From 09dd98df17bd764015a4f5bc9ae0024b8ee6c367 Mon Sep 17 00:00:00 2001
From: ryanhamley <ryan.hamley@mapbox.com>
Date: Tue, 29 Oct 2019 16:46:13 -0700
Subject: [PATCH] Go back to previous algorithm

---
 src/render/painter.js | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/render/painter.js b/src/render/painter.js
index c9991992cc5..166bc4cda85 100644
--- a/src/render/painter.js
+++ b/src/render/painter.js
@@ -432,16 +432,24 @@ class Painter {
 
         if (this.options.showTileBoundaries) {
             //Use source with highest maxzoom
-            let maxZoomSourceCache;
-            for (const source in this.style.sourceCaches) {
-                const cache = this.style.sourceCaches[source];
-                if (!maxZoomSourceCache || cache._source.maxzoom > maxZoomSourceCache._source.maxZoom) {
-                    maxZoomSourceCache = cache;
+            let selectedSource;
+            let sourceCache;
+            const layers = values(this.style._layers);
+
+            layers.forEach((layer) => {
+                if (layer.source && !layer.isHidden(this.transform.zoom)) {
+                    if (layer.source !== (sourceCache && sourceCache.id)) {
+                        sourceCache = this.style.sourceCaches[layer.source];
+                    }
+
+                    if (!selectedSource || (selectedSource.getSource().maxzoom < sourceCache.getSource().maxzoom)) {
+                        selectedSource = sourceCache;
+                    }
                 }
-            }
+            });
 
-            if (maxZoomSourceCache) {
-                draw.debug(this, maxZoomSourceCache, maxZoomSourceCache.getVisibleCoordinates());
+            if (selectedSource) {
+                draw.debug(this, selectedSource, selectedSource.getVisibleCoordinates());
             }
         }