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Improve chances of DirectColor terminal detection

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While ncurses 6.1 adds the `RGB` capability to terminfo, the flag is not
commonly used in terminfo entries as of now. The `COLORTERM` environment
variable is, otoh, commonly present and set to either `truecolor` or
`24bit` value by terminal emulators which support direct color.

Add a check for this if `RGB` is false (or absent)

With this check in I was able to properly appreciate the awesomeness of
notcurses demos :)
This commit is contained in:
Marek Habersack 2019-12-16 22:53:11 +01:00 committed by Nick Black
parent 957549105b
commit ff3ed881c0
2 changed files with 28 additions and 0 deletions
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13
README.md
View File

@ -25,6 +25,7 @@ by [nick black](https://nick-black.com/dankwiki/index.php/Hack_on) (<nickblack@l
* [Features missing relative to NCURSES](#features-missing-relative-to-ncurses)
* [Adapting NCURSES programs](#adapting-ncurses-programs)
* [Environment notes](#environment-notes)
* [DirectColor detection](#DirectColor-detection)
* [Fonts](#fonts)
* [Supplemental material](#supplemental-material)
* [Useful links](#useful-links)
@ -1947,6 +1948,18 @@ These are pretty obvious, implementation-wise.
* The unit tests assume dimensions of at least 80x25. They might work in a
smaller terminal. They might not. Don't file bugs on it.
### DirectColor detection
ncurses aims to use only information found in the terminal's terminfo entry to detect capabilities, DirectColor
being one of them. Support for this is indicated by terminfo having a flag, added in NCURSES 6.1, named `RGB` set
to `true`. However, as of today there are few and far between terminfo entries which have the capability in their
database entry and so DirectColor won't be used in most cases. Terminal emulators have had for years a kludge to
work around this limitation of terminfo in the form of the `COLORTERM` environment variable which, if set to either
`truecolor` or `24bit` does the job of indicating the capability of sending the escapes 48 and 38 together with a
tripartite RGB (0 <= c <= 255 for all three components) to specify fore- and background colors.
Checking for `COLORTERM` admittedly goes against the goal stated at the top of this section but, for all practical
purposes, makes the detection work quite well **today**.
### Fonts
Fonts end up being a whole thing.

15
src/lib/notcurses.c
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@ -545,6 +545,21 @@ interrogate_terminfo(notcurses* nc, const notcurses_options* opts){
char* longname_term = longname();
fprintf(stderr, "Term: %s\n", longname_term ? longname_term : "?");
nc->RGBflag = tigetflag("RGB") == 1;
if (nc->RGBflag == 0) {
// RGB terminfo capability being a new thing (as of ncurses 6.1), it's not commonly found in
// terminal entries today. COLORTERM, however, is a de-facto (if imperfect/kludgy) standard way
// of indicating DirectColor support for a terminal. The variable takes one of two case-sensitive
// values:
//
// truecolor
// 24bit
//
// https://gist.github.com/XVilka/8346728#true-color-detection gives some more information about
// the topic
//
const char* cterm = getenv("COLORTERM");
nc->RGBflag = cterm && (strcmp(cterm, "truecolor") == 0 || strcmp(cterm, "24bit") == 0);
}
nc->CCCflag = tigetflag("ccc") == 1;
if((nc->colors = tigetnum("colors")) <= 0){
fprintf(stderr, "This terminal doesn't appear to support colors\n");