Events

When Game::tick() is called, cerlib polls events that occur in the system and stores them in a queue. This queue is emptied automatically at the beginning of every game tick.

An event is defined as a type switch (std::variant) of concrete event types:

using Event = Variant<WindowShownEvent,
                      WindowHiddenEvent,
                      ...>;

You can handle events using the Game::handleEvents() method:

while (game.tick()) {    
    game.handleEvents(
        [](KeyPressEvent e) {
          logInfo("Key {} was pressed, with modifiers {}.",
                  e.key, e.modifiers);
        },
        [](KeyReleaseEvent e) {
          logInfo("Key {} was released, with modifiers {}.",
                  e.key, e.modifiers);
        },
        cerIgnoreEvent,
    );
}

The cerIgnoreEvent identifier is required in order to ignore all other event types. It’s implemented as a convenience macro that just represents a [](auto){} lambda, which is a closure that accepts any remaining type and discards it.

Iterate events manually#

If you have special requirements for event processing, you can iterate the game’s event queue manually. The Game::events() method returns a span of all currently queued events.

while (game.tick()) {
    auto events = game.events(); // : Span<Event>
    
    for (const auto& event : events()) {
        std::visit(util::VariantSwitch{
            [](KeyPressEvent e) {
              logInfo("Key {} was pressed, with modifiers {}.",
                      e.key, e.modifiers);
            },
            [](KeyReleaseEvent e) {
              logInfo("Key {} was released, with modifiers {}.",
                      e.key, e.modifiers);
            },
            cerIgnoreEvent,
        },
        event);
    }
}