apply newterm patch with tmux support

Applied st-newterm-0.9.diff and st-newterm-0.9-tmux.diff with minor
manual adjustments:
- Added newterm() function declaration to st.h
- Added Ctrl-Shift-Return keybinding to spawn new terminal
- Integrated tmux-aware working directory detection

Benefits:
- Spawn new st instance with Ctrl-Shift-Return
- New terminal inherits current working directory
- Tmux-aware: detects CWD of current process in tmux session
- Improves workflow efficiency for multi-terminal usage

Note: tmux support is Linux-only and requires tmux to be direct child of st

5 files changed, 373 insertions, 0 deletions

diff --git a/config.def.h b/config.def.h
index 319facd..6a86df4 100644
--- a/config.def.h
+++ b/config.def.h
@@ -224,6 +224,7 @@ static Shortcut shortcuts[] = {
     { TERMMOD,              XK_Y,           clippaste,       {.i =  0} },
     { ShiftMask,            XK_Insert,      clippaste,       {.i =  0} },
 	{ TERMMOD,              XK_Num_Lock,    numlock,        {.i =  0} },
+	{ TERMMOD,              XK_Return,      newterm,        {.i =  0} },
 	{ ShiftMask,            XK_Page_Up,     kscrollup,      {.i = -1} },
 	{ ShiftMask,            XK_Page_Down,   kscrolldown,    {.i = -1} },
 };
diff --git a/patches_applied/st-newterm-0.9-tmux.diff b/patches_applied/st-newterm-0.9-tmux.diff
new file mode 100644
index 0000000..cd73e60
--- /dev/null
+++ b/patches_applied/st-newterm-0.9-tmux.diff
@@ -0,0 +1,140 @@
+From 6640cf9809086d8cfb2363571d3e71a1a7a9f6bd Mon Sep 17 00:00:00 2001
+From: meator <meator.dev@gmail.com>
+Date: Tue, 25 Oct 2022 20:19:28 +0200
+Subject: [PATCH] Add support for tmux in newterm
+
+This commit tries to figure out if st's child is tmux and if so, it
+launches a shell with the CWD of the current process in the tmux session
+instead of the tmux client itself.
+
+This is heavily inspired by
+https://gist.github.com/TiddoLangerak/c61e1e48df91192f9554 (but
+converted to C).
+
+Tmux has to be a direct child of st. This means that you'll have to
+usually use the 'exec' shell builtin to attach tmux sessions.
+
+This patch only works on Linux. Other systems use different procfs which
+is incompatible or don't have procfs at all (or it's optional).
+---
+ st.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
+ 1 file changed, 82 insertions(+), 1 deletion(-)
+
+diff --git a/st.c b/st.c
+index 0261283..b95bf7a 100644
+--- a/st.c
++++ b/st.c
+@@ -221,6 +221,8 @@ static char base64dec_getc(const char **);
+ 
+ static ssize_t xwrite(int, const char *, size_t);
+ 
++static int gettmuxpts(void);
++
+ /* Globals */
+ static Term term;
+ static Selection sel;
+@@ -1061,6 +1063,12 @@ tswapscreen(void)
+ void
+ newterm(const Arg* a)
+ {
++	int pts;
++	FILE *fsession, *fpid;
++	char session[5];
++	char pidstr[10];
++	char buf[48];
++	size_t size;
+ 	switch (fork()) {
+ 	case -1:
