The layer and group model

The vocabulary a query is written in — the kinds of layer, how groups nest them, how a calculated layer reads several maps at once, and where the full property list lives.

Mappia reference, section “Model”. Page: https://mappia.earth/reference/layer-and-group-model/ Generated API entries: LayersProperties, LayersFunctions, GroupProperties, GroupFunctions, ConfigLayer, VectorLayer, FileLayer, XYZLayer, SourceConfig, ConfigLayer.operation, FileLayer.type, LayersProperties.source, RawMaps.operations, paramsButtonConfigProperties (https://mappia.earth/assets/api.json)

Everything a query says is said about a layer definition: a plain object. Groups nest those objects and pass properties down to them. This page is the vocabulary: the kinds of layer that exist, what distinguishes them, and which property list applies to each. The exhaustive, generated list of properties lives in the API reference — this page is the map of it.

1. A layer definition

{
  name: "CSR:estados",      // which map(s) — the only property with no default
  title: "States",          // what the layer panel shows
  visibility: true,         // starts visible
  opacity: 0.8,
  group: "background",      // optional: a reserved slot, see §4
}

Two properties decide how everything else is read:

2. The kinds of layer

A layer registered through addRemoteWMSServer behaves as a catalogue layer; the registration says where its server is and whether it needs a proxy.

Only calculated, file and tile (xyz) layers have a panel in the layer list: descriptionHtml (text and widgets), paramsButtonConfig (row buttons) and exclusiveGroupDetails are ignored on published maps, basemaps and servers added with addRemoteWMSServer, while startLegendOpen and hideStyleChooser work on published maps only. maxZoom set in the query is read only by calculated layers; a published map takes it from its catalogue entry.

2.1 type, for file layers

type chooses how a source: "file" layer obtains its features (case-insensitive):

A GeoJSON without a declared CRS is guessed from its first coordinate: EPSG:4326 when it looks like longitude/latitude, otherwise EPSG:3857. CSV and lists of plain objects use the query’s ExtjsUtils.CONFIGURATION.setOptions({ defaultFromProj }), then the link’s defaultFromProj, then the map projection. Declare crs in the GeoJSON, or fromProj on the layer, whenever the data is in anything else (UTM, for example) — a silent misalignment is the usual symptom.

2.2 operation, for calculated layers

A calculated layer’s name lists several maps; operation is a comma-separated list with one token per map, in the same order, saying how each map’s pixels are turned into the numbers expression receives. An empty token leaves that map on the default.

{
  source: "calculate",
  name: "CSR:pop_density_estimate_2015,CSR:estados,CSR:pop_density_estimate_2015",
  operation: "average,,area",   // map 1 averaged, map 2 default, map 3 as area
}

Tokens are case- and whitespace-insensitive. Every token except the default and rgba requires the map to be published with that operation available; if it is not, the console reports Operation X is not defined for layer Y and the layer produces nothing.

3. Groups

Groups come in two kinds, and nest. A top-level group with title and elements becomes an entry of the top menu, which lists all its layers for the reader to turn on (GroupProperties.title). A group with viewTitle and elements becomes a heading in the layer panel, above the layers of it that are on:

[
  {
    viewTitle: "Boundaries",
    color: "#8b0000",
    openGroup: true,
    defaultProperties: { visibility: false, source: "local" },
    elements: [
      { title: "States", name: "CSR:estados", visibility: true },
      { title: "Municipalities", name: "CSR:municipios" },
    ],
  },
]

Interpretation flattens all of this into an ordered list of layers, each remembering its group path. Order inside a group is declaration order unless priority reorders it (higher first).

4. Reserved and special slots

5. Presentation properties, in one place

These do not change what the layer computes, only how it appears. All are documented individually in the API reference under LayersProperties and ConfigLayer. Unless noted, they apply to every kind of layer:

• In the panel: title, startListed, hideListing, hideMetadata, hideLegendButton, showRemoveBtn, useLayerTooltip, customLayerClass, verticalMenu; startLegendOpen and hideStyleChooser (published maps only); description (file and tile layers only); thumbUrl (published maps and tile layers only); legendTitle (calculated layers only).
• On the map: visibility, opacity; minscale, maxscale and hideTilePlaceholder (published maps and calculated layers); insideOpacity and maxZoom (calculated layers only). The map’s extent and attribution come from its catalogue entry, not from the query: limit the area with extents.
• In the legend of a calculated layer: categorical, categoricalPalette, maxQntEntries, showLoadingModal (also on file layers).

6. How to find a property

Where to find it shows, for anything you want to change, where it is written (in a layer, in a group, before the layer list or in the map’s link) and which part of the API reference lists it. If a property appears in an old query and does nothing, check pitfalls and properties that do nothing before trusting it.