From 69393d0b8552f3cc86c8eccd4bc233ef6ed346db Mon Sep 17 00:00:00 2001
From: Peter Hanecak <peter.hanecak@maptiler.com>
Date: Tue, 19 Dec 2023 11:29:44 +0100
Subject: [PATCH] use setMinPixelSizeBelowZoom() instead of uniAreaToMinZoom()

---
 .../java/org/openmaptiles/layers/Poi.java     | 23 ++-------
 .../java/org/openmaptiles/layers/PoiTest.java | 49 -------------------
 2 files changed, 4 insertions(+), 68 deletions(-)

diff --git a/src/main/java/org/openmaptiles/layers/Poi.java b/src/main/java/org/openmaptiles/layers/Poi.java
index 63d4775c..084f5835 100644
--- a/src/main/java/org/openmaptiles/layers/Poi.java
+++ b/src/main/java/org/openmaptiles/layers/Poi.java
@@ -123,8 +123,6 @@ public class Poi implements
   private static final Comparator<Tables.OsmPoiPoint> BY_SUBCLASS = Comparator
     .comparingInt(s -> AGG_STOP_SUBCLASS_ORDER.indexOf(s.subclass()));
   private static final Set<String> BRAND_OPERATOR_REF_SUBCLASSES = Set.of("charging_station", "parcel_locker");
-  private static final double LOG2 = Math.log(2);
-  private static final double SQRT10 = Math.sqrt(10);
   private final MultiExpression.Index<String> classMapping;
   private final Translations translations;
   private final Stats stats;
@@ -154,14 +152,6 @@ private int minzoom(String subclass, String mappingKey) {
     return lowZoom ? 12 : 14;
   }
 
-  public static int uniAreaToMinZoom(double areaWorld) {
-    double oneSideWorld = Math.sqrt(areaWorld);
-    double zoom = -(Math.log(oneSideWorld * SQRT10) / LOG2);
-    int result = (int) Math.floor(zoom - 0.1e-10) + 1;
-
-    return Math.clamp(result, 10, 14);
-  }
-
   @Override
   public void release() {
     aggStops.clear();
@@ -308,16 +298,11 @@ private <T extends Tables.WithSubclass & Tables.WithStation & Tables.WithFunicul
     int poiClassRank = poiClassRank(poiClass);
     int rankOrder = poiClassRank + ((nullOrEmpty(name)) ? 2000 : 0);
 
-    int minzoom;
+    int minzoom = minzoom(element.subclass(), element.mappingKey());
     if (UNIVERSITY_POI_SUBCLASSES.contains(rawSubclass)) {
-      minzoom = 14;
-      try {
-        minzoom = uniAreaToMinZoom(element.source().area());
-      } catch (GeometryException e) {
-        e.log(stats, "omt_poi_polygon", "Unable to get geometry for university polygon " + element.source().id());
-      }
-    } else {
-      minzoom = minzoom(element.subclass(), element.mappingKey());
+      // universities that are at least 10% of a tile may appear from Z10
+      output.setMinPixelSizeBelowZoom(13, 80); // 80x80px is ~10% of a 256x256px tile
+      minzoom = 10;
     }
 
     output.setBufferPixels(BUFFER_SIZE)
diff --git a/src/test/java/org/openmaptiles/layers/PoiTest.java b/src/test/java/org/openmaptiles/layers/PoiTest.java
index 3c2503ea..9027cf55 100644
--- a/src/test/java/org/openmaptiles/layers/PoiTest.java
+++ b/src/test/java/org/openmaptiles/layers/PoiTest.java
@@ -465,53 +465,4 @@ void testChargingStation() {
     ))));
   }
 
-  private record TestEntry(
-    SourceFeature feature,
-    int expectedZoom
-  ) {}
-
-  private void createUniAreaForMinZoomTest(List<TestEntry> testEntries, double area, int expectedZoom, String name) {
-    var feature = polygonFeatureWithArea(area, Map.of(
-      "name", name,
-      "amenity", "university"
-    ));
-    testEntries.add(new TestEntry(
-      feature,
-      Math.clamp(expectedZoom, 10, 14)
-    ));
-  }
-
-  @Test
-  void testUniAreaToMinZoom() throws GeometryException {
-    // threshold is 1/10 of tile area, hence ...
-    // ... side is 1/sqrt(10) tile side: from pixels to world coord, for say Z14 ...
-    //final double PORTION_OF_TILE_SIDE = (256d / Math.sqrt(10)) / Math.pow(2d, 14d + 8d);
-    // ... and then for some lower zoom:
-    //double testAreaSide = PORTION_OF_TILE_SIDE * Math.pow(2, 14 - zoom);
-    // all this then simplified to `testArea` calculation bellow
-
-    final List<TestEntry> testEntries = new ArrayList<>();
-    for (int zoom = 14; zoom >= 0; zoom--) {
-      double testArea = Math.pow(4, -zoom) / 10;
-
-      // slightly bellow the threshold
-      createUniAreaForMinZoomTest(testEntries, testArea * 0.999, zoom + 1, "uni-");
-      // precisely at the threshold
-      createUniAreaForMinZoomTest(testEntries, testArea, zoom, "uni=");
-      // slightly over the threshold
-      createUniAreaForMinZoomTest(testEntries, testArea * 1.001, zoom, "uni+");
-    }
-
-    for (var entry : testEntries) {
-      assertFeatures(14, List.of(Map.of(
-        "_layer", "landuse",
-        "class", "university"
-      ), Map.of(
-        "_layer", "poi",
-        "_type", "point",
-        "_minzoom", entry.expectedZoom,
-        "_maxzoom", 14
-      )), process(entry.feature));
-    }
-  }
 }