Add checking the terminal is xterm compatible

src/main.c

@@ -814,9 +814,9 @@ vim_main2(void)
     /* Must come before the may_req_ calls. */
     starting = 0;
 
-#if defined(FEAT_TERMRESPONSE) && defined(FEAT_MBYTE)
+#if defined(FEAT_TERMRESPONSE)
     /* Must be done before redrawing, puts a few characters on the screen. */
-    may_req_ambiguous_char_width();
+    check_terminal_behavior();
 #endif
 
     RedrawingDisabled = 0;

src/proto/term.pro

@@ -43,7 +43,7 @@ void settmode(int tmode);
 void starttermcap(void);
 void stoptermcap(void);
 void may_req_termresponse(void);
-void may_req_ambiguous_char_width(void);
+void check_terminal_behavior(void);
 void may_req_bg_color(void);
 int swapping_screen(void);
 void setmouse(void);

src/term.c

@@ -146,6 +146,9 @@ static int rcs_status = STATUS_GET;
 
 /* Request windos position report: */
 static int winpos_status = STATUS_GET;
+
+/* xterm compatibility check: */
+static int xcc_status = STATUS_GET;
 # endif
 
 /*
@@ -3397,6 +3400,7 @@ settmode(int tmode)
 					 || rbg_status == STATUS_SENT
 					 || rbm_status == STATUS_SENT
 					 || rcs_status == STATUS_SENT
+					 || xcc_status == STATUS_SENT
 					 || winpos_status == STATUS_SENT))
 		    (void)vpeekc_nomap();
 		check_for_codes_from_term();
@@ -3472,6 +3476,7 @@ stoptermcap(void)
 		    || rbg_status == STATUS_SENT
 		    || rbm_status == STATUS_SENT
 		    || rcs_status == STATUS_SENT
+		    || xcc_status == STATUS_SENT
 		    || winpos_status == STATUS_SENT)
 	    {
 # ifdef UNIX
@@ -3533,53 +3538,91 @@ may_req_termresponse(void)
     }
 }
 
-# if defined(FEAT_MBYTE) || defined(PROTO)
 /*
+ * Check the following behaviors of terminal.
+ *
+ * 1. Ambiguous character width
  * Check how the terminal treats ambiguous character width (UAX #11).
  * First, we move the cursor to (1, 0) and print a test ambiguous character
  * \u25bd (WHITE DOWN-POINTING TRIANGLE) and query current cursor position.
  * If the terminal treats \u25bd as single width, the position is (1, 1),
  * or if it is treated as double width, that will be (1, 2).
+ *
+ * 2. compatible with xterm.
+ * Check the terminal is xterm compatible.
+ * First, we move the cursor to (2, 0) and print a test sequence and query
+ * current cursor position.
+ * If the terminal properly handles unknown DCS string and CSI sequence with
+ * intermediate byte, test sequence is ignored and the cursor does not move,
+ * or the terminal handles test sequence incorrectly, a garbage string is
+ * displayed and the cursor moves.
+ *
  * This function has the side effect that changes cursor position, so
  * it must be called immediately after entering termcap mode.
  */
     void
-may_req_ambiguous_char_width(void)
+check_terminal_behavior(void)
 {
-    if (u7_status == STATUS_GET
+    if ((u7_status == STATUS_GET || xcc_status == STATUS_GET)
 	    && can_get_termresponse()
 	    && starting == 0
-	    && *T_U7 != NUL
-	    && !option_was_set((char_u *)"ambiwidth"))
+	    && *T_U7 != NUL)
     {
-	 char_u	buf[16];
-
-	 LOG_TR(("Sending U7 request"));
-	 /* Do this in the second row.  In the first row the returned sequence
-	  * may be CSI 1;2R, which is the same as <S-F3>. */
-	 term_windgoto(1, 0);
-	 buf[mb_char2bytes(0x25bd, buf)] = 0;
-	 out_str(buf);
-	 out_str(T_U7);
-	 u7_status = STATUS_SENT;
-	 out_flush();
-
-	 /* This overwrites a few characters on the screen, a redraw is needed
-	  * after this. Clear them out for now. */
-	 term_windgoto(1, 0);
-	 out_str((char_u *)"  ");
-	 term_windgoto(0, 0);
-
-	 /* Need to reset the known cursor position. */
-	 screen_start();
-
-	 /* check for the characters now, otherwise they might be eaten by
-	  * get_keystroke() */
-	 out_flush();
-	 (void)vpeekc_nomap();
+# if defined(FEAT_MBYTE) || defined(PROTO)
+	/* Ambiguous character width check */
+	if (u7_status == STATUS_GET
+		&& !option_was_set((char_u *)"ambiwidth"))
+	{
+	    char_u	buf[16];
+
+	    LOG_TR("Sending U7 request");
+	    /* Do this in the second row.  In the first row the returned sequence
+	     * may be CSI 1;2R, which is the same as <S-F3>. */
+	    term_windgoto(1, 0);
+	    buf[mb_char2bytes(0x25bd, buf)] = 0;
+	    out_str(buf);
+	    out_str(T_U7);
+	    u7_status = STATUS_SENT;
+	    out_flush();
+
+	    /* This overwrites a few characters on the screen, a redraw is needed
+	     * after this. Clear them out for now. */
+	    term_windgoto(1, 0);
+	    out_str((char_u *)"  ");
+	}
+# endif
+
+	/* xterm compatibility test */
+	if (xcc_status == STATUS_GET)
+	{
+	    LOG_TR(("Sending xterm compatibility test sequence."));
+	    /* Do this in the third row.  Second row is used by ambiguous
+	     * chararacter width check. */
+	    term_windgoto(2, 0);
+	    /* send the test DCS string. */
+	    out_str((char_u *)"\033Pzz\033\\");
+	    /* send the test CSI sequence with intermediate byte. */
+	    out_str((char_u *)"\033[0%m");
+	    out_str(T_U7);
+	    xcc_status = STATUS_SENT;
+	    out_flush();
+
+	    /* If the terminal handles test sequence incorrectly, garbage
+	     * string is displayed. Clear them out for now. */
+	    term_windgoto(2, 0);
+	    out_str((char_u *)"           ");
+	}
+	term_windgoto(0, 0);
+
+	/* Need to reset the known cursor position. */
+	screen_start();
+
+	/* check for the characters now, otherwise they might be eaten by
+	 * get_keystroke() */
+	out_flush();
+	(void)vpeekc_nomap();
     }
 }
-# endif
 
