Add IPC patch, add as an option. Will likely simplify this soon but for

now, edit config,mk and enable it in toggle.h. It is enabled by default
but not compatible with BSD so comment the lines if you use that.

Makefile

@@ -1,4 +1,4 @@
-# speespeedwm // minimal X window manager designed for productivity and aesthetics.
+# speedwm // minimal X window manager designed for productivity and aesthetics.
 # See LICENSE file for copyright and license details.
 
 include config.mk
@@ -6,7 +6,11 @@ include config.mk
 SRC = drw.c speedwm.c util.c
 OBJ = ${SRC:.c=.o}
 
+ifdef USEIPC
+all: options speedwm speedwm-msg
+else
 all: options speedwm
+endif
 
 options:
 	@echo speedwm build options:
@@ -20,7 +24,12 @@ options:
 ${OBJ}: config.mk
 
 speedwm: ${OBJ}
-	${CC} -o $@ ${OBJ} ${LDFLAGS} ; rm -f drw.o speedwm.o util.o
+	${CC} -o $@ ${OBJ} ${LDFLAGS} ; rm -f *.o
+
+ifdef USEIPC
+speedwm-msg: speedwm-msg.o
+	${CC} -o $@ $< ${LDFLAGS} ; rm -f speedwm-msg.o
+endif
 
 clean:
 	rm -f speedwm ${OBJ} speedwm-spde-${VERSION}.tar.gz && echo "Cleaned!"
@@ -31,12 +40,14 @@ dist: clean
 	tar -cf speedwm-spde-${VERSION}.tar speedwm-spde-${VERSION}
 	gzip speedwm-spde-${VERSION}.tar
 	rm -rf speedwm-spde-${VERSION} speedwm
+	rm -rf speedwm-spde-${VERSION} speedwm-msg
 
 install: all
 	touch drw.o speedwm.o util.o
 	mkdir -p ${DESTDIR}${PREFIX}/bin
-	cp -f speedwm ${DESTDIR}${PREFIX}/bin
+	cp -f speedwm speedwm-msg ${DESTDIR}${PREFIX}/bin
 	chmod 755 ${DESTDIR}${PREFIX}/bin/speedwm
+	[ -f speedwm-msg ] && chmod 755 ${DESTDIR}${PREFIX}/bin/speedwm-msg || :
 	cp -f docs/bindlist ${DESTDIR}${PREFIX}/share/speedwm-bindlist
 	cp -f docs/deplist ${DESTDIR}${PREFIX}/share/speedwm-deplist
 	cp -f docs/about ${DESTDIR}${PREFIX}/share/speedwm-about
@@ -68,7 +79,7 @@ install: all
 	./scripts/speedwm-compatcheck
 	./scripts/speedwm-dm
 	[ -f speedwm.png ] && cp -f speedwm.png ${DESTDIR}${PREFIX}/share/pixmaps/speedwm.png || :
-	rm -f drw.o speedwm.o util.o speedwm ; echo "Installed speedwm to ${DESTDIR}${PREFIX}/bin"
+	rm -f drw.o speedwm.o util.o speedwm speedwm-msg ; echo "Installed speedwm to ${DESTDIR}${PREFIX}/bin"
    
 uninstall:
 	rm -f ${DESTDIR}${PREFIX}/bin/speedwm\

config.mk

@@ -6,6 +6,13 @@
 # If you use OpenBSD, uncomment this line. (remove the # at the start of the line below)
 #FREETYPEINC = ${X11INC}/freetype2
 
+# IPC
+# Whether or not to compile in IPC support.
+# If you use OpenBSD or FreeBSD, this is not supported. In that case set this to false and set USEIPC in options.h to 0.
+USEIPC = false
+YAJLLIBS = -lyajl # Comment if you use IPC
+YAJLINC = /usr/include/yajl # Comment if you use IPC
+
 # Solaris support
 # If you use Solaris, uncomment this line. (remove the # at the start of the line below)
 #CFLAGS = -fast ${INCS} -DVERSION=\"${VERSION}\"
@@ -48,8 +55,8 @@ FREETYPELIBS = -lfontconfig -lXft
 FREETYPEINC = /usr/include/freetype2
 
 # includes and libs
-INCS = -I${X11INC} -I${FREETYPEINC}
+INCS = -I${X11INC} -I${FREETYPEINC} -I${YAJLINC}
-LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS} -lXrender -lImlib2 -lX11-xcb -lxcb -lxcb-res -lXext
+LIBS = -L${X11LIB} -lX11 ${XINERAMALIBS} ${FREETYPELIBS} -lXrender -lImlib2 -lX11-xcb -lxcb -lxcb-res -lXext ${YAJLLIBS}
 
 # flags
 CPPFLAGS = -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_C_SOURCE=200809L -DVERSION=\"${VERSION}\" ${XINERAMAFLAGS}

ipccmd.h

@@ -0,0 +1,16 @@
+static const char *ipcsockpath = "/tmp/speedwm.sock";
+static IPCCommand ipccommands[] = {
+  IPCCOMMAND(  view,                1,      {ARG_TYPE_UINT}   ),
+  IPCCOMMAND(  tagmon,              1,      {ARG_TYPE_UINT}   ),
+  IPCCOMMAND(  focusmon,            1,      {ARG_TYPE_SINT}   ),
+  IPCCOMMAND(  focusstackvis,       1,      {ARG_TYPE_SINT}   ),
+  IPCCOMMAND(  zoom,                1,      {ARG_TYPE_NONE}   ),
+  IPCCOMMAND(  incnmaster,          1,      {ARG_TYPE_SINT}   ),
+  IPCCOMMAND(  killclient,          1,      {ARG_TYPE_SINT}   ),
+  IPCCOMMAND(  togglefloating,      1,      {ARG_TYPE_NONE}   ),
+  IPCCOMMAND(  setmfact,            1,      {ARG_TYPE_FLOAT}  ),
+  IPCCOMMAND(  setlayoutsafe,       1,      {ARG_TYPE_PTR}    ),
+  IPCCOMMAND(  quit,                1,      {ARG_TYPE_NONE}   )
+};
+
+