+ 		die("fork failed: %s\n", strerror(errno));
+@@ -1072,7 +1080,37 @@ newterm(const Arg* a)
+ 			_exit(1);
+ 			break;
+ 		case 0:
+-			chdir_by_pid(pid);
++			signal(SIGCHLD, SIG_DFL); /* pclose() needs to use wait() */
++			pts = gettmuxpts();
++			if (pts != -1) {
++				snprintf(buf, sizeof buf, "tmux lsc -t /dev/pts/%d -F \"#{client_session}\"", pts);
++				fsession = popen(buf, "r");
++				if (!fsession) {
++					fprintf(stderr, "Couldn't launch tmux.");
++					_exit(1);
++				}
++				size = fread(session, 1, sizeof session, fsession);
++				if (pclose(fsession) != 0 || size == 0) {
++					fprintf(stderr, "Couldn't get tmux session.");
++					_exit(1);
++				}
++				session[size - 1] = '\0'; /* size - 1 is used to also trim the \n */
++
++				snprintf(buf, sizeof buf, "tmux list-panes -st %s -F \"#{pane_pid}\"", session);
++				fpid = popen(buf, "r");
++				if (!fpid) {
++					fprintf(stderr, "Couldn't launch tmux.");
++					_exit(1);
++				}
++				size = fread(pidstr, 1, sizeof pidstr, fpid);
++				if (pclose(fpid) != 0 || size == 0) {
++					fprintf(stderr, "Couldn't get tmux session.");
++					_exit(1);
++				}
++				pidstr[size - 1] = '\0';
++			}
++
++			chdir_by_pid(pts != -1 ? atol(pidstr) : pid);
+ 			execl("/proc/self/exe", argv0, NULL);
+ 			_exit(1);
+ 			break;
+@@ -1092,6 +1130,49 @@ chdir_by_pid(pid_t pid)
+ 	return chdir(buf);
+ }
+ 
++/* returns the pty of tmux client or -1 if the child of st isn't tmux */
++static int
++gettmuxpts(void)
++{
++	char buf[32];
++	char comm[17];
++	int tty;
++	FILE *fstat;
++	FILE *fcomm;
++	size_t numread;
++
++	snprintf(buf, sizeof buf, "/proc/%ld/comm", (long)pid);
++
++	fcomm = fopen(buf, "r");
++	if (!fcomm) {
++		fprintf(stderr, "Couldn't open %s: %s\n", buf, strerror(errno));
++		_exit(1);
++	}
++
++	numread = fread(comm, 1, sizeof comm - 1, fcomm);
++	comm[numread] = '\0';
++
++	fclose(fcomm);
++
++	if (strcmp("tmux: client\n", comm) != 0)
++		return -1;
++
++	snprintf(buf, sizeof buf, "/proc/%ld/stat", (long)pid);
++	fstat = fopen(buf, "r");
++	if (!fstat) {
++		fprintf(stderr, "Couldn't open %s: %s\n", buf, strerror(errno));
++		_exit(1);
++	}
++
++	/*
++	 * We can't skip the second field with %*s because it contains a space so
++	 * we skip strlen("tmux: client") + 2 for the braces which is 14.
++	 */
++	fscanf(fstat, "%*d %*14c %*c %*d %*d %*d %d", &tty);
++	fclose(fstat);
++	return ((0xfff00000 & tty) >> 12) | (0xff & tty);
++}
++
+ void
+ tscrolldown(int orig, int n)
+ {
+-- 
+2.38.0
+
diff --git a/patches_applied/st-newterm-0.9.diff b/patches_applied/st-newterm-0.9.diff
new file mode 100644
index 0000000..5525e7a
--- /dev/null
+++ b/patches_applied/st-newterm-0.9.diff
@@ -0,0 +1,112 @@
+From e1cf625f4f225a007a5835421896089669195e02 Mon Sep 17 00:00:00 2001
+From: meator <meator.dev@gmail.com>
+Date: Wed, 26 Oct 2022 13:05:38 +0200
