File emacs-27.2-COLORTERM-24bit.patch of Package emacs.26999
diff --git a/doc/misc/efaq.texi b/doc/misc/efaq.texi
index f5f01848f77f..8f7ed715b523 100644
--- a/doc/misc/efaq.texi
+++ b/doc/misc/efaq.texi
@@ -1595,6 +1595,10 @@ xterm-direct2 xterm with direct-color indexing (old)
xterm-direct xterm with direct-color indexing
@end example
+If Terminfo database is not available, but 24-bit direct color mode is
+supported, it can still be enabled by defining the environment
+variable @env{COLORTERM} to @samp{truecolor}.
+
Terminals with @samp{RGB} capability treat pixels #000001 - #000007 as
indexed colors to maintain backward compatibility with applications
that are unaware of direct color mode. Therefore the seven darkest
diff --git a/src/term.c b/src/term.c
index 94bf013f4a07..5cbb092ad177 100644
--- a/src/term.c
+++ b/src/term.c
@@ -4168,6 +4168,15 @@ use the Bourne shell command 'TERM=...; export TERM' (C-shell:\n\
could return 32767. */
tty->TN_max_colors = 16777216;
}
+ /* Fall back to xterm+direct (semicolon version) if requested
+ by the COLORTERM environment variable. */
+ else if ((bg = getenv("COLORTERM")) != NULL
+ && strcasecmp(bg, "truecolor") == 0)
+ {
+ tty->TS_set_foreground = "\033[%?%p1%{8}%<%t3%p1%d%e38;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%d%;m";
+ tty->TS_set_background = "\033[%?%p1%{8}%<%t4%p1%d%e48;2;%p1%{65536}%/%d;%p1%{256}%/%{255}%&%d;%p1%{255}%&%d%;m";
+ tty->TN_max_colors = 16777216;
+ }
}
#endif