speedwm-msg.c

@@ -0,0 +1,548 @@
+#include <ctype.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+#include <yajl/yajl_gen.h>
+
+#define IPC_MAGIC "DWM-IPC"
+// clang-format off
+#define IPC_MAGIC_ARR { 'D', 'W', 'M', '-', 'I', 'P', 'C' }
+// clang-format on
+#define IPC_MAGIC_LEN 7  // Not including null char
+
+#define IPC_EVENT_TAG_CHANGE "tag_change_event"
+#define IPC_EVENT_CLIENT_FOCUS_CHANGE "client_focus_change_event"
+#define IPC_EVENT_LAYOUT_CHANGE "layout_change_event"
+#define IPC_EVENT_MONITOR_FOCUS_CHANGE "monitor_focus_change_event"
+#define IPC_EVENT_FOCUSED_TITLE_CHANGE "focused_title_change_event"
+#define IPC_EVENT_FOCUSED_STATE_CHANGE "focused_state_change_event"
+
+#define YSTR(str) yajl_gen_string(gen, (unsigned char *)str, strlen(str))
+#define YINT(num) yajl_gen_integer(gen, num)
+#define YDOUBLE(num) yajl_gen_double(gen, num)
+#define YBOOL(v) yajl_gen_bool(gen, v)
+#define YNULL() yajl_gen_null(gen)
+#define YARR(body)                                                             \
+  {                                                                            \
+    yajl_gen_array_open(gen);                                                  \
+    body;                                                                      \
+    yajl_gen_array_close(gen);                                                 \
+  }
+#define YMAP(body)                                                             \
+  {                                                                            \
+    yajl_gen_map_open(gen);                                                    \
+    body;                                                                      \
+    yajl_gen_map_close(gen);                                                   \
+  }
+
+typedef unsigned long Window;
+
+const char *DEFAULT_SOCKET_PATH = "/tmp/speedwm.sock";
+static int sock_fd = -1;
+static unsigned int ignore_reply = 0;
+
+typedef enum IPCMessageType {
+  IPC_TYPE_RUN_COMMAND = 0,
+  IPC_TYPE_GET_MONITORS = 1,
+  IPC_TYPE_GET_TAGS = 2,
+  IPC_TYPE_GET_LAYOUTS = 3,
+  IPC_TYPE_GET_DWM_CLIENT = 4,
+  IPC_TYPE_SUBSCRIBE = 5,
+  IPC_TYPE_EVENT = 6
+} IPCMessageType;
+
+// Every IPC message must begin with this
+typedef struct speedwm_ipc_header {
+  uint8_t magic[IPC_MAGIC_LEN];
+  uint32_t size;
+  uint8_t type;
+} __attribute((packed)) speedwm_ipc_header_t;
+
+static int
+recv_message(uint8_t *msg_type, uint32_t *reply_size, uint8_t **reply)
+{
+  uint32_t read_bytes = 0;
+  const int32_t to_read = sizeof(speedwm_ipc_header_t);
+  char header[to_read];
+  char *walk = header;
+
+  // Try to read header
+  while (read_bytes < to_read) {
+    ssize_t n = read(sock_fd, header + read_bytes, to_read - read_bytes);
+
+    if (n == 0) {
+      if (read_bytes == 0) {
+        fprintf(stderr, "Unexpectedly reached EOF while reading header.");
+        fprintf(stderr,
+                "Read %" PRIu32 " bytes, expected %" PRIu32 " total bytes.\n",
+                read_bytes, to_read);
+        return -2;
+      } else {
+        fprintf(stderr, "Unexpectedly reached EOF while reading header.");
+        fprintf(stderr,
+                "Read %" PRIu32 " bytes, expected %" PRIu32 " total bytes.\n",
+                read_bytes, to_read);
+        return -3;
+      }
+    } else if (n == -1) {
+      return -1;
+    }
+
+    read_bytes += n;
+  }
+
+  // Check if magic string in header matches
+  if (memcmp(walk, IPC_MAGIC, IPC_MAGIC_LEN) != 0) {
+    fprintf(stderr, "Invalid magic string. Got '%.*s', expected '%s'\n",
+            IPC_MAGIC_LEN, walk, IPC_MAGIC);
+    return -3;
+  }
+
+  walk += IPC_MAGIC_LEN;
+
+  // Extract reply size
+  memcpy(reply_size, walk, sizeof(uint32_t));
+  walk += sizeof(uint32_t);
+
+  // Extract message type
+  memcpy(msg_type, walk, sizeof(uint8_t));
+  walk += sizeof(uint8_t);
+
+  (*reply) = malloc(*reply_size);
+
+  // Extract payload
+  read_bytes = 0;
+  while (read_bytes < *reply_size) {
+    ssize_t n = read(sock_fd, *reply + read_bytes, *reply_size - read_bytes);
+
+    if (n == 0) {
+      fprintf(stderr, "Unexpectedly reached EOF while reading payload.");
+      fprintf(stderr, "Read %" PRIu32 " bytes, expected %" PRIu32 " bytes.\n",
+              read_bytes, *reply_size);
+      free(*reply);
+      return -2;
+    } else if (n == -1) {
+      if (errno == EINTR || errno == EAGAIN) continue;
+      free(*reply);
+      return -1;
+    }
+
+    read_bytes += n;
+  }
+
+  return 0;
+}
+
+static int
+read_socket(IPCMessageType *msg_type, uint32_t *msg_size, char **msg)
+{
+  int ret = -1;
+
+  while (ret != 0) {
+    ret = recv_message((uint8_t *)msg_type, msg_size, (uint8_t **)msg);
+
+    if (ret < 0) {
+      // Try again (non-fatal error)
+      if (ret == -1 && (errno == EINTR || errno == EAGAIN)) continue;
+
+      fprintf(stderr, "Error receiving response from socket. ");
+      fprintf(stderr, "The connection might have been lost.\n");
+      exit(2);
+    }
+  }
+
+  return 0;
+}
+
+static ssize_t
+write_socket(const void *buf, size_t count)
+{
+  size_t written = 0;
+
+  while (written < count) {
+    const ssize_t n =
+        write(sock_fd, ((uint8_t *)buf) + written, count - written);
+
+    if (n == -1) {
+      if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)
+        continue;
+      else
+        return n;
+    }
+    written += n;
+  }
+  return written;
+}
+
+static void
+connect_to_socket()
+{
+  struct sockaddr_un addr;
+
+  int sock = socket(AF_UNIX, SOCK_STREAM, 0);
+
+  // Initialize struct to 0
+  memset(&addr, 0, sizeof(struct sockaddr_un));
+
+  addr.sun_family = AF_UNIX;
+  strcpy(addr.sun_path, DEFAULT_SOCKET_PATH);
+
+  connect(sock, (const struct sockaddr *)&addr, sizeof(struct sockaddr_un));
+
+  sock_fd = sock;
+}
+
+static int
+send_message(IPCMessageType msg_type, uint32_t msg_size, uint8_t *msg)
+{
+  speedwm_ipc_header_t header = {
+      .magic = IPC_MAGIC_ARR, .size = msg_size, .type = msg_type};
+
+  size_t header_size = sizeof(speedwm_ipc_header_t);
+  size_t total_size = header_size + msg_size;
+
+  uint8_t buffer[total_size];
+
+  // Copy header to buffer
+  memcpy(buffer, &header, header_size);
+  // Copy message to buffer
+  memcpy(buffer + header_size, msg, header.size);
+
+  write_socket(buffer, total_size);
+
+  return 0;
+}
+
+static int
+is_float(const char *s)
+{
+  size_t len = strlen(s);
+  int is_dot_used = 0;
+  int is_minus_used = 0;
+
+  // Floats can only have one decimal point in between or digits
+  // Optionally, floats can also be below zero (negative)
+  for (int i = 0; i < len; i++) {
+    if (isdigit(s[i]))
+      continue;
+    else if (!is_dot_used && s[i] == '.' && i != 0 && i != len - 1) {
+      is_dot_used = 1;
+      continue;
+    } else if (!is_minus_used && s[i] == '-' && i == 0) {
+      is_minus_used = 1;
+      continue;
+    } else
+      return 0;
+  }
+
+  return 1;
+}
+
+static int
+is_unsigned_int(const char *s)
+{
+  size_t len = strlen(s);
+
+  // Unsigned int can only have digits
+  for (int i = 0; i < len; i++) {
+    if (isdigit(s[i]))
+      continue;
+    else
+      return 0;
+  }
+
+  return 1;
+}
+
+static int
+is_signed_int(const char *s)
+{
+  size_t len = strlen(s);
+
+  // Signed int can only have digits and a negative sign at the start
+  for (int i = 0; i < len; i++) {
+    if (isdigit(s[i]))
+      continue;
+    else if (i == 0 && s[i] == '-') {
+      continue;
+    } else
+      return 0;
+  }
+
+  return 1;
+}
+
+static void
+flush_socket_reply()
+{
+  IPCMessageType reply_type;
+  uint32_t reply_size;
+  char *reply;
+
+  read_socket(&reply_type, &reply_size, &reply);
+
+  free(reply);
+}
+
+static void
+print_socket_reply()
+{
+  IPCMessageType reply_type;
+  uint32_t reply_size;
+  char *reply;
+
+  read_socket(&reply_type, &reply_size, &reply);
+
+  printf("%.*s\n", reply_size, reply);
+  fflush(stdout);
+  free(reply);
+}
+
+static int
+run_command(const char *name, char *args[], int argc)
+{
+  const unsigned char *msg;
+  size_t msg_size;
+
+  yajl_gen gen = yajl_gen_alloc(NULL);
+
+  // Message format:
+  // {
+  //   "command": "<name>",
+  //   "args": [ ... ]
+  // }
+  // clang-format off
+  YMAP(
+    YSTR("command"); YSTR(name);
+    YSTR("args"); YARR(
+      for (int i = 0; i < argc; i++) {
+        if (is_signed_int(args[i])) {
+          long long num = atoll(args[i]);
+          YINT(num);
+        } else if (is_float(args[i])) {
+          float num = atof(args[i]);
+          YDOUBLE(num);
+        } else {
+          YSTR(args[i]);
+        }
+      }
+    )
+  )
+  // clang-format on
+
+  yajl_gen_get_buf(gen, &msg, &msg_size);
+
+  send_message(IPC_TYPE_RUN_COMMAND, msg_size, (uint8_t *)msg);
+
+  if (!ignore_reply)
+    print_socket_reply();
+  else
+    flush_socket_reply();
+
+  yajl_gen_free(gen);
+
+  return 0;
+}
+
+static int
+get_monitors()
+{
+  send_message(IPC_TYPE_GET_MONITORS, 1, (uint8_t *)"");
+  print_socket_reply();
+  return 0;
+}
+
+static int
+get_tags()
+{
+  send_message(IPC_TYPE_GET_TAGS, 1, (uint8_t *)"");
+  print_socket_reply();
+
+  return 0;
+}
+
+static int
+get_layouts()
+{
+  send_message(IPC_TYPE_GET_LAYOUTS, 1, (uint8_t *)"");
+  print_socket_reply();
+
+  return 0;
+}
+
+static int
+get_speedwm_client(Window win)
+{
+  const unsigned char *msg;
+  size_t msg_size;
+
+  yajl_gen gen = yajl_gen_alloc(NULL);
+
+  // Message format:
+  // {
+  //   "client_window_id": "<win>"
+  // }
+  // clang-format off
+  YMAP(
+    YSTR("client_window_id"); YINT(win);
+  )
+  // clang-format on
+
+  yajl_gen_get_buf(gen, &msg, &msg_size);
+
+  send_message(IPC_TYPE_GET_DWM_CLIENT, msg_size, (uint8_t *)msg);
+
+  print_socket_reply();
+
+  yajl_gen_free(gen);
+
+  return 0;
+}
+
+static int
+subscribe(const char *event)
+{
+  const unsigned char *msg;
+  size_t msg_size;
+
+  yajl_gen gen = yajl_gen_alloc(NULL);
+
+  // Message format:
+  // {
+  //   "event": "<event>",
+  //   "action": "subscribe"
+  // }
+  // clang-format off
+  YMAP(
+    YSTR("event"); YSTR(event);
+    YSTR("action"); YSTR("subscribe");
+  )
+  // clang-format on
+
+  yajl_gen_get_buf(gen, &msg, &msg_size);
+
+  send_message(IPC_TYPE_SUBSCRIBE, msg_size, (uint8_t *)msg);
+
+  if (!ignore_reply)
+    print_socket_reply();
+  else
+    flush_socket_reply();
+
+  yajl_gen_free(gen);
+
+  return 0;
+}
+
+static void
+usage_error(const char *prog_name, const char *format, ...)
+{
+  va_list args;
+  va_start(args, format);
+
+  fprintf(stderr, "Error: ");
+  vfprintf(stderr, format, args);
+  fprintf(stderr, "\nusage: %s <command> [...]\n", prog_name);
+  fprintf(stderr, "Try '%s help'\n", prog_name);
+
+  va_end(args);
+  exit(1);
+}
+
+static void
+print_usage(const char *name)
+{
+  printf("usage: %s [options] <command> [...]\n", name);
+  puts("");
+  puts("Commands:");
+  puts("  run_command <name> [args...]    Run an IPC command");
+  puts("");
+  puts("  get_monitors                    Get monitor properties");
+  puts("");
+  puts("  get_tags                        Get list of tags");
+  puts("");
+  puts("  get_layouts                     Get list of layouts");
+  puts("");
+  puts("  get_speedwm_client <window_id>      Get speedwm client proprties");
+  puts("");
+  puts("  subscribe [events...]           Subscribe to specified events");
+  puts("                                  Options: " IPC_EVENT_TAG_CHANGE ",");
+  puts("                                  " IPC_EVENT_LAYOUT_CHANGE ",");
+  puts("                                  " IPC_EVENT_CLIENT_FOCUS_CHANGE ",");
+  puts("                                  " IPC_EVENT_MONITOR_FOCUS_CHANGE ",");
+  puts("                                  " IPC_EVENT_FOCUSED_TITLE_CHANGE ",");
+  puts("                                  " IPC_EVENT_FOCUSED_STATE_CHANGE);
+  puts("");
+  puts("  help                            Display this message");
+  puts("");
+  puts("Options:");
+  puts("  --ignore-reply                  Don't print reply messages from");
+  puts("                                  run_command and subscribe.");
+  puts("");
+}
+
+int
+main(int argc, char *argv[])
+{
+  const char *prog_name = argv[0];
+
+  connect_to_socket();
+  if (sock_fd == -1) {
+    fprintf(stderr, "Failed to connect to socket\n");
+    return 1;
+  }
+
+  int i = 1;
+  if (i < argc && strcmp(argv[i], "--ignore-reply") == 0) {
+    ignore_reply = 1;
+    i++;
+  }
+
+  if (i >= argc) usage_error(prog_name, "Expected an argument, got none");
+
+  if (strcmp(argv[i], "help") == 0)
+    print_usage(prog_name);
+  else if (strcmp(argv[i], "run_command") == 0) {
+    if (++i >= argc) usage_error(prog_name, "No command specified");
+    // Command name
+    char *command = argv[i];
+    // Command arguments are everything after command name
+    char **command_args = argv + ++i;
+    // Number of command arguments
+    int command_argc = argc - i;
+    run_command(command, command_args, command_argc);
+  } else if (strcmp(argv[i], "get_monitors") == 0) {
+    get_monitors();
+  } else if (strcmp(argv[i], "get_tags") == 0) {
+    get_tags();
+  } else if (strcmp(argv[i], "get_layouts") == 0) {
+    get_layouts();
+  } else if (strcmp(argv[i], "get_speedwm_client") == 0) {
+    if (++i < argc) {
+      if (is_unsigned_int(argv[i])) {
+        Window win = atol(argv[i]);
+        get_speedwm_client(win);
+      } else
+        usage_error(prog_name, "Expected unsigned integer argument");
+    } else
+      usage_error(prog_name, "Expected the window id");
+  } else if (strcmp(argv[i], "subscribe") == 0) {
+    if (++i < argc) {
+      for (int j = i; j < argc; j++) subscribe(argv[j]);
+    } else
+      usage_error(prog_name, "Expected event name");
+    // Keep listening for events forever
+    while (1) {
+      print_socket_reply();
+    }
+  } else
+    usage_error(prog_name, "Invalid argument '%s'", argv[i]);
+
+  return 0;
+}