+Subject: [PATCH] Add shortcut to spawn new terminal in the current dir
+
+This commit is inspired by Santtu's st-newterm-20220221-0.8.5.diff. It
+removes the unused res variable, it makes use of _exit() instead of
+exit() and it replaces execlp() with execl() (PATH searching is useless
+when the path is absolute).
+---
+ config.def.h |  1 +
+ st.c         | 38 ++++++++++++++++++++++++++++++++++++++
+ st.h         |  1 +
+ 3 files changed, 40 insertions(+)
+
+diff --git a/config.def.h b/config.def.h
+index 91ab8ca..7c75246 100644
+--- a/config.def.h
++++ b/config.def.h
+@@ -201,6 +201,7 @@ static Shortcut shortcuts[] = {
+ 	{ TERMMOD,              XK_Y,           selpaste,       {.i =  0} },
+ 	{ ShiftMask,            XK_Insert,      selpaste,       {.i =  0} },
+ 	{ TERMMOD,              XK_Num_Lock,    numlock,        {.i =  0} },
++	{ TERMMOD,              XK_Return,      newterm,        {.i =  0} },
+ };
+ 
+ /*
+diff --git a/st.c b/st.c
+index 62def59..0261283 100644
+--- a/st.c
++++ b/st.c
+@@ -20,6 +20,8 @@
+ #include "st.h"
+ #include "win.h"
+ 
++extern char *argv0;
++
+ #if   defined(__linux)
+  #include <pty.h>
+ #elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__APPLE__)
+@@ -153,6 +155,7 @@ typedef struct {
+ } STREscape;
+ 
+ static void execsh(char *, char **);
++static int chdir_by_pid(pid_t pid);
+ static void stty(char **);
+ static void sigchld(int);
+ static void ttywriteraw(const char *, size_t);
+@@ -806,6 +809,7 @@ ttynew(const char *line, char *cmd, const char *out, char **args)
+ 		if (pledge("stdio rpath tty proc", NULL) == -1)
+ 			die("pledge\n");
+ #endif
++		fcntl(m, F_SETFD, FD_CLOEXEC);
+ 		close(s);
+ 		cmdfd = m;
+ 		signal(SIGCHLD, sigchld);
+@@ -1054,6 +1058,40 @@ tswapscreen(void)
+ 	tfulldirt();
+ }
+ 
++void
++newterm(const Arg* a)
++{
++	switch (fork()) {
++	case -1:
++		die("fork failed: %s\n", strerror(errno));
++		break;
++	case 0:
++		switch (fork()) {
++		case -1:
++			fprintf(stderr, "fork failed: %s\n", strerror(errno));
++			_exit(1);
++			break;
++		case 0:
++			chdir_by_pid(pid);
++			execl("/proc/self/exe", argv0, NULL);
++			_exit(1);
++			break;
++		default:
++			_exit(0);
++		}
++	default:
++		wait(NULL);
++	}
++}
++
++static int
++chdir_by_pid(pid_t pid)
++{
++	char buf[32];
++	snprintf(buf, sizeof buf, "/proc/%ld/cwd", (long)pid);
++	return chdir(buf);
++}
++
+ void
+ tscrolldown(int orig, int n)
+ {
+diff --git a/st.h b/st.h
+index fd3b0d8..f2b03b0 100644
+--- a/st.h
++++ b/st.h
+@@ -81,6 +81,7 @@ void die(const char *, ...);
+ void redraw(void);
+ void draw(void);
+ 
++void newterm(const Arg *);
+ void printscreen(const Arg *);
+ void printsel(const Arg *);
+ void sendbreak(const Arg *);
+-- 
+2.38.0
+
diff --git a/st.c b/st.c
index 57feebb..96a8e08 100644
--- a/st.c
+++ b/st.c
@@ -20,6 +20,8 @@
 #include "st.h"
 #include "win.h"
 
