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Fixes a bug when >1 entities are added to and removed from 1 family in the same frame #59

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Fixes a bug when >1 entities are added to and removed from 1 family in the same frame #59

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7 changes: 6 additions & 1 deletion src/engine/entity/include/halley/entity/family.h
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Original file line number Diff line number Diff line change
Expand Up @@ -169,6 +169,8 @@ namespace Halley {
// Move all entities to be removed to the back of the vector
{
int n = int(entities.size());
std::vector<std::pair<int, int>> moves;
moves.reserve( removeCount );
// Note: it's important to scan it forward. Scanning backwards would improve performance for short-lived entities,
// but it causes an issue where an entity is removed and added to the same family in one frame.
for (int i = 0; i < n; i++) {
Expand All @@ -177,7 +179,7 @@ namespace Halley {
if (iter != toRemove.end() && id == *iter) {
toRemove.erase(iter);
if (i != n - 1) {
std::swap(entities[i], entities[n - 1]);
moves.emplace_back( std::make_pair( i, n - 1 ) );
i--;
}
n--;
Expand All @@ -186,6 +188,9 @@ namespace Halley {
}
}
}
for (const std::pair<int, int>& move : moves) {
std::swap(entities[move.first], entities[move.second]);
}
Ensures(size_t(n) + removeCount == entities.size());
}

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