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

11 files changed, 211 insertions, 1 deletions

diff --git a/include/client/cairo.h b/include/client/cairo.h
index 46c53566..e7ef7c7e 100644
--- a/include/client/cairo.h
+++ b/include/client/cairo.h
@@ -6,6 +6,8 @@
 
 void cairo_set_source_u32(cairo_t *cairo, uint32_t color);
 
+cairo_surface_t *cairo_image_surface_scale(cairo_surface_t *image, int width, int height);
+
 #ifdef WITH_GDK_PIXBUF
 #include <gdk-pixbuf/gdk-pixbuf.h>
 
diff --git a/include/sway/commands.h b/include/sway/commands.h
index 078652e7..f67df10f 100644
--- a/include/sway/commands.h
+++ b/include/sway/commands.h
@@ -157,17 +157,21 @@ sway_cmd cmd_workspace;
 sway_cmd cmd_ws_auto_back_and_forth;
 sway_cmd cmd_workspace_layout;
 
+sway_cmd bar_cmd_activate_button;
 sway_cmd bar_cmd_binding_mode_indicator;
 sway_cmd bar_cmd_bindsym;
 sway_cmd bar_cmd_colors;
+sway_cmd bar_cmd_context_button;
 sway_cmd bar_cmd_font;
 sway_cmd bar_cmd_mode;
 sway_cmd bar_cmd_modifier;
 sway_cmd bar_cmd_output;
 sway_cmd bar_cmd_height;
 sway_cmd bar_cmd_hidden_state;
+sway_cmd bar_cmd_icon_theme;
 sway_cmd bar_cmd_id;
 sway_cmd bar_cmd_position;
+sway_cmd bar_cmd_secondary_button;
 sway_cmd bar_cmd_separator_symbol;
 sway_cmd bar_cmd_status_command;
 sway_cmd bar_cmd_pango_markup;
diff --git a/include/sway/config.h b/include/sway/config.h
index 35f8d5f7..999a471a 100644
--- a/include/sway/config.h
+++ b/include/sway/config.h
@@ -133,7 +133,17 @@ struct bar_config {
         char *swaybar_command;
         char *font;
         int height; // -1 not defined
-        int tray_padding;
+
+#ifdef ENABLE_TRAY
+        // Tray
+        char *tray_output;
+        char *icon_theme;
+        uint32_t tray_padding;
+        uint32_t activate_button;
+        uint32_t context_button;
+        uint32_t secondary_button;
+#endif
+
         bool workspace_buttons;
         bool wrap_scroll;
         char *separator_symbol;
diff --git a/include/swaybar/bar.h b/include/swaybar/bar.h
index 697a48c2..010e1f84 100644
--- a/include/swaybar/bar.h
+++ b/include/swaybar/bar.h
@@ -21,6 +21,9 @@ struct output {
         struct window *window;
         struct registry *registry;
         list_t *workspaces;
+#ifdef ENABLE_TRAY
+        list_t *items;
+#endif
         char *name;
         int idx;
         bool focused;
@@ -37,6 +40,9 @@ struct workspace {
 /** Global bar state */
 extern struct bar swaybar;
 
+/** True if sway needs to render */
+extern bool dirty;
+
 /**
  * Setup bar.
  */
diff --git a/include/swaybar/config.h b/include/swaybar/config.h
index 04b12cd4..651f0ee3 100644
--- a/include/swaybar/config.h
+++ b/include/swaybar/config.h
@@ -33,6 +33,17 @@ struct config {
         bool all_outputs;
         list_t *outputs;
 
+#ifdef ENABLE_TRAY
+        // Tray
+        char *tray_output;
+        char *icon_theme;
+
+        uint32_t tray_padding;
+        uint32_t activate_button;
+        uint32_t context_button;
+        uint32_t secondary_button;
+#endif
+
         int height;
 
