Missed bold/highlight font/colors in twterm in Twin v.1.0

[dimitrik-fr]

Trying to move to Twin 1.0 from 0.7.4 version and observing missed font attributes in twterm comparing to before -- it looks like text is no more printed in bold font, nor using highlight/bold colors. While this all was perfectly working in Twin 0.7.4 version.

How to reproduce :

• start Twin as twstart --hw=tty
• execute msgcat --color=test
• see the difference between 1.0 and 0.7.4

NOTE : you can also observe different outputs by explicitly setting TERM=xterm for ex. (comparing to xterm-256color which is now a new default TERM value).

Let me know if you need any more details..

Rgds,
-Dimitri

[cosmos72]

Bold, italic and underline font support has always been very limited on twin.

Up to version 0.9.1, a single bit is used to represent high intensity fg color, bold and/or underline, and each hw display driver independently decides how to actually render such bit.

• the --hw=X11 and --hw=xft drivers always rendered it as high intensity fg color.
• the --hw=tty driver rendered it as ESC [ 1 m which most terminals interpret as bold font.

Italic has always been ignored.

Starting from version 1.0.0, this single bit is merged into truecolor support: it is used to choose between

• the default (ANSI/VGA) 8 colors palette
• the high intensity 8 colors palette

which are also contained in the 256-color palette as, respectively, colors 0...7 and colors 8...15, and are then internally converted to truecolor.

In practice, the new behavior of --hw=tty is the following:

• on 256-color or truecolor terminals, high intensity / underline / bold is always rendered as high intensity
• on 8-color terminals, high intensity / underline / bold is rendered in the traditional way: ESC [ 1 m which most terminals interpret as bold font.

This is certainly limiting, and the main reason for such limitation is memory usage:
due to truecolor support, each character cell in each window consumes 8 bytes:

• 21 bits for the Unicode codepoint (only 20.09 bits are actually needed, to represent 0 ... 0x10FFFF)
• 21 bits for "almost" truecolor foreground (7 bits red, 7 bits green, 7 bits blue)
• 21 bits for "almost" truecolor background (7 bits red, 7 bits green, 7 bits blue)
• 1 bit is spare, my intention is to allocate it for managing double-width glyphs.

Ideally, each character cell would also have space for additional flags such as bold, underline, italic etc.
but as you can see, the current cell representation is already quite large and definitely full.

Until I decide for some kind of "compressed" representation, I'm afraid there's not much room for better rendering the bold, italic and underline attributes.

[dimitrik-fr]

Thanks a lot for so detailed explanation !!
but unfortunately I'm still confused ;-))

I'm using iTerm2 and configured it to use the same bright colors for "bold" and "light" (high intensity), but with the new Twin I'm not getting these bright colors regardless if the text should be bold or light.

However, this is happening when iTerm2 is reporting itself to Twin as "xterm-256color". But if I'll force it to report itself as "linux", then all colors are coming back and printed as expected (similar to 0.7.4) -- but unfortunately then I don't have a mouse support anymore ! ;-))

So, is there any workaround to be able to use Twin with colors like with "linux" terminal, but with mouse like "xterm" ?..

Rgds,
-Dimitri

[cosmos72]

Yes: the workaround is to convince twin --hw=tty that it's displaying inside an 8-color xterm.
In this way you get mouse support, and high intensity/bold/underline is rendered as ESC [ 1 m which iTerm2 should convert to bold font.

The simplest mechanism is to run twin --hw=tty,colors=8

In alternative, you can run

TERM=xterm
unset COLORTERM

before starting twin --hw=tty

For more options, try twin --hw=tty,help

[dimitrik-fr]

Thanks a lot !! works just fine !!

NOTE : I should probably clarify that it's not like something is not working, just that text in terminal is printed with different "bright" colors from what is configured in iTerm2 (but colors are really brighter than normal, probably just coming from a different palette, etc.). So, it's probably just working as expected for many users, and maybe my case is just different..

Thanks again ! and it's great to see so many improvements in the new release !!

Rgds,
-Dimitri

[cosmos72]

I am currently working to expand tcell to 96 bits - see the (unfinished and incomplete) branch https://github.com/cosmos72/twin/tree/tcell96
It will have enough space for accurately representing bold, underline, italic and possibly more attributes.