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A1phaN
69 lines
2.9 KiB
TypeScript
69 lines
2.9 KiB
TypeScript
import { describe, expect, it } from 'vitest'
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import L from 'leaflet'
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import { crsForBasemap, getCrsGcj02 } from './gcj02Crs'
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const CRS_GCJ02 = getCrsGcj02()
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/**
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* What these guard is the one failure that cannot be seen in a screenshot review
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* of a map full of Chinese labels: a marker drawn a few hundred metres from where
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* it belongs still looks like a perfectly plausible map.
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*/
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describe('CRS_GCJ02', () => {
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it('projects a WGS-84 coordinate onto the GCJ-02 tile grid', () => {
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const wgs = L.latLng(39.90869, 116.39124)
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const shifted = CRS_GCJ02.latLngToPoint(wgs, 15)
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const unshifted = L.CRS.EPSG3857.latLngToPoint(wgs, 15)
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// At zoom 15 the GCJ-02 offset is worth several hundred pixels, so a map that
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// silently kept EPSG3857 would fail here rather than being off by a rounding.
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const dx = Math.abs(shifted.x - unshifted.x)
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const dy = Math.abs(shifted.y - unshifted.y)
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expect(Math.hypot(dx, dy)).toBeGreaterThan(20)
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})
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it('round-trips a coordinate through the pixel plane', () => {
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const wgs = L.latLng(31.2304, 121.4737)
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const back = CRS_GCJ02.pointToLatLng(CRS_GCJ02.latLngToPoint(wgs, 18), 18)
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// Sub-metre at zoom 18, i.e. the click handler and the marker agree.
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expect(back.lat).toBeCloseTo(wgs.lat, 6)
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expect(back.lng).toBeCloseTo(wgs.lng, 6)
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})
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it('leaves a coordinate outside China exactly where EPSG3857 puts it', () => {
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// Otherwise choosing an Amap basemap would move every foreign trip in the
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// account, which is a far bigger failure than the one this file prevents.
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const paris = L.latLng(48.8566, 2.3522)
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const shifted = CRS_GCJ02.latLngToPoint(paris, 15)
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const plain = L.CRS.EPSG3857.latLngToPoint(paris, 15)
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expect(shifted.x).toBeCloseTo(plain.x, 6)
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expect(shifted.y).toBeCloseTo(plain.y, 6)
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})
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it('keeps the Web Mercator tile grid, because Amap uses the standard one', () => {
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// Same scale and same transformation as EPSG3857: only the datum differs. If
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// this drifts, tiles are requested at the wrong zoom or the wrong origin and
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// the map is visibly broken rather than subtly offset.
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expect(CRS_GCJ02.scale(12)).toBe(L.CRS.EPSG3857.scale(12))
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expect(CRS_GCJ02.code).toBe('TREK:GCJ02')
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})
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it('measures distance in WGS-84, since that is what it is handed', () => {
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const a = L.latLng(39.90869, 116.39124)
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const b = L.latLng(39.91869, 116.39124)
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expect(CRS_GCJ02.distance(a, b)).toBeCloseTo(L.CRS.EPSG3857.distance(a, b), 6)
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})
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})
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describe('crsForBasemap', () => {
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it('returns undefined for a WGS-84 basemap so the map keeps Leaflet\u2019s default', () => {
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// Not L.CRS.EPSG3857: passing the prop at all pins the CRS, and the point is
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// that a map on an ordinary basemap is constructed exactly as it was before.
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expect(crsForBasemap(false)).toBeUndefined()
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})
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it('returns the shifted CRS for a GCJ-02 basemap', () => {
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expect(crsForBasemap(true)).toBe(getCrsGcj02())
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})
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})
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