Implement Tray Icons

This commit implements the StatusNotifierItem protocol, and enables
swaybar to show tray icons. It also uses `xembedsniproxy` in order to
communicate with xembed applications.
The tray is completely optional, and can be disabled on compile time
with the `enable-tray` option. Or on runtime with the bar config option
`tray_output none`.

Overview of changes:
In swaybar very little is changed outside the tray subfolder except
that all events are now polled in `event_loop.c`, this creates no
functional difference.

Six bar configuration options were added, these are detailed in
sway-bar(5)

The tray subfolder is where all protocol implementation takes place and
is organised as follows:

tray/sni_watcher.c:
	This file contains the StatusNotifierWatcher. It keeps track of
	items and hosts and reports when they come or go.
tray/tray.c
	This file contains the StatusNotifierHost. It keeps track of
	sway's version of the items and represents the tray itself.
tray/sni.c
	This file contains the StatusNotifierItem struct and all
	communication with individual items.
tray/icon.c
	This file implements the icon theme protocol. It allows for
	finding icons by name, rather than by pixmap.
tray/dbus.c
	This file allows for asynchronous DBus communication.

See #986 #343

1 files changed, 26 insertions, 0 deletions

diff --git a/include/swaybar/event_loop.h b/include/swaybar/event_loop.h
new file mode 100644
index 00000000..a0cde07f
--- /dev/null
+++ b/include/swaybar/event_loop.h
@@ -0,0 +1,26 @@
+#ifndef _SWAYBAR_EVENT_LOOP_H
+#define _SWAYBAR_EVENT_LOOP_H
+
+#include <stdbool.h>
+#include <time.h>
+
+void add_event(int fd, short mask,
+                void(*cb)(int fd, short mask, void *data),
+                void *data);
+
+// Not guaranteed to notify cb immediately
+void add_timer(timer_t timer,
+                void(*cb)(timer_t timer, void *data),
+                void *data);
+
+// Returns false if nothing exists, true otherwise
+bool remove_event(int fd);
+
+// Returns false if nothing exists, true otherwise
+bool remove_timer(timer_t timer);
+
+// Blocks and returns after sending callbacks
+void event_loop_poll();
+
+void init_event_loop();
+#endif /*_SWAYBAR_EVENT_LOOP_H */