Re: use of graphics characters recently disabled in xterm
- From: Theodore Kilgore <kilgota auburn edu>
- To: Thomas Dickey <dickey his com>
- Cc: <mc gnome org>
- Subject: Re: use of graphics characters recently disabled in xterm
- Date: Mon, 11 Sep 2017 11:03:23 -0500
Thomas,
The output of locale (invoked without arguments) is as follows, between
the two lines.
--------------------------------------------------------------------
kilgota@khayyam:/etc/X11/app-defaults$ locale |less
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE=C
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
-------------------------------------------------------------------
Now, what is also interesting is that after reading closely the man page
for xterm and trying to make sense of it, I discovered that there are two
things which one can do in order to make the settings in an xterm to be
visible. There are two things called "menu" and one can get to them by
holding down a control key and clicking either the left or the right mouse
button while the pointer is in the window. The right button click displays
a window called "VT fonts" and it contains relevant information.
Unfortunately, I do not know if it is possible to mouse-copy its contents
because it goes away immediately as soon as one lets go of that button.
This VT Font menu depicts the current settings by a check mark in front
of whichever setting is highlighted. One can scroll down that menu and
change a setting by hand, by leaving the highlighting on top of that
particular setting and then closing the menu. Also, the settings in this
menu are specific to the xterm which has been opened. They remain as they
previously were if one opens another xterm next to the one in which the
settings have already been set by hand. And in the same manner those
settings cannot be saved for another X session. A further description of
possibly relevant settings in this window follows.
There is a line called "line-drawing characters" which is *not* turned on.
It is unclear to me what this does (see the xterm man page for an
explanation, which is not totally clear). What it might be doing is
turning on the line-drawing characters from X itself, to replace the ones
which are provided by the font, or alternatively what it might be doing is
enabling the line-drawing characters which are already provided by the
font. As I said, the explanation in the man page is not very clear and
these two meanings are obviously opposite to each other. In any event, to
toggle this setting on and off all by itself, when other settings are
not changed, seems to have no effect.
There are also lines in that menu for UTF-8 Encoding, UTF-8 Fonts, and
UTF-8 Titles. These are also apparently not turned on (no check marks in
front).
Setting UTF-Encoding *and* UTF-8 Fonts *and* Line-Drawing Characters all
to be on seems to solve the problem. But by default all three of them are
turned off.
Why are all three of these settings turned off by default? I have no idea.
In particular, this is even more amazing because it seems to be in
conflict with the locale settings displayed above. So, in order to get
back to the bottom of this problem it seems to me that what needs to be
done is to set up a way to turn all three of these settings on. However, I
do not know what I am supposed to do in order to carry that out. Change
some configuration file, I suppose, or else do a local override. But I
suspect that the settings are already set correctly in some file somewhere
and that somehow the settings in that file are being ignored.
Theodore Kilgore
On Sun, 10 Sep 2017, Thomas Dickey wrote:
On Sun, Sep 10, 2017 at 01:58:38PM -0500, Theodore Kilgore wrote:
On Sun, 10 Sep 2017, Thomas Dickey wrote:
On Fri, Sep 08, 2017 at 05:57:33PM -0500, Theodore Kilgore wrote:
I have recently done some upgrades, keeping current with
slackware-64-current. And what has happened is that suddenly MC
started to print funny characters around the panels instead of
a screenshot would help:
In the screenshot, I see a single character, which is always the same value:
226 (octal 342).
That happens to be the first byte of the UTF-8 encoding for the various
line-drawing characters which is odd, since they are all 3-bytes:
\342\224\214 0x250c /* upper left corner */
\342\224\224 0x2514 /* lower left corner */
\342\224\220 0x2510 /* upper right corner */
\342\224\230 0x2518 /* lower right corner */
\342\224\234 0x251c /* tee pointing left */
\342\224\244 0x2524 /* tee pointing right */
\342\224\264 0x2534 /* tee pointing up */
\342\224\254 0x252c /* tee pointing down */
\342\224\200 0x2500 /* horizontal line */
\342\224\202 0x2502 /* vertical line */
\342\224\274 0x253c /* large plus or crossover */
Those 22x's are mostly in the C1 control range (200 to 237 octal),
so it's possible that xterm is not using UTF-8 encoding, and simply
discarding the control characters (with an occasional glitch for
the tee's and plus signs).
