widget.h

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#ifndef ASW_MODULES_UI_WIDGET_H
#define ASW_MODULES_UI_WIDGET_H
 
#include <memory>
#include <type_traits>
#include <vector>
 
#include "event.h"
 
namespace asw::ui {
 
class Context;
 
enum class Anchor {
    None,
    TopLeft,
    Top,
    TopRight,
    Left,
    Center,
    Right,
    BottomLeft,
    Bottom,
    BottomRight,
};
 
using WidgetId = uint32_t;
 
class Widget {
public:
    Widget()
        : _id(generate_id()) { };
 
    virtual ~Widget() = default;
 
    Widget(Widget&& other) noexcept;
 
    Widget& operator=(Widget&& other) noexcept;
 
    Widget(const Widget&) = delete;
    Widget& operator=(const Widget&) = delete;
 
    WidgetId id() const
    {
        return _id;
    }
 
    bool visible = true;
 
    bool enabled = true;
 
    bool focusable = false;
 
    Widget* nav_up = nullptr;
 
    Widget* nav_down = nullptr;
 
    Widget* nav_left = nullptr;
 
    Widget* nav_right = nullptr;
 
    bool focus_ring = true;
 
    Widget* parent = nullptr;
 
    const std::vector<std::unique_ptr<Widget>>& children() const
    {
        return _children;
    }
 
    virtual void measure(Context& ctx);
 
    virtual void layout(Context& ctx);
 
    virtual bool on_event(Context& ctx, const UIEvent& e);
 
    virtual void on_focus_changed(Context& ctx, bool focused);
 
    virtual void activate(Context& ctx);
 
    virtual void draw(Context& ctx);
 
    template <class T, class... Args> T& add_child(Args&&... args)
    {
        static_assert(std::is_base_of_v<Widget, T>, "add_child<T>: T must derive from Widget");
        auto ptr = std::make_unique<T>(std::forward<Args>(args)...);
        ptr->parent = this;
        auto& ref = *ptr;
        _children.emplace_back(std::move(ptr));
        return ref;
    }
 
    bool remove_child(const Widget& child);
 
    void clear_children();
 
    asw::Quad<float> transform;
 
    Anchor anchor = Anchor::None;
 
    asw::Vec2<float> anchor_margin { 0.0F, 0.0F };
 
    bool is_hovered() const { return _hovered; }
 
    bool is_pressed() const { return _pressed; }
 
    bool is_focused() const { return _focused; }
 
    bool is_captured() const { return _captured; }
 
    bool is_highlighted(const Context& ctx) const;
 
protected:
    // Set by Root and FocusManager
    friend class Root;
    friend class FocusManager;
 
    void place_anchored(Widget& child) const;
 
    bool _hovered = false;
    bool _pressed = false;
    bool _focused = false;
    bool _captured = false;
 
private:
    // Point every child at this widget as its parent
    void adopt_children();
 
    // Move every child to _removed
    void detach_children();
 
    // Child widgets, private so only add_child, remove_child and
    // clear_children change them
    std::vector<std::unique_ptr<Widget>> _children;
 
    // Children removed from the tree, kept alive until Root frees them
    std::vector<std::unique_ptr<Widget>> _removed;
 
    static inline int _id_counter { 1 };
 
    static int generate_id()
    {
        return _id_counter++;
    }
 
    WidgetId _id;
};
 
} // namespace asw::ui
 
#endif // ASW_MODULES_UI_WIDGET_H