WIP: implement battery status querying on GNU/Linux

This code is supposed to work in theory, but in practice (at least on my
PC) it fails with this error message:

The name org.freedesktop.UPower was not provided by any .service files

I'll need to investigate later on why it's happening.

src/CMakeLists.txt

@@ -279,7 +279,7 @@ endif(APPLE)
 if(LIBDBUS_FOUND)
 	set(libwesnoth-game_STAT_SRC
 		${libwesnoth-game_STAT_SRC}
-		desktop/dbus_notification.cpp
+		desktop/dbus_features.cpp
 	)
 endif(LIBDBUS_FOUND)
 

src/SConscript

@@ -95,7 +95,7 @@ if env["PLATFORM"] == 'darwin':
     wesnoth_client_sources.append("desktop/apple_version.mm")
 
 if env["notifications"]:
-    wesnoth_client_sources.append("desktop/dbus_notification.cpp")
+    wesnoth_client_sources.append("desktop/dbus_features.cpp")
 
 libwesnoth_client = client_env.Library("wesnoth-client", wesnoth_client_sources)
 

src/desktop/battery_info.cpp

@@ -22,6 +22,10 @@
 #include "apple_battery_info.hpp"
 #endif
 
+#ifdef HAVE_LIBDBUS
+#include "desktop/dbus_features.hpp"
+#endif
+
 namespace desktop {
 namespace battery_info {
 
@@ -31,6 +35,8 @@ bool does_device_have_battery()
 	return windows_battery_info::does_device_have_battery();
 #elif defined(__APPLE__)
 	return desktop::battery_info::apple::does_device_have_battery();
+#elif defined(HAVE_LIBDBUS)
+	return dbus::does_device_have_battery();
 #else
 	return false;
 #endif
@@ -42,6 +48,8 @@ double get_battery_percentage()
 	return windows_battery_info::get_battery_percentage();
 #elif defined(__APPLE__)
 	return desktop::battery_info::apple::get_battery_percentage();
+#elif defined(HAVE_LIBDBUS)
+	return dbus::get_battery_percentage();
 #else
 	return -1;
 #endif

src/desktop/dbus_notification.cpp → src/desktop/dbus_features.cpp

@@ -12,14 +12,14 @@
    See the COPYING file for more details.
 */
 
-#include "desktop/dbus_notification.hpp"
+#include "desktop/dbus_features.hpp"
 
 #include "filesystem.hpp"
 #include "game_config.hpp"
 #include "log.hpp"
 
 #ifndef HAVE_LIBDBUS
-#error "The HAVE_LIBDBUS symbol is not defined, you do not have lib dbus available, you should not be trying to compile dbus_notification.cpp"
+#error "The HAVE_LIBDBUS symbol is not defined, you do not have lib dbus available, you should not be trying to compile dbus_features.cpp"
 #endif
 
 #include <dbus/dbus.h>
@@ -28,6 +28,8 @@
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/member.hpp>
 #include <cstdlib>
+#include <functional>
+#include <memory>
 #include <string>
 
 #pragma GCC diagnostic ignored "-Wold-style-cast"
@@ -196,6 +198,45 @@ uint32_t send_dbus_notification(DBusConnection *connection, uint32_t replaces_id
 	return id;
 }
 
+template<typename T>
+T get_power_source_property(const std::string &name, int type, T fallback)
+{
+	DBusConnection *connection = get_dbus_connection();
+	if (!connection) return fallback;
+
+	std::unique_ptr<DBusMessage, std::function<void(DBusMessage*)>> msg(dbus_message_new_method_call(
+			"org.freedesktop.UPower",
+			"/org/freedesktop/UPower/devices/DisplayDevice",
+			"org.freedesktop.DBus.Properties",
+			"Get"),
+		dbus_message_unref);
+
+	const char *interface_name = "org.freedesktop.UPower.Device";
+	const char *property_name = name.data();
+	dbus_message_append_args(msg.get(),
+		DBUS_TYPE_STRING, &interface_name,
+		DBUS_TYPE_STRING, &property_name,
+		DBUS_TYPE_INVALID);
+
+	DBusError err;
+	dbus_error_init(&err);
+
+	std::unique_ptr<DBusMessage, std::function<void(DBusMessage*)>> ret(dbus_connection_send_with_reply_and_block(
+		connection, msg.get(), 1000, &err), dbus_message_unref);
+	if (ret == nullptr) {
+		DBG_DU << "Failed to query power source properties: " << err.message << '\n';
+		dbus_error_free(&err);
+		return fallback;
+	}
+
+	T value;
+	dbus_message_get_args(ret.get(), nullptr,
+		type, &value,
+		DBUS_TYPE_INVALID);
+
+	return value;
+}
+
 } // end anonymous namespace
 
 namespace dbus {
@@ -243,4 +284,14 @@ void send_notification(const std::string & owner, const std::string & message, b
 	}
 }
 
+bool does_device_have_battery()
+{
+	return get_power_source_property<uint32_t>("Type", DBUS_TYPE_UINT32, 0) == 2;
+}
+
+double get_battery_percentage()
+{
+	return get_power_source_property<double>("Percentage", DBUS_TYPE_DOUBLE, 0.0);
+}
+
 } // end namespace dbus

src/desktop/dbus_notification.hpp → src/desktop/dbus_features.hpp

@@ -18,4 +18,6 @@
 
 namespace dbus {
 	void send_notification(const std::string& owner, const std::string& message, bool with_history);
+	bool does_device_have_battery();
+	double get_battery_percentage();
 }

src/desktop/notifications.cpp

@@ -20,7 +20,7 @@
 #include "video.hpp" //CVideo::get_singleton().window_state()
 
 #ifdef HAVE_LIBDBUS
-#include "desktop/dbus_notification.hpp"
+#include "desktop/dbus_features.hpp"
 #endif
 
 #ifdef __APPLE__