Refactor camera helper to split the logic for vertical-perspective and mercator

src/geo/projection/camera_helper.ts

@@ -1,12 +1,13 @@
-import type Point from '@mapbox/point-geometry';
+import Point from '@mapbox/point-geometry';
 import {type IReadonlyTransform, type ITransform} from '../transform_interface';
 import {type LngLat, type LngLatLike} from '../lng_lat';
 import {type CameraForBoundsOptions, type PointLike} from '../../ui/camera';
 import {type PaddingOptions} from '../edge_insets';
 import {type LngLatBounds} from '../lng_lat_bounds';
-import {getRollPitchBearing, type RollPitchBearing, rollPitchBearingToQuat, warnOnce} from '../../util/util';
+import {degreesToRadians, getRollPitchBearing, type RollPitchBearing, rollPitchBearingToQuat, scaleZoom, warnOnce, zoomScale} from '../../util/util';
 import {quat} from 'gl-matrix';
 import {interpolates} from '@maplibre/maplibre-gl-style-spec';
+import {projectToWorldCoordinates, unprojectFromWorldCoordinates} from './mercator_utils';
 
 export type MapControlsDeltas = {
     panDelta: Point;
@@ -151,3 +152,70 @@
         args.tr.setBearing(interpolates.number(args.startEulerAngles.bearing, args.endEulerAngles.bearing, args.k));
     }
 }
+
+export function cameraForBoxAndBearing(options: CameraForBoundsOptions, padding: PaddingOptions, bounds: LngLatBounds, bearing: number, tr: IReadonlyTransform): CameraForBoxAndBearingHandlerResult {
+    const edgePadding = tr.padding;
+
+    // Consider all corners of the rotated bounding box derived from the given points
+    // when find the camera position that fits the given points.
+
+    const nwWorld = projectToWorldCoordinates(tr.worldSize, bounds.getNorthWest());
+    const neWorld = projectToWorldCoordinates(tr.worldSize, bounds.getNorthEast());
+    const seWorld = projectToWorldCoordinates(tr.worldSize, bounds.getSouthEast());
+    const swWorld = projectToWorldCoordinates(tr.worldSize, bounds.getSouthWest());
+
+    const bearingRadians = degreesToRadians(-bearing);
+
+    const nwRotatedWorld = nwWorld.rotate(bearingRadians);
+    const neRotatedWorld = neWorld.rotate(bearingRadians);
+    const seRotatedWorld = seWorld.rotate(bearingRadians);
+    const swRotatedWorld = swWorld.rotate(bearingRadians);
+
+    const upperRight = new Point(
+        Math.max(nwRotatedWorld.x, neRotatedWorld.x, swRotatedWorld.x, seRotatedWorld.x),
+        Math.max(nwRotatedWorld.y, neRotatedWorld.y, swRotatedWorld.y, seRotatedWorld.y)
+    );
+
+    const lowerLeft = new Point(
+        Math.min(nwRotatedWorld.x, neRotatedWorld.x, swRotatedWorld.x, seRotatedWorld.x),
+        Math.min(nwRotatedWorld.y, neRotatedWorld.y, swRotatedWorld.y, seRotatedWorld.y)
+    );
+
+    // Calculate zoom: consider the original bbox and padding.
+    const size = upperRight.sub(lowerLeft);
+
+    const availableWidth = (tr.width - (edgePadding.left + edgePadding.right + padding.left + padding.right));
+    const availableHeight = (tr.height - (edgePadding.top + edgePadding.bottom + padding.top + padding.bottom));
+    const scaleX = availableWidth / size.x;
+    const scaleY = availableHeight / size.y;
+
+    if (scaleY < 0 || scaleX < 0) {
+        cameraBoundsWarning();
+        return undefined;
+    }
+
+    const zoom = Math.min(scaleZoom(tr.scale * Math.min(scaleX, scaleY)), options.maxZoom);
+
+    // Calculate center: apply the zoom, the configured offset, as well as offset that exists as a result of padding.
+    const offset = Point.convert(options.offset);
+    const paddingOffsetX = (padding.left - padding.right) / 2;
+    const paddingOffsetY = (padding.top - padding.bottom) / 2;
+    const paddingOffset = new Point(paddingOffsetX, paddingOffsetY);
+    const rotatedPaddingOffset = paddingOffset.rotate(degreesToRadians(bearing));
+    const offsetAtInitialZoom = offset.add(rotatedPaddingOffset);
+    const offsetAtFinalZoom = offsetAtInitialZoom.mult(tr.scale / zoomScale(zoom));
+
+    const center = unprojectFromWorldCoordinates(
+        tr.worldSize,
+        // either world diagonal can be used (NW-SE or NE-SW)
+        nwWorld.add(seWorld).div(2).sub(offsetAtFinalZoom)
+    );
+
+    const result = {
+        center,
+        zoom,
+        bearing
+    };
+
+    return result;
+}