Add ORBPathCallbacksExtended and isExtended flag support (#16)

Author: Kyle-Ye

.gitignore

@@ -9,3 +9,4 @@ DerivedData/
 .claude/
 .rb_template/
 .augment/
+/.build-debug

Package.resolved

@@ -0,0 +1,305 @@
+//
+//  NestedCallbacks.cpp
+//  OpenRenderBox
+
+// TODO: Implement NestedCallbacks
+
+#include <OpenRenderBoxCxx/Path/NestedCallbacks.hpp>
+#include <mutex>
+#if ORB_TARGET_OS_DARWIN
+#include <os/lock.h>
+#endif
+#include <OpenRenderBoxCxx/Vector/vector.hpp>
+
+namespace ORB {
+namespace Path {
+
+#if ORB_TARGET_OS_DARWIN
+
+namespace {
+
+struct CacheEntry {
+    const ORBPathCallbacks* callbacks;
+    size_t index;
+    const NestedCallbacks* result;
+};
+
+struct Cache {
+    ORB::vector<CacheEntry, 0, size_t> entries;
+    os_unfair_lock lock;
+
+    Cache() : entries(), lock(OS_UNFAIR_LOCK_INIT) {}
+};
+
+Cache* gCache = nullptr;
+
+// Helper to call bezierOrder on callbacks
+inline uint32_t callBezierOrder(const void* object, const ORBPathCallbacks* callbacks) {
+    if (callbacks->bezierOrder) {
+        return callbacks->bezierOrder(object);
+    }
+    return 3; // Default: cubic bezier
+}
+
+} // anonymous namespace
+
+NestedCallbacks::NestedCallbacks(const ORBPathCallbacks* callbacks, size_t index)
+    : extended{}
+    , originalCallbacks(callbacks)
+    , nestedIndex(index)
+{
+    // Set isExtended flag (byte at offset 0x2)
+    extended.flags.isExtended = 1;
+
+    // Copy retain/release from original callbacks
+    extended.retain = reinterpret_cast<decltype(extended.retain)>(callbacks->retain);
+    extended.release = reinterpret_cast<decltype(extended.release)>(callbacks->release);
+
+    extended.apply = +[](const void *object, void *info, ORBPathApplyCallback callback, const ORBPathCallbacksExtended *ext) -> bool {
+        auto self = reinterpret_cast<const NestedCallbacks*>(ext);
+        auto original = self->originalCallbacks;
+        if (original->apply) {
+            return original->apply(object, info, callback);
+        }
+        return true;
+    };
+
+    extended.isEqual = nullptr;
+
+    extended.isEmpty = +[](const void *object, const ORBPathCallbacksExtended *ext) -> bool {
+        auto self = reinterpret_cast<const NestedCallbacks*>(ext);
+        auto original = self->originalCallbacks;
+        if (original->apply) {
+            // Use single_element_callback to detect emptiness
+            struct Info {
+                size_t count;
+                size_t depth;
+                bool sawClose;
+            } info = {0, 0, false};
+            info.depth = self->nestedIndex;
+            original->apply(object, &info, NestedCallbacks::single_element_callback);
+            return info.count == 1;
+        }
+        return true;
+    };
+
+    extended.bezierOrder = +[](const void *object, const ORBPathCallbacksExtended *ext) -> uint32_t {
+        auto self = reinterpret_cast<const NestedCallbacks*>(ext);
+        return callBezierOrder(object, self->originalCallbacks);
+    };
+
+    extended.isSingleElement = nullptr;
+    extended.boundingRect = nullptr;
+    extended.cgPath = nullptr;
+
+    extended.next = +[](const void *object, const ORBPathCallbacksExtended *ext) -> const ORBPathCallbacksExtended* {
+        auto self = reinterpret_cast<const NestedCallbacks*>(ext);
+        auto nextCallbacks = NestedCallbacks::get(self->originalCallbacks, self->nestedIndex + 1);
+        return &nextCallbacks->extended;
+    };
+}
+
+const NestedCallbacks* NestedCallbacks::get(const ORBPathCallbacks* callbacks, size_t index) {
+    // Lazy initialization of global cache
+    static std::once_flag initFlag;
+    std::call_once(initFlag, []() {
+        gCache = new Cache();
+    });
+
+    os_unfair_lock_lock(&gCache->lock);
+
+    // Binary search for existing entry
+    auto& entries = gCache->entries;
+    size_t lo = 0;
+    size_t hi = entries.size();
+
+    while (lo < hi) {
+        size_t mid = lo + (hi - lo) / 2;
+        const auto& entry = entries[mid];
+
+        if (entry.callbacks < callbacks) {
+            lo = mid + 1;
+        } else if (entry.callbacks > callbacks) {
+            hi = mid;
+        } else if (entry.index < index) {
+            lo = mid + 1;
+        } else if (entry.index > index) {
+            hi = mid;
+        } else {
+            // Found exact match
+            const NestedCallbacks* result = entry.result;
+            os_unfair_lock_unlock(&gCache->lock);
+            return result;
+        }
+    }
+
+    // Not found, create new NestedCallbacks
+    auto* nested = new NestedCallbacks(callbacks, index);
+
+    // Insert at position 'lo' to maintain sorted order
+    entries.reserve(entries.size() + 1);
+
+    // Shift elements to make room
+    if (lo < entries.size()) {
+        // Use memmove for efficiency
+        size_t count = entries.size() - lo;
+        memmove(&entries[lo + 1], &entries[lo], count * sizeof(CacheEntry));
