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implement persistence for child bodies during reset #1251

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implement persistence for child bodies during reset #1251

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029efe2
implement persistence for child bodies during reset
Vareniel Mar 3, 2026
1332ceb
unecessary return
Vareniel Mar 3, 2026
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15 changes: 15 additions & 0 deletions packages/melonjs/src/physics/world.js
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Original file line number Diff line number Diff line change
Expand Up @@ -125,9 +125,24 @@ export default class World extends Container {
// call the parent method
super.reset();

// save persistent child bodies
const persistentBodies = [];
this.bodies.forEach((value) => {
if (value.ancestor && value.ancestor.isPersistent) {
Comment on lines +128 to +131
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Copilot AI Mar 3, 2026

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The persistence filter only keeps bodies whose owning renderable is marked isPersistent. Bodies belonging to non-persistent renderables inside a persistent container will still remain in the scene after super.reset(), but will be dropped from this.bodies by the subsequent clear() and never re-added, causing those objects to stop being stepped/collided. Consider retaining any body whose body.ancestor is still attached to this world after super.reset() (e.g., via the renderable’s container chain/root ancestor), or rebuilding this.bodies from the post-reset scene graph instead of checking only isPersistent on the body ancestor.

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// save persistent child bodies
const persistentBodies = [];
this.bodies.forEach((value) => {
if (value.ancestor && value.ancestor.isPersistent) {
// save bodies whose owning renderable is still attached to this world
const persistentBodies = [];
this.bodies.forEach((value) => {
const owner = value.ancestor;
if (!owner) {
return;
}
// Walk up the container chain to check if the owner is still under this world
let current = owner;
while (current && current !== this && current.ancestor) {
current = current.ancestor;
}
if (current === this) {

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persistentBodies.push(value);
}
});

// empty the list of active physic bodies
// Note: this should be empty already when calling the parent method
this.bodies.clear();

// insert persistent child bodies into the new state
if (persistentBodies.length > 0) {
persistentBodies.forEach((body) => {
this.bodies.add(body);
});
}
Comment on lines +128 to +145
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Copilot AI Mar 3, 2026

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This introduces/changes behavior around which bodies survive World.reset(), but there doesn’t appear to be coverage for world reset + persistence in the current test suite. Adding a unit test that exercises a persistent container (with non-persistent children that have bodies) and/or a persistent renderable with a body would help prevent regressions.

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}

/**
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