# Objective
We are currently inserting an `input` into `pressed` even if it is already pressed. This also applies to releasing an input. This is not a big deal, but since we are already checking if the `input` is pressed or not we might as well remove the cost of the value update caused by the `pressed.insert` method.
Related to #4209
## Solution
Only insert or remove input if needed.
# Objective
- Fixes#4208
## Solution
- Adds a check before inserting into an `Input`'s `just_released` set, in the same way that one exists for adding into the `just_pressed` set.
For some keys, it is too expensive to hash them on every lookup. Historically in Bevy, we have regrettably done the "wrong" thing in these cases (pre-computing hashes, then re-hashing them) because Rust's built in hashed collections don't give us the tools we need to do otherwise. Doing this is "wrong" because two different values can result in the same hash. Hashed collections generally get around this by falling back to equality checks on hash collisions. You can't do that if the key _is_ the hash. Additionally, re-hashing a hash increase the odds of collision!
#3959 needs pre-hashing to be viable, so I decided to finally properly solve the problem. The solution involves two different changes:
1. A new generalized "pre-hashing" solution in bevy_utils: `Hashed<T>` types, which store a value alongside a pre-computed hash. And `PreHashMap<K, V>` (which uses `Hashed<T>` internally) . `PreHashMap` is just an alias for a normal HashMap that uses `Hashed<T>` as the key and a new `PassHash` implementation as the Hasher.
2. Replacing the `std::collections` re-exports in `bevy_utils` with equivalent `hashbrown` impls. Avoiding re-hashes requires the `raw_entry_mut` api, which isn't stabilized yet (and may never be ... `entry_ref` has favor now, but also isn't available yet). If std's HashMap ever provides the tools we need, we can move back to that. The latest version of `hashbrown` adds support for the `entity_ref` api, so we can move to that in preparation for an std migration, if thats the direction they seem to be going in. Note that adding hashbrown doesn't increase our dependency count because it was already in our tree.
In addition to providing these core tools, I also ported the "table identity hashing" in `bevy_ecs` to `raw_entry_mut`, which was a particularly egregious case.
The biggest outstanding case is `AssetPathId`, which stores a pre-hash. We need AssetPathId to be cheaply clone-able (and ideally Copy), but `Hashed<AssetPath>` requires ownership of the AssetPath, which makes cloning ids way more expensive. We could consider doing `Hashed<Arc<AssetPath>>`, but cloning an arc is still a non-trivial expensive that needs to be considered. I would like to handle this in a separate PR. And given that we will be re-evaluating the Bevy Assets implementation in the very near future, I'd prefer to hold off until after that conversation is concluded.
# Objective
- As part of exploring input event suppression in bevy_egui here: 53c1773583
- I found that the only way to suppress events properly, is to allow to clone the relevant Input<Whatever>, and update with events manually from within the system. This cloned Input then is discarded, the Events<*> structs are cleared, and bevy_input's normal update of Input proceeds, without the events that have been suppressed.
## Solution
- This enables Input to be cloned, allowing it to be manually updated with events.
# Objective
Make it easier to check if some set of inputs matches a key, such as if you want to allow all of space or up or w for jumping.
Currently, this requires:
```rust
if keyboard.pressed(KeyCode::Space)
|| keyboard.pressed(KeyCode::Up)
|| keyboard.pressed(KeyCode::W) {
// ...
```
## Solution
Add an implementation of the helper methods, which very simply iterate through the items, used as:
```rust
if keyboard.any_pressed([KeyCode::Space, KeyCode::Up, KeyCode::W]) {
```
fix a few dead links
* Links in `Input` missed a refactor
* `Reflect::downcast` can't use the intra doc link format, as it's not a link to a trait function, but to a function implemented on `dyn Reflect`
noticed in https://github.com/bevyengine/bevy/pull/1781#discussion_r619777879
related to #1700
This PR:
* documents all methods on `Input<T>`
* adds documentation on the struct about how to use it, and how to implement it for a new input type
* renames method `update` to a easier to understand `clear`
* adds two methods to check for state and clear it after, allowing easier use in the case of #1700
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