speedwm.c

@@ -15,6 +15,10 @@
 #include <stdint.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include "toggle.h"
+#if USEIPC
+#include <sys/epoll.h>
+#endif
 #include <X11/cursorfont.h>
 #include <X11/keysym.h>
 #include <X11/Xatom.h>
@@ -91,9 +95,23 @@ enum { DWMTags, DWMLast };
 enum { ClkTagBar, ClkLtSymbol, ClkStatusText, ClkWinTitle,
        ClkClientWin, ClkRootWin, ClkLast }; /* clicks */
 
+#if USEIPC
+typedef struct TagState TagState;
+struct TagState {
+	int selected;
+	int occupied;
+	int urgent;
+};
+
+typedef struct ClientState ClientState;
+struct ClientState {
+	int isfixed, isfloating, isurgent, neverfocus, oldstate, isfullscreen;
+};
+#endif
+
 typedef union {
-	int i;
+	long i;
-	unsigned int ui;
+	unsigned long ui;
 	float f;
 	const void *v;
 } Arg;
@@ -129,6 +147,9 @@ struct Client {
 	Client *swallowing;
 	Monitor *mon;
 	Window win;
+#if USEIPC
+	ClientState prevstate;
+#endif
 };
 
 typedef struct {
@@ -153,6 +174,9 @@ typedef struct {
 typedef struct Pertag Pertag;
 struct Monitor {
 	char ltsymbol[16];
+#if USEIPC
+	char lastltsymbol[16];
+#endif
 	float mfact;
 	int nmaster;
 	int num;
@@ -169,6 +193,9 @@ struct Monitor {
 	unsigned int seltags;
 	unsigned int sellt;
 	unsigned int tagset[2];
+#if USEIPC
+	TagState tagstate;
+#endif
 	int previewshow;
 	int showbar;
 	int barposition;
@@ -176,6 +203,9 @@ struct Monitor {
 	int mouseactivated;
 	Client *clients;
 	Client *sel;
+#if USEIPC
+	Client *lastsel;
+#endif
 	Client *stack;
 	Monitor *next;
 	Window barwin;
@@ -183,6 +213,9 @@ struct Monitor {
 	Window tagwin;
 	Pixmap *tagmap;
 	const Layout *lt[2];
+#if USEIPC
+	const Layout *lastlt;
+#endif
 	Pertag *pertag;
 };
 
