diff --git a/runtime/doc/tags b/runtime/doc/tags

index b7e16df..f5201aa 100644

--- a/runtime/doc/tags

+++ b/runtime/doc/tags

@@ -920,6 +920,7 @@ $VIMRUNTIME	starting.txt	/*$VIMRUNTIME*

 't_KJ'	term.txt	/*'t_KJ'*

 't_KK'	term.txt	/*'t_KK'*

 't_KL'	term.txt	/*'t_KL'*

+'t_RB'	term.txt	/*'t_RB'*

 't_RI'	term.txt	/*'t_RI'*

 't_RV'	term.txt	/*'t_RV'*

 't_SI'	term.txt	/*'t_SI'*

@@ -7987,6 +7988,7 @@ t_KI	term.txt	/*t_KI*

 t_KJ	term.txt	/*t_KJ*

 t_KK	term.txt	/*t_KK*

 t_KL	term.txt	/*t_KL*

+t_RB	term.txt	/*t_RB*

 t_RI	term.txt	/*t_RI*

 t_RV	term.txt	/*t_RV*

 t_SI	term.txt	/*t_SI*

diff --git a/runtime/doc/term.txt b/runtime/doc/term.txt

index c11ddea..bdd6aba 100644

--- a/runtime/doc/term.txt

+++ b/runtime/doc/term.txt

@@ -300,6 +300,8 @@ Added by Vim (there are no standard codes for these):

 		|xterm-8bit| |v:termresponse| |'ttymouse'| |xterm-codes|

 	t_u7	request cursor position (for xterm)		*t_u7* *'t_u7'*

 		see |'ambiwidth'|

+	t_RB	request terminal background color		*t_RB* *'t_RB'*

+		see |'ambiwidth'|

 KEY CODES

 Note: Use the <> form if possible

diff --git a/src/ascii.h b/src/ascii.h

index a3cfecf..7ed736a 100644

--- a/src/ascii.h

+++ b/src/ascii.h

@@ -34,10 +34,6 @@

 #define ESC_STR_nc	"\033"

 #define DEL		0x7f

 #define DEL_STR		(char_u *)"\177"

-#define CSI		0x9b	/* Control Sequence Introducer */

-#define CSI_STR		"\233"

-#define DCS		0x90	/* Device Control String */

-#define STERM		0x9c	/* String Terminator */

 #define POUND		0xA3

@@ -117,11 +113,6 @@

 #define ESC_STR_nc	"\x27"

 #define DEL		0x07

 #define DEL_STR		(char_u *)"\007"

-/* TODO: EBCDIC Code page dependent (here 1047) */

-#define CSI		0x9b	/* Control Sequence Introducer */

-#define CSI_STR		"\233"

-#define DCS		0x90	/* Device Control String */

-#define STERM		0x9c	/* String Terminator */

 #define POUND		0xB1

@@ -173,6 +164,13 @@ extern char MetaCharTable[];

 #endif /* defined EBCDIC */

+/* TODO: EBCDIC Code page dependent (here 1047) */

+#define CSI		0x9b	/* Control Sequence Introducer */

+#define CSI_STR		"\233"

+#define DCS		0x90	/* Device Control String */

+#define OSC		0x9d	/* Operating System Command */

+#define STERM		0x9c	/* String Terminator */

+

 /*

  * Character that separates dir names in a path.

  * For MS-DOS, WIN32 and OS/2 we use a backslash.  A slash mostly works

diff --git a/src/main.c b/src/main.c

index 885192b..41c2c41 100644

--- a/src/main.c

+++ b/src/main.c

@@ -825,8 +825,11 @@ vim_main2(int argc UNUSED, char **argv UNUSED)

     starttermcap();	    /* start termcap if not done by wait_return() */

     TIME_MSG("start termcap");

-#if defined(FEAT_TERMRESPONSE) && defined(FEAT_MBYTE)

+#if defined(FEAT_TERMRESPONSE)

+# if defined(FEAT_MBYTE)

     may_req_ambiguous_char_width();

+# endif

+    may_req_bg_color();

 #endif

 #ifdef FEAT_MOUSE

diff --git a/src/proto/term.pro b/src/proto/term.pro

index b3d0df3..f0c2a01 100644

--- a/src/proto/term.pro

+++ b/src/proto/term.pro

@@ -36,6 +36,7 @@ void starttermcap __ARGS((void));

 void stoptermcap __ARGS((void));

 void may_req_termresponse __ARGS((void));

 void may_req_ambiguous_char_width __ARGS((void));

