From d50535abb03c6887dfa75b42b1ec35c30d6ec2c4 Mon Sep 17 00:00:00 2001
From: Eugene Maksymenko <maxigene@gmail.com>
Date: Mon, 7 Dec 2020 21:07:17 +0200
Subject: [PATCH] Implement placemark level of details selector
 (https://github.com/WorldWindEarth/worldwindjs/issues/34)

---
 src/shapes/Placemark.js | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/shapes/Placemark.js b/src/shapes/Placemark.js
index ee38d37c1..5be0b577a 100644
--- a/src/shapes/Placemark.js
+++ b/src/shapes/Placemark.js
@@ -424,13 +424,7 @@ define([
          * cannot be created or should not be created at the time this method is called.
          */
         Placemark.prototype.makeOrderedRenderable = function (dc) {
-            var w, h, s,
-                offset;
-
-            this.determineActiveAttributes(dc);
-            if (!this.activeAttributes) {
-                return null;
-            }
+            var w, h, s, offset;
 
             // Compute the placemark's model point and corresponding distance to the eye point. If the placemark's
             // position is terrain-dependent but off the terrain, then compute it ABSOLUTE so that we have a point for
@@ -442,6 +436,14 @@ define([
 
             this.eyeDistance = this.alwaysOnTop ? 0 : dc.eyePoint.distanceTo(this.placePoint);
 
+            // Extension point to override placemark attributes depending on camera distance
+            this.selectLevelOfDetail(dc, this, this.eyeDistance);
+
+            this.determineActiveAttributes(dc);
+            if (!this.activeAttributes) {
+                return null;
+            }
+
             if (this.mustDrawLeaderLine(dc)) {
                 dc.surfacePointForMode(this.position.latitude, this.position.longitude, 0,
                     this.altitudeMode, this.groundPoint);
@@ -513,6 +515,17 @@ define([
             return this;
         };
 
+        /**
+         * Set the placemark attributes for the current distance to the camera and highlighted state.
+         *
+         * @param {DrawContext} dc The current render context
+         * @param {Placemark} placemark The placemark needing a level of detail selection
+         * @param {Number} cameraDistance The distance from the placemark to the camera (meters)
+         */
+        Placemark.prototype.selectLevelOfDetail = function (dc, placemark, cameraDistance) {
+            // Intentionally empty. Can be override in application if required.
+        };
+
         // Internal. Intentionally not documented.
         Placemark.prototype.determineActiveAttributes = function (dc) {
             if (this.highlighted && this.highlightAttributes) {