shmlog: store meta information in the buffer itself, store path as X11 atom

This makes i3-dump-log completely independent of a running i3 instance.

src/ipc.c

@@ -643,48 +643,6 @@ IPC_HANDLER(get_bar_config) {
     y(free);
 }
 
-/*
- * Formats the reply message for a GET_LOG_MARKERS request and sends it to the
- * client.
- *
- */
-IPC_HANDLER(get_log_markers) {
-#if YAJL_MAJOR >= 2
-    yajl_gen gen = yajl_gen_alloc(NULL);
-#else
-    yajl_gen gen = yajl_gen_alloc(NULL, NULL);
-#endif
-
-    int offset_next_write, offset_last_wrap, logsize;
-    get_log_markers(&offset_next_write, &offset_last_wrap, &logsize);
-
-    y(map_open);
-    ystr("offset_next_write");
-    y(integer, offset_next_write);
-
-    ystr("offset_last_wrap");
-    y(integer, offset_last_wrap);
-
-    ystr("shmname");
-    ystr(shmlogname);
-
-    ystr("size");
-    y(integer, logsize);
-
-    y(map_close);
-
-    const unsigned char *payload;
-#if YAJL_MAJOR >= 2
-    size_t length;
-#else
-    unsigned int length;
-#endif
-    y(get_buf, &payload, &length);
-
-    ipc_send_message(fd, length, I3_IPC_REPLY_TYPE_LOG_MARKERS, payload);
-    y(free);
-}
-
 /*
  * Callback for the YAJL parser (will be called when a string is parsed).
  *
@@ -770,7 +728,7 @@ IPC_HANDLER(subscribe) {
 
 /* The index of each callback function corresponds to the numeric
  * value of the message type (see include/i3/ipc.h) */
-handler_t handlers[8] = {
+handler_t handlers[7] = {
     handle_command,
     handle_get_workspaces,
     handle_subscribe,
@@ -778,7 +736,6 @@ handler_t handlers[8] = {
     handle_tree,
     handle_get_marks,
     handle_get_bar_config,
-    handle_get_log_markers
 };
 
 /*

src/log.c

@@ -23,6 +23,7 @@
 #include "log.h"
 #include "i3.h"
 #include "libi3.h"
+#include "shmlog.h"
 
 /* loglevels.h is autogenerated at make time */
 #include "loglevels.h"
@@ -52,6 +53,20 @@ static int logbuffer_size;
 /* File descriptor for shm_open. */
 static int logbuffer_shm;
 
+/*
+ * Writes the offsets for the next write and for the last wrap to the
+ * shmlog_header.
+ * Necessary to print the i3 SHM log in the correct order.
+ *
+ */
+static void store_log_markers() {
+    i3_shmlog_header *header = (i3_shmlog_header*)logbuffer;
+
+    header->offset_next_write = (logwalk - logbuffer);
+    header->offset_last_wrap = (loglastwrap - logbuffer);
+    header->size = logbuffer_size;
+}
+
 /*
  * Initializes logging by creating an error logfile in /tmp (or
  * XDG_RUNTIME_DIR, see get_process_filename()).
@@ -103,8 +118,9 @@ void init_logging() {
             logbuffer = NULL;
             return;
         }
-        logwalk = logbuffer;
+        logwalk = logbuffer + sizeof(i3_shmlog_header);
         loglastwrap = logbuffer + logbuffer_size;
+        store_log_markers();
     }
 }
 
@@ -141,17 +157,6 @@ void add_loglevel(const char *level) {
     }
 }
 
-/*
- * Returns the offsets for the next write and for the last wrap.
- * Necessary to print the i3 SHM log in the correct order.
- *
- */
-void get_log_markers(int *offset_next_write, int *offset_last_wrap, int *size) {
-    *offset_next_write = (logwalk - logbuffer);
-    *offset_last_wrap = (loglastwrap - logbuffer);
-    *size = logbuffer_size;
-}
-
 /*
  * Logs the given message to stdout (if print is true) while prefixing the
  * current time to it. Additionally, the message will be saved in the i3 SHM
@@ -208,7 +213,7 @@ static void vlog(const bool print, const char *fmt, va_list args) {
          * beginning again. */
         if ((len+1) >= (logbuffer_size - (logwalk - logbuffer))) {
             loglastwrap = logwalk;
-            logwalk = logbuffer;
+            logwalk = logbuffer + sizeof(i3_shmlog_header);
         }
 
         /* Copy the buffer, terminate it, move the write pointer to the byte after
@@ -217,6 +222,8 @@ static void vlog(const bool print, const char *fmt, va_list args) {
         logwalk[len] = '\0';
         logwalk += len + 1;
 
+        store_log_markers();
+
         if (print)
             fwrite(message, len, 1, stdout);
     }

src/main.c

@@ -335,7 +335,7 @@ int main(int argc, char *argv[]) {
                     break;
                 } else if (strcmp(long_options[option_index].name, "get-socketpath") == 0 ||
                            strcmp(long_options[option_index].name, "get_socketpath") == 0) {
-                    char *socket_path = socket_path_from_x11();
+                    char *socket_path = root_atom_contents("I3_SOCKET_PATH");
                     if (socket_path) {
                         printf("%s\n", socket_path);
                         return 0;
@@ -416,7 +416,7 @@ int main(int argc, char *argv[]) {
             optind++;
         }
         LOG("Command is: %s (%d bytes)\n", payload, strlen(payload));
-        char *socket_path = socket_path_from_x11();
+        char *socket_path = root_atom_contents("I3_SOCKET_PATH");
         if (!socket_path) {
             ELOG("Could not get i3 IPC socket path\n");
             return 1;

src/x.c

@@ -928,6 +928,8 @@ void x_set_i3_atoms() {
                         current_socketpath);
     xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_CONFIG_PATH, A_UTF8_STRING, 8,
                         strlen(current_configpath), current_configpath);
+    xcb_change_property(conn, XCB_PROP_MODE_REPLACE, root, A_I3_SHMLOG_PATH, A_UTF8_STRING, 8,
+                        strlen(shmlogname), shmlogname);
 }
 
 /*