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/*!
\page location-plugin-osm.html
\title Qt Location Open Street Map Plugin
\ingroup QtLocation-plugins

\brief Uses Open Street Map and related services.

\section1 Overview

This geo services plugin allows applications to access
\l {http://openstreetmap.org}{Open Street Map} location based services using the Qt Location API.

Data, imagery and map information provided by \l {http://korona.geog.uni-heidelberg.de/}{OpenMapSurfer},
\l {http://www.thunderforest.com/}{ThunderForest}, OpenStreetMap and contributors. The data is
available under the \l {http://www.opendatacommons.org/licenses/odbl}{Open Database License}.

The Open Street Map geo services plugin can be loaded by using the plugin key "osm".

\note Since Qt 5.6.2, the available map types offered by this plugin may change (or be removed)
without notice depending on the actual availability of a viable openly accessible provider for each type.
This also implies that providers serving tiles over HTTPS may be used.
This becomes relevant when using the OSM plugin on platforms, such as Android, for which SSL support is not built into Qt by default.
To prevent these changes, either a different geo service plugin should be used, or the plugin
parameter \e osm.mapping.providersrepository.address should be set to a user-specified repository, in order to take full control over
(and accept \b responsibility for) selecting the provider that is used for each map type.
Since Qt 5.9.6 the default nominatim endpoint, used for geocoding and places, has also changed to HTTPS-only.

\section1 Parameters

\section2 Optional parameters
The following table lists optional parameters that can be passed to the Open Street Map plugin.

\note Since Qt 5.5 all parameters below must be prefixed with \c osm. Previous versions did not require
a prefix.

\table
\header
    \li Parameter
    \li Description
\row
    \li osm.geocoding.host
    \li Url string set when making network requests to the geocoding server.  This parameter should be set to a
        valid server url with the correct osm API. If not specified the default \l {http://nominatim.openstreetmap.org/}{url} will be used.
        \note The API documentation is available at \l {https://wiki.openstreetmap.org/wiki/Nominatim}{Project OSM Nominatim}.
\row
    \li osm.geocoding.debug_query
    \li Instructs the plugin to inject the query url to nominatim into the geocode reply, for debugging purposes.
\row
    \li osm.geocoding.include_extended_data
    \li Instructs the plugin to include Nominatim-specific information (such as geometry and class) into the returned Location
        objects, exposed as extendedAttributes.
\row
    \li osm.mapping.cache.directory
    \li Absolute path to map tile cache directory used as network disk cache.

    The default place for the cache is the \c{QtLocation/osm} subdirectory in the location returned by
    QStandardPaths::writableLocation(), called with QStandardPaths::GenericCacheLocation  as a parameter.
    On systems that have no concept of a shared cache, the application-specific \l{QStandardPaths::CacheLocation} is used instead.
\row
    \li osm.mapping.cache.disk.cost_strategy
    \li The cost strategy to use to cache map tiles on disk.
    Valid values are \b bytesize and \b unitary.
    Using \b bytesize, the related size parameter (\b osm.mapping.cache.disk.size) will
    be interpreted as bytes.
    Using \b unitary, they will be interpreted as number of tiles.
    The default value for this parameter is \b bytesize.
\row
    \li osm.mapping.cache.disk.size
    \li Disk cache size for map tiles. The default size of the cache is 50 MiB when \b bytesize is the cost
    strategy for this cache, or 1000 tiles, when \b unitary is the cost strategy.
\row
    \li osm.mapping.cache.memory.cost_strategy
    \li The cost strategy to use to cache map tiles in memory.
    Valid values are \b bytesize and \b unitary.
    Using \b bytesize, the related size parameter (\b osm.mapping.cache.memory.size) will
    be interpreted as bytes.
    Using \b unitary, they will be interpreted as number of tiles.
    The default value for this parameter is \b bytesize.
\row
    \li osm.mapping.cache.memory.size
    \li Memory cache size for map tiles. The default size of the cache is 3 MiB when \b bytesize is the cost
    strategy for this cache, or 100 tiles, when \b unitary is the cost strategy.
\row
    \li osm.mapping.cache.texture.cost_strategy
    \li The cost strategy to use to cache decompressed map tiles in memory.
    Valid values are \b bytesize and \b unitary.
    Using \b bytesize, the related size parameter (\b osm.mapping.cache.texture.size) will
    be interpreted as bytes.
    Using \b unitary, they will be interpreted as number of tiles.
    The default value for this parameter is \b bytesize.
\row
    \li osm.mapping.cache.texture.size
    \li Texture cache size for map tiles. The default size of the cache is 6 MiB when \b bytesize is the cost
    strategy for this cache, or 30 tiles, when \b unitary is the cost strategy.
    Note that the texture cache has a hard minimum size which depends on the size of the map viewport
    (it must contain enough data to display the tiles currently visible on the display).
    This value is the amount of cache to be used in addition to the bare minimum.
\row
    \li osm.mapping.custom.datacopyright
    \li Custom data copryright string is used when setting the \l{Map::activeMapType} to \l{MapType}.CustomMap via urlprefix parameter.
        This copyright will only be used when using the CustomMap from above. If empty no data copyright will be displayed for the custom map.
\row
    \li osm.mapping.custom.host
    \li Url string of a custom tile server.  This parameter should be set to a valid server url offering the correct osm API.
        To use this server, the \l{Map::activeMapType} parameter of the \l Map should be set to the supported map type
        whose type is \l{MapType}.CustomMap.
        This map type is only be available if this plugin parameter is set, in which case it is
        always \l{Map::supportedMapTypes}[supportedMapTypes.length - 1].
        \note Setting the mapping.custom.host parameter to a new server renders the map tile cache useless for the old custommap style.
\row
    \li osm.mapping.custom.mapcopyright
    \li Custom map copryright string is used when setting the \l{Map::activeMapType} to \l{MapType}.CustomMap via urlprefix parameter.
        This copyright will only be used when using the CustomMap from above. If empty no map copyright will be displayed for the custom map.
\row
    \li osm.mapping.highdpi_tiles
    \li Whether or not to request high dpi tiles. Valid values are \b true and \b false. The default value is \b false.
    Please note that not all map types are available in high dpi. Setting this parameter to true might even have no effect if
    no map type is available in high dpi at the moment. Provider information files for high dpi tiles are named
    \tt{street-hires}, \tt{satellite-hires}, \tt{cycle-hires}, \tt{transit-hires}, \tt{night-transit-hires}, \tt{terrain-hires} and \tt{hiking-hires}.
    These are fetched from the same location used for the low dpi counterparts.
\row
    \li osm.mapping.offline.directory
    \li Absolute path to a directory containing map tiles used as an offline storage. If specified, it will work together with the network disk cache, but tiles won't get automatically
    inserted, removed or updated. The format of the tiles is the same used by the network disk cache.
    There is no default value, and if this property is not set, no directory will be indexed and only the network disk cache will be used
    to reduce network usage or to act as an offline storage for the currently cached tiles.
\row
    \li osm.mapping.prefetching_style
    \li This parameter allows to provide a hint how tile prefetching is to be performed by the engine. The default value,
    \tt{TwoNeighbourLayers}, makes the engine prefetch tiles for the layer above and the one below the current tile
    layer, providing ready tiles when zooming in or out from the current zoom level.
    \tt{OneNeighbourLayer} only prefetches the one layer closest to the current zoom level.
    Finally, \tt{NoPrefetching} allows to disable the prefetching, so only tiles that are visible will be fetched.
    Note that, depending on the active map type, this hint might be ignored.
\row
    \li osm.mapping.providersrepository.address
    \li The OpenStreetMap plugin retrieves the provider's information from a remote repository. This is done to prevent using hardcoded
    servers by default, which may become unavailable. By default this information is fetched from \l {http://maps-redirect.qt.io} {maps-redirect.qt.io}.
    Setting this parameter changes the provider repository address to a user-specified one, which must contain the files
    \tt{street}, \tt{satellite}, \tt{cycle}, \tt{transit}, \tt{night-transit}, \tt{terrain} and \tt{hiking}, each of which must contain valid provider information.
\row
    \li osm.mapping.providersrepository.disabled
    \li By default, the OpenStreetMap plugin retrieves the provider's information from a remote repository to avoid a loss of service due to unavailability of hardcoded services.
    The plugin, however, still contains fallback hardcoded provider data, in case the provider repository becomes unreachable.
    Setting this parameter to \b true makes the plugin use the hardcoded urls only and therefore prevents the plugin from fetching provider data from the remote repository.