 /*
  * Similar to requesting the version string: Request the terminal background
@@ -4571,6 +4614,16 @@ check_termcode(
 # endif
 			}
 		    }
+		    /* Third row is xterm compatibility test */
+		    else if (row_char == '3')
+		    {
+			/* Cursor is not on a first column. Then terminal
+			 * is not xterm compatible. */
+			if (col != 1)
+			    is_not_xterm = TRUE;
+
+			xcc_status = STATUS_GOT;
+		    }
 		    key_name[0] = (int)KS_EXTRA;
 		    key_name[1] = (int)KE_IGNORE;
 		    slen = i + 1;
@@ -4671,23 +4724,13 @@ check_termcode(
 			 * "xterm-256colors"  but are not fully xterm
 			 * compatible. */
 
-			/* Gnome terminal sends 1;3801;0, 1;4402;0 or 1;2501;0.
-			 * xfce4-terminal sends 1;2802;0.
-			 * screen sends 83;40500;0
-			 * Assuming any version number over 2500 is not an
-			 * xterm (without the limit for rxvt and screen). */
-			if (col >= 2500)
-			    is_not_xterm = TRUE;
-
-			/* PuTTY sends 0;136;0
-			 * vandyke SecureCRT sends 1;136;0 */
-			if (version == 136
-				&& STRNCMP(tp + extra - 1, ";136;0c", 7) == 0)
-			    is_not_xterm = TRUE;
-
-			/* Konsole sends 0;115;0 */
-			if (version == 115
-				&& STRNCMP(tp + extra - 2, "0;115;0c", 8) == 0)
+			/* GNU screen sends 83;30600;0. 30600 is a version
+			 * number of GNU screen. DA2 support is added on 3.6.
+			 * DCS string has a special meaning to GNU screen,
+			 * but xterm compatibility checking does not detect
+			 * GNU screen. */
+			if (col >= 30600
+				&& STRNCMP(tp + extra - 3, "83;", 3) == 0)
 			    is_not_xterm = TRUE;
 
 			/* Only request the cursor style if t_SH and t_RS are