How to get white (or other) color on FBTERM and CURSES without scrambling BOX drawing characters?

Question

My question & current states:

I'm writing TUI software that is on fbterm using python-curses library.

• My objective here is to get some colors, most importantly PURE WHITE color.
• My current state: Instead of white, I'm getting somewhat gray color (not full brightness).
• Or If get white full brightness, I got my boxes (rectangles) get scrambled up

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How I set color in python-curses:

I initialed color pair as below (documentation here), & used this pair of color all over my code:

    curses.init_pair(1, curses.COLOR_BLACK, curses.COLOR_WHITE)

It's not full white, I've seen full white in this display.

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My guess what is happening:

Note: if you examined the black white values, those are 0 7 respectively.

>>> import curses
>>> print(curses.COLOR_BLACK, curses.COLOR_WHITE)
0 7

And when list out the available color on fbterm with for i in {0..255}; do echo -ne "\E[2;$i}$i "; done; tput sgr0; echo (read from this thread or just see the image). 0=black, 7=gray, 15=white

So, when my python is trying to send a white color (python-curses thinks white is 7) and gives to fbterm. fbterm receives 7 and thinks it is gray.

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What things I've tried so far:

1st-Try. set my white in color pair to 15:

My rationale: If python-curses send 15 to fbterm, it might think it is a white.

    curses.init_pair(1, curses.COLOR_BLACK, 15)

with this I come to following 2 results:

• if executed within fbterm, it get err: _curses.error: init_pair() returned ERR
• if executed from my laptop (ssh-ed), Software is working and white is more WHITE.

My guess on 1st try:

These 2 different outputs, might be caused different environmental variables:

• my laptop (on lxterminal): $TERM is xterm-256color
• on the device (on fbterm): $TERM is linux

2nd-Try. set TERM variable to fbterm

My rationale: fbterm didn't set correct env variables -> can't use 256 colors. (below is from man page):

... By default, FbTerm sets environment variable "TERM" to value "linux", user need run "TERM=fbterm /path/to/program" to enable 256 color mode.

So I set manually executed TERM=fbterm (or TERM=fbterm python3 main.py), and executed my python code. It shows full-bright white color, but texts are all scrambled:

 ÚÄÄÄÄÄ¿
 ³Meas.³
 ÀÄÄÄÄÄÙ ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿
 ÚÄÄÄÄÄ¿ ³1-shot      ³³n-shot      ³
 ³Setup³ ³            ³³            ³
 ÀÄÄÄÄÄÙ ³            ³³            ³
 ÚÄÄÄÄÄ¿ ³            ³³            ³
 ³Data ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÄÄÙ
 ÀÄÄÄÄÄÙ
 ÚÄÄÄÄÄ¿
 ³About³ ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿ÚÄÄÄÄÄÄÄÄÄÄÄÄ¿
 ÀÄÄÄÄÄÙ ³Target      ³³Weather     ³
 ÚÄÄÄÄÄ¿ ³            ³³            ³
 ³Sys. ³ ÀÄÄÄÄÄÄÄÄÄÄÄÄÙÀÄÄÄÄÄÄÄÄÄÄÄÄÙ
 ÀÄÄÄÄÄÙ

My guess on 2nd-try: NO IDEA

It seems characters like | - (and 90 deg thingy) for drawing boxes are scrambled, but the actual text-strings are OK.

/ps: these rectangles were drawn by window.box() which it self generated by curses.newwin()/

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Can you help me to get color here? without scrambling my text?.

What Should I try next?

/P.S Reason of trying get PURE WHITE: is to increase contrast to black color parts for visibility. (the device (which is handheld) is going to be used in daylight/outside). Also, tips for better visibility are welcome. Thank you. /

Can you help me to get color here? without scrambling my text?.

Answer 1

According to its documentation, fbterm supports a variant of xterm's 256-color extension:

256 COLOR EXTENSION
       FbTerm  supports  xterm's 256 color mode extension. The first 16 colors
       are the default terminal colors. Additionally, there's  a  6x6x6  color
       cube,  and  24  grayscale tones. But xterm's 256 color escape sequences
       conflict with the linux sequences implemented by FbTerm, so private es‐
       cape sequences were introduced to support this feature:

           ESC [ 1 ; n }                   set foreground color to n (0 - 255)
           ESC [ 2 ; n }                   set background color to n (0 - 255)
           ESC  [  3 ; n ; r ; g ; b }       set color n to (r, g, b) ,  n, r,
       g, b all in (0 - 255)

       A new terminfo database entry named "fbterm" was  added  to  use  these
       private  sequences,  all program based on terminfo should work with it.
       By default, FbTerm sets environment variable "TERM" to value  "fbterm".
       Alternatively, the "TERM" variable can be set to "linux", in which case
       the 256 color mode will be unavailable.

With the xterm 256-color palette, your pure white is color number 15:

ncurses provides a terminal description for fbterm, which you may find in the complete terminal database, e.g., "ncurses-term".

Neither "linux" (with 8 colors) nor "xterm-256color" (different escape sequences needed for both color and line-drawing) will work for fbterm. Use infocmp to show the differences.