From 58670dc2d2be6f971c37a9969c2f4b2307acab4f Mon Sep 17 00:00:00 2001
From: Oliver Tacke <o.tacke@posteo.de>
Date: Thu, 4 Jan 2024 12:46:14 +0100
Subject: [PATCH] Clean up IntersectionObserver

---
 .../components/media-screen/media-screen.js   | 28 ++++------------
 src/scripts/services/focus-trap.js            | 27 +++++----------
 src/scripts/services/util.js                  | 33 +++++++++++++++++++
 3 files changed, 49 insertions(+), 39 deletions(-)

diff --git a/src/scripts/components/media-screen/media-screen.js b/src/scripts/components/media-screen/media-screen.js
index 35a0af2..12f29de 100644
--- a/src/scripts/components/media-screen/media-screen.js
+++ b/src/scripts/components/media-screen/media-screen.js
@@ -206,27 +206,13 @@ export default class MediaScreen {
       this.dom.replaceChild(newVisuals, this.visuals);
       this.visuals = newVisuals;
 
-      // iOS is behind ... Again ...
-      const callback = window.requestIdleCallback ?
-        window.requestIdleCallback :
-        window.requestAnimationFrame;
-
-      /*
-      * Get started once visible and ready. YouTube requires the video to be
-      * attached to the DOM.
-      */
-      callback(() => {
-        this.observer = new IntersectionObserver((entries) => {
-          if (entries[0].isIntersecting) {
-            this.observer.unobserve(this.dom);
-            this.initMedia();
-          }
-        }, {
-          root: document.documentElement,
-          threshold: 0
-        });
-        this.observer.observe(this.dom);
-      });
+      Util.callOnceVisible(
+        this.dom,
+        () => {
+          this.initMedia();
+        },
+        { root: document.documentElement }
+      );
     }
     else {
       this.visuals.classList.add('display-none');
diff --git a/src/scripts/services/focus-trap.js b/src/scripts/services/focus-trap.js
index 4ba3975..d77230e 100644
--- a/src/scripts/services/focus-trap.js
+++ b/src/scripts/services/focus-trap.js
@@ -1,3 +1,5 @@
+import Util from '@services/util.js';
+
 export default class FocusTrap {
 
   /**
@@ -38,24 +40,13 @@ export default class FocusTrap {
 
     this.isActivated = true;
 
-    // iOS is behind ... Again ...
-    const callback = window.requestIdleCallback ?
-      window.requestIdleCallback :
-      window.requestAnimationFrame;
-
-    callback(() => {
-      this.observer = this.observer || new IntersectionObserver((entries) => {
-        if (entries[0].isIntersecting) {
-          this.observer.unobserve(this.params.trapElement);
-
-          this.handleVisible();
-        }
-      }, {
-        root: document.documentElement,
-        threshold: 0
-      });
-      this.observer.observe(this.params.trapElement);
-    });
+    Util.callOnceVisible(
+      this.params.trapElement,
+      () => {
+        this.handleVisible();
+      },
+      { root: document.documentElement }
+    );
   }
 
   /**
diff --git a/src/scripts/services/util.js b/src/scripts/services/util.js
index c05c454..ed7af9c 100644
--- a/src/scripts/services/util.js
+++ b/src/scripts/services/util.js
@@ -121,4 +121,37 @@ export default class Util {
 
     return text;
   }
+
+  /**
+   * Call callback function once dom element gets visible in viewport.
+   * @param {HTMLElement} dom DOM element to wait for.
+   * @param {function} callback Function to call once DOM element is visible.
+   * @param {object} [options] IntersectionObserver options.
+   */
+  static callOnceVisible(dom, callback, options = {}) {
+    if (typeof dom !== 'object' || typeof callback !== 'function') {
+      return; // Invalid arguments
+    }
+
+    options.threshold = options.threshold || 0;
+
+    // iOS is behind ... Again ...
+    const idleCallback = window.requestIdleCallback ?
+      window.requestIdleCallback :
+      window.requestAnimationFrame;
+
+    idleCallback(() => {
+      // Get started once visible and ready
+      const observer = new IntersectionObserver((entries) => {
+        if (entries[0].isIntersecting) {
+          observer.unobserve(dom);
+          callback();
+        }
+      }, {
+        ...(options.root && { root: options.root }),
+        threshold: options.threshold,
+      });
+      observer.observe(dom);
+    });
+  }
 }