+void may_req_bg_color __ARGS((void));

 int swapping_screen __ARGS((void));

 void setmouse __ARGS((void));

 int mouse_has __ARGS((int c));

diff --git a/src/term.c b/src/term.c

index 46274d8..660df07 100644

--- a/src/term.c

+++ b/src/term.c

@@ -124,6 +124,11 @@ static int crv_status = CRV_GET;

 #  define U7_SENT	2	/* did send T_U7, waiting for answer */

 #  define U7_GOT	3	/* received T_U7 response */

 static int u7_status = U7_GET;

+/* Request background color report: */

+#  define RBG_GET	1	/* send T_RBG when switched to RAW mode */

+#  define RBG_SENT	2	/* did send T_RBG, waiting for answer */

+#  define RBG_GOT	3	/* received T_RBG response */

+static int rbg_status = RBG_GET;

 # endif

 /*

@@ -949,6 +954,7 @@ static struct builtin_term builtin_termcaps[] =

     {(int)KS_CWP,	IF_EB("\033[3;%d;%dt", ESC_STR "[3;%d;%dt")},

 #  endif

     {(int)KS_CRV,	IF_EB("\033[>c", ESC_STR "[>c")},

+    {(int)KS_RBG,	IF_EB("\033]11;?\007", ESC_STR "]11;?\007")},

     {(int)KS_U7,	IF_EB("\033[6n", ESC_STR "[6n")},

     {K_UP,		IF_EB("\033O*A", ESC_STR "O*A")},

@@ -1240,6 +1246,7 @@ static struct builtin_term builtin_termcaps[] =

 #  endif

     {(int)KS_CRV,	"[CRV]"},

     {(int)KS_U7,	"[U7]"},

+    {(int)KS_RBG,	"[RBG]"},

     {K_UP,		"[KU]"},

     {K_DOWN,		"[KD]"},

     {K_LEFT,		"[KL]"},

@@ -2357,7 +2364,7 @@ term_7to8bit(p)

 	if (p[1] == '[')

 	    return CSI;

 	if (p[1] == ']')

-	    return 0x9d;

+	    return OSC;

 	if (p[1] == 'O')

 	    return 0x8f;

     }

@@ -3224,7 +3231,8 @@ settmode(tmode)

 		 * doesn't work in Cooked mode, an external program may get

 		 * them. */

 		if (tmode != TMODE_RAW && (crv_status == CRV_SENT

-					 || u7_status == U7_SENT))

+					 || u7_status == U7_SENT

+					 || rbg_status == RBG_SENT))

 		    (void)vpeekc_nomap();

 		check_for_codes_from_term();

 	    }

@@ -3285,8 +3293,9 @@ stoptermcap()

 	if (!gui.in_use && !gui.starting)

 # endif

 	{

-	    /* May need to discard T_CRV or T_U7 response. */

-	    if (crv_status == CRV_SENT || u7_status == U7_SENT)

+	    /* May need to discard T_CRV, T_U7 or T_RBG response. */

+	    if (crv_status == CRV_SENT || u7_status == U7_SENT

+						     || rbg_status == RBG_SENT)

 	    {

 # ifdef UNIX

 		/* Give the terminal a chance to respond. */

@@ -3398,6 +3407,36 @@ may_req_ambiguous_char_width()

 }

 # endif

+#if defined(FEAT_TERMRESPONSE) || defined(PROTO)

+/*

+ * Similar to requesting the version string: Request the terminal background

+ * color when it is the right moment.

+ */

+    void

+may_req_bg_color()

+{

+    if (rbg_status == RBG_GET

+	    && cur_tmode == TMODE_RAW

+	    && termcap_active

+	    && p_ek

+#  ifdef UNIX

+	    && isatty(1)

+	    && isatty(read_cmd_fd)

+#  endif

+	    && *T_RBG != NUL

+	    && !option_was_set((char_u *)"bg"))

+    {

+	LOG_TR("Sending BG request");

+	out_str(T_RBG);

+	rbg_status = RBG_SENT;

+	/* check for the characters now, otherwise they might be eaten by

+	 * get_keystroke() */

+	out_flush();

+	(void)vpeekc_nomap();

+    }

+}

+# endif

+

 # ifdef DEBUG_TERMRESPONSE

     static void

 log_tr(char *msg)

@@ -4204,11 +4243,12 @@ check_termcode(max_offset, buf, bufsize, buflen)

 	     *   The final byte must be 'R'. It is used for checking the

 	     *   ambiguous-width character state.

