Fix geo projections losing their D3 default rotation

draftlogs/7976_fix.md

@@ -0,0 +1 @@
+ - Fix geo `albers`, `bertin1953`, `gringorten quincuncial`, `peirce quincuncial`, `sinu mollweide` and `wiechel` projections losing their D3 default rotation to the default `projection.rotation` values, and compose user-specified rotation on top of the projection's canonical orientation [[#7976](https://github.com/plotly/plotly.js/pull/7976)]

src/plots/geo/geo.js

@@ -304,7 +304,11 @@ proto.updateProjection = function(geoCalcData, fullLayout) {
     // set 'pre-fit' projection
     projection
         .center([center.lon - rotation.lon, center.lat - rotation.lat])
-        .rotate([-rotation.lon, -rotation.lat, rotation.roll])
+        .rotate([
+            -rotation.lon + projection.defaultRotation[0],
+            -rotation.lat + projection.defaultRotation[1],
+            rotation.roll + projection.defaultRotation[2]
+        ])
         .parallels(projLayout.parallels);
 
     // fit projection 'scale' and 'translate' to set lon/lat ranges
@@ -716,6 +720,12 @@ function getProjection(geoLayout) {
     projName = 'geo' + Lib.titleCase(projName);
     var projFn = geo[projName] || geoProjection[projName];
     var projection = projFn();
+    // Capture the rotation the projection factory ships with (identity for
+    // most projections, but e.g. albers defaults to [96, 0, 0]) so that the
+    // default projection.rotation attributes do not discard the canonical
+    // orientation. See #7949.
+    var projDefaultRotation = typeof projection.rotate === 'function' ?
+        projection.rotate() : [0, 0, 0];
 
     var clipAngle =
         geoLayout._isSatellite ? Math.acos(1 / projLayout.distance) * 180 / Math.PI :
@@ -754,6 +764,8 @@ function getProjection(geoLayout) {
         return projection.getPath().bounds(object);
     };
 
+    projection.defaultRotation = projDefaultRotation;
+
     projection.precision(constants.precision);
 
     if(geoLayout._isSatellite) {

test/jasmine/tests/geo_test.js

@@ -2876,3 +2876,42 @@ describe('plotly_relayouting', function() {
         });
     });
 });
+
+describe('Test geo projection D3 default rotation (#7949)', function() {
+    var gd;
+
+    beforeEach(function() { gd = createGraphDiv(); });
+    afterEach(destroyGraphDiv);
+
+    function subplot() { return gd._fullLayout.geo._subplot; }
+
+    it('preserves the projection factory rotation at default projection.rotation', function(done) {
+        Plotly.newPlot(gd, [{ type: 'scattergeo', lon: [], lat: [] }], {
+            geo: { projection: { type: 'albers' } }
+        }).then(function() {
+            // d3-geo albers ships with rotation [96, 0, 0]; plotly's default
+            // projection.rotation attributes must not discard it.
+            // Compare with a tight numeric tolerance: the composed factory +
+            // user rotation can pick up float64 dust (e.g. 96.00000000000001
+            // on linux runners), so exact equality is environment-dependent.
+            [0, 1, 2].forEach(function(axis) {
+                expect(subplot().projection.defaultRotation[axis]).toBeCloseTo([96, 0, 0][axis], 9);
+                expect(subplot().projection.rotate()[axis]).toBeCloseTo([96, 0, 0][axis], 9);
+            });
+        }).then(function() {
+            return Plotly.relayout(gd, { 'geo.projection.rotation.lon': 10 });
+        }).then(function() {
+            // user rotation composes on top of the factory rotation
+            expect(subplot().projection.rotate()[0]).toBeCloseTo(86, 9);
+        }).then(done, done.fail);
+    });
+
+    it('keeps identity-rotation projections exactly as before', function(done) {
+        Plotly.newPlot(gd, [{ type: 'scattergeo', lon: [], lat: [] }], {
+            geo: { projection: { type: 'mercator' } }
+        }).then(function() {
+            expect(subplot().projection.defaultRotation).toEqual([0, 0, 0]);
+            expect(subplot().projection.rotate()).toEqual([0, 0, 0]);
+        }).then(done, done.fail);
+    });
+});