LayerChooser

The tool offers layer selection to the user.

Scope

The LayerChooser offers an additive (usually Overlays, technically named with type: 'mask') and an exclusive (usually background maps, type: 'background') selection of layers to the users.

Order of layers within a layer is currently always as initially configured.

Configuration

The tool does not require any configuration for itself, but is based on the mapConfiguration.layers. It will infer id and name from that configuration.

This plugin requires the configuration of mapConfiguration.layer.type. Also, this plugin also supports the optional configuration parameters mapConfiguration.layer.hideInMenu, mapConfiguration.layer.minZoom, mapConfiguration.layer.maxZoom, mapConfiguration.layer.options and mapConfiguration.layer.visibility which are described in more depth in the following table.

fieldName type description
type enum["background", "mask"] Layer handling. Backgrounds are mutually exclusive, masks ("overlays") can be stacked.
hideInMenu boolean? Can be set for layers of type 'mask' to hide them in the selection menu.
maxZoom number? If set, layer only available (and selectable) up to this zoom level.
minZoom number? If set, layer only available (and selectable) from this zoom level on.
options options? Shows a layer-specific sub-menu; its contents are configurable.
visibility boolean? Initial visibility. Defaults to false.

For details on the displayComponent attribute, refer to the Global Plugin Parameters section of @polar/core.

Example configuration:

layers: [
  {
    id: backgroundmap,
    visibility: true,
    type: 'background',
    name: 'Basemap Grayscale',
  },
  {
    id: memorialsWFS,
    visibility: false,
    hideInMenu: true,
    type: 'mask',
    name: 'Memorial (WFS)',
    minZoom: 7,
  },
]

layer.options

An option wheel will appear in the layer chooser that allows opening a sub-menu with configured configuration options for the end user.

fieldName type description
layers layer.options.layers If configured, all configured layers of the layer can be turned off and on by the user. ⚠️ Only implemented for WMS. Only implemented for top layers; that is, only first level of nesting is considered.

Example configuration:

options: {
  layers: {
    order: '6,24,25,4,3,2,1,0',
    title: {
      '6': 'Monument area',
      '24': 'Majority of structures',
      '25': 'Material group',
      '4': 'Architectural monument',
      '3': 'Natural monument',
      '2': 'Water bodies',
      '1': 'Architectural monument (area)',
      '0': 'Natural monument (area)',
    },
    legend: true,
  },
},

layer.options.layers

This field is named like this to match the OGC specification for their name; that is, layers have layers that may have layers that may have layers, and so on. However, only the first level (a layer's layers) is currently implemented.

fieldName type description
legend boolean | Record<name, legendUrl>? Legend image to be used for sub-layer. If false, no image is displayed. If true, it is assumed an image exists in the layer's GetCapabilities, and that will be used. If Record, it maps the layer name to a linked image. The legendUrl can be any valid reachable image URL.
order string? Optional. If not given, field layers from service description will be used, and defines order of options. If layer defined in service description's layers and order, it's initially on. If only in order, it's initially off. If only in layers, it's always-on. If in neither, it's always-off.
title boolean | Record<name, layerName>? Title to be displayed for sub-layer. If false, layer name itself will be used as given in service description 'layers' field. If true, it is assumed a name exists in the layer's GetCapabilities, and that will be used. If Record, it maps the layer name to an arbitrary display name given by the configuration. The layerName can be any string.

Example configuration:

layers: {
  order: '6,24,25,4,3,2,1,0',
  title: {
    '6': 'Monument area',
    '24': 'Majority of structures',
    '25': 'Material group',
    '4': 'Architectural monument',
    '3': 'Natural monument',
    '2': 'Water bodies',
    '1': 'Architectural monument (area)',
    '0': 'Natural monument (area)',
  },
  legend: true,
},
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