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#pragma once
#include <mbgl/util/noncopyable.hpp>
#include <mbgl/storage/resource.hpp>
namespace mbgl {
class FileSource;
class AsyncRequest;
class Response;
class Tileset;
namespace style {
class UpdateParameters;
}
template <typename T>
class TileSource : private util::noncopyable {
public:
// TileSources can have two states: optional or required.
// - optional means that only low-cost actions should be taken to obtain the data
// (e.g. load from cache, but accept stale data)
// - required means that every effort should be taken to obtain the data (e.g. load
// from internet and keep the data fresh if it expires)
enum class Necessity : bool {
Optional = false,
Required = true,
};
TileSource(T&,
const OverscaledTileID&,
const style::UpdateParameters&,
const Tileset&);
void setNecessity(Necessity newNecessity) {
if (newNecessity != necessity) {
necessity = newNecessity;
if (necessity == Necessity::Required) {
makeRequired();
} else {
makeOptional();
}
}
}
private:
bool isOptional() const {
return necessity == Necessity::Optional;
}
bool isRequired() const {
return necessity == Necessity::Required;
}
// called when the tile is one of the ideal tiles that we want to show definitely. the tile source
// should try to make every effort (e.g. fetch from internet, or revalidate existing resources).
void makeRequired();
// called when the zoom level no longer corresponds to the displayed one, but
// we're still interested in retaining the tile, e.g. for backfill.
// subclassed TileSources should cancel actions they are taking to provide
// an up-to-date version or load new data
void makeOptional();
void loadOptional();
void loadedData(const Response&);
void loadRequired();
T& tileData;
Necessity necessity;
Resource resource;
FileSource& fileSource;
std::unique_ptr<AsyncRequest> request;
};
} // namespace mbgl
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