include/rive/constraints/scrolling/scroll_virtualizer.hpp

#ifndef _RIVE_SCROLL_VIRTUALIZER_HPP_
#define _RIVE_SCROLL_VIRTUALIZER_HPP_
#include "rive/artboard.hpp"
#include "rive/math/vec2d.hpp"
#include "rive/world_transform_component.hpp"
#include "rive/virtualizing_component.hpp"
#include <stdio.h>
#include <vector>
namespace rive
{
class LayoutNodeProvider;
class ScrollConstraint;
class VirtualLayout;

// Realizes the items of the scroll's VirtualLayout that the viewport reaches,
// recycling the rest. Owns no geometry.
class ScrollVirtualizer
{
private:
  // First item on screen after the last pass, where its line started, and
  // how many items there were; -1 when there's nothing to anchor.
  int m_anchorItem = -1;
  float m_anchorStart = 0;
  int m_anchorItemCount = 0;
  // The anchor's realized instance, which a list update moves along with
  // its item; null when the anchor isn't a list item.
  Virtualizable* m_anchorInstance = nullptr;
  float m_offset = 0;
  bool m_infinite = false;
  float m_viewportSize = 0;
  // Scrolled both ways, the offset along the lines. A grid windows columns
  // over this span of its content.
  bool m_windowsColumns = false;
  // Whether the last pass pinned grid cells, which the next must undo.
  bool m_pinnedCells = false;
  float m_flowOffset = 0;
  float m_columnStart = 0;
  float m_columnViewport = 0;
  VirtualizedDirection m_direction = VirtualizedDirection::horizontal;

public:
  ~ScrollVirtualizer();
  void reset();
  bool constrain(
      ScrollConstraint* scroll,
      std::vector<LayoutNodeProvider*>& children,
      float offset,
      VirtualizedDirection direction,
      float flowOffset = 0.0f,
      float columnStart = 0.0f,
      float columnViewport = 0.0f,
      bool windowsColumns = false);
  void virtualize(
      ScrollConstraint* scroll,
      std::vector<LayoutNodeProvider*>& children);
  // How far the anchor item's line moved along the scroll axis since the
  // last pass, given the rebuilt layout; 0 when there's no anchor.
  float anchorMoved(
      const VirtualLayout& layout,
      std::vector<LayoutNodeProvider*>& children) const;
};
} // namespace rive

#endif