# Objective
sending events tends to be low-frequency so ergonomics can be
prioritized over efficiency.
add `Commands::send_event` to send any type of event without needing a
writer in hand.
i don't know how we feel about these kind of ergonomic things, i add
this to all my projects and find it useful. adding `mut
this_particular_event_writer: EventWriter<ThisParticularEvent>` every
time i want to send something is unnecessarily cumbersome.
it also simplifies the "send and receive in the same system" pattern
significantly.
basic example before:
```rs
fn my_func(
q: Query<(Entity, &State)>,
mut damage_event_writer: EventWriter<DamageEvent>,
mut heal_event_writer: EventWriter<HealEvent>,
) {
for (entity, state) in q.iter() {
if let Some(damage) = state.get_damage() {
damage_event_writer.send(DamageEvent { entity, damage });
}
if let Some(heal) = state.get_heal() {
heal_event_writer.send(HealEvent { entity, heal });
}
}
}
```
basic example after:
```rs
import bevy::ecs::event::SendEventEx;
fn my_func(
mut commands: Commands,
q: Query<(Entity, &State)>,
) {
for (entity, state) in q.iter() {
if let Some(damage) = state.get_damage() {
commands.send_event(DamageEvent { entity, damage });
}
if let Some(heal) = state.get_heal() {
commands.send_event(HealEvent { entity, heal });
}
}
}
```
send/receive in the same system before:
```rs
fn send_and_receive_param_set(
mut param_set: ParamSet<(EventReader<DebugEvent>, EventWriter<DebugEvent>)>,
) {
// We must collect the events to resend, because we can't access the writer while we're iterating over the reader.
let mut events_to_resend = Vec::new();
// This is p0, as the first parameter in the `ParamSet` is the reader.
for event in param_set.p0().read() {
if event.resend_from_param_set {
events_to_resend.push(event.clone());
}
}
// This is p1, as the second parameter in the `ParamSet` is the writer.
for mut event in events_to_resend {
event.times_sent += 1;
param_set.p1().send(event);
}
}
```
after:
```rs
use bevy::ecs::event::SendEventEx;
fn send_via_commands_and_receive(
mut reader: EventReader<DebugEvent>,
mut commands: Commands,
) {
for event in reader.read() {
if event.resend_via_commands {
commands.send_event(DebugEvent {
times_sent: event.times_sent + 1,
..event.clone()
});
}
}
}
```
---------
Co-authored-by: Jan Hohenheim <jan@hohenheim.ch>
# Objective
- Often in games you will want to create chains of systems that modify
some event. For example, a chain of damage systems that handle a
DamageEvent and modify the underlying value before the health system
finally consumes the event. Right now this requires either:
* Using a component added to the entity
* Consuming and refiring events
Neither is ideal when really all we want to do is read the events value,
modify it, and write it back.
## Solution
- Create an EventMutator class similar to EventReader but with ResMut<T>
and iterators that return &mut so that events can be mutated.
## Testing
- I replicated all the existing tests for EventReader to make sure
behavior was the same (I believe) and added a number of tests specific
to testing that 1) events can actually be mutated, and that 2)
EventReader sees changes from EventMutator for events it hasn't already
seen.
## Migration Guide
Users currently using `ManualEventReader` should use `EventCursor`
instead. `ManualEventReader` will be removed in Bevy 0.16. Additionally,
`Events::get_reader` has been replaced by `Events::get_cursor`.
Users currently directly accessing the `Events` resource for mutation
should move to `EventMutator` if possible.
---------
Co-authored-by: poopy <gonesbird@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
# Objective
Add ability to de-register events from the EventRegistry (and the
associated World).
The initial reasoning relates to retaining support for Event hot
reloading in `dexterous_developer`.
## Solution
Add a `deregister_events<T: Event>(&mut world)` method to the
`EventRegistry` struct.
## Testing
Added an automated test that verifies the event registry adds and
removes `Events<T>` from the world.
---------
Co-authored-by: BD103 <59022059+BD103@users.noreply.github.com>
# Objective
- Fix issue #13821
## Solution
- Rewrote the test to ensure that it actually tests the functionality
correctly. Then made the par_read function correctly change the values
of self.reader.last_event_count.
## Testing
- Rewrote the test for par_read to run the system schedule twice,
checking the output each time
---------
Co-authored-by: Martín Maita <47983254+mnmaita@users.noreply.github.com>
# Objective
As discovered in
https://github.com/Leafwing-Studios/leafwing-input-manager/issues/538,
there appears to be some real weirdness going on in how event updates
are processed between Bevy 0.13 and Bevy 0.14.
To identify the cause and prevent regression, I've added tests to
validate the intended behavior.
My initial suspicion was that this would be fixed by
https://github.com/bevyengine/bevy/pull/13762, but that doesn't seem to
be the case.
Instead, events appear to never be updated at all when using `bevy_app`
by itself. This is part of the problem resolved by
https://github.com/bevyengine/bevy/pull/11528, and introduced by
https://github.com/bevyengine/bevy/pull/10077.
After some investigation, it appears that `signal_event_update_system`
is never added using a bare-bones `App`, and so event updates are always
skipped.
This can be worked around by adding your own copy to a
later-in-the-frame schedule, but that's not a very good fix.
## Solution
Ensure that if we're not using a `FixedUpdate` schedule, events are
always updated every frame.
To do this, I've modified the logic of `event_update_condition` and
`event_update_system` to clearly and correctly differentiate between the
two cases: where we're waiting for a "you should update now" signal and
where we simply don't care.
To encode this, I've added the `ShouldUpdateEvents` enum, replacing a
simple `bool` in `EventRegistry`'s `needs_update` field.
Now, both tests pass as expected, without having to manually add a
system!
## Testing
I've written two parallel unit tests to cover the intended behavior:
1. Test that `iter_current_update_events` works as expected in
`bevy_ecs`.
2. Test that `iter_current_update_events` works as expected in
`bevy_app`
I've also added a test to verify that event updating works correctly in
the presence of a fixed main schedule, and a second test to verify that
fixed updating works at all to help future authors narrow down failures.
## Outstanding
- [x] figure out why the `bevy_app` version of this test fails but the
`bevy_ecs` version does not
- [x] figure out why `EventRegistry::run_updates` isn't working properly
- [x] figure out why `EventRegistry::run_updates` is never getting
called
- [x] figure out why `event_update_condition` is always returning false
- [x] figure out why `EventRegistry::needs_update` is always false
- [x] verify that the problem is a missing `signal_events_update_system`
---------
Co-authored-by: Mike <mike.hsu@gmail.com>
# Objective
- Split the bevy_ecs::events module so it's easier to work with
## Solution
- Split the event.rs file across multiple files, made sure all tests
passed, and exports from the module were the same as previous
## Testing
- All automated tests pass.
