# Objective
Correctly order picking events. Resolves
https://github.com/bevyengine/bevy/issues/5984.
## Solution
Event ordering [very long standing
problem](https://github.com/aevyrie/bevy_mod_picking/issues/294) with
mod picking, stemming from two related issues. The first problem was
that `Pointer<T>` events of different types couldn't be ordered, but we
have already gotten around that in the upstream by switching to
observers. Since observers run in the order they are triggered, this
isn't an issue.
The second problem was that the underlying event streams that picking
uses to create it's pointer interaction events *also* lacked ordering,
and the systems that generated the points couldn't interleave events.
This PR fixes that by unifying the event streams and integrating the
various interaction systems.
The concrete changes are as follows:
+ `bevy_winit::WinitEvent` has been moved to `bevy_window::WindowEvent`.
This provides a unified (and more importantly, *ordered*) input stream
for both `bevy_window` and `bevy_input` events.
+ Replaces `InputMove` and `InputPress` with `PointerInput`, a new
unified input event which drives picking and interaction. This event is
built to have drop-in forward compatibility with [winit's upcoming
pointer abstraction](https://github.com/rust-windowing/winit/pull/3876).
I have added code to emulate it using the current winit input
abstractions, but this entire thing will be much more robust when it
lands.
+ Rolls `pointer_events` `send_click_and_drag_events` and
`send_drag_over_events` into a single system, which operates directly on
`PointerEvent` and triggers observers as output.
The PR also improves docs and takes the opportunity to
refactor/streamline the pointer event dispatch logic.
## Status & Testing
This PR is now feature complete and documented. While it is
theoretically possible to add unit tests for the ordering, building the
picking mocking for that will take a little while.
Feedback on the chosen ordering of events is within-scope.
## Migration Guide
For users switching from `bevy_mod_picking` to `bevy_picking`:
+ Instead of adding an `On<T>` component, use `.observe(|trigger:
Trigger<T>|)`. You may now apply multiple handlers to the same entity
using this command.
+ Pointer interaction events now have semi-deterministic ordering which
(more or less) aligns with the order of the raw input stream. Consult
the docs on `bevy_picking::event::pointer_events` for current
information. You may need to adjust your event handling logic
accordingly.
+ `PointerCancel` has been replaced with `Pointer<Cancled>`, which now
has the semantics of an OS touch pointer cancel event.
+ `InputMove` and `InputPress` have been merged into `PointerInput`. The
use remains exactly the same.
+ Picking interaction events are now only accessible through observers,
and no `EventReader`. This functionality may be re-implemented later.
For users of `bevy_winit`:
+ The event `bevy_winit::WinitEvent` has moved to
`bevy_window::WindowEvent`. If this was the only thing you depended on
`bevy_winit` for, you should switch your dependency to `bevy_window`.
+ `bevy_window` now depends on `bevy_input`. The dependencies of
`bevy_input` are a subset of the existing dependencies for `bevy_window`
so this should be non-breaking.
# Objective
This is the first of a series of PRs intended to begin the upstreaming
process for `bevy_mod_picking`. The purpose of this PR is to:
+ Create the new `bevy_picking` crate
+ Upstream `CorePlugin` as `PickingPlugin`
+ Upstream the core pointer and backend abstractions.
This code has been ported verbatim from the corresponding files in
[bevy_picking_core](https://github.com/aevyrie/bevy_mod_picking/tree/main/crates/bevy_picking_core/src)
with a few tiny naming and docs tweaks.
The work here is only an initial foothold to get the up-streaming
process started in earnest. We can do refactoring and improvements once
this is in-tree.
---------
Co-authored-by: Aevyrie <aevyrie@gmail.com>
Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
