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do not new object as possible #17809

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Nov 6, 2024
+22 −8
Merged

do not new object as possible #17809

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30 changes: 22 additions & 8 deletions cocos/ui/scroll-view.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -893,6 +893,7 @@ export class ScrollView extends ViewGroup {
this._setContentPosition(position);
}

// Should not use _tempVec3 and also can not invoke any functions that use _tempVec3 as invoker may pass _tempVec3.
private _setContentPosition (position: Readonly<Vec3>): void {
if (!this._content) {
return;
Expand Down Expand Up @@ -1079,9 +1080,10 @@ export class ScrollView extends ViewGroup {
return;
}

const deltaMove = new Vec3();
const wheelPrecision = -0.1;
const scrollY = event.getScrollY();

const deltaMove = _tempVec3;
if (self.vertical) {
deltaMove.set(0, scrollY * wheelPrecision, 0);
} else if (self.horizontal) {
Expand Down Expand Up @@ -1242,9 +1244,11 @@ export class ScrollView extends ViewGroup {
}

protected _startInertiaScroll (touchMoveVelocity: Vec3): void {
const inertiaTotalMovement = new Vec3(touchMoveVelocity);
inertiaTotalMovement.multiplyScalar(MOVEMENT_FACTOR);
this._startAttenuatingAutoScroll(inertiaTotalMovement, touchMoveVelocity);
_tempVec3.set(touchMoveVelocity);
_tempVec3.multiplyScalar(MOVEMENT_FACTOR);

// this._startAttenuatingAutoScroll will clone _tempVec3, so can pass _tempVec3.
this._startAttenuatingAutoScroll(_tempVec3, touchMoveVelocity);
}

protected _calculateAttenuatedFactor (distance: number): number {
Expand Down Expand Up @@ -1332,7 +1336,8 @@ export class ScrollView extends ViewGroup {
if (totalTime <= 0 || totalTime >= 0.5) {
out.set(Vec3.ZERO);
} else {
let totalMovement = new Vec3();
let totalMovement = _tempVec3;
totalMovement.set(0, 0, 0);
totalMovement = this._touchMoveDisplacements.reduce((a, b) => {
a.add(b);
return a;
Expand All @@ -1358,6 +1363,9 @@ export class ScrollView extends ViewGroup {
_tempVec3.set(this._getContentPosition());
_tempVec3.add(adjustedMove);
_tempVec3.set(Math.round(_tempVec3.x * TOLERANCE) * EPSILON, Math.round(_tempVec3.y * TOLERANCE) * EPSILON, _tempVec3.z);

// Important: Pass a global variable _tempVec3 to other class member function is dangerous. As `this._setContentPosition`
// doesn't use _tempVec3 and it doesn't invoke any functions that use _tempVec3. So it is safe to pass _tempVec3 here.
this._setContentPosition(_tempVec3);
const outOfBoundary = this._getHowMuchOutOfBoundary();
_tempVec2.set(outOfBoundary.x, outOfBoundary.y);
Expand Down Expand Up @@ -1403,7 +1411,9 @@ export class ScrollView extends ViewGroup {
}

protected _getHowMuchOutOfBoundary (addition?: Vec3): Vec3 {
addition = addition || new Vec3();
if (!addition) {
addition = Vec3.ZERO;
}
if (addition.equals(Vec3.ZERO, EPSILON) && !this._outOfBoundaryAmountDirty) {
return this._outOfBoundaryAmount;
}
Expand Down Expand Up @@ -1494,6 +1504,9 @@ export class ScrollView extends ViewGroup {
if (_isOutOfBoundary) {
_tempVec3.set(this._getContentPosition());
_tempVec3.add(outOfBoundary);

// Important: Pass a global variable _tempVec3 to other class member function is dangerous. As `this._setContentPosition`
// doesn't use _tempVec3 and it doesn't invoke any functions that use _tempVec3. So it is safe to pass _tempVec3 here.
this._setContentPosition(_tempVec3);
this._updateScrollBar(Vec2.ZERO);
}
Expand Down Expand Up @@ -1750,7 +1763,7 @@ export class ScrollView extends ViewGroup {
const bounceBackStarted = this._startBounceBackIfNeeded();
if (!bounceBackStarted && this.inertia) {
const touchMoveVelocity = this._calculateTouchMoveVelocity();
if (!touchMoveVelocity.equals(_tempVec3, EPSILON) && this.brake < 1) {
if (!touchMoveVelocity.equals(Vec3.ZERO, EPSILON) && this.brake < 1) {
this._startInertiaScroll(touchMoveVelocity);
}
}
Expand Down Expand Up @@ -1999,9 +2012,10 @@ export class ScrollView extends ViewGroup {
return;
}

const deltaMove = new Vec3();
const wheelPrecision = -62.5;
const scrollY = event.y;

const deltaMove = _tempVec3;
if (self.vertical) {
deltaMove.set(0, scrollY * wheelPrecision, 0);
} else if (self.horizontal) {
Expand Down
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