From b5a100b0cce7b377b83e5d2dada36f6515a93f09 Mon Sep 17 00:00:00 2001
From: Julian Rubisch <julian@julianrubisch.at>
Date: Mon, 18 Sep 2023 11:45:58 +0200
Subject: [PATCH] feat: Also track  document.visibilityState

---
 javascript/elements/updates_for_element.js  | 24 +++++++++----------
 javascript/observers/appearance_observer.js | 26 ++++++++++++++++++++-
 2 files changed, 37 insertions(+), 13 deletions(-)

diff --git a/javascript/elements/updates_for_element.js b/javascript/elements/updates_for_element.js
index fec69741..08630fac 100644
--- a/javascript/elements/updates_for_element.js
+++ b/javascript/elements/updates_for_element.js
@@ -40,8 +40,8 @@ export default class UpdatesForElement extends SubscribingElement {
 
     this.appearanceObserver = new AppearanceObserver(this)
 
-    this.intersecting = false
-    this.didTransitionToIntersecting = false
+    this.visible = false
+    this.didTransitionToVisible = false
   }
 
   async connectedCallback () {
@@ -94,7 +94,7 @@ export default class UpdatesForElement extends SubscribingElement {
 
     // first <cable-ready-updates-for> element in the DOM *at any given moment* updates all of the others
     // if the element becomes visible though, we have to overrule and load it
-    if (blocks[0].element !== this && !this.didTransitionToIntersecting) {
+    if (blocks[0].element !== this && !this.didTransitionToVisible) {
       this.triggerElementLog.push(
         `${new Date().toLocaleString()}: ${Log.cancel(
           this.lastUpdateTimestamp,
@@ -146,16 +146,16 @@ export default class UpdatesForElement extends SubscribingElement {
   }
 
   appearedInViewport () {
-    if (!this.intersecting) {
-      // transition from non-intersecting to intersecting forces update
-      this.didTransitionToIntersecting = true
+    if (!this.visible) {
+      // transition from invisible to visible forces update
+      this.didTransitionToVisible = true
       this.update({})
     }
-    this.intersecting = true
+    this.visible = true
   }
 
   disappearedFromViewport () {
-    this.intersecting = false
+    this.visible = false
   }
 
   get query () {
@@ -220,7 +220,7 @@ class Block {
       onBeforeElUpdated: shouldMorph(operation),
       onElUpdated: _ => {
         this.element.removeAttribute('updating')
-        this.element.didTransitionToIntersecting = false
+        this.element.didTransitionToVisible = false
         dispatch(this.element, 'cable-ready:after-update', operation)
         assignFocus(operation.focusSelector)
       }
@@ -275,7 +275,7 @@ class Block {
     return (
       !this.ignoresInnerUpdates &&
       this.hasChangesSelectedForUpdate(data) &&
-      (!this.observeAppearance || this.intersecting)
+      (!this.observeAppearance || this.visible)
     )
   }
 
@@ -312,8 +312,8 @@ class Block {
     return this.element.query
   }
 
-  get intersecting () {
-    return this.element.intersecting
+  get visible () {
+    return this.element.visible
   }
 
   get observeAppearance () {
diff --git a/javascript/observers/appearance_observer.js b/javascript/observers/appearance_observer.js
index 7b5dba32..6cf64b96 100644
--- a/javascript/observers/appearance_observer.js
+++ b/javascript/observers/appearance_observer.js
@@ -3,6 +3,7 @@ export class AppearanceObserver {
     this.delegate = delegate
     this.element = element || delegate
     this.started = false
+    this.intersecting = false
 
     this.intersectionObserver = new IntersectionObserver(this.intersect)
   }
@@ -11,6 +12,7 @@ export class AppearanceObserver {
     if (!this.started) {
       this.started = true
       this.intersectionObserver.observe(this.element)
+      this.observeVisibility()
     }
   }
 
@@ -18,18 +20,40 @@ export class AppearanceObserver {
     if (this.started) {
       this.started = false
       this.intersectionObserver.unobserve(this.element)
+      this.unobserveVisibility()
     }
   }
 
+  observeVisibility = () => {
+    document.addEventListener('visibilitychange', this.handleVisibilityChange)
+  }
+
+  unobserveVisibility = () => {
+    document.removeEventListener(
+      'visibilitychange',
+      this.handleVisibilityChange
+    )
+  }
+
   intersect = entries => {
     entries.forEach(entry => {
       if (entry.target === this.element) {
-        if (entry.isIntersecting) {
+        if (entry.isIntersecting && document.visibilityState === 'visible') {
+          this.intersecting = true
           this.delegate.appearedInViewport()
         } else {
+          this.intersecting = false
           this.delegate.disappearedFromViewport()
         }
       }
     })
   }
+
+  handleVisibilityChange = event => {
+    if (document.visibilityState === 'visible' && this.intersecting) {
+      this.delegate.appearedInViewport()
+    } else {
+      this.delegate.disappearedFromViewport()
+    }
+  }
 }