From 38ac2b59aa4fcfe639c8dc684ba74393a2a6343e Mon Sep 17 00:00:00 2001
From: David Manthey <david.manthey@kitware.com>
Date: Tue, 5 Apr 2022 11:12:49 -0400
Subject: [PATCH] perf: Reduce tile layer updates.

When updating one tile layer's z index, possibly through adding the
layer, other tile layers would needlessly rerender.
---
 CHANGELOG.md           | 6 ++++++
 src/webgl/tileLayer.js | 7 +++++--
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f9e9d95a10..768b6afacb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,11 @@
 # GeoJS Change Log
 
+## Version 1.8.2
+
+### Improvements
+
+- Reduce tile layer updates ([#1196](../../pull/1196))
+
 ## Version 1.8.1
 
 ### Improvements
diff --git a/src/webgl/tileLayer.js b/src/webgl/tileLayer.js
index c5c31f1e34..026c32f4bb 100644
--- a/src/webgl/tileLayer.js
+++ b/src/webgl/tileLayer.js
@@ -134,7 +134,7 @@ var webgl_tileLayer = function () {
    * @returns {number|this}
    */
   this.zIndex = function (zIndex, allowDuplicate) {
-    if (zIndex !== undefined) {
+    if (zIndex !== undefined && m_this.autoshareRenderer()) {
       m_this._clearQuads();
     }
     return s_zIndex.apply(m_this, arguments);
@@ -148,7 +148,10 @@ var webgl_tileLayer = function () {
    *    triggered this.  If `undefined`, clear the quads but don't redraw.
    */
   this._clearQuads = function (evt) {
-    if (evt && (!evt.layer || !(evt.layer instanceof tileLayer))) {
+    if (evt && (!evt.layer || !(evt.layer instanceof tileLayer) || (
+      (evt.event === geo_event.layerAdd || evt.event === geo_event.layerRemove) &&
+      m_this.map().layers().every(l => l === evt.layer || evt.layer.zIndex() > l.zIndex())
+    ))) {
       return;
     }
     m_this.clear();