         struct {
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 */
diff --git a/include/swaybar/tray/dbus.h b/include/swaybar/tray/dbus.h
new file mode 100644
index 00000000..eb9cfea7
--- /dev/null
+++ b/include/swaybar/tray/dbus.h
@@ -0,0 +1,18 @@
+#ifndef _SWAYBAR_DBUS_H
+#define _SWAYBAR_DBUS_H
+
+#include <stdbool.h>
+#include <dbus/dbus.h>
+extern DBusConnection *conn;
+
+/**
+ * Should be called in main loop to dispatch events
+ */
+void dispatch_dbus();
+
+/**
+ * Initializes async dbus communication
+ */
+int dbus_init();
+
+#endif /* _SWAYBAR_DBUS_H */
diff --git a/include/swaybar/tray/icon.h b/include/swaybar/tray/icon.h
new file mode 100644
index 00000000..1cc6ff9c
--- /dev/null
+++ b/include/swaybar/tray/icon.h
@@ -0,0 +1,16 @@
+#ifndef _SWAYBAR_ICON_H
+#define _SWAYBAR_ICON_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <client/cairo.h>
+
+/**
+ * Returns the image found by `name` that is closest to `size`
+ */
+cairo_surface_t *find_icon(const char *name, int size);
+
+/* Struct used internally only */
+struct subdir;
+
+#endif /* _SWAYBAR_ICON_H */
diff --git a/include/swaybar/tray/sni.h b/include/swaybar/tray/sni.h
new file mode 100644
index 00000000..83809b2d
--- /dev/null
+++ b/include/swaybar/tray/sni.h
@@ -0,0 +1,81 @@
+#ifndef _SWAYBAR_SNI_H
+#define _SWAYBAR_SNI_H
+
+#include <stdbool.h>
+#include <client/cairo.h>
+
+struct StatusNotifierItem {
+        /* Name registered to sni watcher */
+        char *name;
+        /* Unique bus name, needed for determining signal origins */
+        char *unique_name;
+        bool kde_special_snowflake;
+
+        cairo_surface_t *image;
+        bool dirty;
+};
+
+/* Each output holds an sni_icon_ref of each item to render */
+struct sni_icon_ref {
+        cairo_surface_t *icon;
+        struct StatusNotifierItem *ref;
+};
+
+struct sni_icon_ref *sni_icon_ref_create(struct StatusNotifierItem *item,
+                int height);
+
+void sni_icon_ref_free(struct sni_icon_ref *sni_ref);
+
+/**
+ * Will return a new item and get its icon. (see warning below)
+ */
+struct StatusNotifierItem *sni_create(const char *name);
+
+/**
+ * `item` must be a struct StatusNotifierItem *
+ * `str` must be a NUL terminated char *
+ *
+ * Returns 0 if `item` has a name of `str`
+ */
+int sni_str_cmp(const void *item, const void *str);
+
+/**
+ * Returns 0 if `item` has a unique name of `str` or if
+ * `item->unique_name == NULL`
+ */
+int sni_uniq_cmp(const void *item, const void *str);
+
+/**
+ * Gets an icon for the given item if found.
+ *
+ * XXX
+ * This function keeps a reference to the item until it gets responses, make
+ * sure that the reference and item are valid during this time.
+ */
+void get_icon(struct StatusNotifierItem *item);
+
+/**
+ * Calls the "activate" method on the given StatusNotifierItem
+ *
+ * x and y should be where the item was clicked
+ */
+void sni_activate(struct StatusNotifierItem *item, uint32_t x, uint32_t y);
+
+/**
+ * Asks the item to draw a context menu at the given x and y coords
+ */
+void sni_context_menu(struct StatusNotifierItem *item, uint32_t x, uint32_t y);
+
+/**
+ * Calls the "secondary activate" method on the given StatusNotifierItem
+ *
+ * x and y should be where the item was clicked
+ */
+void sni_secondary(struct StatusNotifierItem *item, uint32_t x, uint32_t y);
+
+/**
+ * Deconstructs `item`
+ */
+void sni_free(struct StatusNotifierItem *item);
+
+#endif /* _SWAYBAR_SNI_H */
diff --git a/include/swaybar/tray/sni_watcher.h b/include/swaybar/tray/sni_watcher.h
new file mode 100644
index 00000000..25ddfcd2
--- /dev/null
+++ b/include/swaybar/tray/sni_watcher.h
@@ -0,0 +1,10 @@
+#ifndef _SWAYBAR_SNI_WATCHER_H
+#define _SWAYBAR_SNI_WATCHER_H
+
+/**
+ * Starts the sni_watcher, the watcher is practically a black box and should
+ * only be accessed though functions described in its spec
+ */
+int init_sni_watcher();
+
+#endif /* _SWAYBAR_SNI_WATCHER_H */
diff --git a/include/swaybar/tray/tray.h b/include/swaybar/tray/tray.h
new file mode 100644
index 00000000..7d371008
--- /dev/null
+++ b/include/swaybar/tray/tray.h
@@ -0,0 +1,26 @@
+#ifndef _SWAYBAR_TRAY_H
+#define _SWAYBAR_TRAY_H
+
+#include <stdint.h>
+#include <stdbool.h>
+#include "swaybar/tray/dbus.h"
+#include "swaybar/tray/sni.h"
+#include "list.h"
+
+extern struct tray *tray;
+
+struct tray {
+        list_t *items;
+};
+
+/**
+ * Initializes the tray host with D-Bus
+ */
+int init_tray();
+
+/**
+ * Returns an item if `x` and `y` collide with it and NULL otherwise
+ */
+struct StatusNotifierItem *collides_with_sni(int x, int y);
+
+#endif /* _SWAYBAR_TRAY_H */