+extern char *argv0;
+
 #if   defined(__linux)
  #include <pty.h>
 #elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__APPLE__)
@@ -181,6 +183,7 @@ typedef struct {
 } STREscape;
 
 static void execsh(char *, char **);
+static int chdir_by_pid(pid_t pid);
 static void stty(char **);
 static void sigchld(int);
 static void ttywriteraw(const char *, size_t);
@@ -260,6 +263,8 @@ static char base64dec_getc(const char **);
 
 static ssize_t xwrite(int, const char *, size_t);
 
+static int gettmuxpts(void);
+
 /* Globals */
 static Term term;
 static Selection sel;
@@ -881,6 +886,7 @@ ttynew(const char *line, char *cmd, const char *out, char **args)
 		if (pledge("stdio rpath tty proc", NULL) == -1)
 			die("pledge\n");
 #endif
+		fcntl(m, F_SETFD, FD_CLOEXEC);
 		close(s);
 		cmdfd = m;
 		signal(SIGCHLD, sigchld);
@@ -1127,6 +1133,119 @@ treset(void)
 }
 
 void
+newterm(const Arg* a)
+{
+	int pts;
+	FILE *fsession, *fpid;
+	char session[5];
+	char pidstr[10];
+	char buf[48];
+	size_t size;
+	switch (fork()) {
+	case -1:
+		die("fork failed: %s\n", strerror(errno));
+		break;
+	case 0:
+		switch (fork()) {
+		case -1:
+			fprintf(stderr, "fork failed: %s\n", strerror(errno));
+			_exit(1);
+			break;
+		case 0:
+			signal(SIGCHLD, SIG_DFL); /* pclose() needs to use wait() */
+			pts = gettmuxpts();
+			if (pts != -1) {
+				snprintf(buf, sizeof buf, "tmux lsc -t /dev/pts/%d -F \"#{client_session}\"", pts);
+				fsession = popen(buf, "r");
+				if (!fsession) {
+					fprintf(stderr, "Couldn't launch tmux.");
+					_exit(1);
+				}
+				size = fread(session, 1, sizeof session, fsession);
+				if (pclose(fsession) != 0 || size == 0) {
+					fprintf(stderr, "Couldn't get tmux session.");
+					_exit(1);
+				}
+				session[size - 1] = '\0'; /* size - 1 is used to also trim the \n */
+
+				snprintf(buf, sizeof buf, "tmux list-panes -st %s -F \"#{pane_pid}\"", session);
+				fpid = popen(buf, "r");
+				if (!fpid) {
+					fprintf(stderr, "Couldn't launch tmux.");
+					_exit(1);
+				}
+				size = fread(pidstr, 1, sizeof pidstr, fpid);
+				if (pclose(fpid) != 0 || size == 0) {
+					fprintf(stderr, "Couldn't get tmux session.");
+					_exit(1);
+				}
+				pidstr[size - 1] = '\0';
+			}
+
+			chdir_by_pid(pts != -1 ? atol(pidstr) : pid);
+			execl("/proc/self/exe", argv0, NULL);
+			_exit(1);
+			break;
+		default:
+			_exit(0);
+		}
+	default:
+		wait(NULL);
+	}
+}
+
+static int
+chdir_by_pid(pid_t pid)
+{
+	char buf[32];
+	snprintf(buf, sizeof buf, "/proc/%ld/cwd", (long)pid);
+	return chdir(buf);
+}
+
+/* returns the pty of tmux client or -1 if the child of st isn't tmux */
+static int
+gettmuxpts(void)
+{
+	char buf[32];
+	char comm[17];
+	int tty;
+	FILE *fstat;
+	FILE *fcomm;
+	size_t numread;
+
+	snprintf(buf, sizeof buf, "/proc/%ld/comm", (long)pid);
+
+	fcomm = fopen(buf, "r");
+	if (!fcomm) {
+		fprintf(stderr, "Couldn't open %s: %s\n", buf, strerror(errno));
+		_exit(1);
+	}
+
+	numread = fread(comm, 1, sizeof comm - 1, fcomm);
+	comm[numread] = '\0';
+
+	fclose(fcomm);
+
+	if (strcmp("tmux: client\n", comm) != 0)
+		return -1;
+
+	snprintf(buf, sizeof buf, "/proc/%ld/stat", (long)pid);
+	fstat = fopen(buf, "r");
+	if (!fstat) {
+		fprintf(stderr, "Couldn't open %s: %s\n", buf, strerror(errno));
+		_exit(1);
+	}
+
+	/*
+	 * We can't skip the second field with %*s because it contains a space so
+	 * we skip strlen("tmux: client") + 2 for the braces which is 14.
+	 */
+	fscanf(fstat, "%*d %*14c %*c %*d %*d %*d %d", &tty);
+	fclose(fstat);
+	return ((0xfff00000 & tty) >> 12) | (0xff & tty);
+}
+
+void
 tnew(int col, int row)
 {
 	int i, j;
diff --git a/st.h b/st.h
index e320538..9cf12fd 100644
--- a/st.h
+++ b/st.h
@@ -87,6 +87,7 @@ void draw(void);
 
 void kscrolldown(const Arg *);
 void kscrollup(const Arg *);
+void newterm(const Arg *);
 void printscreen(const Arg *);
 void printsel(const Arg *);
 void sendbreak(const Arg *);