gKeyMapper/src/daemonclient.cpp

// gKeyMapper - talk to gkeymapper-daemon over the session bus.

#include "daemonclient.h"

#include <cstdio>

#include "ipc_ids.h"

namespace gkeymapper {

namespace {

// The daemon answers within one loop iteration, but it may have to be started
// first (D-Bus activation), so allow for a slow first reply.
constexpr int kCallTimeoutMs = 5000;

constexpr const char* kDBusName = "org.freedesktop.DBus";
constexpr const char* kDBusPath = "/org/freedesktop/DBus";

} // namespace

DaemonClient::~DaemonClient() {
    if (connection_ == nullptr) {
        return;
    }
    if (signal_subscription_ != 0) {
        g_dbus_connection_signal_unsubscribe(connection_, signal_subscription_);
    }
    if (name_subscription_ != 0) {
        g_dbus_connection_signal_unsubscribe(connection_, name_subscription_);
    }
    g_object_unref(connection_);
}

void DaemonClient::init(StatusFn onStatus, KeyFn onKey) {
    onStatus_ = std::move(onStatus);
    onKey_ = std::move(onKey);
    if (started_) {
        return; // a second activation reuses the existing connection
    }
    started_ = true;
    g_bus_get(G_BUS_TYPE_SESSION, nullptr, &DaemonClient::on_bus_ready, this);
}

void DaemonClient::on_bus_ready(GObject* /*source*/, GAsyncResult* result, gpointer userData) {
    auto* self = static_cast<DaemonClient*>(userData);

    GError* error = nullptr;
    GDBusConnection* connection = g_bus_get_finish(result, &error);
    if (connection == nullptr) {
        // No session bus: the GUI still edits and saves the file, it just
        // cannot show the daemon state.
        std::fprintf(stderr, "gkeymapper: no session bus: %s\n",
                     error != nullptr ? error->message : "unknown error");
        g_clear_error(&error);
        self->report_unreachable();
        return;
    }

    self->connection_ = connection;
    self->watch_signals();
    self->fetch_status();
}

void DaemonClient::watch_signals() {
    signal_subscription_ = g_dbus_connection_signal_subscribe(
        connection_, ipc::kBusName, ipc::kInterface, nullptr, ipc::kObjectPath, nullptr,
        G_DBUS_SIGNAL_FLAGS_NONE, &DaemonClient::on_daemon_signal, this, nullptr);

    // Lets the footer follow the daemon: it flips to "not reachable" when it
    // stops and back when it (or D-Bus activation) starts it again.
    name_subscription_ = g_dbus_connection_signal_subscribe(
        connection_, kDBusName, kDBusName, "NameOwnerChanged", kDBusPath, ipc::kBusName,
        G_DBUS_SIGNAL_FLAGS_NONE, &DaemonClient::on_name_owner_changed, this, nullptr);
}

void DaemonClient::on_daemon_signal(GDBusConnection* /*connection*/, const gchar* /*sender*/,
                                    const gchar* /*objectPath*/, const gchar* /*interfaceName*/,
                                    const gchar* signalName, GVariant* parameters,
                                    gpointer userData) {
    auto* self = static_cast<DaemonClient*>(userData);

    if (g_strcmp0(signalName, "KeyPressed") == 0) {
        guint32 index = 0;
        const gchar* action = nullptr;
        g_variant_get(parameters, "(u&s)", &index, &action);
        if (self->onKey_) {
            self->onKey_(static_cast<int>(index), action != nullptr ? action : "");
        }
        return;
    }

    // ConfigReloaded and DeviceChanged carry no state the footer does not
    // already get from GetStatus, so just refresh it.
    self->fetch_status();
}

void DaemonClient::on_name_owner_changed(GDBusConnection* /*connection*/, const gchar* /*sender*/,
                                         const gchar* /*objectPath*/,
                                         const gchar* /*interfaceName*/,
                                         const gchar* /*signalName*/, GVariant* parameters,
                                         gpointer userData) {
    auto* self = static_cast<DaemonClient*>(userData);

    const gchar* name = nullptr;
    const gchar* oldOwner = nullptr;
    const gchar* newOwner = nullptr;
    g_variant_get(parameters, "(&s&s&s)", &name, &oldOwner, &newOwner);

    if (newOwner == nullptr || *newOwner == '\0') {
        self->report_unreachable();
    } else {
        self->fetch_status();
    }
}

void DaemonClient::fetch_status() {
    if (connection_ == nullptr) {
        return;
    }
    // A call to a name without an owner makes the bus activate the service, so
    // this also brings the daemon up on demand.
    g_dbus_connection_call(connection_, ipc::kBusName, ipc::kObjectPath, ipc::kInterface,
                           "GetStatus", nullptr, G_VARIANT_TYPE("(sbss)"),
                           G_DBUS_CALL_FLAGS_NONE, kCallTimeoutMs, nullptr,
                           &DaemonClient::on_status_reply, this);
}

void DaemonClient::on_status_reply(GObject* /*source*/, GAsyncResult* result, gpointer userData) {
    auto* self = static_cast<DaemonClient*>(userData);

    GError* error = nullptr;
    GVariant* reply = g_dbus_connection_call_finish(self->connection_, result, &error);
    if (reply == nullptr) {
        // Normal when the daemon is not installed or not running.
        g_clear_error(&error);
        self->report_unreachable();
        return;
    }

    const gchar* version = nullptr;
    const gchar* device = nullptr;
    const gchar* configPath = nullptr;
    gboolean running = FALSE;
    g_variant_get(reply, "(&sb&s&s)", &version, &running, &device, &configPath);
    g_variant_unref(reply);

    DaemonStatus status;
    status.reachable = true;
    status.version = version != nullptr ? version : "";
    status.device = device != nullptr ? device : "";
    status.configPath = configPath != nullptr ? configPath : "";
    self->publish(status);
}

void DaemonClient::reload() {
    if (connection_ == nullptr) {
        return;
    }
    g_dbus_connection_call(connection_, ipc::kBusName, ipc::kObjectPath, ipc::kInterface,
                           "Reload", nullptr, nullptr, G_DBUS_CALL_FLAGS_NONE, kCallTimeoutMs,
                           nullptr, &DaemonClient::on_reload_reply, this);
}

void DaemonClient::on_reload_reply(GObject* /*source*/, GAsyncResult* result, gpointer userData) {
    auto* self = static_cast<DaemonClient*>(userData);

    GError* error = nullptr;
    GVariant* reply = g_dbus_connection_call_finish(self->connection_, result, &error);
    if (reply != nullptr) {
        g_variant_unref(reply);
    }
    if (error != nullptr) {
        // The file watch applies the save anyway, so a missing daemon is fine.
        g_clear_error(&error);
    }
}

void DaemonClient::report_unreachable() {
    DaemonStatus status;
    status.reachable = false;
    publish(status);
}

void DaemonClient::publish(const DaemonStatus& status) {
    if (onStatus_) {
        onStatus_(status);
    }
}

} // namespace gkeymapper