Merge pull request #4630 from kwvanderlinde/refactor/4506-improved-ar…

…ea-union

Improve last path exposure with better unions

src/main/java/net/rptools/lib/GeometryUtil.java

@@ -19,6 +19,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Objects;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.locationtech.jts.awt.ShapeReader;
@@ -61,6 +62,52 @@ public static double getAngleDelta(double sourceAngle, double targetAngle) {
     return targetAngle;
   }
 
+  /**
+   * Unions several areas into one.
+   *
+   * <p>The results are the same as progressively `.add()`ing all areas in the collection, but
+   * performs much better when the result is complicated.
+   *
+   * @param areas The areas to union.
+   * @return The union of {@code areas}
+   */
+  public static Area union(Collection<Area> areas) {
+    final var copy = new ArrayList<>(areas);
+    copy.replaceAll(Area::new);
+
+    return destructiveUnion(copy);
+  }
+
+  /**
+   * Like {@link #union(java.util.Collection)}, but will modify the areas and collection for
+   * performance gains.
+   *
+   * @param areas The areas to union.
+   * @return The union of {@code areas}
+   */
+  public static Area destructiveUnion(List<Area> areas) {
+    areas.removeIf(Area::isEmpty);
+
+    // Union two-by-two, on repeat until only one is left.
+    while (areas.size() >= 2) {
+      for (int i = 0; i + 1 < areas.size(); i += 2) {
+        final var a = areas.get(i);
+        final var b = areas.get(i + 1);
+
+        a.add(b);
+        areas.set(i + 1, null);
+      }
+      areas.removeIf(Objects::isNull);
+    }
+
+    if (areas.isEmpty()) {
+      // Just in case, maybe it's possible for Area() to have edge cases the produce empty unions?
+      return new Area();
+    }
+
+    return areas.getFirst();
+  }
+
   public static PrecisionModel getPrecisionModel() {
     return precisionModel;
   }

src/main/java/net/rptools/maptool/client/ui/zone/FogUtil.java

@@ -360,7 +360,7 @@ public static void exposeLastPath(final ZoneRenderer renderer, final Set<GUID> t
 
             final Token tokenClone = new Token(token);
             final ZoneView zoneView = renderer.getZoneView();
-            Area visionArea = new Area();
+            final var visibleAreas = new ArrayList<Area>();
 
             // Lee: get path according to zone's way point exposure toggle...
             List<? extends AbstractPoint> processPath =
@@ -371,6 +371,7 @@ public static void exposeLastPath(final ZoneRenderer renderer, final Set<GUID> t
             int stepCount = processPath.size();
             log.debug("Path size = " + stepCount);
 
+            timer.start("Get visible areas");
             Consumer<ZonePoint> revealAt =
                 zp -> {
                   tokenClone.setX(zp.x);
@@ -379,8 +380,7 @@ public static void exposeLastPath(final ZoneRenderer renderer, final Set<GUID> t
                   Area currVisionArea =
                       zoneView.getVisibleArea(tokenClone, renderer.getPlayerView());
                   if (currVisionArea != null) {
-                    visionArea.add(currVisionArea);
-                    meta.addToExposedAreaHistory(currVisionArea);
+                    visibleAreas.add(currVisionArea);
                   }
 
                   zoneView.flush(tokenClone);
@@ -397,15 +397,31 @@ public static void exposeLastPath(final ZoneRenderer renderer, final Set<GUID> t
               assert finalCell instanceof ZonePoint;
               revealAt.accept((ZonePoint) finalCell);
             }
+            timer.stop("Get visible areas");
+
+            timer.start("Union visible areas");
+            Area visionArea = GeometryUtil.destructiveUnion(visibleAreas);
+            timer.stop("Union visible areas");
+
+            timer.start("Add to token exposed area");
+            meta.addToExposedAreaHistory(visionArea);
+            timer.stop("Add to token exposed area");
 
-            timer.stop("exposeLastPath-" + token.getName());
             renderer.flush(tokenClone);
 
             filteredToks.clear();
             filteredToks.add(token.getId());
+
+            timer.start("Update zone");
             zone.putToken(token);
+            timer.stop("Update zone");
+
+            timer.start("Send results");
             MapTool.serverCommand().exposeFoW(zone.getId(), visionArea, filteredToks);
             MapTool.serverCommand().updateExposedAreaMeta(zone.getId(), exposedGUID, meta);
+            timer.stop("Send results");
+
+            timer.stop("exposeLastPath-" + token.getName());
           }
         });
   }