 	     */

-	    p = tp[0] == CSI ? tp + 1 : tp + 2;

+	    char_u *argp = tp[0] == ESC ? tp + 2 : tp + 1;

+

 	    if ((*T_CRV != NUL || *T_U7 != NUL)

-			&& ((tp[0] == ESC && tp[1] == '[' && len >= 3)

+			&& ((tp[0] == ESC && len >= 3 && tp[1] == '[')

 			    || (tp[0] == CSI && len >= 2))

-			&& (VIM_ISDIGIT(*p) || *p == '>' || *p == '?'))

+			&& (VIM_ISDIGIT(*argp) || *argp == '>' || *argp == '?'))

 	    {

 #ifdef FEAT_MBYTE

 		int col;

@@ -4346,18 +4386,78 @@ check_termcode(max_offset, buf, bufsize, buflen)

 		}

 	    }

-	    /* Check for '<Esc>P1+r<hex bytes><Esc>\'.  A "0" instead of the

-	     * "1" means an invalid request. */

+	    /* Check for background color response from the terminal:

+	     *

+	     *       {lead}11;rgb:{rrrr}/{gggg}/{bbbb}{tail}

+	     *

+	     * {lead} can be <Esc>] or OSC

+	     * {tail} can be '\007', <Esc>\ or STERM.

+	     *

+	     * Consume any code that starts with "{lead}11;", it's also

+	     * possible that "rgba" is following.

+	     */

+	    else if (*T_RBG != NUL

+			&& ((tp[0] == ESC && len >= 2 && tp[1] == ']')

+			    || tp[0] == OSC))

+	    {

+		j = 1 + (tp[0] == ESC);

+		if (len >= j + 3 && (argp[0] != '1'

+					 || argp[1] != '1' || argp[2] != ';'))

+		  i = 0; /* no match */

+		else

+		  for (i = j; i < len; ++i)

+		    if (tp[i] == '\007' || (tp[0] == OSC ? tp[i] == STERM

+			: (tp[i] == ESC && i + 1 < len && tp[i + 1] == '\\')))

+		    {

+			if (i - j >= 21 && STRNCMP(tp + j + 3, "rgb:", 4) == 0

+			    && tp[j + 11] == '/' && tp[j + 16] == '/'

+			    && !option_was_set((char_u *)"bg"))

+			{/* TODO: don't set option when already the right value */

+			    LOG_TR("Received RBG");

+			    rbg_status = RBG_GOT;

+			    set_option_value((char_u *)"bg", 0L, (char_u *)(

+				    (3 * '6' < tp[j+7] + tp[j+12] + tp[j+17])

+				    ? "light" : "dark"), 0);

+			    reset_option_was_set((char_u *)"bg");

+			    redraw_asap(CLEAR);

+			}

+

+			/* got finished code: consume it */

+			key_name[0] = (int)KS_EXTRA;

+			key_name[1] = (int)KE_IGNORE;

+			slen = i + 1 + (tp[i] == ESC);

+			break;

+		    }

+		if (i == len)

+		{

+		    LOG_TR("not enough characters for RB");

+		    return -1;

+		}

+	    }

+

+	    /* Check for key code response from xterm:

+	     *

+	     * {lead}{flag}+r<hex bytes><{tail}

+	     *

+	     * {lead} can be <Esc>P or DCS

+	     * {flag} can be '0' or '1'

+	     * {tail} can be Esc>\ or STERM

+	     *

+	     * Consume any code that starts with "{lead}.+r".

+	     */

 	    else if (check_for_codes

-		    && ((tp[0] == ESC && tp[1] == 'P' && len >= 2)

+		    && ((tp[0] == ESC && len >= 2 && tp[1] == 'P')

 			|| tp[0] == DCS))

 	    {

-		j = 1 + (tp[0] != DCS);

-		for (i = j; i < len; ++i)

-		    if ((tp[i] == ESC && tp[i + 1] == '\\' && i + 1 < len)

+		j = 1 + (tp[0] == ESC);

+		if (len >= j + 3 && (argp[1] != '+' || argp[2] != 'r'))

+		  i = 0; /* no match */

+		else

+		  for (i = j; i < len; ++i)

+		    if ((tp[i] == ESC && i + 1 < len && tp[i + 1] == '\\')

 			    || tp[i] == STERM)

