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

sway/commands/bar/activate_button.c

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include "sway/commands.h"
+#include "log.h"
+
+struct cmd_results *bar_cmd_activate_button(int argc, char **argv) {
+	const char *cmd_name = "activate_button";
+#ifndef ENABLE_TRAY
+	return cmd_results_new(CMD_INVALID, cmd_name, "Invalid %s command "
+			"%s called, but sway was compiled without tray support",
+			cmd_name, cmd_name);
+#else
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, cmd_name, EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+
+	if (!config->current_bar) {
+		return cmd_results_new(CMD_FAILURE, cmd_name, "No bar defined.");
+	}
+
+	// User should be able to prefix with 0x or whatever they want
+	config->current_bar->secondary_button = strtoul(argv[0], NULL, 0);
+
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+#endif
+}

sway/commands/bar/context_button.c

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include "sway/commands.h"
+#include "log.h"
+
+struct cmd_results *bar_cmd_context_button(int argc, char **argv) {
+	const char *cmd_name = "context_button";
+#ifndef ENABLE_TRAY
+	return cmd_results_new(CMD_INVALID, cmd_name, "Invalid %s command "
+			"%s called, but sway was compiled without tray support",
+			cmd_name, cmd_name);
+#else
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, cmd_name, EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+
+	if (!config->current_bar) {
+		return cmd_results_new(CMD_FAILURE, cmd_name, "No bar defined.");
+	}
+
+	// User should be able to prefix with 0x or whatever they want
+	config->current_bar->context_button = strtoul(argv[0], NULL, 0);
+
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+#endif
+}

sway/commands/bar/icon_theme.c

@@ -0,0 +1,25 @@
+#define _XOPEN_SOURCE 500
+#include <string.h>
+#include "sway/commands.h"
+
+struct cmd_results *bar_cmd_icon_theme(int argc, char **argv) {
+	const char *cmd_name = "tray_output";
+#ifndef ENABLE_TRAY
+	return cmd_results_new(CMD_INVALID, cmd_name, "Invalid %s command "
+			"%s called, but sway was compiled without tray support",
+			cmd_name, cmd_name);
+#else
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, cmd_name, EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+
+	if (!config->current_bar) {
+		return cmd_results_new(CMD_FAILURE, cmd_name, "No bar defined.");
+	}
+
+	config->current_bar->icon_theme = strdup(argv[0]);
+
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+#endif
+}

sway/commands/bar/secondary_button.c

@@ -0,0 +1,26 @@
+#include <stdlib.h>
+#include "sway/commands.h"
+#include "log.h"
+
+struct cmd_results *bar_cmd_secondary_button(int argc, char **argv) {
+	const char *cmd_name = "secondary_button";
+#ifndef ENABLE_TRAY
+	return cmd_results_new(CMD_INVALID, cmd_name, "Invalid %s command "
+			"%s called, but sway was compiled without tray support",
+			cmd_name, cmd_name);
+#else
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, cmd_name, EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+
+	if (!config->current_bar) {
+		return cmd_results_new(CMD_FAILURE, cmd_name, "No bar defined.");
+	}
+
+	// User should be able to prefix with 0x or whatever they want
+	config->current_bar->secondary_button = strtoul(argv[0], NULL, 0);
+
+	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+#endif
+}

sway/commands/bar/tray_output.c

@@ -1,7 +1,29 @@
+#define _XOPEN_SOURCE 500
+#include <string.h>
 #include "sway/commands.h"
-#include "log.h"
 
 struct cmd_results *bar_cmd_tray_output(int argc, char **argv) {
-	sway_log(L_ERROR, "Warning: tray_output is not supported on wayland");
+	const char *cmd_name = "tray_output";
+#ifndef ENABLE_TRAY
+	return cmd_results_new(CMD_INVALID, cmd_name, "Invalid %s command "
+			"%s called, but sway was compiled without tray support",
+			cmd_name, cmd_name);
+#else
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, cmd_name, EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+
+	if (!config->current_bar) {
+		return cmd_results_new(CMD_FAILURE, cmd_name, "No bar defined.");
+	}
+
+	if (strcmp(argv[0], "all") == 0) {
+		// Default behaviour
+		return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+	}
+	config->current_bar->tray_output = strdup(argv[0]);
+
 	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+#endif
 }

sway/commands/bar/tray_padding.c

@@ -1,30 +1,34 @@
 #include <stdlib.h>
-#include <string.h>
 #include <strings.h>
 #include "sway/commands.h"
 #include "log.h"
 
 struct cmd_results *bar_cmd_tray_padding(int argc, char **argv) {
+	const char *cmd_name = "tray_padding";
+#ifndef ENABLE_TRAY
+	return cmd_results_new(CMD_INVALID, cmd_name, "Invalid %s command"
+			"%s called, but sway was compiled without tray support",
+			cmd_name, cmd_name);
+#else
 	struct cmd_results *error = NULL;
-	if ((error = checkarg(argc, "tray_padding", EXPECTED_AT_LEAST, 1))) {
+	if ((error = checkarg(argc, cmd_name, EXPECTED_AT_LEAST, 1))) {
 		return error;
 	}
 
 	if (!config->current_bar) {
-		return cmd_results_new(CMD_FAILURE, "tray_padding", "No bar defined.");
+		return cmd_results_new(CMD_FAILURE, cmd_name, "No bar defined.");
 	}
 
-	int padding = atoi(argv[0]);
-	if (padding < 0) {
-		return cmd_results_new(CMD_INVALID, "tray_padding",
-				"Invalid padding value %s, minimum is 0", argv[0]);
+	if (argc == 1 || (argc == 2 && strcasecmp("px", argv[1]) == 0)) {
+		char *inv;
+		uint32_t padding = strtoul(argv[0], &inv, 10);
+		if (*inv == '\0' || strcasecmp(inv, "px") == 0) {
+			config->current_bar->tray_padding = padding;
+			sway_log(L_DEBUG, "Enabling tray padding of %d px on bar: %s", padding, config->current_bar->id);
+			return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+		}
 	}
-
-	if (argc > 1 && strcasecmp("px", argv[1]) != 0) {
-		return cmd_results_new(CMD_INVALID, "tray_padding",
-				"Unknown unit %s", argv[1]);
-	}
-	config->current_bar->tray_padding = padding;
-	sway_log(L_DEBUG, "Enabling tray padding of %d px on bar: %s", padding, config->current_bar->id);
-	return cmd_results_new(CMD_SUCCESS, NULL, NULL);
+	return cmd_results_new(CMD_FAILURE, cmd_name,
+		"Expected 'tray_padding <padding>[px]'");
+#endif
 }