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My understanding is that bold text on a VT100/VT102 is more intense than ordinary text; I might say that normal text is 80% grey and bold text is 100% grey=pure white, for the sake of illustration.

Assuming that's correct, what happens when bold and reverse video are combined? Does the white background behind the black text change intensity or not?

I've tried this in gnome-terminal and xterm:

$ echo -e '\033[7mxxxxx\033[1mxxxxx\033[m'

and on xterm the white background to all the 'x's is the same shade:

enter image description here

whereas on gnome-terminal there are two distinct shades of white in the background: enter image description here

What happens on the real hardware? Was it common for programs to use bold reverse video at all?

  • Don't know for a VT100/VT102, but I've seen terminals/video cards where bold always means "extra intensity" (realized by a hardware bit), so "bold reverse" means "background brighter than normal". And yes, there were programs that used it. And you have to imagine "normal intensity" as "normal green/amber dots", and "bright" as "extra bright dots, a bit larger, a bit more whitish in the center" on an analog monitor. "80% grey" and "100% grey/white" somehow gives the false impression. Maybe there are youtube videos somewhere that illustrate the look. – dirkt Aug 10 '17 at 5:26
  • What @dirkt said certainly describes the VT220 and DEC Rainbow 100 perfectly. – OmarL Aug 10 '17 at 6:54
  • By the way, what are those escape codes? – OmarL Aug 10 '17 at 6:55
  • 7m = reverse, 1m = bright - see termsys.demon.co.uk/vtansi.htm – cup Aug 10 '17 at 10:47
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    Ask someone over on the vcfed.org forums to take a picture of their VT100 showing the above ESC sequences? – legalize Nov 3 '17 at 23:42
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The approach I remember liking on some terminals of that era that I liked (not sure if I noticed DEC ones doing this, or some other company's) was that there were four intensity levels (including off). Normal text was 2/3 intensity. Inverse text was black on a 1/3 intensity background. Highlighted was full intensity. Highlighted reverse was 2/3 intensity (same as normal text).

Interestingly, flashing text went between 1/3 and 2/3 intensity (rather than flashing on and off); and flashing highlighted went between 2/3 and full. I don't remember what flashing inverse text did.

It's too bad I've not seen modern terminal emulation software adopt such an approach, since it really worked well.

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  • That was one of the complaints when we moved from 80x24 terminals to high resolution workstations: the text could not be flashed. This was in 1986. The so-called system experts told us to implement some other mechanism to highlight text. I haven't seen flashing since other than when it is manually implemented in GUIs. The problem with flashing is that it has to be too fast otherwise it brings on epilepsy in some people. – cup Dec 20 '17 at 21:22
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    @cup: A second problem with flashing is that it more often implemented by making things appear and disappear, rather than merely altering the contrast of things which continue to be visible. A slight contrast adjustment will be sufficient to call attention to flashing text, while being far less annoying than having text appear and disappear or--even more annoyingly--flashing between normal and reverse video. – supercat Dec 20 '17 at 22:16

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