Places

Show places on a map the host draws. Give a place as lat and lon in decimal degrees, or as an address the host looks up. Never give a tile or a map URL: the host chooses the map and where its tiles come from, and a block cannot name either.

import { useState } from 'react';
import { DemoBlock } from '../shared/intelligent-ui.tsx';
import { bound, ui } from '../shared/intelligent-ui-tree.ts';

export default function PlacesDemo() {
    const [picked, setPicked] = useState<unknown>('');
    return (
        <DemoBlock
            nodes={[
                bound(
                    ui(
                        'Map',
                        {},
                        ui('Place', { lat: 52.0907, lon: 5.1214, value: 'dom', detail: 'Climb the tower' }, 'Domtoren'),
                        ui('Place', { address: 'Oudegracht 245, Utrecht', value: 'gracht' }, 'Oudegracht'),
                        ui('Place', { lat: 52.0894, lon: 5.1103, value: 'station' }, 'Station')
                    ),
                    picked,
                    setPicked
                )
            ]}
            context={{ place: (nodeId) => (nodeId.endsWith('.1') ? { lat: 52.0849, lon: 5.1181 } : undefined) }}
        />
    );
}

$picked = ""
<Map value={$picked}>
<Place lat={52.0907} lon={5.1214} value="dom" detail="Climb the tower">Domtoren</Place>
<Place address="Oudegracht 245, Utrecht" value="gracht">Oudegracht</Place>
<Place lat={52.0894} lon={5.1103} value="station">Station</Place>
</Map>
<Choices><Choice context={"Plan the walk around " + $picked}>Plan the walk</Choice></Choices>

Map

One to 50 places, with a numbered list of them under the map. A complete Map without a Place or with more than 50 written is refused. An Each or a Show inside it is counted again once it drew: a Map that draws none fails as a whole, and one that draws more than 50 shows the first 50 with the diagnostic too_many_children and a line under the list that says how many were left out (UiViewNode.omitted). The list is the accessible form of the map and the form a page shows when it has no tiles, so every place appears in it, also one the map could not place.

Prop	Type	Required	Notes
value	scalar	No	Bindable; the value of the place a person picked

A Map is not an input unless it is bound. Bound, a row of the list is a button when its Place has a value, and picking it sets the binding. A Choice carries the value only when a place of that map offers it, or when it still has its default.

Place

One place. It stands only inside Map, and its children are the name.

Prop	Type	Required	Notes
lat	number	With lon	From -90 to 90
lon	number	With lat	From -180 to 180
address	string	Or lat and lon	At most 512 characters; looked up by the host
detail	string	No	A line under the name
value	scalar	No	What picking the place sets on the bound Map

A Place that gives lat without lon (or the other way round), or neither coordinates nor an address, fails alone and draws as its text. Give both and the host's lookup of the address wins: the point it finds is the one drawn, and lat and lon stand while the lookup is on its way, when it finds nothing and when the host looks nothing up.

Looking up an address

A renderer does not look anything up. UiRenderContext.place(nodeId, address) hands it the point the host read for that address, which is undefined until the block is frozen, and null for an address with no point. A reading counts only for the address it was made for, so a place that moved to another node (an Each that reordered) or whose address changed never wears another place's point. A reply the machine keeps no readings for reads as not found at once. The list says Looking up for the first and Not on the map for the second; a place without a point has no marker. Live queries says how the machine freezes the points.

What the host draws

The host chooses the map, so a block cannot name tiles, a style or a vendor. A renderer that draws the picture has the host's tiles when it has them, and otherwise an outline of the world with the same numbered markers, always with the list under it. The picture is not part of the block: it is not saved, and the same block reads on a page without tiles. A point drawn at street level on the outline would be a blank patch, so the outline never zooms closer than about a country. The outline is the 110m land of Natural Earth, which is in the public domain.

Fallback

A Map falls back to a numbered list, one line per place that drew (a place that failed stays unnumbered, as its text): 1. Domtoren (52.0907, 5.1214): Climb the tower. The coordinates, the address and the detail are all in it, so another agent reading the reply sees where the places are.