@@ -290,6 +323,9 @@ static void grabbuttons(Client *c, int focused);
 static void hide(const Arg *arg);
 static void hidewin(Client *c);
 static void incnmaster(const Arg *arg);
+#if USEIPC
+static int handlexevent(struct epoll_event *ev);
+#endif
 static void keypress(XEvent *e);
 static int fake_signal(void);
 static void killclient(const Arg *arg);
@@ -344,9 +380,15 @@ static void incrogaps(const Arg *arg);
 static void togglegaps(const Arg *arg);
 static void defaultgaps(const Arg *arg);
 static void setlayout(const Arg *arg);
+#if USEIPC
+static void setlayoutsafe(const Arg *arg);
+#endif
 static void setcfact(const Arg *arg);
 static void setmfact(const Arg *arg);
 static void setup(void);
+#if USEIPC
+static void setupepoll(void);
+#endif
 static void seturgent(Client *c, int urg);
 static void show(const Arg *arg);
 static void showwin(Client *c);
@@ -445,6 +487,10 @@ static void (*handler[LASTEvent]) (XEvent *) = {
 	[UnmapNotify] = unmapnotify
 };
 static Atom wmatom[WMLast], netatom[NetLast], dwmatom[DWMLast], motifatom;
+#if USEIPC
+static int epoll_fd;
+static int dpy_fd;
+#endif
 static int running = 1;
 static int restart = 0;
 static Cur *cursor[CurLast];
@@ -453,6 +499,9 @@ static Clr **tagscheme;
 static Display *dpy;
 static Drw *drw;
 static Monitor *mons, *selmon;
+#if USEIPC
+static Monitor *lastselmon; /* IPC */
+#endif
 
 static Window root, wmcheckwin;
 
@@ -470,6 +519,10 @@ static Colormap cmap;
 static xcb_connection_t *xcon;
 #define FORCE_VSPLIT forcevsplit
 
+#if USEIPC
+#include "toggle/ipc.c"
+#endif
+
 /* configuration, allows nested code to access above variables */
 #include <X11/XF86keysym.h> /* Enable multimedia button support */
 #include "options.h" /* Include options */
@@ -481,6 +534,12 @@ static xcb_connection_t *xcon;
 #include "xresources.h" /* Include .Xresources/Pywal support */
 #include "keybinds.h" /* Include keybinds */
 
+#if USEIPC
+#include "ipccmd.h" /* Include IPC */
+#include "toggle/ipc-cli.c"
+#include "toggle/ipc-yajl.c"
+#endif
+
 static const char *statuscmd[] = { shell, "-c", NULL, NULL };
 
 #include "mouse.h" /* Include mouse support */
@@ -1045,6 +1104,14 @@ cleanup(void)
 	XSync(dpy, False);
 	XSetInputFocus(dpy, PointerRoot, RevertToPointerRoot, CurrentTime);
 	XDeleteProperty(dpy, root, netatom[NetActiveWindow]);
+
+#if USEIPC
+	ipc_cleanup();
+
+	if (close(epoll_fd) < 0) {
+			fprintf(stderr, "Failed to close epoll file descriptor\n");
+	}
+#endif
 }
 
 void
@@ -2104,6 +2171,27 @@ hidewin(Client *c) {
 	XUngrabServer(dpy);
 }
 
+#if USEIPC
+int
+handlexevent(struct epoll_event *ev)
+{
+	if (ev->events & EPOLLIN) {
+		XEvent ev;
+		while (running && XPending(dpy)) {
+			XNextEvent(dpy, &ev);
+			if (handler[ev.type]) {
+				handler[ev.type](&ev); /* call handler */
+				ipc_send_events(mons, &lastselmon, selmon);
+			}
+		}
+	} else if (ev-> events & EPOLLHUP) {
+		return -1;
+	}
+
+	return 0;
+}
+#endif
+
 void
 incnmaster(const Arg *arg)
 {
@@ -3423,12 +3511,44 @@ restack(Monitor *m)
 void
 run(void)
 {
-	XEvent ev;
+#if USEIPC
-	/* main event loop */
+	int event_count = 0;
+	const int MAX_EVENTS = 10;
+	struct epoll_event events[MAX_EVENTS];
+#endif
+
 	XSync(dpy, False);
-	while (running && !XNextEvent(dpy, &ev))
+
-		if (handler[ev.type])
+#if USEIPC
-			handler[ev.type](&ev); /* call handler */
+	/* main event loop */
+	while (running) {
+		event_count = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
+
+		for (int i = 0; i < event_count; i++) {
+			int event_fd = events[i].data.fd;
+			DEBUG("Got event from fd %d\n", event_fd);
+
+			if (event_fd == dpy_fd) {
+				// -1 means EPOLLHUP
+				if (handlexevent(events + i) == -1)
+					return;
+			} else if (event_fd == ipc_get_sock_fd()) {
+				ipc_handle_socket_epoll_event(events + i);
+			} else if (ipc_is_client_registered(event_fd)){
+				if (ipc_handle_client_epoll_event(events + i, mons, &lastselmon, selmon,
+							LENGTH(tags), layouts, LENGTH(layouts)) < 0) {
+					fprintf(stderr, "Error handling IPC event on fd %d\n", event_fd);
+				}
+			} else {
+				fprintf(stderr, "Got event from unknown fd %d, ptr %p, u32 %d, u64 %lu",
+						event_fd, events[i].data.ptr, events[i].data.u32,
+						events[i].data.u64);
+				fprintf(stderr, " with events %d\n", events[i].events);
+				return;
+			}
+		}
+	}
+#endif
 }
 
 void spawnscratch(const Arg *arg)
@@ -3747,6 +3867,20 @@ setcfact(const Arg *arg) {
 	arrange(selmon);
 }
 
+#if USEIPC
+void
+setlayoutsafe(const Arg *arg)
+{
+	const Layout *ltptr = (Layout *)arg->v;
+	if (ltptr == 0)
+			setlayout(arg);
+	for (int i = 0; i < LENGTH(layouts); i++) {
+		if (ltptr == &layouts[i])
+			setlayout(arg);
+	}
+}
+#endif
+
 /* arg > 1.0 will set mfact absolutely */
 void
 setmfact(const Arg *arg)
@@ -3877,6 +4011,9 @@ setup(void)
 	XSelectInput(dpy, root, wa.event_mask);
 	grabkeys();
 	focus(NULL);
+#if USEIPC
+	setupepoll();
+#endif
 	spawnbar();
 }
 
@@ -3886,6 +4023,36 @@ setviewport(void){
 	XChangeProperty(dpy, root, netatom[NetDesktopViewport], XA_CARDINAL, 32, PropModeReplace, (unsigned char *)data, 2);
 }
 
+#if USEIPC
+void
+setupepoll(void)
+{
+	epoll_fd = epoll_create1(0);
+	dpy_fd = ConnectionNumber(dpy);
+	struct epoll_event dpy_event;
+
+	// Initialize struct to 0
+	memset(&dpy_event, 0, sizeof(dpy_event));
+
+	DEBUG("Display socket is fd %d\n", dpy_fd);
+
+	if (epoll_fd == -1) {
+		fputs("Failed to create epoll file descriptor", stderr);
+	}
+
+	dpy_event.events = EPOLLIN;
+	dpy_event.data.fd = dpy_fd;
+	if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, dpy_fd, &dpy_event)) {
+		fputs("Failed to add display file descriptor to epoll", stderr);
+		close(epoll_fd);
+		exit(1);
+	}
+
+	if (ipc_init(ipcsockpath, epoll_fd, ipccommands, LENGTH(ipccommands)) < 0) {
+		fputs("Failed to initialize IPC\n", stderr);
+	}
+}
+#endif
 
 void
 seturgent(Client *c, int urg)
@@ -4670,11 +4837,22 @@ updaterules(Client *c)
 void
 updatetitle(Client *c)
 {
+#if USEIPC
+    char oldname[sizeof(c->name)];
+	strcpy(oldname, c->name);
+#endif
 	if (!gettextprop(c->win, netatom[NetWMName], c->name, sizeof c->name))
 		gettextprop(c->win, XA_WM_NAME, c->name, sizeof c->name);
     
