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refactor: Use a temp vector for delta calculations of FollowBehavior #3230

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merged 2 commits into from
Jul 21, 2024
Merged

refactor: Use a temp vector for delta calculations of FollowBehavior #3230

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81a7ea3
Use a temp vector for delta calculations
ufrshubham Jul 20, 2024
c7e093e
Avoid redundant calculations
ufrshubham Jul 21, 2024
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23 changes: 12 additions & 11 deletions packages/flame/lib/src/camera/behaviors/follow_behavior.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ import 'package:flame/src/camera/viewport.dart';
import 'package:flame/src/components/core/component.dart';
import 'package:flame/src/components/position_component.dart';
import 'package:flame/src/effects/provider_interfaces.dart';
import 'package:vector_math/vector_math_64.dart';

/// This behavior will make the [owner] follow the [target].
///
Expand Down Expand Up @@ -46,6 +47,8 @@ class FollowBehavior extends Component {
final bool horizontalOnly;
final bool verticalOnly;

final _tempDelta = Vector2.zero();

@override
void onMount() {
if (_owner == null) {
Expand All @@ -59,19 +62,17 @@ class FollowBehavior extends Component {

@override
void update(double dt) {
final delta = target.position - owner.position;
if (horizontalOnly) {
delta.y = 0;
}
if (verticalOnly) {
delta.x = 0;
}
final distance = delta.length;
_tempDelta.setValues(
verticalOnly ? 0 : target.position.x - owner.position.x,
horizontalOnly ? 0 : target.position.y - owner.position.y,
);

final distance = _tempDelta.length;
if (distance > _speed * dt) {
delta.scale(_speed * dt / distance);
_tempDelta.scale(_speed * dt / distance);
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}
if (delta.x != 0 || delta.y != 0) {
owner.position = delta..add(owner.position);
if (_tempDelta.x != 0 || _tempDelta.y != 0) {
owner.position = _tempDelta..add(owner.position);
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to go all the way avoiding object creation entirely, this could be owner.position.setValues(owner.position.x + delta.x, ...)

sadly we lose all the easiness of using vectorial math at all when doing things like this

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this could be owner.position.setValues(owner.position.x + delta.x, ...)

I thought the same. But unfortunately doing so causes some of the tests to fail, because the .setValues bypasses the position setter of PositionProvider. Some components do extra stuff in that setter.

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oof, seems like a footgun waiting to happen :(

}
}
}
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