patch 8.2.2345: no focus events in a terminal

Problem:    No focus events in a terminal.
Solution:   Add the t_fd and t_fe termcap entries and implement detecting
            focus events. (Hayaki Saito, Magnus Groß, closes #7673,
            closes #609, closes #5526)

runtime/doc/term.txt

@@ -373,6 +373,10 @@ Added by Vim (there are no standard codes for these):
 	t_Ri	restore icon text from stack			*t_Ri* *'t_Ri'*
 	t_TE	end of "raw" mode				*t_TE* *'t_TE'*
 	t_TI	put terminal into "raw" mode 			*t_TI* *'t_TI'*
+	t_fd	disable focus-event tracking 			*t_TI* *'t_TI'*
+		|xterm-focus-event|
+	t_fe	enable focus-event tracking 			*t_TI* *'t_TI'*
+		|xterm-focus-event|
 
 Some codes have a start, middle and end part.  The start and end are defined
 by the termcap option, the middle part is text.
@@ -546,6 +550,16 @@ And run "xrdb -merge .Xresources" to make it effective.  You can check the
 value with the context menu (right mouse button while CTRL key is pressed),
 there should be a tick at allow-window-ops.
 
+							*xterm-focus-event*
+Some terminals including xterm support the focus event tracking feature.
+If this feature is enabled by the 't_fe' sequence, special key sequences are
+sent from the terminal to Vim every time the terminal gains or loses focus.
+Vim fires focus events (|FocusGained|/|FocusLost|) by handling them accordingly.
+Focus event tracking is disabled by a 't_fd' sequence when exiting "raw" mode.
+If you would like to disable this feature, add the following to your .vimrc:
+	`set t_fd=`
+	`set t_fe=`
+
 							*termcap-colors*
 Note about colors: The 't_Co' option tells Vim the number of colors available.
 When it is non-zero, the 't_AB' and 't_AF' options are used to set the color.

src/optiondefs.h

@@ -2957,6 +2957,8 @@ static struct vimoption options[] =
     p_term("t_EC", T_CEC)
     p_term("t_EI", T_CEI)
     p_term("t_fs", T_FS)
+    p_term("t_fd", T_FD)
+    p_term("t_fe", T_FE)
     p_term("t_GP", T_CGP)
     p_term("t_IE", T_CIE)
     p_term("t_IS", T_CIS)

src/term.c

@@ -196,6 +196,11 @@ static char_u *vim_tgetstr(char *s, char_u **pp);
 
 static int  detected_8bit = FALSE;	// detected 8-bit terminal
 
+#if (defined(UNIX) || defined(VMS))
+static int focus_mode = FALSE; // xterm's "focus reporting" availability
+static int focus_state = FALSE; // TRUE if the terminal window gains focus
+#endif
+
 #ifdef FEAT_TERMRESPONSE
 // When the cursor shape was detected these values are used:
 // 1: block, 2: underline, 3: vertical bar
@@ -908,6 +913,10 @@ static struct builtin_term builtin_termcaps[] =
     {(int)KS_CRT,	IF_EB("\033[23;2t", ESC_STR "[23;2t")},
     {(int)KS_SSI,	IF_EB("\033[22;1t", ESC_STR "[22;1t")},
     {(int)KS_SRI,	IF_EB("\033[23;1t", ESC_STR "[23;1t")},
+#  if (defined(UNIX) || defined(VMS))
+    {(int)KS_FD,	IF_EB("\033[?1004l", ESC_STR "[?1004l")},
+    {(int)KS_FE,	IF_EB("\033[?1004h", ESC_STR "[?1004h")},
+#  endif
 
     {K_UP,		IF_EB("\033O*A", ESC_STR "O*A")},
     {K_DOWN,		IF_EB("\033O*B", ESC_STR "O*B")},
@@ -2044,6 +2053,27 @@ set_termname(char_u *term)
     set_mouse_termcode(KS_MOUSE, (char_u *)"\233M");
 #endif
 
