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perf: Skip lifecycle processing work when the queue is empty #3978

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spydon wants to merge 2 commits into from
+13 −4
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perf: Skip lifecycle processing work when the queue is empty #3978

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896be2f
perf: Skip lifecycle processing work when the queue is empty
spydon Aug 5, 2026
08b3910
refactor: Address review feedback on the empty-queue early-out
spydon Aug 5, 2026
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17 changes: 13 additions & 4 deletions packages/flame/lib/src/components/core/component_tree_root.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -137,10 +137,18 @@ class ComponentTreeRoot extends Component {
}

void processLifecycleEvents() {
if (!hasLifecycleEvents) {
assert(
_lifecycleEventsCompleter == null,
'The completer is only ever created while events are queued, so it '
'should never exist while the queue is empty',
);
return;
}
// reorder events to process later grouped by parent
final reorderParents = <Component>{};
Set<Component>? reorderParents;
LifecycleEventStatus handleReorderEvent(Component parent) {
reorderParents.add(parent);
(reorderParents ??= {}).add(parent);
return LifecycleEventStatus.done;
}

Expand All @@ -151,7 +159,8 @@ class ComponentTreeRoot extends Component {
for (final event in queue) {
final child = event.child!;
final parent = event.parent!;
if (_blocked.contains(child) || _blocked.contains(parent)) {
if (_blocked.isNotEmpty &&

@luanpotter luanpotter Aug 5, 2026

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is the isNotEmpty saving any time here, the contains should be O(0) in that case?

@spydon spydon Aug 5, 2026

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It saves a little bit since it has to calculate the identityHashCode in contains, meanwhile isNotEmpty is virtually free.

@luanpotter luanpotter Aug 7, 2026

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is this because _blocked is almost always empty? that doesn't appear to necessarily be the case here.

I honestly don't see how a hash check could be any sort of bottleneck, in fact if it were wouldn't the set contains implementation do this? according to clanker the dart identityHashCode implementation is cached per object and saved on the 64-bit pointer header.
I am ok with keeping if we have evidence but I am in favour of having commented out justifications for non-obvious micro-optimizations such as this. as is this looks like a silly mistake. a simple one line comment justifying the cost and why this is such a hot path would make it more clear.

thinking more broadly I am now wondering if this repeat with blocked thing is not ideal to begin with, there might be a way to sort the events in a deterministically correct order, but that is out of scope, just a thought.

(_blocked.contains(child) || _blocked.contains(parent))) {
continue;
}

Expand All @@ -176,7 +185,7 @@ class ComponentTreeRoot extends Component {
_blocked.clear();
}

for (final parent in reorderParents) {
for (final parent in reorderParents ?? const <Component>{}) {
parent.rebalanceChildren();
}

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