From f0382afd837f40bb8f6e899ae5ecdead3f6efe95 Mon Sep 17 00:00:00 2001
From: N-Pex <npexdev@gmail.com>
Date: Thu, 19 Jun 2025 10:47:16 +0200
Subject: [PATCH] Fixes for "scroll to latest"

---
 src/assets/css/chat.scss |  6 +++
 src/components/Chat.vue  | 83 +++++++++++++++++++++++-----------------
 2 files changed, 54 insertions(+), 35 deletions(-)

diff --git a/src/assets/css/chat.scss b/src/assets/css/chat.scss
index 630d959..e4537b0 100644
--- a/src/assets/css/chat.scss
+++ b/src/assets/css/chat.scss
@@ -369,10 +369,16 @@ body {
     position: absolute;
     bottom: 102px;
     right: 16px;
+    opacity: 1;
+    transition: opacity 0.3s linear;
     &.reversed {
       top: 120px;
       transform: rotate(180deg);
     }
+    &.hidden {
+      pointer-events: none;
+      opacity: 0;
+    }
   }
 
   .op-button {
diff --git a/src/components/Chat.vue b/src/components/Chat.vue
index 4f46401..fe57934 100644
--- a/src/components/Chat.vue
+++ b/src/components/Chat.vue
@@ -120,7 +120,7 @@
     </div>
 
     <!-- "Scroll to end"-button -->
-    <v-btn v-if="!useVoiceMode" icon="arrow_downward" :class="{'scroll-to-end': true, 'reversed': reverseOrder}" v-show="showScrollToEnd" theme="dark" size="x-small" elevation="0" color="black"
+    <v-btn v-if="!useVoiceMode" icon="arrow_downward" :class="{'scroll-to-end': true, 'reversed': reverseOrder, 'hidden': !showScrollToEnd}" theme="dark" size="x-small" elevation="0" color="black"
       @click.stop="scrollToEndOfTimeline">
     </v-btn>
 
@@ -410,6 +410,7 @@ export default {
       timelineWindowPaginating: false,
 
       scrollPosition: null,
+      scrollUpdateTimer: null,
       uploadBatch: undefined,
       showEmojiPicker: false,
       selectedEvent: null,
@@ -1210,13 +1211,7 @@ export default {
           this.handleScrolledToLatest(false);
         }
       }
-
-      this.showScrollToEnd =
-        container.scrollHeight === container.clientHeight
-          ? false
-          : (this.reverseOrder ? (container.scrollTop.toFixed(0) > 0) : (container.scrollHeight - container.scrollTop.toFixed(0) > container.clientHeight)) ||
-          (this.timelineWindow && this.timelineWindow.canPaginate(EventTimeline.FORWARDS));
-
+      this.delayedUpdateOfScrollToBottom();
       this.restartRRTimer();
     },
 
@@ -1284,6 +1279,24 @@ export default {
         }
     },
 
+    delayedUpdateOfScrollToBottom() {
+      if (this.scrollUpdateTimer) {
+        clearTimeout(this.scrollUpdateTimer);
+      }
+      this.scrollUpdateTimer = setTimeout(() => {
+        this.scrollUpdateTimer = null;
+        const container = this.chatContainer;
+        if (!container) {
+          return;
+        }
+        this.showScrollToEnd =
+          container.scrollHeight === container.clientHeight
+            ? false
+            : (this.reverseOrder ? (container.scrollTop.toFixed(0) > 0) : (container.scrollHeight - container.scrollTop.toFixed(0) > container.clientHeight)) ||
+            (this.timelineWindow && this.timelineWindow.canPaginate(EventTimeline.FORWARDS));
+      }, 1000);
+    },
+
     onEvent(event) {
       //console.log("OnEvent", JSON.stringify(event));
       if (event.getRoomId() !== this.roomId) {
@@ -1307,16 +1320,7 @@ export default {
       if (loadingDone && event.forwardLooking && (!event.isRelation() || event.isMxThread || event.threadRootId || event.parentThread)) {
         // If we are at bottom, scroll to see new events...
         var scrollToSeeNew = !event.isRedaction() && event.getSender() == this.$matrix.currentUserId; // When we sent, scroll
-        const container = this.chatContainer;
-        if (container) {
-          if (this.reverseOrder && container.scrollTop.toFixed(0) == 0) {
-            scrollToSeeNew = true;
-          }
-          else if (!this.reverseOrder && container.scrollHeight - container.scrollTop.toFixed(0) == container.clientHeight) {
-            scrollToSeeNew = true;
-          }
-        }
-        this.handleScrolledToLatest(scrollToSeeNew);
+        this.handleScrolledToLatest(scrollToSeeNew || !this.showScrollToEnd);
 
         // If kick or ban event, redirect to "goodbye"...
         if (event.getType() === "m.room.member" &&
@@ -1516,32 +1520,41 @@ export default {
     },
 
     smoothScrollToLatest() {
-      this.$nextTick(function () {
+      this.$nextTick(() => {
+        // TODO - fix this. We need to wait until the "lastChild" below has been
+        // laid out correctly. If we do it "too early" it will have zero height and
+        // thus not correctly scrolled into the viewport. So we wait a few ticks...
+        window.requestAnimationFrame(() => {
+        window.requestAnimationFrame(() => {
+        window.requestAnimationFrame(() => {
+        window.requestAnimationFrame(() => {
         const container = this.chatContainer;
         if (container && container.children.length > 0) {
           if (this.reverseOrder) {
             const firstChild = container.children[0];
-          console.log("Scroll into view", firstChild);
-          window.requestAnimationFrame(() => {
-            firstChild.scrollIntoView({
-              behavior: "smooth",
-              block: "end",
-              inline: "nearest",
+            window.requestAnimationFrame(() => {
+              firstChild.scrollIntoView({
+                behavior: "smooth",
+                block: "end",
+                inline: "nearest",
+              });
             });
-          });
           } else {
-          const lastChild = container.children[container.children.length - 1];
-          console.log("Scroll into view", lastChild);
-          window.requestAnimationFrame(() => {
-            lastChild.scrollIntoView({
-              behavior: "smooth",
-              block: "start",
-              inline: "nearest",
+            const lastChild = container.children[container.children.length - 1];
+            window.requestAnimationFrame(() => {
+              lastChild.scrollIntoView({
+                behavior: "smooth",
+                block: "start",
+                inline: "nearest",
+              });
             });
-          });
+          }
         }
-      }
       });
+    })
+    })
+    })
+    })
     },
 
     showMoreMessageOperations(e) {