OpenSpace/modules/globebrowsing/tile/tileprovider/tileprovider.h

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 * OpenSpace                                                                             *
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 * Copyright (c) 2014-2017                                                               *
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#ifndef __OPENSPACE_MODULE_GLOBEBROWSING___TILE_PROVIDER___H__
#define __OPENSPACE_MODULE_GLOBEBROWSING___TILE_PROVIDER___H__

#include <modules/globebrowsing/tile/chunktile.h>
#include <modules/globebrowsing/tile/tile.h>
#include <modules/globebrowsing/other/lrucache.h>

#include <vector>

namespace openspace {
namespace globebrowsing {
namespace tileprovider {
    
/**
 * Interface for providing <code>Tile</code>s given a 
 * <code>TileIndex</code>. 
 */
class TileProvider {
public:
    /**
     * Factory method for instantiating different implementations of 
     * <code>TileProviders</code>. The provided dictionary must 
     * define a key specifying what implementation of TileProvider
     * to be instantiated.
     */
    static std::unique_ptr<TileProvider> createFromDictionary(const ghoul::Dictionary& dictionary);

    /** 
     * Empty default constructor 
     */
    TileProvider() = default;

    /**
     * Implementations of the TileProvider interface must implement 
     * a constructor taking a dictionary as input. The provided 
     * dictionary must define a key specifying what implementation 
     * of TileProvider to be instantiated.
     */
    TileProvider(const ghoul::Dictionary& dictionary);

    /**
     * Virtual destructor that subclasses should override to do
     * clean up.
     */
    virtual ~TileProvider() { }

    /**
     * Method for querying tiles, given a specified <code>TileIndex</code>.
     *
     * This method is expected to be invoked multiple times per frame,
     *  and should therefore return quickly, e.g. not perform heavy I/O 
     * operations. However, invoking this method may spawn separate threads
     * to perform such operations. Therefore, programmers shoud 
     *  note that there is no guarantee that the <code>Tile</code> 
     * status and texture will be consistent over different invocations
     * of this method.
     * 
     * \param tileIndex specifying a region of a map for which 
     * we want tile data.
     * 
     * \returns The tile corresponding to the TileIndex by the time
     * the method was invoked.
     */
    virtual Tile getTile(const TileIndex& tileIndex) = 0;


    virtual ChunkTile getChunkTile(TileIndex tileIndex, int parents = 0,
        int maxParents = 1337);

    virtual ChunkTilePile getChunkTilePile(TileIndex tileIndex, int pileSize);

    /**
     * TileProviders must be able to provide a defualt
     * <code>Tile</code> which may be used by clients in cases when
     * requested tiles were unavailable.
     *
     * \returns A default tile
     */
    virtual Tile getDefaultTile() = 0;

    /**
     * Returns the status of a <code>Tile</code>. The <code>Tile::Status</code>
     * corresponds the <code>Tile</code> that would be returned
     * if the function <code>getTile</code> would be invoked with the same
     * <code>TileIndex</code> argument at this point in time.
     */
    virtual Tile::Status getTileStatus(const TileIndex& index) = 0;

    /**
     * Get the associated depth transform for this TileProvider.
     * This is necessary for TileProviders serving height map 
     * data, in order to correcly map pixel values to meters.
     */
    virtual TileDepthTransform depthTransform() = 0;

    /**
     * This method should be called once per frame. Here, TileProviders
     * are given the opportunity to update their internal state.
     */
    virtual void update() = 0;

    /**
     * Provides a uniform way of all TileProviders to reload or 
     * restore all of its internal state. This is mainly useful 
     * for debugging purposes.
     */
    virtual void reset() = 0;

    /**
     * \returns The maximum level as defined by <code>TileIndex</code>
     * that this TileProvider is able provide.
     */
    virtual int maxLevel() = 0;
        
    /**
     * \returns the no data value for the dataset. Default is the minimum float avalue.
     */
    virtual float noDataValueAsFloat();
};

using TileCache = LRUCache<TileIndex::TileHashKey, Tile>;

} // namespace tileprovider
} // namespace globebrowsing
} // namespace openspace

#endif // __OPENSPACE_MODULE_GLOBEBROWSING___TILE_PROVIDER___H__