I'm using mapbox as source of tiles in my map component which is working fine, however when I try to set the retina prefix it prints out an error message:

Unknown map format "@2x.png"

    Plugin {
        id: mapPlugin
        name: "mapbox"

        PluginParameter {
            name: "mapbox.map_id"
            value: "mapbox.streets"
        }

        PluginParameter {
            name: "mapbox.access_token"
            value: "xxx"
        }

        PluginParameter {
            name: "mapbox.format"
            value: "@2x.png"
        }
    }

The way the format parameter is working right now in Qt is related with the "image format" rather than representing the "format" itself which allows to have the dpi version as prefix and the image format as suffix.

Mapbox's api documentation about it:

https://www.mapbox.com/api-documentation/#retina
and
https://www.mapbox.com/api-documentation/#retrieve-tiles