 	if (c->name[0] == '\0')
 		strcpy(c->name, broken);
+
+#if USEIPC
+	for (Monitor *m = mons; m; m = m->next) {
+		if (m->sel == c && strcmp(oldname, c->name) != 0)
+			ipc_focused_title_change_event(m->num, c->win, oldname, c->name);
+	}
+#endif
 }
 
 void

toggle.h

@@ -0,0 +1,4 @@
+/* Toggle patches
+ * This header allows you to enable/disable patches that can break compability with certain OSes or configurations.
+ */
+#define USEIPC 1 /* Whether or not to use IPC. If you set this to 1, set  USEIPC to true in config.mk and comment the YAJLLIBS and YAJLINC lines in config.mk. Not compatible with BSDs so for those, set this to 0. */

toggle/ipc-cli.c

@@ -0,0 +1,66 @@
+#include "ipc-cli.h"
+
+#include <string.h>
+#include <sys/epoll.h>
+
+#include "../util.h"
+
+IPCClient *
+ipc_client_new(int fd)
+{
+  IPCClient *c = (IPCClient *)malloc(sizeof(IPCClient));
+
+  if (c == NULL) return NULL;
+
+  // Initialize struct
+  memset(&c->event, 0, sizeof(struct epoll_event));
+
+  c->buffer_size = 0;
+  c->buffer = NULL;
+  c->fd = fd;
+  c->event.data.fd = fd;
+  c->next = NULL;
+  c->prev = NULL;
+  c->subscriptions = 0;
+
+  return c;
+}
+
+void
+ipc_list_add_client(IPCClientList *list, IPCClient *nc)
+{
+  DEBUG("Adding client with fd %d to list\n", nc->fd);
+
+  if (*list == NULL) {
+    // List is empty, point list at first client
+    *list = nc;
+  } else {
+    IPCClient *c;
+    // Go to last client in list
+    for (c = *list; c && c->next; c = c->next)
+      ;
+    c->next = nc;
+    nc->prev = c;
+  }
+}
+
+void
+ipc_list_remove_client(IPCClientList *list, IPCClient *c)
+{
+  IPCClient *cprev = c->prev;
+  IPCClient *cnext = c->next;
+
+  if (cprev != NULL) cprev->next = c->next;
+  if (cnext != NULL) cnext->prev = c->prev;
+  if (c == *list) *list = c->next;
+}
+
+IPCClient *
+ipc_list_get_client(IPCClientList list, int fd)
+{
+  for (IPCClient *c = list; c; c = c->next) {
+    if (c->fd == fd) return c;
+  }
+
+  return NULL;
+}

toggle/ipc-cli.h

@@ -0,0 +1,61 @@
+#ifndef IPC_CLIENT_H_
+#define IPC_CLIENT_H_
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/epoll.h>
+
+typedef struct IPCClient IPCClient;
+/**
+ * This structure contains the details of an IPC Client and pointers for a
+ * linked list
+ */
+struct IPCClient {
+  int fd;
+  int subscriptions;
+
+  char *buffer;
+  uint32_t buffer_size;
+
+  struct epoll_event event;
+  IPCClient *next;
+  IPCClient *prev;
+};
+
+typedef IPCClient *IPCClientList;
+
+/**
+ * Allocate memory for new IPCClient with the specified file descriptor and
+ * initialize struct.
+ *
+ * @param fd File descriptor of IPC client
+ *
+ * @return Address to allocated IPCClient struct
+ */
+IPCClient *ipc_client_new(int fd);
+
+/**
+ * Add an IPC Client to the specified list
+ *
+ * @param list Address of the list to add the client to
+ * @param nc Address of the IPCClient
+ */
+void ipc_list_add_client(IPCClientList *list, IPCClient *nc);
+
+/**
+ * Remove an IPCClient from the specified list
+ *
+ * @param list Address of the list to remove the client from
+ * @param c Address of the IPCClient
+ */
+void ipc_list_remove_client(IPCClientList *list, IPCClient *c);
+
+/**
+ * Get an IPCClient from the specified IPCClient list
+ *
+ * @param list List to remove the client from
+ * @param fd File descriptor of the IPCClient
+ */
+IPCClient *ipc_list_get_client(IPCClientList list, int fd);
+
+#endif  // IPC_CLIENT_H_

