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++ // Copyright (C) 2026 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
++
++ // Walks the world's bodies while one of them has been deleted. A deleted node
++ // leaves its backend behind until a frame takes it out, so the world is stopped
++ // first, since nothing else clears it, and then each of the three things that
++ // walk every body is asked for: a new default density, debug drawing off, and a
++ // move to another scene. Each of them crashed.
++ //
++ // Reaching the end is the assertion. The walks are named across the top and lit
++ // as they are survived, so the scene can be judged by eye too.
++
++ import QtQuick
++ import QtTest
++ import QtQuick3D
++ import QtQuick3D.Physics
++ import QtQuick3D.Physics.TestUtils
++
++ Item {
++ width: 640
++ height: 480
++ visible: true
++
++ PhysicsWorld {
++ id: world
++ gravity: Qt.vector3d(0, -981, 0)
++ running: true
++ forceDebugDraw: true
++ typicalLength: 100
++ typicalSpeed: 1000
++ minimumTimestep: 15
++ maximumTimestep: 15
++ scene: viewport.scene
++ }
++
++ QtObject {
++ id: walked
++ property bool density: false
++ property bool debugDraw: false
++ property bool scene: false
++ }
++
++ // A step apart, so the delete the first one asks for, which is deferred,
++ // has happened by the time the next one walks the bodies.
++ Timer {
++ interval: 300
++ repeat: true
++ running: true
++ property int step: 0
++ onTriggered: {
++ switch (++step) {
++ case 1:
++ // Stopped, so no frame takes the removed backend out from
++ // under the walks below.
++ world.running = false;
++ boxes.model = 2;
++ break;
++ case 2:
++ world.defaultDensity = 0.002;
++ walked.density = true;
++ break;
++ case 3:
++ world.forceDebugDraw = false;
++ walked.debugDraw = true;
++ break;
++ case 4:
++ world.scene = elsewhere;
++ walked.scene = true;
++ break;
++ }
++ }
++ }
++
++ View3D {
++ id: viewport
++ anchors.fill: parent
++
++ environment: SceneEnvironment {
++ clearColor: "#151a3f"
++ backgroundMode: SceneEnvironment.Color
++ }
++
++ PerspectiveCamera {
++ position: Qt.vector3d(0, 100, 600)
++ clipFar: 4000
++ }
++
++ DirectionalLight {
++ eulerRotation: Qt.vector3d(-35, 25, 0)
++ brightness: 1.5
++ ambientColor: "#3a3a44"
++ }
++
++ // What the world is moved to, so that moving it means every body
++ // leaves the scene it is in.
++ Node {
++ id: elsewhere
++ }
++
++ StaticRigidBody {
++ position: Qt.vector3d(0, -150, 0)
++ collisionShapes: BoxShape {
++ extents: Qt.vector3d(800, 40, 400)
++ }
++ Model {
++ source: "#Cube"
++ scale: Qt.vector3d(8, 0.4, 4)
++ materials: PrincipledMaterial {
++ baseColor: "#3f8f4f"
++ roughness: 0.85
++ }
++ }
++ }
++
++ // The last of these is the one that gets deleted.
++ Repeater3D {
++ id: boxes
++ model: 3
++ DynamicRigidBody {
++ required property int index
++ position: Qt.vector3d(index * 120 - 120, 200, 0)
++ collisionShapes: BoxShape {
++ extents: Qt.vector3d(60, 60, 60)
++ }
++ Model {
++ source: "#Cube"
++ scale: Qt.vector3d(0.6, 0.6, 0.6)
++ materials: PrincipledMaterial {
++ baseColor: index === 2 ? "#c0504d" : "#4a86e8"
++ roughness: 0.5
++ }
++ }
++ }
++ }
++ }
++
++ Row {
++ anchors.top: parent.top
++ anchors.horizontalCenter: parent.horizontalCenter
++ anchors.topMargin: 12
++ spacing: 24
++
++ component Marker: Text {
++ required property bool done
++ color: done ? "#7ee08a" : "#9aa0b4"
++ font.pixelSize: 16
++ }
++
++ Marker { text: "density"; done: walked.density }
++ Marker { text: "debug draw"; done: walked.debugDraw }
++ Marker { text: "scene"; done: walked.scene }
++ }
++
++ PhysicsTestCase {
++ name: "giving every body a new default density"
++ goalReached: walked.density
++ }
++
++ PhysicsTestCase {
++ name: "taking every body's debug drawing away"
++ goalReached: walked.debugDraw
++ }
++
++ PhysicsTestCase {
++ name: "moving every body to another scene"
++ goalReached: walked.scene
++ }
++ }