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Fix to map jumping when bounds cross longitude 180 #10903

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merged 8 commits into from Aug 13, 2021
Merged

Fix to map jumping when bounds cross longitude 180 #10903

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b96ad6c
Added tests, should be failing
SnailBones Jul 30, 2021
794fd7e
Tests passing. Added comments in transform.js
SnailBones Jul 30, 2021
528bd8d
Added wrapping to bounds check. More tests and debug page.
SnailBones Jul 31, 2021
4f8f121
Changed wrapping approach to fix bug where map could be forced to oth…
SnailBones Aug 1, 2021
72f3b83
Clean up misleading variables
SnailBones Aug 1, 2021
bee55d7
Removing log from test
SnailBones Aug 1, 2021
69e8f84
Suggestions from rreusser
SnailBones Aug 9, 2021
f7ecfcc
Apply ricky's suggestions to debug
SnailBones Aug 12, 2021
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41 changes: 41 additions & 0 deletions debug/antimeridian.html
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@@ -0,0 +1,41 @@
<!DOCTYPE html>
<html>
<head>
<title>Mapbox GL JS debug page</title>
<meta charset='utf-8'>
<meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
<link rel='stylesheet' href='../dist/mapbox-gl.css' />
<style>
body { margin: 0; padding: 0; }
html, body, #map { height: 100%; }
</style>
</head>

<body>
<div id='map'></div>

<script src='../dist/mapbox-gl-dev.js'></script>
<script src='../debug/access_token_generated.js'></script>

<script>

var map = new mapboxgl.Map({
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container: 'map',
style: 'mapbox://styles/mapbox/streets-v11',
zoom: 6,
center: [179.012, -18.124],
maxBounds: [[175, -25], [-175, -10]]
});
map.transform.center = new mapboxgl.LngLat(190, -40);

document.addEventListener('keypress', (e) => {
console.log(e.key);
if (e.key === " ") {
console.log(map.transform.center);
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console.log(map.transform.point);
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}
});

</script>
</body>
</html>
39 changes: 26 additions & 13 deletions src/geo/transform.js
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Expand Up @@ -887,17 +887,20 @@ class Transform {
zoomScale(zoom: number) { return Math.pow(2, zoom); }
scaleZoom(scale: number) { return Math.log(scale) / Math.LN2; }

// World coordinates from LngLat
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Just an idea: It doesn't transfer directly, but when I added comments to explain numerical units, I added ranges since that's the easiest way for me to immediately understand the meaning:

mapbox-gl-js/src/geo/transform.js

Lines 82 to 88 in e0d6a56

// Transform from screen coordinates to GL NDC, [0, w] x [h, 0] --> [-1, 1] x [-1, 1]
// Roughly speaking, applies pixelsToGLUnits scaling with a translation
glCoordMatrix: Float32Array;
// Inverse of glCoordMatrix, from NDC to screen coordinates, [-1, 1] x [-1, 1] --> [0, w] x [h, 0]
labelPlaneMatrix: Float32Array;

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Great idea!

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@SnailBones SnailBones Aug 9, 2021 •
edited

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How's this?

Suggested change
// World coordinates from LngLat
// Transform from LngLat to world coordinates [-180, 180] x [90, -90] --> [0, this.worldSize] x [0, this.worldSize]

project(lnglat: LngLat) {
const lat = clamp(lnglat.lat, -this.maxValidLatitude, this.maxValidLatitude);
return new Point(
mercatorXfromLng(lnglat.lng) * this.worldSize,
mercatorYfromLat(lat) * this.worldSize);
}

// LngLat from world coordinates
unproject(point: Point): LngLat {
return new MercatorCoordinate(point.x / this.worldSize, point.y / this.worldSize).toLngLat();
}

// Point at center in world coordinates.
get point(): Point { return this.project(this.center); }

setLocationAtPoint(lnglat: LngLat, point: Point) {
Expand Down Expand Up @@ -1210,7 +1213,10 @@ class Transform {
*/
setMaxBounds(bounds?: LngLatBounds) {
if (bounds) {
this.lngRange = [bounds.getWest(), bounds.getEast()];
const eastBound = bounds.getEast();
const westBound = bounds.getWest();
// Unwrap bounds if they cross the 180th meridian
this.lngRange = [westBound, eastBound > westBound ? eastBound : eastBound + 360];
this.latRange = [bounds.getSouth(), bounds.getNorth()];
this._constrain();
} else {
Expand Down Expand Up @@ -1355,11 +1361,9 @@ class Transform {

this._constraining = true;

let minY = -90;
let maxY = 90;
let minX = -180;
let maxX = 180;
let sy, sx, x2, y2;
let minY = 0;
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let maxY = 0;
let minX, maxX, sy, sx, y2;
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const size = this.size,
unmodified = this._unmodified;

