From 5f8005274ee0f379cfe31d4cde65951816595aad Mon Sep 17 00:00:00 2001
From: Vladimir Kharlampidi <nolimits4web@gmail.com>
Date: Tue, 23 Feb 2021 14:16:15 +0300
Subject: [PATCH] feat(core): added support to use ResizeObserver with new
 "resizeObserver" parameter

Ref #4244
---
 src/components/core/defaults.js |  1 +
 src/modules/resize/resize.js    | 38 +++++++++++++++++++++++++++++++++
 src/types/swiper-options.d.ts   |  7 ++++++
 3 files changed, 46 insertions(+)

diff --git a/src/components/core/defaults.js b/src/components/core/defaults.js
index c9d4664ef..521649047 100644
--- a/src/components/core/defaults.js
+++ b/src/components/core/defaults.js
@@ -6,6 +6,7 @@ export default {
   speed: 300,
   cssMode: false,
   updateOnWindowResize: true,
+  resizeObserver: false,
   nested: false,
 
   // Overrides
diff --git a/src/modules/resize/resize.js b/src/modules/resize/resize.js
index 90c4d1056..27e9e0c25 100644
--- a/src/modules/resize/resize.js
+++ b/src/modules/resize/resize.js
@@ -1,12 +1,45 @@
 import { getWindow } from 'ssr-window';
 import { extend } from '../../utils/utils';
 
+const supportsResizeObserver = () => {
+  const window = getWindow();
+  return typeof window.ResizeObserver !== 'undefined';
+};
+
 export default {
   name: 'resize',
   create() {
     const swiper = this;
     extend(swiper, {
       resize: {
+        observer: null,
+        createObserver() {
+          if (!swiper || swiper.destroyed || !swiper.initialized) return;
+          swiper.resize.observer = new ResizeObserver((entries) => {
+            const { width, height } = swiper;
+            let newWidth = width;
+            let newHeight = height;
+            entries.forEach(({ contentBoxSize, contentRect, target }) => {
+              if (target && target !== swiper.el) return;
+              newWidth = contentRect
+                ? contentRect.width
+                : (contentBoxSize[0] || contentBoxSize).inlineSize;
+              newHeight = contentRect
+                ? contentRect.height
+                : (contentBoxSize[0] || contentBoxSize).blockSize;
+            });
+            if (newWidth !== width || newHeight !== height) {
+              swiper.resize.resizeHandler();
+            }
+          });
+          swiper.resize.observer.observe(swiper.el);
+        },
+        removeObserver() {
+          if (swiper.resize.observer && swiper.resize.observer.unobserve && swiper.el) {
+            swiper.resize.observer.unobserve(swiper.el);
+            swiper.resize.observer = null;
+          }
+        },
         resizeHandler() {
           if (!swiper || swiper.destroyed || !swiper.initialized) return;
           swiper.emit('beforeResize');
@@ -22,6 +55,10 @@ export default {
   on: {
     init(swiper) {
       const window = getWindow();
+      if (swiper.params.resizeObserver && supportsResizeObserver()) {
+        swiper.resize.createObserver();
+        return;
+      }
       // Emit resize
       window.addEventListener('resize', swiper.resize.resizeHandler);
 
@@ -30,6 +67,7 @@ export default {
     },
     destroy(swiper) {
       const window = getWindow();
+      swiper.resize.removeObserver();
       window.removeEventListener('resize', swiper.resize.resizeHandler);
       window.removeEventListener('orientationchange', swiper.resize.orientationChangeHandler);
     },
diff --git a/src/types/swiper-options.d.ts b/src/types/swiper-options.d.ts
index 2cf46b7ff..a743e216d 100644
--- a/src/types/swiper-options.d.ts
+++ b/src/types/swiper-options.d.ts
@@ -36,6 +36,13 @@ export interface SwiperOptions {
    */
   updateOnWindowResize?: boolean;
 
+  /**
+   * When enabled it will use ResizeObserver (if supported by browser) on swiper container to detect container resize (instead of watching for window resize)
+   *
+   * @default false
+   */
+  resizeObserver?: boolean;
+
   /**
    * Index number of initial slide.
    *