+
+#ifndef HAVE_GTK_WINDOW_PRESENT_WITH_TIME
+static guint32
+get_startup_time (void)
+{
+ const char *envvar, *timestamp;
+ unsigned long value;
+ char *end;
+
+ envvar = getenv ("DESKTOP_STARTUP_ID");
+
+ if (envvar == NULL)
+ return 0;
+
+/* DESKTOP_STARTUP_ID is of form "<unique>_TIME<timestamp>".
+ *
+ * <unique> might contain a T but <timestamp> is an integer. As such,
+ * the last 'T' in the string must be the start of "TIME".
+ */
+ timestamp = rindex (envvar, 'T');
+
+/* Maybe the word "TIME" was not found... */
+ if (timestamp == NULL || strncmp (timestamp, "TIME", 4))
+ return 0;
+
+ timestamp += 4;
+
+/* strtoul sets errno = ERANGE on overflow, but it is not specified
+ * if it sets it to 0 on success. Doing so ourselves is the only
+ * way to know for sure.
+ */
+ errno = 0;
+ value = strtoul (timestamp, &end, 10);
+
+/* unsigned long might be 64bit, so double-check! */
+ if (errno != 0 || *end != '\0' || value > G_MAXINT32)
+ return 0;
+
+ return value;
+}
+#endif
+