Expand Down Expand Up @@ -1400,18 +1404,27 @@ class Transform {
if (y + h2 > maxY) y2 = maxY - h2;
}

if (this.lngRange) {
const x = point.x,
w2 = size.x / 2;
let x = point.x;

if (x - w2 < minX) x2 = minX + w2;
if (x + w2 > maxX) x2 = maxX - w2;
if (this.lngRange) {
// Translate to positive positions with the map center in the center position.
// This ensures that the map snaps to the correct edge.
const shift = this.worldSize / 2 - (minX + maxX) / 2;
x = (x + shift + this.worldSize) % this.worldSize;
minX += shift;
maxX += shift;

const w2 = size.x / 2;
if (x - w2 < minX) x = minX + w2;
if (x + w2 > maxX) x = maxX - w2;

x -= shift;
}

// pan the map if the screen goes off the range
if (x2 !== undefined || y2 !== undefined) {
if (x !== point.x || y2 !== undefined) {
this.center = this.unproject(new Point(
x2 !== undefined ? x2 : point.x,
x,
y2 !== undefined ? y2 : point.y));
}

Expand Down
106 changes: 106 additions & 0 deletions test/unit/geo/transform.test.js
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Expand Up @@ -117,6 +117,112 @@ test('transform', (t) => {
t.end();
});

t.test('maxBounds should not jump to the wrong side when crossing 180th meridian (#10447)', (t) => {
t.test(' to the East', (t) => {
const transform = new Transform();
transform.zoom = 6;
transform.resize(500, 500);
transform.lngRange = [160, 190];
transform.latRange = [-55, -23];

transform.center = new LngLat(-170, -40);
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Where does -170 come from? I'd expect (160 + 190) / 2 --> 175. -170 is equivalent to 190, so is it using the east bound as the center?

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Yes, this test sets the center to the east bound in order to test that the map position snaps to the correct side. The exact position is arbitrary, it could be any position out of bounds on the east side of the map.


t.ok(transform.center.lng < 190);
t.ok(transform.center.lng > 175);

t.end();
});

t.test('to the West', (t) => {
const transform = new Transform();
transform.zoom = 6;
transform.resize(500, 500);
transform.lngRange = [-190, -160];
transform.latRange = [-55, -23];

transform.center = new LngLat(170, -40);

t.ok(transform.center.lng > -190);
t.ok(transform.center.lng < -175);

t.end();
});

t.test('longitude 0 - 360', (t) => {
const transform = new Transform();
transform.zoom = 6;
transform.resize(500, 500);
transform.lngRange = [0, 360];
transform.latRange = [-90, 90];

transform.center = new LngLat(-155, 0);

t.same(transform.center, new LngLat(205, 0));

t.end();
});

t.test('longitude -360 - 0', (t) => {
const transform = new Transform();
transform.zoom = 6;
transform.resize(500, 500);
transform.lngRange = [-360, 0];
transform.latRange = [-90, 90];

transform.center = new LngLat(160, 0);
t.same(transform.center.lng.toFixed(10), -200);

t.end();
});

t.end();

});

t.test('maxBounds snaps in the correct direction (no forcing to other edge when width < 360)', (t) => {
const transform = new Transform();
transform.zoom = 6;
transform.resize(500, 500);
transform.setMaxBounds(new LngLatBounds([-160, -20], [160, 20]));

transform.center = new LngLat(170, 0);
t.ok(transform.center.lng > 150);
t.ok(transform.center.lng < 160);

transform.center = new LngLat(-170, 0);
t.ok(transform.center.lng > -160);
t.ok(transform.center.lng < -150);

t.end();
});

t.test('maxBounds works with unwrapped values across the 180th meridian (#6985)', (t) => {
const transform = new Transform();
transform.zoom = 6;
transform.resize(500, 500);
transform.setMaxBounds(new LngLatBounds([160, -20], [-160, 20])); //East bound is "smaller"

const wrap = val => ((val + 360) % 360);

transform.center = new LngLat(170, 0);
t.same(wrap(transform.center.lng), 170);

transform.center = new LngLat(-170, 0);
t.same(wrap(transform.center.lng), wrap(-170));

transform.center = new LngLat(150, 0);
let lng = wrap(transform.center.lng);
t.ok(lng > 160);
t.ok(lng < 180);

transform.center = new LngLat(-150, 0);
lng = wrap(transform.center.lng);
t.ok(lng < 360 - 160);
t.ok(lng > 360 - 180);

t.end();
});

t.test('_minZoomForBounds respects latRange and lngRange', (t) => {
t.test('it returns 0 when latRange and lngRange are undefined', (t) => {
const transform = new Transform();
Expand Down