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)
creation by GCC-2.6.3. Casting pointers to unsigned char
to volatile pointers to unsigned char seemed to produce
better results on the ia32 architecture with old versions
of GCC.
The current FreeBSD system compiler GCC-3.2.1 emits
better sign extension code for non-volatile variables:
volatile char c;
int i = c;
is compiled to:
...
movb -1(%ebp), %al
movbsl %al, %eax
movl %eax, -8(%ebp)
...
char c;
int i = c;
is compiled to:
...
movbsl -1(%ebp), %eax
movl %eax, -8(%ebp)
...
The same holds for zero-extension of dereferenced pointers
to volatile unsigned char.
When compiled on alpha or sparc64, the code produced for the
two examples above does not differ.
It may cause misterious chars appearse in the middle of the scrolled lines.
The bug trigger: enter
grep P_32 /usr/include/*.h
command and see misterious "db.\" filename.
- 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.