+    }
+
+    // Insert new entry
+    entries[lo] = CacheEntry{callbacks, index, nested};
+
+    os_unfair_lock_unlock(&gCache->lock);
+    return nested;
+}
+
+// Mask for nesting elements (bits 17-20,21-24): used to detect depth changes
+// From assembly: 0x1de0000 = bits for elements 17, 18, 19, 20, 22, 23, 24
+static constexpr uint32_t kNestingElementMask = 0x1de0000;
+
+// Helper to check if an element affects nesting depth
+static inline bool isNestingElement(ORBPathElement element) {
+    if (element > 0x18) return false;
+    return ((1u << element) & kNestingElementMask) != 0;
+}
+
+// Helper to check if element is in range 0x0-0x3 (move/line/quad/curve)
+static inline bool isDrawingElement(ORBPathElement element) {
+    return element < 4;
+}
+
+// apply_elements_callback: tracks nesting depth during path enumeration
+// Info structure: { context, callback, depth, elementCount, sawClose }
+bool NestedCallbacks::apply_elements_callback(void* info, ORBPathElement element, const double* points, const void* userInfo) {
+    struct ApplyInfo {
+        void* context;
+        ORBPathApplyCallback callback;
+        size_t depth;
+    };
+    auto* applyInfo = static_cast<ApplyInfo*>(info);
+
+    if (element > 0x18) {
+        // Forward to user callback if we're at depth 0
+        if (applyInfo->depth == 0) {
+            return applyInfo->callback(applyInfo->context, element, points, userInfo);
+        }
+        return false;
+    }
+
+    uint32_t mask = 1u << element;
+    if (mask & kNestingElementMask) {
+        // Nesting element: increment depth
+        applyInfo->depth++;
+        return false;
+    }
+
+    if (element == 0x10) { // Close subpath
+        if (applyInfo->depth > 0) {
+            applyInfo->depth--;
+        }
+        return false;
+    }
+
+    // Forward non-nesting elements at depth 0
+    if (applyInfo->depth == 0) {
+        return applyInfo->callback(applyInfo->context, element, points, userInfo);
+    }
+    return false;
+}
+
+// single_element_callback: checks if path is a single element
+// Info structure: { depth, elementCount, sawClose }
+bool NestedCallbacks::single_element_callback(void* info, ORBPathElement element, const double* points, const void* userInfo) {
+    struct SingleInfo {
+        size_t depth;
+        size_t count;
+        bool sawClose;
+    };
+    auto* singleInfo = static_cast<SingleInfo*>(info);
+
+    if (element > 0x18) {
+        // Elements > 0x18: count as elements at depth 0
+        if (singleInfo->depth == singleInfo->count) {
+            singleInfo->count++;
+            if (element == 0x13) { // Specific element marker
+                singleInfo->sawClose = false;
+            } else {
+                singleInfo->sawClose = true;
+            }
+        }
+        return false;
+    }
+
+    uint32_t mask = 1u << element;
+
+    // Handle nesting elements
+    if ((mask & 0xf000) != 0) {
+        // Elements 12-15
+        if (singleInfo->depth == singleInfo->count) {
+            singleInfo->sawClose = true;
+            singleInfo->count++;
+        }
+        return false;
+    }
+
+    if (mask & kNestingElementMask) {
+        // Other nesting elements: increment depth
+        if (singleInfo->depth == singleInfo->count) {
+            singleInfo->count++;
+        }
+        return false;
+    }
+
+    if (element == 0x10) { // Close subpath
+        if (singleInfo->depth > 0) {
+            singleInfo->depth--;
+        }
+        if (singleInfo->depth == singleInfo->count && singleInfo->sawClose) {
+            singleInfo->sawClose = false;
+            singleInfo->count++;
+        }
+        return false;
+    }
+
+    // Drawing elements (0-3)
+    if (isDrawingElement(element)) {
+        if (singleInfo->depth == singleInfo->count) {
+            singleInfo->sawClose = true;
+            singleInfo->count++;
+        }
+    }
+
+    // Return true if count >= 2 (stop enumeration)
+    return singleInfo->count >= 2;
+}
+
+// apply_elements_fast: fast path for Storage
+bool NestedCallbacks::apply_elements_fast(const Storage& storage, void* info) {
+    // TODO: Implement fast path using Storage iterator
+    (void)storage;
+    (void)info;
+    return true;
+}
+
+// single_element_fast: fast path for single element detection on Storage
+bool NestedCallbacks::single_element_fast(const Storage& storage, void* info) {
+    // TODO: Implement fast path using Storage iterator
+    (void)storage;
+    (void)info;
+    return true;
+}
+
+// first_element: find first element at given nesting depth
+bool NestedCallbacks::first_element(const Storage& storage, void* iterator, size_t depth) {
+    // TODO: Implement using Storage iterator
+    (void)storage;
+    (void)iterator;
+    (void)depth;
+    return false;
+}
+
+#endif /* ORB_TARGET_OS_DARWIN */
+
+} /* namespace Path */
+} /* namespace ORB */
+