Fix 5486 (#5518)

* add failing unit test

* fix 5486. Do not allow variable zoom tiles just because the top padding is non-zero. Only allow variable zoom at high pitch or when terrain is enabled.

* update changelog

CHANGELOG.md

@@ -10,6 +10,7 @@
 - _...Add new stuff here..._
 - Fix how padding is applied when using flyTo() with Globe ([#5406](https://github.com/maplibre/maplibre-gl-js/pull/5406))
 - Fix URL hash validation to support bearing range -180 to 180 ([#5461](https://github.com/maplibre/maplibre-gl-js/issues/5461))
+- Fix variable zoom tile calculation when padding is set ([#5486](https://github.com/maplibre/maplibre-gl-js/issues/5486))
 
 ## 5.1.0
 

src/geo/projection/covering_tiles.test.ts

@@ -219,6 +219,22 @@ describe('coveringTiles', () => {
                 new OverscaledTileID(10, 0, 10, 511, 512),
                 new OverscaledTileID(10, 0, 10, 512, 512)]);
 
+            transform.resize(2048, 128);
+            transform.setZoom(9);
+            transform.setPadding({top: 16});
+            expect(coveringTiles(transform, options)).toEqual([
+                new OverscaledTileID(9, 0, 9, 255, 255),
+                new OverscaledTileID(9, 0, 9, 256, 255),
+                new OverscaledTileID(9, 0, 9, 255, 256),
+                new OverscaledTileID(9, 0, 9, 256, 256),
+                new OverscaledTileID(9, 0, 9, 254, 255),
+                new OverscaledTileID(9, 0, 9, 254, 256),
+                new OverscaledTileID(9, 0, 9, 257, 255),
+                new OverscaledTileID(9, 0, 9, 257, 256),
+                new OverscaledTileID(9, 0, 9, 253, 255),
+                new OverscaledTileID(9, 0, 9, 253, 256)]);
+
+            transform.setPadding({top: 0});
             transform.setZoom(5.1);
             transform.setPitch(60.0);
             transform.setBearing(32.0);

src/geo/projection/mercator_covering_tiles_details_provider.ts

@@ -42,7 +42,7 @@ export class MercatorCoveringTilesDetailsProvider implements CoveringTilesDetail
     allowVariableZoom(transform: IReadonlyTransform, options: CoveringTilesOptions): boolean {
         const zfov = transform.fov * (Math.abs(Math.cos(transform.rollInRadians)) * transform.height + Math.abs(Math.sin(transform.rollInRadians)) * transform.width) / transform.height;
         const maxConstantZoomPitch = clamp(78.5 - zfov / 2, 0.0, 60.0);
-        return (!!options.terrain || transform.pitch > maxConstantZoomPitch || transform.padding.top >= 0.1);
+        return (!!options.terrain || transform.pitch > maxConstantZoomPitch);
     }
 
     allowWorldCopies(): boolean {