Attached.
+ If it's 2-3 characters rather than a single character, that indicates that
xterm's not using UTF-8 (a resource problem perhaps). You would set in
the right-menu-mouse menu that "UTF-8 Encoding" is not checked.
This could be the problem, even though X is completely up to date
and the file /etc/X11/app-defaults/XTerm does contain the following
lines:
*fontMenu*utf8-mode*Label: UTF-8 Encoding
*fontMenu*utf8-fonts*Label: UTF-8 Fonts
*fontMenu*utf8-title*Label: UTF-8 Titles
What is interesting about this is the following. Yesterday evening I
did some experimenting. The xterm man page contains the following
options
-lc Turn on support of various encodings according to the
users'
locale setting, i.e., LC_ALL, LC_CTYPE, or LANG environment
variables. This is achieved by turning on UTF-8 mode
and by
invoking luit for conversion between locale encodings and
UTF-8. (luit is not invoked in UTF-8 locales.) This
corresponds to the locale resource.
The actual list of encodings which are supported is
determined
by luit. Consult the luit manual page for further details.
See also the discussion of the -u8 option which
supports UTF-8
locales.
+lc Turn off support of automatic selection of locale
encodings.
Conventional 8bit mode or, in UTF-8 locales or with
-u8 option,
UTF-8 mode will be used.
Both of the above options restore MC to sane behavior.
That's saying that turning the switch on or off has the same effect :-(
Aksi there is the -u8 option.
-u8 This option sets the utf8 resource. When utf8 is
set, xterm
interprets incoming data as UTF-8. This sets the wideChars
resource as a side-effect, but the UTF-8 mode set by this
option prevents it from being turned off. If you must turn
UTF-8 encoding on and off, use the -wc option or the
corresponding wideChars resource, rather than the -u8
option.
This option and the utf8 resource are overridden by
the -lc and
-en options and locale resource. That is, if xterm
has been
compiled to support luit, and the locale resource is not
false this option is ignored. We recommend using the -lc
option or the locale: true resource in UTF-8 locales when
your operating system supports locale, or -en UTF-8
option or
the locale: UTF-8 resource when your operating system does
not support locale.
The option xterm -en UTF-8 works, too, as it is supposed to. I also
tried I tested each one of the above options by opening an xterm and
then typing the command. When I hit "enter" it created a new window
beside the old one, and then opened MC in the new window.
The option xterm -en UTF-8 works, too, as it is supposed to. I also tried
using "luit" as the sterm man page suggests to do, but that option appears
to be superfluous.
So, what I could do about this is to associate one of these options
with the command to fire up an xterm in my configuration file for my
window
manager, which is fvwm2. But, alas, I just now tried all of them and
none of them work when they are put into the $HOME/.fvwm/.fvwmrc
file. So, now I am really puzzled. They all work as stated if I fire
them up from another xterm, but none of them work when put into the
fvwm configuration file. And using the same configuration file with
the same window manager on my office machine (which has the Intel
video in it) I do not have these problems. Mystery.
What does "locale" tell you?
It's also possible that locale variables are set, but the locale tables
are not installed. When that happens, some applications (and shells)
will complain about it. If you're running everything from a desktop,
it's easy to overlook those warning messages.
Morever, what I still cannot figure out in the first place is why
this started to happen. It appears to me that UTF-8 is the default
in the XTerm app defaults file, and clearly it is also set so in the
console because in the console there is not any problem. So, I
cannot help but to wonder where exactly the problem is.
It's the default if your locale uses UTF-8 encoding. Otherwise,
it may turn on UTF-8 encoding if it is able to use luit to convert
between your locale's encoding and UTF-8.
Theodore Kilgore
+ If it's a single character, then that could be a problem with the video
driver (or fontconfig, etc). For this, you could try using xterm's
built-in line-drawing using the "Line-Drawing Characters" menu option.
printing vertical and horizontal lines. This happens only in an
xterm, not in the console terminal where all remains OK. The command
mc -a replaces the straight lines with vertical and horizontal
dashes, but that does not look nearly so nice.
--
Thomas E. Dickey <dickey invisible-island net>
http://invisible-island.net
ftp://ftp.invisible-island.net
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