Re: How come i wrote a NO-BREAK SPACE in xterm+bash ?

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

> Well, it seems that there's some confusion. By "Alt", I meant the
> ISO_Level3_Shift key, which is bound to the physical Alt and AltGr
> keys in my keyboard configuration.

Mine is a US QWERTY. Two "Alt" keys, no "AltGr".
  https://en.wikipedia.org/wiki/Template:Keyboard
xkbdcomp reports it as "pc105".
The two Windows keys (Super_L and Super_R) are occupied by
fvwm2 pop-up-down function "RaiseLower".


> Now, there's the Meta key (mod1, bound to the physical Windows key in
> my keyboard configuration), often called Alt in other applications,
> which gives the Escape character because I've set eightBitInput to
> false.

I added it to /etc/X11/app-defaults/XTerm :

  *eightBitInput: false

and disabled my workaround VT100.Translations.

With this setting, Alt+Spacebar does nothing visible. It emits
the two bytes ESC and SPACE now. Many other Alt+keys cause beeps.


> I get ISO-8859-1 characters (translated
> into UTF-8): the ASCII character with the 8th bit set. For space,
> 0x20 is changed to 0x80|0x20 = 0xA0, which is the NO-BREAK SPACE in
> ISO-8859-1.

Aha. That's a simple rule, at least.
I verified it by checking a few Alt+keys against man iso_8859-1
and man ascii, while eightBitInput was true.
man xterm explains it in confusing detail.


Having the choice between totally invisible, but not empty
Alt+Spacebar plus beeping Alt+keys on the one hand,
and visible Alt+keys "±²³´µ¶·¸¹°­½ñ÷åòôùõéïðÛÝÜáóäæçèêë컧úøãöâîí¬®¯"
plus a real blank as Alt+Spacebar, on the other hand, i choose
the latter.

(Not that i would be able to memorize the location of our
 national umlauts, ligature, and symbols.)


> IMHO, eightBitInput = true (the default) does not make much sense.

It's not too bad if only NO-BREAK SPACE had a visible glyph.
Something like four dots at the corners of its rectangle.


Thanks for clarifying what's going on.


Have a nice day :)

Thomas