\row
    \li osm.places.debug_query
    \li Set this parameter to true to have an extended attribute in each result named "requestUrl", and containing the
    url used for the query. Default is \b false.
\row
    \li osm.places.host
    \li Url string set when making network requests to the places server.
        This parameter should be set to a valid server url with the correct osm API.
        If not specified the default  \l {http://nominatim.openstreetmap.org/search}{url}
        will be used.
        \note The API documentation is available at \l {https://wiki.openstreetmap.org/wiki/Nominatim}{Project OSM Nominatim}.
\row
    \li osm.places.page_size
    \li The amount of results in a page. Note that this value might be clamped server side. The typical maximum in standard
    nominatim instances is 50.

\row
    \li osm.routing.apiversion
    \li String defining the api version of the (custom) OSRM server. Valid values are \b{v4} and \b{v5}. The default is \b{v5}.
        This parameter should be set only if \tt{osm.routing.host} is set, and is an OSRM v4 server.
\row
    \li osm.routing.host
    \li Url string set when making network requests to the routing server.  This parameter should be set to a
        valid server url with the correct osrm API. If not specified the default \l {http://router.project-osrm.org/route/v1/driving/}{url} will be used.
        \note The API documentation and sources are available at \l {http://project-osrm.org/}{Project OSRM}.

\row
    \li osm.useragent
    \li User agent string set when making network requests.  This parameter should be set to a
        value that uniquely identifies the application. Note that providers might block applications not setting this
        parameter, leaving it to the stock plugin user agent (e.g., \l {http://wiki.openstreetmap.org/wiki/Nominatim_usage_policy}{Nominatim}
        for geocoding)
\endtable

\section1 Parameter Usage Example

The following example shows how to create an OSM plugin instance with
parameters supplied for an useragent, and if necessary, a custom server url plus the corresponding copyright information for the tile provider.
Additionally, it is possible to choose another routing server than the public osrm one.

\section2 QML

\code
Plugin {
    name: "osm"
    PluginParameter { name: "osm.useragent"; value: "My great Qt OSM application" }
    PluginParameter { name: "osm.mapping.host"; value: "http://osm.tile.server.address/" }
    PluginParameter { name: "osm.mapping.copyright"; value: "All mine" }
    PluginParameter { name: "osm.routing.host"; value: "http://osrm.server.address/viaroute" }
    PluginParameter { name: "osm.geocoding.host"; value: "http://geocoding.server.address" }
}
\endcode

\section1 Other Plugin-specific Information

\section2 Tile cache

The tiles are cached in a \c{QtLocation/osm} directory in \l {QStandardPaths::writableLocation()}{QStandardPaths::writableLocation}
(\l{QStandardPaths::GenericCacheLocation}). On systems that have no concept of a shared cache, the application-specific
\l{QStandardPaths::CacheLocation} is used instead.
*/
