Add possibility to control Placemark visibility from LevelOfDetailsSelector via return parameter instead of nulling PlacamerkAttributes.

Author: EMaksymenko

worldwind-examples/src/main/java/gov/nasa/worldwindx/PlacemarksDemoActivity.java

@@ -142,9 +142,11 @@ public PlaceLevelOfDetailSelector(Resources resources, Place place) {
          * @param rc
          * @param placemark      The placemark needing a level of detail selection
          * @param cameraDistance The distance from the placemark to the camera (meters)
+         *
+         * @return if placemark should display or skip its rendering
          */
         @Override
-        public void selectLevelOfDetail(RenderContext rc, Placemark placemark, double cameraDistance) {
+        public boolean selectLevelOfDetail(RenderContext rc, Placemark placemark, double cameraDistance) {
 
             boolean highlighted = placemark.isHighlighted();
             boolean highlightChanged = this.lastHighlightState != highlighted;
@@ -213,7 +215,13 @@ public void selectLevelOfDetail(RenderContext rc, Placemark placemark, double ca
             this.lastHighlightState = highlighted;
 
             // Update the placemark's attributes bundle
-            placemark.setAttributes(this.attributes);
+            if (this.attributes != null) {
+                this.attributes.setDrawLabel(highlighted || cameraDistance <= LEVEL_1_DISTANCE);
+                placemark.setAttributes(this.attributes);
+                return true; // Placemark visible
+            } else {
+                return false; // Placemark invisible
+            }
         }
 
         protected static PlacemarkAttributes getPlacemarkAttributes(Resources resources, Place place) {

worldwind-examples/src/main/java/gov/nasa/worldwindx/milstd2525/MilStd2525LevelOfDetailSelector.java

@@ -59,9 +59,11 @@ public static void setNearThreshold(double nearThreshold) {
      * @param rc             The current render contents
      * @param placemark      The placemark needing a level of detail selection
      * @param cameraDistance The distance from the placemark to the camera (meters)
+     *
+     * @return if placemark should display or skip its rendering
      */
     @Override
-    public void selectLevelOfDetail(RenderContext rc, Placemark placemark, double cameraDistance) {
+    public boolean selectLevelOfDetail(RenderContext rc, Placemark placemark, double cameraDistance) {
         if (!(placemark instanceof MilStd2525Placemark)) {
             throw new IllegalArgumentException(
                 Logger.logMessage(Logger.ERROR, "MilStd2525LevelOfDetailSelector", "selectLevelOfDetail",
@@ -108,5 +110,7 @@ public void selectLevelOfDetail(RenderContext rc, Placemark placemark, double ca
         if (this.placemarkAttributes != null) {
             milStdPlacemark.setAttributes(this.placemarkAttributes);
         }
+
+        return true; // Placemark is always visible
     }
 }

worldwind/src/main/java/gov/nasa/worldwind/shape/Placemark.java

@@ -49,8 +49,10 @@ public interface LevelOfDetailSelector {
          * @param rc             The current render context
          * @param placemark      The placemark needing a level of detail selection
          * @param cameraDistance The distance from the placemark to the camera (meters)
+         *
+         * @return if placemark should display or skip its rendering
          */
-        void selectLevelOfDetail(RenderContext rc, Placemark placemark, double cameraDistance);
+        boolean selectLevelOfDetail(RenderContext rc, Placemark placemark, double cameraDistance);
     }
 
     /**
@@ -702,8 +704,9 @@ protected void doRender(RenderContext rc) {
         }
 
         // Allow the placemark to adjust the level of detail based on distance to the camera
-        if (this.levelOfDetailSelector != null) {
-            this.levelOfDetailSelector.selectLevelOfDetail(rc, this, this.cameraDistance);
+        if (this.levelOfDetailSelector != null
+                && !this.levelOfDetailSelector.selectLevelOfDetail(rc, this, this.cameraDistance)) {
+            return; // skip rendering
         }
 
         // Determine the attributes to use for the current render pass.