 		    {

-			if (i - j >= 3 && tp[j + 1] == '+' && tp[j + 2] == 'r')

+			if (i - j >= 3)

 			    got_code_from_term(tp + j, i);

 			key_name[0] = (int)KS_EXTRA;

 			key_name[1] = (int)KE_IGNORE;

@@ -4367,8 +4467,10 @@ check_termcode(max_offset, buf, bufsize, buflen)

 		if (i == len)

 		{

+		    /* These codes arrive many together, each code can be

+		     * truncated at any point. */

 		    LOG_TR("not enough characters for XT");

-		    return -1;		/* not enough characters */

+		    return -1;

 		}

 	    }

 	}

diff --git a/src/term.h b/src/term.h

index 28390a2..4925599 100644

--- a/src/term.h

+++ b/src/term.h

@@ -79,6 +79,7 @@ enum SpecialKey

     KS_CWP,	/* set window position in pixels */

     KS_CWS,	/* set window size in characters */

     KS_CRV,	/* request version string */

+    KS_RBG,	/* request background color */

     KS_CSI,	/* start insert mode (bar cursor) */

     KS_CEI,	/* end insert mode (block cursor) */

 #ifdef FEAT_VERTSPLIT

@@ -160,6 +161,7 @@ extern char_u *(term_strings[]);    /* current terminal strings */

 #define T_CSI	(term_str(KS_CSI))	/* start insert mode */

 #define T_CEI	(term_str(KS_CEI))	/* end insert mode */

 #define T_CRV	(term_str(KS_CRV))	/* request version string */

+#define T_RBG	(term_str(KS_RBG))	/* request background RGB */

 #define T_OP	(term_str(KS_OP))	/* original color pair */

 #define T_U7	(term_str(KS_U7))	/* request cursor position */

diff --git a/src/option.c b/src/option.c

index e20efc1..7da18a5 100644

--- a/src/option.c

+++ b/src/option.c

@@ -2939,11 +2939,11 @@ static struct vimoption

 #ifdef FEAT_VERTSPLIT

     p_term("t_CV", T_CSV)

 #endif

-    p_term("t_ut", T_UT)

     p_term("t_da", T_DA)

     p_term("t_db", T_DB)

     p_term("t_DL", T_CDL)

     p_term("t_dl", T_DL)

+    p_term("t_EI", T_CEI)

     p_term("t_fs", T_FS)

     p_term("t_IE", T_CIE)

     p_term("t_IS", T_CIS)

@@ -2957,27 +2957,28 @@ static struct vimoption

     p_term("t_ms", T_MS)

     p_term("t_nd", T_ND)

     p_term("t_op", T_OP)

+    p_term("t_RB", T_RBG)

     p_term("t_RI", T_CRI)

     p_term("t_RV", T_CRV)

-    p_term("t_u7", T_U7)

     p_term("t_Sb", T_CSB)

-    p_term("t_Sf", T_CSF)

     p_term("t_se", T_SE)

+    p_term("t_Sf", T_CSF)

+    p_term("t_SI", T_CSI)

     p_term("t_so", T_SO)

     p_term("t_sr", T_SR)

-    p_term("t_ts", T_TS)

     p_term("t_te", T_TE)

     p_term("t_ti", T_TI)

+    p_term("t_ts", T_TS)

+    p_term("t_u7", T_U7)

     p_term("t_ue", T_UE)

     p_term("t_us", T_US)

+    p_term("t_ut", T_UT)

     p_term("t_vb", T_VB)

     p_term("t_ve", T_VE)

     p_term("t_vi", T_VI)

     p_term("t_vs", T_VS)

     p_term("t_WP", T_CWP)

     p_term("t_WS", T_CWS)

-    p_term("t_SI", T_CSI)

-    p_term("t_EI", T_CEI)

     p_term("t_xn", T_XN)

     p_term("t_xs", T_XS)

     p_term("t_ZH", T_CZH)

diff --git a/src/term.c b/src/term.c

index 660df07..b4b0c4b 100644

--- a/src/term.c

+++ b/src/term.c

@@ -1622,7 +1622,7 @@ set_termname(term)

 				{KS_TS, "ts"}, {KS_FS, "fs"},

 				{KS_CWP, "WP"}, {KS_CWS, "WS"},

 				{KS_CSI, "SI"}, {KS_CEI, "EI"},

-				{KS_U7, "u7"},

+				{KS_U7, "u7"}, {KS_RBG, "RB"},

 				{(enum SpecialKey)0, NULL}

 			    };