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Avoid unnecessary change detection resulting from component lens #91

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bonsairobo opened this issue Jun 30, 2023 · 3 comments · Fixed by #124
Closed

Avoid unnecessary change detection resulting from component lens #91

bonsairobo opened this issue Jun 30, 2023 · 3 comments · Fixed by #124
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enhancement New feature or request

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@bonsairobo
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bonsairobo commented Jun 30, 2023 •
edited

Right now the Lens trait's lerp method takes &mut T for T: Component, but it should only need Mut<T>.

The system invokes DerefMut so we have no chance to avoid change detection in a custom lens:

bevy_tweening/src/plugin.rs

Line 87 in 3c6b10e

&mut target,

Specifically, I have a custom lens that acts like a discrete switch that changes from one value to another at a specific ratio. This would only require a single DerefMut, but in fact it happens every frame that the Animator is running.
@bonsairobo
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bonsairobo commented Jun 30, 2023 •
edited

A workaround is to create a proxy component that acts continuously (by syncing with the ratio) and then have a separate system to do the discrete switch.

@djeedai djeedai added the enhancement New feature or request label Oct 28, 2023
djeedai added a commit that referenced this issue Apr 26, 2024
@djeedai
Enable lenses to avoid change detection
55517af 
Add the ability for all `Lens`es to avoid triggering change detection if
they don't make any actual change to their target (component or asset).

This change modifies the signature of `Lerp::lerp()` to take `&mut dyn
Targetable<T>` instead of `&mut T`. The `Targetable<T>` acts as a
`Mut<T>`, marking the target as changed only if actually dereferenced
mutably.

Note that we cannot use `Mut<T>` directly because we can't obtain a
`Mut<A: Asset>` without marking the asset as mutable; see
bevyengine/bevy#13104.

Fixes #91
@djeedai djeedai mentioned this issue Apr 26, 2024
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@djeedai
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djeedai commented Apr 26, 2024

@bonsairobo better late than never ;) this should work now, by mean of Targetable<T> which is really the same as Mut<T>, being passed to Lens::lerp().

@bonsairobo
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@djeedai Thanks! I'll give it a try when I jump back into my project.

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Enable lenses to avoid change detection djeedai/bevy_tweening
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@bonsairobo @djeedai