From a9a0dc9efd0713c906565b35e609bfd7171ff1a9 Mon Sep 17 00:00:00 2001
From: Stepan Kuzmin <stepan.kuzmin@mapbox.com>
Date: Mon, 8 May 2023 15:29:12 +0300
Subject: [PATCH] Postpone tiles preloading until source is loaded

---
 src/source/source.js       |  1 +
 src/source/source_cache.js | 14 ++++++++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/source/source.js b/src/source/source.js
index a3a1e92a424..951f055c7d5 100644
--- a/src/source/source.js
+++ b/src/source/source.js
@@ -60,6 +60,7 @@ export interface Source {
 
     fire(event: Event): mixed;
     on(type: MapEvent, listener: (Object) => any): Evented;
+    off(type: MapEvent, listener: (Object) => any): Evented;
     setEventedParent(parent: ?Evented, data?: Object | () => Object): Evented;
 
     +onAdd?: (map: Map) => void;
diff --git a/src/source/source_cache.js b/src/source/source_cache.js
index f7d2dc41ce3..e00ebc77872 100644
--- a/src/source/source_cache.js
+++ b/src/source/source_cache.js
@@ -994,6 +994,17 @@ class SourceCache extends Evented {
      * @returns {Object} Returns `this` | Promise.
      */
     _preloadTiles(transform: Transform | Array<Transform>, callback: Callback<any>) {
+        if (!this._sourceLoaded) {
+            const waitUntilSourceLoaded = () => {
+                if (!this._sourceLoaded) return;
+                this._source.off('data', waitUntilSourceLoaded);
+                this._preloadTiles(transform, callback);
+            };
+
+            this._source.on('data', waitUntilSourceLoaded);
+            return;
+        }
+
         const coveringTilesIDs: Map<number, OverscaledTileID> = new Map();
         const transforms = Array.isArray(transform) ? transform : [transform];
 
@@ -1020,10 +1031,9 @@ class SourceCache extends Evented {
         }
 
         const tileIDs = Array.from(coveringTilesIDs.values());
-        const tileZoom = this.transform ? this.transform.tileZoom : this.map.transform.tileZoom;
 
         asyncAll(tileIDs, (tileID, done) => {
-            const tile = new Tile(tileID, this._source.tileSize * tileID.overscaleFactor(), tileZoom, this.map.painter, this._isRaster);
+            const tile = new Tile(tileID, this._source.tileSize * tileID.overscaleFactor(), this.transform.tileZoom, this.map.painter, this._isRaster);
             this._loadTile(tile, (err) => {
                 if (this._source.type === 'raster-dem' && tile.dem) this._backfillDEM(tile);
                 done(err, tile);