tilepyramidlayer.h

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#ifndef TILEPYRAMIDLAYER_H
#define TILEPYRAMIDLAYER_H
 
#include "layers/openswmmvislayer.h"
 
#include <QCache>
#include <QHash>
#include <QImage>
#include <QMutex>
#include <QPair>
#include <QRectF>
#include <QString>
 
class TilePyramidLayer : public OpenSWMMVisLayer
{
    Q_OBJECT
 
public:
    explicit TilePyramidLayer(OpenSWMMVisWorkspace *parent = nullptr);
    ~TilePyramidLayer() override;
 
protected:
    struct TileDraw
    {
        QImage img;
        QRectF src;
        bool   exact = false;
    };
 
    void cacheTile(const QString &key, const QImage &img,
                   const MapExtent &extent, int level);
 
    [[nodiscard]] bool isTileCached(const QString &key) const;
 
    [[nodiscard]] QImage cachedTileImage(const QString &key) const;
 
    void clearTiles();
 
    void setTileCacheCapacity(int maxTiles);
    [[nodiscard]] int tileCacheCapacity() const;
 
    [[nodiscard]] bool resolveTileForDraw(const QString &key,
                                          const MapExtent &tileExtent,
                                          double maxSpanRatio,
                                          TileDraw &out) const;
 
private:
    struct CachedTile
    {
        QImage    img;
        MapExtent extent;
        int       level = 0;
    };
 
    mutable QMutex m_tileMutex;
    QCache<QString, CachedTile> m_tileCache{256};
    // extent/level side-index of the cache contents, iterated by the fallback
    // search (QCache itself can't be walked without promoting entries).
    // QCache evicts silently, so the index is pruned lazily on lookup misses
    // and swept whenever it outgrows the cache capacity.
    mutable QHash<QString, QPair<MapExtent, int>> m_tileIndex;
 
    void pruneIndexLocked();
};
 
#endif // TILEPYRAMIDLAYER_H