pending_damage.hpp

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#pragma once
 
#include <pulp/view/geometry.hpp>
 
#include <algorithm>
 
namespace pulp::view {

class PendingDamage {
public:
    class Snapshot {
    public:
        bool is_full() const noexcept { return full_; }
        bool has_bounds() const noexcept { return have_bounds_; }
        Rect bounds() const noexcept { return bounds_; }

        bool is_bounded() const noexcept { return !full_ && have_bounds_; }
 
    private:
        friend class PendingDamage;
        bool full_ = true;
        bool have_bounds_ = false;
        Rect bounds_{};
    };

    void mark_full() { full_ = true; }

    void mark(const Rect& root_rect) {
        if (root_rect.width <= 0 || root_rect.height <= 0) {
            mark_full();  // degenerate region → be conservative
            return;
        }
        if (full_) return;  // sticky: never widen back out of a full repaint
        if (!have_bounds_) {
            bounds_ = root_rect;
            have_bounds_ = true;
            return;
        }
        const float nx = std::min(bounds_.x, root_rect.x);
        const float ny = std::min(bounds_.y, root_rect.y);
        bounds_ = {nx, ny,
                   std::max(bounds_.right(), root_rect.right()) - nx,
                   std::max(bounds_.bottom(), root_rect.bottom()) - ny};
    }
 
    bool is_full() const { return full_; }
    bool has_bounds() const { return have_bounds_; }
    Rect bounds() const { return bounds_; }

    void clear() {
        full_ = false;
        have_bounds_ = false;
        bounds_ = {};
    }

    Snapshot take() {
        Snapshot s;
        s.full_ = full_;
        s.have_bounds_ = have_bounds_;
        s.bounds_ = bounds_;
        clear();
        return s;
    }

    void restore(const Snapshot& s) {
        if (s.full_) {
            mark_full();
            return;
        }
        if (s.have_bounds_) mark(s.bounds_);
    }
 
private:
    bool full_ = true;  
    bool have_bounds_ = false;
    Rect bounds_{};
};
 
}  // namespace pulp::view