toggle/ipc-yajl.c

@@ -0,0 +1,350 @@
+#include "ipc-yajl.h"
+#include <stdint.h>
+
+int
+dump_tag(yajl_gen gen, const char *name, const int tag_mask)
+{
+  // clang-format off
+  YMAP(
+    YSTR("bit_mask"); YINT(tag_mask);
+    YSTR("name"); YSTR(name);
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_tags(yajl_gen gen, int tags_len)
+{
+  // clang-format off
+  YARR(
+    for (int i = 0; i < tags_len; i++)
+      dump_tag(gen, tags[i], 1 << i);
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_client(yajl_gen gen, Client *c)
+{
+  // clang-format off
+  YMAP(
+    YSTR("name"); YSTR(c->name);
+    YSTR("tags"); YINT(c->tags);
+    YSTR("window_id"); YINT(c->win);
+    YSTR("monitor_number"); YINT(c->mon->num);
+
+    YSTR("geometry"); YMAP(
+      YSTR("current"); YMAP (
+        YSTR("x"); YINT(c->x);
+        YSTR("y"); YINT(c->y);
+        YSTR("width"); YINT(c->w);
+        YSTR("height"); YINT(c->h);
+      )
+      YSTR("old"); YMAP(
+        YSTR("x"); YINT(c->oldx);
+        YSTR("y"); YINT(c->oldy);
+        YSTR("width"); YINT(c->oldw);
+        YSTR("height"); YINT(c->oldh);
+      )
+    )
+
+    YSTR("size_hints"); YMAP(
+      YSTR("base"); YMAP(
+        YSTR("width"); YINT(c->basew);
+        YSTR("height"); YINT(c->baseh);
+      )
+      YSTR("step"); YMAP(
+        YSTR("width"); YINT(c->incw);
+        YSTR("height"); YINT(c->inch);
+      )
+      YSTR("max"); YMAP(
+        YSTR("width"); YINT(c->maxw);
+        YSTR("height"); YINT(c->maxh);
+      )
+      YSTR("min"); YMAP(
+        YSTR("width"); YINT(c->minw);
+        YSTR("height"); YINT(c->minh);
+      )
+      YSTR("aspect_ratio"); YMAP(
+        YSTR("min"); YDOUBLE(c->mina);
+        YSTR("max"); YDOUBLE(c->maxa);
+      )
+    )
+
+    YSTR("border_width"); YMAP(
+      YSTR("current"); YINT(c->bw);
+      YSTR("old"); YINT(c->oldbw);
+    )
+
+    YSTR("states"); YMAP(
+      YSTR("is_fixed"); YBOOL(c->isfixed);
+      YSTR("is_floating"); YBOOL(c->isfloating);
+      YSTR("is_urgent"); YBOOL(c->isurgent);
+      YSTR("never_focus"); YBOOL(c->neverfocus);
+      YSTR("old_state"); YBOOL(c->oldstate);
+      YSTR("is_fullscreen"); YBOOL(c->isfullscreen);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_monitor(yajl_gen gen, Monitor *mon, int is_selected)
+{
+  // clang-format off
+  YMAP(
+    YSTR("master_factor"); YDOUBLE(mon->mfact);
+    YSTR("num_master"); YINT(mon->nmaster);
+    YSTR("num"); YINT(mon->num);
+    YSTR("is_selected"); YBOOL(is_selected);
+
+    YSTR("monitor_geometry"); YMAP(
+      YSTR("x"); YINT(mon->mx);
+      YSTR("y"); YINT(mon->my);
+      YSTR("width"); YINT(mon->mw);
+      YSTR("height"); YINT(mon->mh);
+    )
+
+    YSTR("window_geometry"); YMAP(
+      YSTR("x"); YINT(mon->wx);
+      YSTR("y"); YINT(mon->wy);
+      YSTR("width"); YINT(mon->ww);
+      YSTR("height"); YINT(mon->wh);
+    )
+
+    YSTR("tagset"); YMAP(
+      YSTR("current");  YINT(mon->tagset[mon->seltags]);
+      YSTR("old"); YINT(mon->tagset[mon->seltags ^ 1]);
+    )
+
+    YSTR("tag_state"); dump_tag_state(gen, mon->tagstate);
+
+    YSTR("clients"); YMAP(
+      YSTR("selected"); YINT(mon->sel ? mon->sel->win : 0);
+      YSTR("stack"); YARR(
+        for (Client* c = mon->stack; c; c = c->snext)
+          YINT(c->win);
+      )
+      YSTR("all"); YARR(
+        for (Client* c = mon->clients; c; c = c->next)
+          YINT(c->win);
+      )
+    )
+
+    YSTR("layout"); YMAP(
+      YSTR("symbol"); YMAP(
+        YSTR("current"); YSTR(mon->ltsymbol);
+        YSTR("old"); YSTR(mon->lastltsymbol);
+      )
+      YSTR("address"); YMAP(
+        YSTR("current"); YINT((uintptr_t)mon->lt[mon->sellt]);
+        YSTR("old"); YINT((uintptr_t)mon->lt[mon->sellt ^ 1]);
+      )
+    )
+
+    YSTR("bar"); YMAP(
+      YSTR("y"); YINT(mon->by);
+      YSTR("is_shown"); YBOOL(mon->showbar);
+      YSTR("is_top"); YBOOL(mon->barposition);
+      YSTR("window_id"); YINT(mon->barwin);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_monitors(yajl_gen gen, Monitor *mons, Monitor *selmon)
+{
+  // clang-format off
+  YARR(
+    for (Monitor *mon = mons; mon; mon = mon->next) {
+      if (mon == selmon)
+        dump_monitor(gen, mon, 1);
+      else
+        dump_monitor(gen, mon, 0);
+    }
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_layouts(yajl_gen gen, const Layout layouts[], const int layouts_len)
+{
+  // clang-format off
+  YARR(
+    for (int i = 0; i < layouts_len; i++) {
+      YMAP(
+        // Check for a NULL pointer. The cycle layouts patch adds an entry at
+        // the end of the layouts array with a NULL pointer for the symbol
+        YSTR("symbol"); YSTR((layouts[i].symbol ? layouts[i].symbol : ""));
+        YSTR("address"); YINT((uintptr_t)(layouts + i));
+      )
+    }
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_tag_state(yajl_gen gen, TagState state)
+{
+  // clang-format off
+  YMAP(
+    YSTR("selected"); YINT(state.selected);
+    YSTR("occupied"); YINT(state.occupied);
+    YSTR("urgent"); YINT(state.urgent);
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_tag_event(yajl_gen gen, int mon_num, TagState old_state,
+               TagState new_state)
+{
+  // clang-format off
+  YMAP(
+    YSTR("tag_change_event"); YMAP(
+      YSTR("monitor_number"); YINT(mon_num);
+      YSTR("old_state"); dump_tag_state(gen, old_state);
+      YSTR("new_state"); dump_tag_state(gen, new_state);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_client_focus_change_event(yajl_gen gen, Client *old_client,
+                               Client *new_client, int mon_num)
+{
+  // clang-format off
+  YMAP(
+    YSTR("client_focus_change_event"); YMAP(
+      YSTR("monitor_number"); YINT(mon_num);
+      YSTR("old_win_id"); old_client == NULL ? YNULL() : YINT(old_client->win);
+      YSTR("new_win_id"); new_client == NULL ? YNULL() : YINT(new_client->win);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_layout_change_event(yajl_gen gen, const int mon_num,
+                         const char *old_symbol, const Layout *old_layout,
+                         const char *new_symbol, const Layout *new_layout)
+{
+  // clang-format off
+  YMAP(
+    YSTR("layout_change_event"); YMAP(
+      YSTR("monitor_number"); YINT(mon_num);
+      YSTR("old_symbol"); YSTR(old_symbol);
+      YSTR("old_address"); YINT((uintptr_t)old_layout);
+      YSTR("new_symbol"); YSTR(new_symbol);
+      YSTR("new_address"); YINT((uintptr_t)new_layout);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_monitor_focus_change_event(yajl_gen gen, const int last_mon_num,
+                                const int new_mon_num)
+{
+  // clang-format off
+  YMAP(
+    YSTR("monitor_focus_change_event"); YMAP(
+      YSTR("old_monitor_number"); YINT(last_mon_num);
+      YSTR("new_monitor_number"); YINT(new_mon_num);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_focused_title_change_event(yajl_gen gen, const int mon_num,
+                                const Window client_id, const char *old_name,
+                                const char *new_name)
+{
+  // clang-format off
+  YMAP(
+    YSTR("focused_title_change_event"); YMAP(
+      YSTR("monitor_number"); YINT(mon_num);
+      YSTR("client_window_id"); YINT(client_id);
+      YSTR("old_name"); YSTR(old_name);
+      YSTR("new_name"); YSTR(new_name);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_client_state(yajl_gen gen, const ClientState *state)
+{
+  // clang-format off
+  YMAP(
+    YSTR("old_state"); YBOOL(state->oldstate);
+    YSTR("is_fixed"); YBOOL(state->isfixed);
+    YSTR("is_floating"); YBOOL(state->isfloating);
+    YSTR("is_fullscreen"); YBOOL(state->isfullscreen);
+    YSTR("is_urgent"); YBOOL(state->isurgent);
+    YSTR("never_focus"); YBOOL(state->neverfocus);
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_focused_state_change_event(yajl_gen gen, const int mon_num,
+                                const Window client_id,
+                                const ClientState *old_state,
+                                const ClientState *new_state)
+{
+  // clang-format off
+  YMAP(
+    YSTR("focused_state_change_event"); YMAP(
+      YSTR("monitor_number"); YINT(mon_num);
+      YSTR("client_window_id"); YINT(client_id);
+      YSTR("old_state"); dump_client_state(gen, old_state);
+      YSTR("new_state"); dump_client_state(gen, new_state);
+    )
+  )
+  // clang-format on
+
+  return 0;
+}
+
+int
+dump_error_message(yajl_gen gen, const char *reason)
+{
+  // clang-format off
+  YMAP(
+    YSTR("result"); YSTR("error");
+    YSTR("reason"); YSTR(reason);
+  )
+  // clang-format on
+
+  return 0;
+}

toggle/ipc-yajl.h

@@ -0,0 +1,65 @@
+#ifndef YAJL_DUMPS_H_
+#define YAJL_DUMPS_H_
+
+#include <string.h>
+#include <yajl/yajl_gen.h>
+
+#define YSTR(str) yajl_gen_string(gen, (unsigned char *)str, strlen(str))
+#define YINT(num) yajl_gen_integer(gen, num)
+#define YDOUBLE(num) yajl_gen_double(gen, num)
+#define YBOOL(v) yajl_gen_bool(gen, v)
+#define YNULL() yajl_gen_null(gen)
+#define YARR(body)                                                             \
+  {                                                                            \
+    yajl_gen_array_open(gen);                                                  \
+    body;                                                                      \
+    yajl_gen_array_close(gen);                                                 \
+  }
+#define YMAP(body)                                                             \
+  {                                                                            \
+    yajl_gen_map_open(gen);                                                    \
+    body;                                                                      \
+    yajl_gen_map_close(gen);                                                   \
+  }
+
+int dump_tag(yajl_gen gen, const char *name, const int tag_mask);
+
+int dump_tags(yajl_gen gen, int tags_len);
+
+int dump_client(yajl_gen gen, Client *c);
+
+int dump_monitor(yajl_gen gen, Monitor *mon, int is_selected);
+
+int dump_monitors(yajl_gen gen, Monitor *mons, Monitor *selmon);
+
+int dump_layouts(yajl_gen gen, const Layout layouts[], const int layouts_len);
+
+int dump_tag_state(yajl_gen gen, TagState state);
+
+int dump_tag_event(yajl_gen gen, int mon_num, TagState old_state,
+                   TagState new_state);
+
+int dump_client_focus_change_event(yajl_gen gen, Client *old_client,
+                                   Client *new_client, int mon_num);
+
+int dump_layout_change_event(yajl_gen gen, const int mon_num,
+                             const char *old_symbol, const Layout *old_layout,
+                             const char *new_symbol, const Layout *new_layout);
+
+int dump_monitor_focus_change_event(yajl_gen gen, const int last_mon_num,
+                                    const int new_mon_num);
+
+int dump_focused_title_change_event(yajl_gen gen, const int mon_num,
+                                    const Window client_id,
+                                    const char *old_name, const char *new_name);
+
+int dump_client_state(yajl_gen gen, const ClientState *state);
+
+int dump_focused_state_change_event(yajl_gen gen, const int mon_num,
+                                    const Window client_id,
+                                    const ClientState *old_state,
+                                    const ClientState *new_state);
+
+int dump_error_message(yajl_gen gen, const char *reason);
+
+#endif  // YAJL_DUMPS_H_

