From 88029111263ff3ebfe8fa8bab8d2e0810d46d53e Mon Sep 17 00:00:00 2001
From: Paul Chavard <pro@paul.chavard.net>
Date: Thu, 31 Aug 2023 18:16:14 +0200
Subject: [PATCH] fix(carte): initialize map only when container is visible

fix #9417
---
 .../components/shared/maplibre/MapLibre.tsx   |  7 ++--
 .../components/shared/maplibre/hooks.ts       | 35 ++++++++++++++++++-
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/app/javascript/components/shared/maplibre/MapLibre.tsx b/app/javascript/components/shared/maplibre/MapLibre.tsx
index a7ddf4191..a6ae5f181 100644
--- a/app/javascript/components/shared/maplibre/MapLibre.tsx
+++ b/app/javascript/components/shared/maplibre/MapLibre.tsx
@@ -13,7 +13,7 @@ import type { Style } from 'maplibre-gl';
 
 import invariant from 'tiny-invariant';
 
-import { useStyle } from './hooks';
+import { useStyle, useElementVisible } from './hooks';
 import { StyleControl } from './StyleControl';
 
 const Context = createContext<{ map?: Map | null }>({});
@@ -35,6 +35,7 @@ export function MapLibre({ children, layers }: MapLibreProps) {
     []
   );
   const containerRef = useRef<HTMLDivElement>(null);
+  const visible = useElementVisible(containerRef);
   const [map, setMap] = useState<Map | null>();
 
   const onStyleChange = useCallback(
@@ -48,7 +49,7 @@ export function MapLibre({ children, layers }: MapLibreProps) {
   const { style, ...mapStyleProps } = useStyle(layers, onStyleChange);
 
   useEffect(() => {
-    if (isSupported && !map) {
+    if (isSupported && visible && !map) {
       invariant(containerRef.current, 'Map container not found');
       const map = new Map({
         container: containerRef.current,
@@ -59,7 +60,7 @@ export function MapLibre({ children, layers }: MapLibreProps) {
         setMap(map);
       });
     }
-  }, [map, style, isSupported]);
+  }, [map, style, visible, isSupported]);
 
   if (!isSupported) {
     return (
diff --git a/app/javascript/components/shared/maplibre/hooks.ts b/app/javascript/components/shared/maplibre/hooks.ts
index 56a59ddf3..078e5fb15 100644
--- a/app/javascript/components/shared/maplibre/hooks.ts
+++ b/app/javascript/components/shared/maplibre/hooks.ts
@@ -1,4 +1,10 @@
-import { useCallback, useEffect, useState, useMemo } from 'react';
+import {
+  useCallback,
+  useEffect,
+  useState,
+  useMemo,
+  type RefObject
+} from 'react';
 import type {
   LngLatBoundsLike,
   LngLat,
@@ -118,3 +124,30 @@ export function useStyle(
 
   return { style, layers, setStyle, setLayerEnabled, setLayerOpacity };
 }
+
+function isElementVisible(
+  element: HTMLElement,
+  callback: (visible: boolean) => void
+) {
+  if (element.offsetWidth > 0 && element.offsetHeight > 0) {
+    callback(true);
+  } else {
+    callback(false);
+    const observer = new IntersectionObserver(
+      (entries) => callback(entries[0].isIntersecting == true),
+      { threshold: [0] }
+    );
+    observer.observe(element);
+    return () => observer.unobserve(element);
+  }
+}
+
+export function useElementVisible(element: RefObject<HTMLElement>) {
+  const [visible, setVisible] = useState(false);
+  useEffect(() => {
+    if (element.current) {
+      return isElementVisible(element.current, setVisible);
+    }
+  }, [element]);
+  return visible;
+}