Write to swaynag pipe fd directly on config errors

include/sway/swaynag.h

@@ -0,0 +1,33 @@
+#ifndef _SWAY_SWAYNAG_H
+#define _SWAY_SWAYNAG_H
+
+struct swaynag_instance {
+	const char *args;
+	pid_t pid;
+	int fd[2];
+	bool detailed;
+};
+
+// Copy all fields of one instance to another
+void swaynag_clone(struct swaynag_instance *dest,
+		struct swaynag_instance *src);
+
+// Spawn swaynag. If swaynag->detailed, then swaynag->fd[1] will left open
+// so it can be written to. Call swaynag_show when done writing. This will
+// be automatically called by swaynag_log if the instance is not spawned and
+// swaynag->detailed is true.
+bool swaynag_spawn(const char *swaynag_command,
+		struct swaynag_instance *swaynag);
+
+// Kill the swaynag instance
+void swaynag_kill(struct swaynag_instance *swaynag);
+
+// Write a log message to swaynag->fd[1]. This will fail when swaynag->detailed
+// is false.
+void swaynag_log(const char *swaynag_command, struct swaynag_instance *swaynag,
+		const char *fmt, ...);
+
+// If swaynag->detailed, close swaynag->fd[1] so swaynag displays
+void swaynag_show(struct swaynag_instance *swaynag);
+
+#endif