io/ipchandler: add signal listener support

src/launch/command.cpp

@@ -411,6 +411,10 @@ int ipcCommand(CommandState& cmd) {
 			return qs::io::ipc::comm::queryMetadata(&client, *cmd.ipc.target, *cmd.ipc.name);
 		} else if (*cmd.ipc.getprop) {
 			return qs::io::ipc::comm::getProperty(&client, *cmd.ipc.target, *cmd.ipc.name);
+		} else if (*cmd.ipc.wait) {
+			return qs::io::ipc::comm::listenToSignal(&client, *cmd.ipc.target, *cmd.ipc.name, true);
+		} else if (*cmd.ipc.listen) {
+			return qs::io::ipc::comm::listenToSignal(&client, *cmd.ipc.target, *cmd.ipc.name, false);
 		} else {
 			QVector<QString> arguments;
 			for (auto& arg: cmd.ipc.arguments) {

src/launch/launch_p.hpp

@@ -74,6 +74,8 @@ struct CommandState {
 		CLI::App* show = nullptr;
 		CLI::App* call = nullptr;
 		CLI::App* getprop = nullptr;
+		CLI::App* wait = nullptr;
+		CLI::App* listen = nullptr;
 		bool showOld = false;
 		QStringOption target;
 		QStringOption name;

src/launch/parsecommand.cpp

@@ -1,6 +1,7 @@
 #include <cstddef>
 #include <limits>
 #include <memory>
+#include <utility>
 
 #include <CLI/App.hpp>
 #include <CLI/CLI.hpp> // NOLINT: Need to include this for impls of some CLI11 classes
@@ -226,6 +227,16 @@ int parseCommand(int argc, char** argv, CommandState& state) {
 			    ->allow_extra_args();
 		}
 
+		auto signalCmd = [&](std::string cmd, std::string desc) {
+			auto* scmd = sub->add_subcommand(std::move(cmd), std::move(desc));
+			scmd->add_option("target", state.ipc.target, "The target to listen on.");
+			scmd->add_option("signal", state.ipc.name, "The signal to listen for.");
+			return scmd;
+		};
+
+		state.ipc.wait = signalCmd("wait", "Wait for one IpcHandler signal.");
+		state.ipc.listen = signalCmd("listen", "Listen for IpcHandler signals.");
+
 		{
 			auto* prop =
 			    sub->add_subcommand("prop", "Manipulate IpcHandler properties.")->require_subcommand();