component_dragger.hpp

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#pragma once

 
#include <algorithm>
#include <pulp/view/geometry.hpp>
#include <pulp/view/view.hpp>
 
namespace pulp::view {
 
class ComponentDragger {
public:
    ComponentDragger() = default;

    void start_dragging(View& view, Point mouse_local) {
        mouse_start_ = mouse_local;
        bounds_start_ = view.bounds();
        active_ = true;
    }

    void drag_view(View& view, Point mouse_local) {
        if (!active_) return;
        const Point delta{mouse_local.x - mouse_start_.x,
                          mouse_local.y - mouse_start_.y};
        Rect target = bounds_start_;
        target.x += delta.x;
        target.y += delta.y;
 
        if (constrain_to_parent_) {
            if (auto* p = view.parent()) {
                const Rect parent_local = p->local_bounds();
                target.x = std::clamp(target.x,
                                      parent_local.x,
                                      std::max(parent_local.x,
                                               parent_local.right() - target.width));
                target.y = std::clamp(target.y,
                                      parent_local.y,
                                      std::max(parent_local.y,
                                               parent_local.bottom() - target.height));
            }
        }
        view.set_bounds(target);
        if (on_drag) on_drag(target);
    }

    void end_dragging() {
        active_ = false;
        if (on_end) on_end();
    }

    void set_constrain_to_parent(bool yes) { constrain_to_parent_ = yes; }
    bool constrain_to_parent() const { return constrain_to_parent_; }
 
    bool is_dragging() const { return active_; }

    Point mouse_start() const { return mouse_start_; }
    Rect bounds_start() const { return bounds_start_; }

    std::function<void(Rect)> on_drag;
    std::function<void()> on_end;
 
private:
    bool active_ = false;
    bool constrain_to_parent_ = true;
    Point mouse_start_{};
    Rect bounds_start_{};
};
 
} // namespace pulp::view