30class SHIT_API SHIT_REFLECT(BlackList) PhysicsSystem2D final : public System {

31 SHIT_REFLECT_BODY(PhysicsSystem2D)

32 public:

33 explicit PhysicsSystem2D(int priority = 50);

34 ~PhysicsSystem2D() override;

35

36 void init() override;

37 void update() override;

39 void fixedUpdate(float fixedDt) override;

40 void destroy() override;

41

42 // 反射字段被检查器直写后回调（把重力等变更实时同步到 Box2D 世界）

43 void onFieldChanged(const std::string& fieldName) override;

44

45 // 组件认领：RigidBody2D（创建/销毁物理体）

46 bool onComponentAttached(Component* component) override;

47 void onComponentDetached(Component* component) override;

48

49 // --- 配置（必须在 init() 之前调用） ---

50 void setGravity(const Vector2& gravity);

51 const Vector2& getGravity() const { return m_gravity; }

54 void setPixelsPerMeter(float ppm);

56 float getPixelsPerMeter() const { return m_pixelsPerMeter; }

57

58 // --- 供 RigidBody2D 内部调用 ---

59 void registerRigidBody(RigidBody2D* body);

60 void unregisterRigidBody(RigidBody2D* body);

62 void createRigidBody(RigidBody2D* body);

64 void destroyRigidBody(RigidBody2D* body);

65

66 // --- 供 Joint2D 内部调用 ---

68 void registerJoint(Joint2D* joint);

70 void unregisterJoint(Joint2D* joint);

72 void createJoint(Joint2D* joint);

74 void destroyJoint(Joint2D* joint);

76 void rebuildJoint(Joint2D* joint);

77

78private:

79 friend class RigidBody2D;

82 struct ContactPair {

83 const RigidBody2D* a = nullptr;

84 const RigidBody2D* b = nullptr;

85 bool operator==(const ContactPair& o) const { return a == o.a && b == o.b; }

86 };

87 struct ContactPairHash {

88 size_t operator()(const ContactPair& p) const {

89 std::hash<const void*> h;

90 return h(p.a) ^ (h(p.b) << 1);

91 }

92 };

95 enum class CollisionPhase { Enter, Stay, Exit };

98 static ContactPair makeContactPair(const RigidBody2D* a, const RigidBody2D* b);

101 RigidBody2D* findRigidBody(int32_t bodyIndex, uint16_t world0, uint16_t generation) const;

104 void cleanupContactPairs(const RigidBody2D* body);

108 void collectContactEvents(std::vector<ContactPair>& entered, std::vector<ContactPair>& exited);

111 void ensureSimulationState();

113 void syncTransformsFromBodies();

115 void processContactEventsForStep();

118 void dispatchContact(const ContactPair& pair, CollisionPhase phase);

121 void invokeCollisionCallbacks(GameObject* self, GameObject* other, CollisionPhase phase);

122

123 SHIT_META(({.displayName = "Gravity", .tooltip = "重力（像素/秒²）"}))

124 Vector2 m_gravity{ 0.0f, 320.0f };

125

126 SHIT_META(Disable)

127 std::vector<RigidBody2D*> m_bodies;

128 SHIT_META(Disable)

129 std::vector<Joint2D*> m_joints;

130 // 当前接触中的刚体对集合（进入/持续/结束 基于它判定；元素仅作键，不触碰指针所指对象）

131 SHIT_META(Disable)

132 std::unordered_set<ContactPair, ContactPairHash> m_activeContacts;

133 // b2WorldId = {uint16_t index1; uint16_t generation;}

134 SHIT_META(Disable)

135 uint16_t m_worldIndex = 0;

136 SHIT_META(Disable)

137 uint16_t m_worldGeneration = 0;

138 SHIT_META(Disable)

139 bool m_initialized = false;

140

141 // 像素↔米比例（实例字段；init() 时应用 b2SetLengthUnitsPerMeter——

142 // 该 API 是 Box2D 进程级全局，多实例不同比例时后者生效，属 Box2D 限制）

143 SHIT_META(({.displayName = "Pixels Per Meter", .tooltip = "每米对应的像素数（默认 32，下次 init 生效）", .range = {1, 1024}, .step = 1}))

144 float m_pixelsPerMeter = 32.0f;

145 };