86 arches use an inconsistently named header for the file containing
"pc" attributes, and the ifdef messes to include the right header were out
of date in the 2 files that I added to the MI files list.
Only amd64, arm, i386, mips, powerpc and sparc64 are supposed to support
syscons. Only arm and mips were out of date in the ifdef. Test
coverage for of syscons in arm is broken (turned off) in NOTES, but
syscons is in some other arm config files which universe detects as broken.
arm64 and riscv remain broken due to the opposite bug of not turning off
sc in NOTES, the same as before r344458 (see r344443).
The header is MD to contain possibly-non-"pc" encodings of attributes, but
since the attributes are essentially virtual in graphics mode and non-x86
arches only support graphics mode, the header has always been the same on
all arches except for different style bugs, so there should be only 1 MI
copy of it for syscons' use. It was used in pcvt and still gives an an
API and an ABI, so it should be public and MI near or in sys/consio.h.
First remove ifdefs of the unsupported option SC_DUMB_TERMINAL which
prevented building using both in the same kernel and broke regression
tests. This option will be replaced by per-emulator supported options.
The dumb emulator rotted with KSE in r83366, but usually compiled since
it is ifdefed to nothing unless SC_DUMB_TERMINAL is defined. The type
of an unused function parameter changed.
Both emulators rotted when 2 new methods were added while the emulators
were removed. Only null methods are needed, but null function pointers
give panics instead.
The wildcard in the default for the unsupported option SC_DFLT_TERM
never really worked. It tends to prefer the dumb emulator when multiple
emulators are configured. Change it to prefer scteken for compatibility.
will be committed later.
The "sc" emulator has the advantages of full support for cons25 and running
about 8 times faster than teken (for writing to the frame buffer).
The "dumb" emulator has the advantage of being simple.
Runtime choice of the emulator is good, but compile time choice is bad.
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)
- Split terminal emulation code from the main part of the driver so
that we can have alternative terminal emulator modules if we like in
the future. (We are not quite there yet, though.)
- Put sysmouse related code in a separate file, thus, simplifying the
main part of the driver.
As some files are added to the source tree, you need to run config(8)
before you compile a new kernel next time.
You shouldn't see any functional change by this commit; this is only
internal code reorganization.