toggle/ipc.h

@@ -0,0 +1,318 @@
+#ifndef IPC_H_
+#define IPC_H_
+
+#include <stdint.h>
+#include <sys/epoll.h>
+#include <yajl/yajl_gen.h>
+
+#include "ipc-cli.h"
+
+// clang-format off
+#define IPC_MAGIC "DWM-IPC"
+#define IPC_MAGIC_ARR { 'D', 'W', 'M', '-', 'I', 'P', 'C'}
+#define IPC_MAGIC_LEN 7 // Not including null char
+
+#define IPCCOMMAND(FUNC, ARGC, TYPES)                                          \
+  { #FUNC, {FUNC }, ARGC, (ArgType[ARGC])TYPES }
+// clang-format on
+
+typedef enum IPCMessageType {
+  IPC_TYPE_RUN_COMMAND = 0,
+  IPC_TYPE_GET_MONITORS = 1,
+  IPC_TYPE_GET_TAGS = 2,
+  IPC_TYPE_GET_LAYOUTS = 3,
+  IPC_TYPE_GET_DWM_CLIENT = 4,
+  IPC_TYPE_SUBSCRIBE = 5,
+  IPC_TYPE_EVENT = 6
+} IPCMessageType;
+
+typedef enum IPCEvent {
+  IPC_EVENT_TAG_CHANGE = 1 << 0,
+  IPC_EVENT_CLIENT_FOCUS_CHANGE = 1 << 1,
+  IPC_EVENT_LAYOUT_CHANGE = 1 << 2,
+  IPC_EVENT_MONITOR_FOCUS_CHANGE = 1 << 3,
+  IPC_EVENT_FOCUSED_TITLE_CHANGE = 1 << 4,
+  IPC_EVENT_FOCUSED_STATE_CHANGE = 1 << 5
+} IPCEvent;
+
+typedef enum IPCSubscriptionAction {
+  IPC_ACTION_UNSUBSCRIBE = 0,
+  IPC_ACTION_SUBSCRIBE = 1
+} IPCSubscriptionAction;
+
+/**
+ * Every IPC packet starts with this structure
+ */
+typedef struct dwm_ipc_header {
+  uint8_t magic[IPC_MAGIC_LEN];
+  uint32_t size;
+  uint8_t type;
+} __attribute((packed)) dwm_ipc_header_t;
+
+typedef enum ArgType {
+  ARG_TYPE_NONE = 0,
+  ARG_TYPE_UINT = 1,
+  ARG_TYPE_SINT = 2,
+  ARG_TYPE_FLOAT = 3,
+  ARG_TYPE_PTR = 4,
+  ARG_TYPE_STR = 5
+} ArgType;
+
+/**
+ * An IPCCommand function can have either of these function signatures
+ */
+typedef union ArgFunction {
+  void (*single_param)(const Arg *);
+  void (*array_param)(const Arg *, int);
+} ArgFunction;
+
+typedef struct IPCCommand {
+  char *name;
+  ArgFunction func;
+  unsigned int argc;
+  ArgType *arg_types;
+} IPCCommand;
+
+typedef struct IPCParsedCommand {
+  char *name;
+  Arg *args;
+  ArgType *arg_types;
+  unsigned int argc;
+} IPCParsedCommand;
+
+/**
+ * Initialize the IPC socket and the IPC module
+ *
+ * @param socket_path Path to create the socket at
+ * @param epoll_fd File descriptor for epoll
+ * @param commands Address of IPCCommands array defined in config.h
+ * @param commands_len Length of commands[] array
+ *
+ * @return int The file descriptor of the socket if it was successfully created,
+ *   -1 otherwise
+ */
+int ipc_init(const char *socket_path, const int p_epoll_fd,
+             IPCCommand commands[], const int commands_len);
+
+/**
+ * Uninitialize the socket and module. Free allocated memory and restore static
+ * variables to their state before ipc_init
+ */
+void ipc_cleanup();
+
+/**
+ * Get the file descriptor of the IPC socket
+ *
+ * @return int File descriptor of IPC socket, -1 if socket not created.
+ */
+int ipc_get_sock_fd();
+
+/**
+ * Get address to IPCClient with specified file descriptor
+ *
+ * @param fd File descriptor of IPC Client
+ *
+ * @return Address to IPCClient with specified file descriptor, -1 otherwise
+ */
+IPCClient *ipc_get_client(int fd);
+
+/**
+ * Check if an IPC client exists with the specified file descriptor
+ *
+ * @param fd File descriptor
+ *
+ * @return int 1 if client exists, 0 otherwise
+ */
+int ipc_is_client_registered(int fd);
+
+/**
+ * Disconnect an IPCClient from the socket and remove the client from the list
+ *   of known connected clients
+ *
+ * @param c Address of IPCClient
+ *
+ * @return 0 if the client's file descriptor was closed successfully, the
+ * result of executing close() on the file descriptor otherwise.
+ */
+int ipc_drop_client(IPCClient *c);
+
+/**
+ * Accept an IPC Client requesting to connect to the socket and add it to the
+ *   list of clients
+ *
+ * @return File descriptor of new client, -1 on error
+ */
+int ipc_accept_client();
+
+/**
+ * Read an incoming message from an accepted IPC client
+ *
+ * @param c Address of IPCClient
+ * @param msg_type Address to IPCMessageType variable which will be assigned
+ *   the message type of the received message
+ * @param msg_size Address to uint32_t variable which will be assigned the size
+ *   of the received message
+ * @param msg Address to char* variable which will be assigned the address of
+ *   the received message. This must be freed using free().
+ *
+ * @return 0 on success, -1 on error reading message, -2 if reading the message
+ * resulted in EAGAIN, EINTR, or EWOULDBLOCK.
+ */
+int ipc_read_client(IPCClient *c, IPCMessageType *msg_type, uint32_t *msg_size,
+                    char **msg);
+
+/**
+ * Write any pending buffer of the client to the client's socket
+ *
+ * @param c Client whose buffer to write
+ *
+ * @return Number of bytes written >= 0, -1 otherwise. errno will still be set
+ * from the write operation.
+ */
+ssize_t ipc_write_client(IPCClient *c);
+
+/**
+ * Prepare a message in the specified client's buffer.
+ *
+ * @param c Client to prepare message for
+ * @param msg_type Type of message to prepare
+ * @param msg_size Size of the message in bytes. Should not exceed
+ *   MAX_MESSAGE_SIZE
+ * @param msg Message to prepare (not including header). This pointer can be
+ *   freed after the function invocation.
+ */
+void ipc_prepare_send_message(IPCClient *c, const IPCMessageType msg_type,
+                              const uint32_t msg_size, const char *msg);
+
+/**
+ * Prepare an error message in the specified client's buffer
+ *
+ * @param c Client to prepare message for
+ * @param msg_type Type of message
+ * @param format Format string following vsprintf
+ * @param ... Arguments for format string
+ */
+void ipc_prepare_reply_failure(IPCClient *c, IPCMessageType msg_type,
+                               const char *format, ...);
+
+/**
+ * Prepare a success message in the specified client's buffer
+ *
+ * @param c Client to prepare message for
+ * @param msg_type Type of message
+ */
+void ipc_prepare_reply_success(IPCClient *c, IPCMessageType msg_type);
+
+/**
+ * Send a tag_change_event to all subscribers. Should be called only when there
+ * has been a tag state change.
+ *
+ * @param mon_num The index of the monitor (Monitor.num property)
+ * @param old_state The old tag state
+ * @param new_state The new (now current) tag state
+ */
+void ipc_tag_change_event(const int mon_num, TagState old_state,
+                          TagState new_state);
+
+/**
+ * Send a client_focus_change_event to all subscribers. Should be called only
+ * when the client focus changes.
+ *
+ * @param mon_num The index of the monitor (Monitor.num property)
+ * @param old_client The old DWM client selection (Monitor.oldsel)
+ * @param new_client The new (now current) DWM client selection
+ */
+void ipc_client_focus_change_event(const int mon_num, Client *old_client,
+                                   Client *new_client);
+
+/**
+ * Send a layout_change_event to all subscribers. Should be called only
+ * when there has been a layout change.
+ *
+ * @param mon_num The index of the monitor (Monitor.num property)
+ * @param old_symbol The old layout symbol
+ * @param old_layout Address to the old Layout
+ * @param new_symbol The new (now current) layout symbol
+ * @param new_layout Address to the new Layout
+ */
+void ipc_layout_change_event(const int mon_num, const char *old_symbol,
+                             const Layout *old_layout, const char *new_symbol,
+                             const Layout *new_layout);
+
+/**
+ * Send a monitor_focus_change_event to all subscribers. Should be called only
+ * when the monitor focus changes.
+ *
+ * @param last_mon_num The index of the previously selected monitor
+ * @param new_mon_num The index of the newly selected monitor
+ */
+void ipc_monitor_focus_change_event(const int last_mon_num,
+                                    const int new_mon_num);
+
+/**
+ * Send a focused_title_change_event to all subscribers. Should only be called
+ * if a selected client has a title change.
+ *
+ * @param mon_num Index of the client's monitor
+ * @param client_id Window XID of client
+ * @param old_name Old name of the client window
+ * @param new_name New name of the client window
+ */
+void ipc_focused_title_change_event(const int mon_num, const Window client_id,
+                                    const char *old_name, const char *new_name);
+
+/**
+ * Send a focused_state_change_event to all subscribers. Should only be called
+ * if a selected client has a state change.
+ *
+ * @param mon_num Index of the client's monitor
+ * @param client_id Window XID of client
+ * @param old_state Old state of the client
+ * @param new_state New state of the client
+ */
+void ipc_focused_state_change_event(const int mon_num, const Window client_id,
+                                    const ClientState *old_state,
+                                    const ClientState *new_state);
+/**
+ * Check to see if an event has occured and call the *_change_event functions
+ * accordingly
+ *
+ * @param mons Address of Monitor pointing to start of linked list
+ * @param lastselmon Address of pointer to previously selected monitor
+ * @param selmon Address of selected Monitor
+ */
+void ipc_send_events(Monitor *mons, Monitor **lastselmon, Monitor *selmon);
+
+/**
+ * Handle an epoll event caused by a registered IPC client. Read, process, and
+ * handle any received messages from clients. Write pending buffer to client if
+ * the client is ready to receive messages. Drop clients that have sent an
+ * EPOLLHUP.
+ *
+ * @param ev Associated epoll event returned by epoll_wait
+ * @param mons Address of Monitor pointing to start of linked list
+ * @param selmon Address of selected Monitor
+ * @param lastselmon Address of pointer to previously selected monitor
+ * @param tags Array of tag names
+ * @param tags_len Length of tags array
+ * @param layouts Array of available layouts
+ * @param layouts_len Length of layouts array
+ *
+ * @return 0 if event was successfully handled, -1 on any error receiving
+ * or handling incoming messages or unhandled epoll event.
+ */
+int ipc_handle_client_epoll_event(struct epoll_event *ev, Monitor *mons,
+                                  Monitor **lastselmon, Monitor *selmon, const int tags_len,
+                                  const Layout *layouts, const int layouts_len);
+/**
+ * Handle an epoll event caused by the IPC socket. This function only handles an
+ * EPOLLIN event indicating a new client requesting to connect to the socket.
+ *
+ * @param ev Associated epoll event returned by epoll_wait
+ *
+ * @return 0, if the event was successfully handled, -1 if not an EPOLLIN event
+ * or if a new IPC client connection request could not be accepted.
+ */
+int ipc_handle_socket_epoll_event(struct epoll_event *ev);
+
+#endif /* IPC_H_ */

