Add UI core node lifetime handles

src/ui_core/node_lifetime.h

@@ -0,0 +1,127 @@
+#pragma once
+
+#include "foundation/result.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <functional>
+#include <vector>
+
+namespace pp::ui {
+
+inline constexpr std::uint32_t invalid_node_slot = 0xffffffffU;
+inline constexpr std::uint32_t invalid_connection_slot = 0xffffffffU;
+
+struct NodeHandle {
+    std::uint32_t slot = invalid_node_slot;
+    std::uint32_t generation = 0;
+
+    [[nodiscard]] constexpr bool valid() const noexcept
+    {
+        return slot != invalid_node_slot && generation != 0U;
+    }
+};
+
+[[nodiscard]] constexpr bool operator==(NodeHandle left, NodeHandle right) noexcept
+{
+    return left.slot == right.slot && left.generation == right.generation;
+}
+
+[[nodiscard]] constexpr bool operator!=(NodeHandle left, NodeHandle right) noexcept
+{
+    return !(left == right);
+}
+
+struct UiConnection {
+    std::uint32_t slot = invalid_connection_slot;
+    std::uint32_t generation = 0;
+
+    [[nodiscard]] constexpr bool valid() const noexcept
+    {
+        return slot != invalid_connection_slot && generation != 0U;
+    }
+};
+
+[[nodiscard]] constexpr bool operator==(UiConnection left, UiConnection right) noexcept
+{
+    return left.slot == right.slot && left.generation == right.generation;
+}
+
+[[nodiscard]] constexpr bool operator!=(UiConnection left, UiConnection right) noexcept
+{
+    return !(left == right);
+}
+
+class NodeLifetimeTree;
+
+class ScopedUiConnection {
+public:
+    ScopedUiConnection() noexcept = default;
+    ScopedUiConnection(NodeLifetimeTree& tree, UiConnection connection) noexcept;
+    ScopedUiConnection(const ScopedUiConnection&) = delete;
+    ScopedUiConnection& operator=(const ScopedUiConnection&) = delete;
+    ScopedUiConnection(ScopedUiConnection&& other) noexcept;
+    ScopedUiConnection& operator=(ScopedUiConnection&& other) noexcept;
+    ~ScopedUiConnection();
+
+    void reset() noexcept;
+
+    [[nodiscard]] UiConnection connection() const noexcept;
+    [[nodiscard]] bool connected() const noexcept;
+
+private:
+    NodeLifetimeTree* tree_ = nullptr;
+    UiConnection connection_ {};
+};
+
+class NodeLifetimeTree {
+public:
+    using Callback = std::function<void(NodeHandle)>;
+
+    [[nodiscard]] pp::foundation::Result<NodeHandle> create_root();
+    [[nodiscard]] pp::foundation::Result<NodeHandle> create_child(NodeHandle parent);
+
+    [[nodiscard]] bool contains(NodeHandle node) const noexcept;
+    [[nodiscard]] pp::foundation::Result<NodeHandle> parent_of(NodeHandle node) const noexcept;
+    [[nodiscard]] pp::foundation::Result<std::size_t> child_count(NodeHandle node) const noexcept;
+    [[nodiscard]] pp::foundation::Result<NodeHandle> child_at(NodeHandle node, std::size_t index) const noexcept;
+    [[nodiscard]] pp::foundation::Status destroy_subtree(NodeHandle node) noexcept;
+
+    [[nodiscard]] pp::foundation::Result<UiConnection> connect(NodeHandle node, Callback callback);
+    [[nodiscard]] pp::foundation::Result<ScopedUiConnection> scoped_connect(NodeHandle node, Callback callback);
+    [[nodiscard]] pp::foundation::Status disconnect(UiConnection connection) noexcept;
+    [[nodiscard]] pp::foundation::Result<std::size_t> live_connection_count(NodeHandle node) const noexcept;
+    [[nodiscard]] pp::foundation::Status dispatch(NodeHandle node);
+
+private:
+    struct NodeSlot {
+        std::uint32_t generation = 1;
+        bool alive = false;
+        NodeHandle parent {};
+        std::vector<NodeHandle> children;
+        std::vector<UiConnection> connections;
+    };
+
+    struct ConnectionSlot {
+        std::uint32_t generation = 1;
+        bool alive = false;
+        NodeHandle node {};
+        Callback callback;
+    };
+
+    [[nodiscard]] NodeSlot* node_slot(NodeHandle node) noexcept;
+    [[nodiscard]] const NodeSlot* node_slot(NodeHandle node) const noexcept;
+    [[nodiscard]] ConnectionSlot* connection_slot(UiConnection connection) noexcept;
+    [[nodiscard]] const ConnectionSlot* connection_slot(UiConnection connection) const noexcept;
+
+    [[nodiscard]] pp::foundation::Result<NodeHandle> allocate_node(NodeHandle parent);
+    void unlink_from_parent(NodeHandle node) noexcept;
+    void release_connection(UiConnection connection) noexcept;
+
+    std::vector<NodeSlot> nodes_;
+    std::vector<std::uint32_t> free_nodes_;
+    std::vector<ConnectionSlot> connections_;
+    std::vector<std::uint32_t> free_connections_;
+};
+
+}