OSC 11 Text Background Color

OSC 11 ; Pt ST sets the color of the default background, behind text with no SGR background color, and OSC 11 ; ? ST asks what it is. OSC 111 puts it back as it started. It is one of xterm’s dynamic colors, and works as OSC 10 explains: Pt is any color X11 can parse, and a further ; in the same sequence moves on to color 12.

A default xterm starts it as the background resource, white (charproc.c), so in the terminal the cases run in, set up as a default xterm, it is reported as rgb:ffff/ffff/ffff.

libghostty-vt has it, and agrees with xterm.

Validation

OSC11-1: Ask for it

\e]11;?\a

|____|
reply \e]11;rgb:ffff/ffff/ffff\a

OSC11-2: Change it

\e]11;#0080ff\a
\e]11;?\a

|____|
reply \e]11;rgb:0000/8080/ffff\a

OSC11-3: The answer ends as the question did

\e]11;?\e\\

|____|
reply \e]11;rgb:ffff/ffff/ffff\e\\

OSC11-4: RIS leaves it alone

\e]11;red\a
\ec
\e]11;?\a

|____|
reply \e]11;rgb:ffff/0000/0000\a