util.c

@@ -3,6 +3,11 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include "toggle.h"
+#ifdef USEIPC
+#include <errno.h>
+#include <sys/stat.h>
+#endif
 
 #include "util.h"
 
@@ -33,3 +38,138 @@ die(const char *fmt, ...) {
 
 	exit(1);
 }
+
+#if USEIPC
+int
+normalizepath(const char *path, char **normal)
+{
+  size_t len = strlen(path);
+  *normal = (char *)malloc((len + 1) * sizeof(char));
+  const char *walk = path;
+  const char *match;
+  size_t newlen = 0;
+
+  while ((match = strchr(walk, '/'))) {
+    // Copy everything between match and walk
+    strncpy(*normal + newlen, walk, match - walk);
+    newlen += match - walk;
+    walk += match - walk;
+
+    // Skip all repeating slashes
+    while (*walk == '/')
+      walk++;
+
+    // If not last character in path
+    if (walk != path + len)
+      (*normal)[newlen++] = '/';
+  }
+
+  (*normal)[newlen++] = '\0';
+
+  // Copy remaining path
+  strcat(*normal, walk);
+  newlen += strlen(walk);
+
+  *normal = (char *)realloc(*normal, newlen * sizeof(char));
+
+  return 0;
+}
+
+int
+parentdir(const char *path, char **parent)
+{
+  char *normal;
+  char *walk;
+
+  normalizepath(path, &normal);
+
+  // Pointer to last '/'
+  if (!(walk = strrchr(normal, '/'))) {
+    free(normal);
+    return -1;
+  }
+
+  // Get path up to last '/'
+  size_t len = walk - normal;
+  *parent = (char *)malloc((len + 1) * sizeof(char));
+
+  // Copy path up to last '/'
+  strncpy(*parent, normal, len);
+  // Add null char
+  (*parent)[len] = '\0';
+
+  free(normal);
+
+  return 0;
+}
+
+int
+mkdirp(const char *path)
+{
+  char *normal;
+  char *walk;
+  size_t normallen;
+
+  normalizepath(path, &normal);
+  normallen = strlen(normal);
+  walk = normal;
+
+  while (walk < normal + normallen + 1) {
+    // Get length from walk to next /
+    size_t n = strcspn(walk, "/");
+
+    // Skip path /
+    if (n == 0) {
+      walk++;
+      continue;
+    }
+
+    // Length of current path segment
+    size_t curpathlen = walk - normal + n;
+    char curpath[curpathlen + 1];
+    struct stat s;
+
+    // Copy path segment to stat
+    strncpy(curpath, normal, curpathlen);
+    strcpy(curpath + curpathlen, "");
+    int res = stat(curpath, &s);
+
+    if (res < 0) {
+      if (errno == ENOENT) {
+        DEBUG("Making directory %s\n", curpath);
+        if (mkdir(curpath, 0700) < 0) {
+          fprintf(stderr, "Failed to make directory %s\n", curpath);
+          perror("");
+          free(normal);
+          return -1;
+        }
+      } else {
+        fprintf(stderr, "Error statting directory %s\n", curpath);
+        perror("");
+        free(normal);
+        return -1;
+      }
+    }
+
+    // Continue to next path segment
+    walk += n;
+  }
+
+  free(normal);
+
+  return 0;
+}
+
+int
+nullterminate(char **str, size_t *len)
+{
+  if ((*str)[*len - 1] == '\0')
+    return 0;
+
+  (*len)++;
+  *str = (char*)realloc(*str, *len * sizeof(char));
+  (*str)[*len - 1] = '\0';
+
+  return 0;
+}
+#endif

util.h

@@ -4,5 +4,19 @@
 #define MIN(A, B)               ((A) < (B) ? (A) : (B))
 #define BETWEEN(X, A, B)        ((A) <= (X) && (X) <= (B))
 
+#ifdef USEIPC
+#ifdef _DEBUG
+#define DEBUG(...) fprintf(stderr, __VA_ARGS__)
+#else
+#define DEBUG(...)
+#endif
+#endif
+
 void die(const char *fmt, ...);
 void *ecalloc(size_t nmemb, size_t size);
+#ifdef USEIPC
+int normalizepath(const char *path, char **normal);
+int mkdirp(const char *path);
+int parentdir(const char *path, char **parent);
+int nullterminate(char **str, size_t *len);
+#endif