+#if (defined(UNIX) || defined(VMS))
+    // focus reporting is supported by xterm compatible terminals and tmux.
+    if (use_xterm_like_mouse(term))
+    {
+	char_u name[3];
+	name[0] = (int)KS_EXTRA;
+	name[2] = NUL;
+
+	// handle focus in event
+	name[1] = (int)KE_FOCUSGAINED;
+	add_termcode(name, (char_u *)"\033[I", FALSE);
+
+	// handle focus out event
+	name[1] = (int)KE_FOCUSLOST;
+	add_termcode(name, (char_u *)"\033[O", FALSE);
+
+	focus_mode = TRUE;
+	focus_state = TRUE;
+    }
+#endif
+
 #ifdef USE_TERM_CONSOLE
     // DEFAULT_TERM indicates that it is the machine console.
     if (STRCMP(term, DEFAULT_TERM) != 0)
@@ -2519,7 +2549,10 @@ out_flush(void)
 	if (ch_log_output)
 	{
 	    out_buf[len] = NUL;
-	    ch_log(NULL, "raw terminal output: \"%s\"", out_buf);
+	    ch_log(NULL, "raw %s output: \"%s\"",
+			(gui.in_use && !gui.dying && !gui.starting)
+							  ? "GUI" : "terminal",
+			out_buf);
 	    ch_log_output = FALSE;
 	}
 #endif
@@ -3582,6 +3615,13 @@ starttermcap(void)
 	out_str(T_CTI);			// start "raw" mode
 	out_str(T_KS);			// start "keypad transmit" mode
 	out_str(T_BE);			// enable bracketed paste mode
+
+#if (defined(UNIX) || defined(VMS))
+	// enable xterm's focus reporting mode
+	if (focus_mode && *T_FE != NUL)
+	    out_str(T_FE);
+#endif
+
 	out_flush();
 	termcap_active = TRUE;
 	screen_start();			// don't know where cursor is now
@@ -3633,6 +3673,13 @@ stoptermcap(void)
 #ifdef FEAT_JOB_CHANNEL
 	ch_log_output = TRUE;
 #endif
+
+#if (defined(UNIX) || defined(VMS))
+	// disable xterm's focus reporting mode
+	if (focus_mode && *T_FD != NUL)
+	    out_str(T_FD);
+#endif
+
 	out_str(T_BD);			// disable bracketed paste mode
 	out_str(T_KE);			// stop "keypad transmit" mode
 	out_flush();
@@ -5647,6 +5694,45 @@ check_termcode(
 # endif // !USE_ON_FLY_SCROLL
 #endif // FEAT_GUI
 
+#if (defined(UNIX) || defined(VMS))
+	/*
+	 * Handle FocusIn/FocusOut event sequences reported by XTerm.
+	 * (CSI I/CSI O)
+	 */
+	if (focus_mode
+# ifdef FEAT_GUI
+		&& !gui.in_use
+# endif
+		&& key_name[0] == KS_EXTRA
+	    )
+	{
+	    int did_aucmd = FALSE;
+
+	    if (key_name[1] == KE_FOCUSGAINED && !focus_state)
+	    {
+		did_aucmd = apply_autocmds(EVENT_FOCUSGAINED,
+						    NULL, NULL, FALSE, curbuf);
+		did_cursorhold = TRUE;
+		focus_state = TRUE;
+		key_name[1] = (int)KE_IGNORE;
+	    }
+	    else if (key_name[1] == KE_FOCUSLOST && focus_state)
+	    {
+		did_aucmd = apply_autocmds(EVENT_FOCUSLOST,
+						    NULL, NULL, FALSE, curbuf);
+		did_cursorhold = TRUE;
+		focus_state = FALSE;
+		key_name[1] = (int)KE_IGNORE;
+	    }
+	    if (did_aucmd && (State & (NORMAL | INSERT | TERMINAL)))
+	    {
+		// in case a message was displayed: reposition the cursor
+		setcursor();
+		out_flush();
+	    }
+	}
+#endif
+
 	/*
 	 * Change <xHome> to <Home>, <xUp> to <Up>, etc.
 	 */

src/term.h

@@ -109,10 +109,12 @@ enum SpecialKey
     KS_CST,	// save window title
     KS_CRT,	// restore window title
     KS_SSI,	// save icon text
-    KS_SRI	// restore icon text
+    KS_SRI,	// restore icon text
+    KS_FD,	// disable focus event tracking
+    KS_FE	// enable focus event tracking
 };
 
-#define KS_LAST	    KS_SRI
+#define KS_LAST	    KS_FE
 
 /*
  * the terminal capabilities are stored in this array
@@ -212,6 +214,8 @@ extern char_u *(term_strings[]);    // current terminal strings
 #define T_CRT	(TERM_STR(KS_CRT))	// restore window title
 #define T_SSI	(TERM_STR(KS_SSI))	// save icon text
 #define T_SRI	(TERM_STR(KS_SRI))	// restore icon text
+#define T_FD	(TERM_STR(KS_FD))	// disable focus event tracking
+#define T_FE	(TERM_STR(KS_FE))	// enable focus event tracking
 
 typedef enum {
     TMODE_COOK,	    // terminal mode for external cmds and Ex mode

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2345,
 /**/
     2344,
 /**/