refactor(instance): implemented GetDescendant and replaced GetChildren in renderer and simulation with it

core/src/objects/base/instance.cpp

@@ -108,6 +108,15 @@ std::optional<std::shared_ptr<Instance>> Instance::GetParent() {
     return parent.value().lock();
 }
 
+static std::shared_ptr<Instance> DUMMY_INSTANCE;
+DescendantsIterator Instance::GetDescendantsStart() {
+    return DescendantsIterator(GetChildren().size() > 0 ? GetChildren()[0] : DUMMY_INSTANCE);
+}
+
+DescendantsIterator Instance::GetDescendantsEnd() {
+    return DescendantsIterator(DUMMY_INSTANCE);
+}
+
 bool Instance::IsParentLocked() {
     return this->parentLocked;
 }
@@ -231,4 +240,49 @@ InstanceRef Instance::Deserialize(pugi::xml_node* node) {
     }
 
     return object;
+}
+
+// DescendantsIterator
+
+DescendantsIterator::DescendantsIterator(std::shared_ptr<Instance> current) : current(current), root(current == DUMMY_INSTANCE ? DUMMY_INSTANCE : current->GetParent()), siblingIndex { 0 } { }
+
+DescendantsIterator::self_type DescendantsIterator::operator++(int _) {
+    // If the current item is dummy, an error has occurred, this is not supposed to happen.
+    if (current == DUMMY_INSTANCE) {
+        Logger::fatalError("Attempt to increment a descendant iterator past its end\n");
+        panic();
+    }
+
+    // If the current item has children, enter it
+    if (current->GetChildren().size() > 0) {
+        siblingIndex.push_back(0);
+        current = current->GetChildren()[0];
+        return *this;
+    }
+
+    // Otherwise, we move to the next sibling, if applicable.
+
+    // But not if one up is null or the root element
+    if (!current->GetParent() || current == root) {
+        current = DUMMY_INSTANCE;
+        return *this;
+    }
+
+    // If we've hit the end of this item's children, move one up
+    while (current->GetParent() && current->GetParent().value()->GetChildren().size() <= (siblingIndex.back() + 1)) {
+        siblingIndex.pop_back();
+        current = current->GetParent().value();
+
+        // But not if one up is null or the root element
+        if (!current->GetParent() || current == root) {
+            current = DUMMY_INSTANCE;
+            return *this;
+        }
+    }
+
+    // Now move to the next sibling
+    siblingIndex.back()++;
+    current = current->GetParent().value()->GetChildren()[siblingIndex.back()];
+
+    return *this;
 }

core/src/objects/base/instance.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <iterator>
 #include <vector>
 #include <memory>
 #include <optional>
@@ -30,6 +31,8 @@ struct InstanceType {
     std::string explorerIcon = "";
 };
 
+class DescendantsIterator;
+
 // Base class for all instances in the data model
                  // Note: enable_shared_from_this HAS to be public or else its field will not be populated
                  // Maybe this could be replaced with a friendship? But that seems unnecessary.
@@ -69,7 +72,9 @@ public:
     std::optional<std::shared_ptr<Instance>> GetParent();
     bool IsParentLocked();
     inline const std::vector<std::shared_ptr<Instance>> GetChildren() { return children; }
-
+    
+    DescendantsIterator GetDescendantsStart();
+    DescendantsIterator GetDescendantsEnd();
     // Utility functions
     inline void AddChild(std::shared_ptr<Instance> object) { object->SetParent(this->shared_from_this()); }
 
@@ -87,4 +92,28 @@ public:
 };
 
 typedef std::shared_ptr<Instance> InstanceRef;
-typedef std::weak_ptr<Instance> InstanceRefWeak;
+typedef std::weak_ptr<Instance> InstanceRefWeak;
+
+// https://gist.github.com/jeetsukumaran/307264
+class DescendantsIterator {
+public:
+    typedef DescendantsIterator self_type;
+    typedef std::shared_ptr<Instance> value_type;
+    typedef std::shared_ptr<Instance>& reference;
+    typedef std::shared_ptr<Instance> pointer;
+    typedef std::forward_iterator_tag iterator_category;
+    typedef int difference_type;
+
+    DescendantsIterator(std::shared_ptr<Instance> current);
+    inline self_type operator++() { self_type i = *this; ++*this; return i; }
+    inline std::shared_ptr<Instance> operator*() { return current; }
+    inline std::shared_ptr<Instance> operator->() { return current; }
+    inline bool operator==(const self_type& rhs) { return current == rhs.current; }
+    inline bool operator!=(const self_type& rhs) { return current != rhs.current; }
+
+    self_type operator++(int _);
+private:
+    std::optional<std::shared_ptr<Instance>> root;
+    std::shared_ptr<Instance> current;
+    std::vector<int> siblingIndex;
+};

core/src/physics/simulation.cpp

@@ -77,7 +77,8 @@ void physicsStep(float deltaTime) {
 
     // Naive implementation. Parts are only considered so if they are just under Workspace
     // TODO: Add list of tracked parts in workspace based on their ancestry using inWorkspace property of Instance
-    for (InstanceRef obj : gWorkspace()->GetChildren()) {
+    for (auto it = gWorkspace()->GetDescendantsStart(); it != gWorkspace()->GetDescendantsEnd(); it++) {
+        InstanceRef obj = *it;
         if (obj->GetClass()->className != "Part") continue; // TODO: Replace this with a .IsA call instead of comparing the class name directly
         std::shared_ptr<Part> part = std::dynamic_pointer_cast<Part>(obj);
         const rp::Transform& transform = part->rigidBody->getTransform();

core/src/rendering/renderer.cpp

@@ -125,7 +125,8 @@ void renderParts() {
 
     // Sort by nearest
     std::map<float, std::shared_ptr<Part>> sorted;
-    for (InstanceRef inst : gWorkspace()->GetChildren()) {
+    for (auto it = gWorkspace()->GetDescendantsStart(); it != gWorkspace()->GetDescendantsEnd(); it++) {
+        InstanceRef inst = *it;
         if (inst->GetClass()->className != "Part") continue;
         std::shared_ptr<Part> part = std::dynamic_pointer_cast<Part>(inst);
         if (part->transparency > 0.00001) {