From f5b6767253abebe65cbbfe34ddb5ab967fdec6ea Mon Sep 17 00:00:00 2001
From: Benjamin Bouvier <benjamin@bouvier.cc>
Date: Wed, 19 Mar 2025 16:09:37 +0100
Subject: [PATCH] feat(timeline): add a timeline start virtual item

---
 bindings/matrix-sdk-ffi/src/timeline/mod.rs        |  4 ++++
 crates/matrix-sdk-ui/src/timeline/date_dividers.rs | 11 +++++++----
 crates/matrix-sdk-ui/src/timeline/virtual_item.rs  |  4 ++++
 labs/multiverse/src/main.rs                        |  3 +++
 4 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/bindings/matrix-sdk-ffi/src/timeline/mod.rs b/bindings/matrix-sdk-ffi/src/timeline/mod.rs
index 143d9c3ce..19c2eefe2 100644
--- a/bindings/matrix-sdk-ffi/src/timeline/mod.rs
+++ b/bindings/matrix-sdk-ffi/src/timeline/mod.rs
@@ -974,6 +974,7 @@ impl TimelineItem {
         match self.0.as_virtual()? {
             VItem::DateDivider(ts) => Some(VirtualTimelineItem::DateDivider { ts: (*ts).into() }),
             VItem::ReadMarker => Some(VirtualTimelineItem::ReadMarker),
+            VItem::TimelineStart => Some(VirtualTimelineItem::TimelineStart),
         }
     }
 
@@ -1254,6 +1255,9 @@ pub enum VirtualTimelineItem {
 
     /// The user's own read marker.
     ReadMarker,
+
+    /// The timeline start, that is, the *oldest* event in time for that room.
+    TimelineStart,
 }
 
 /// A [`TimelineItem`](super::TimelineItem) that doesn't correspond to an event.
diff --git a/crates/matrix-sdk-ui/src/timeline/date_dividers.rs b/crates/matrix-sdk-ui/src/timeline/date_dividers.rs
index b3ce04704..42082b99f 100644
--- a/crates/matrix-sdk-ui/src/timeline/date_dividers.rs
+++ b/crates/matrix-sdk-ui/src/timeline/date_dividers.rs
@@ -153,7 +153,8 @@ impl DateDividerAdjuster {
                     latest_event_ts = Some(ts);
                 }
 
-                TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker) => {
+                TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker)
+                | TimelineItemKind::Virtual(VirtualTimelineItem::TimelineStart) => {
                     // Nothing to do.
                 }
             }
@@ -242,8 +243,9 @@ impl DateDividerAdjuster {
                 return true;
             }
 
-            TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker) => {
-                // Nothing to do for read markers.
+            TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker)
+            | TimelineItemKind::Virtual(VirtualTimelineItem::TimelineStart) => {
+                // Nothing to do.
             }
         }
 
@@ -304,7 +306,8 @@ impl DateDividerAdjuster {
                 }
             }
 
-            TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker) => {
+            TimelineItemKind::Virtual(VirtualTimelineItem::ReadMarker)
+            | TimelineItemKind::Virtual(VirtualTimelineItem::TimelineStart) => {
                 // Nothing to do.
             }
         }
diff --git a/crates/matrix-sdk-ui/src/timeline/virtual_item.rs b/crates/matrix-sdk-ui/src/timeline/virtual_item.rs
index 727a44c2f..68e4bcbc4 100644
--- a/crates/matrix-sdk-ui/src/timeline/virtual_item.rs
+++ b/crates/matrix-sdk-ui/src/timeline/virtual_item.rs
@@ -26,4 +26,8 @@ pub enum VirtualTimelineItem {
 
     /// The user's own read marker.
     ReadMarker,
+
+    /// The timeline start, that is, an indication that we've seen all the
+    /// events for that timeline.
+    TimelineStart,
 }
diff --git a/labs/multiverse/src/main.rs b/labs/multiverse/src/main.rs
index 20bf9a60a..2000bd627 100644
--- a/labs/multiverse/src/main.rs
+++ b/labs/multiverse/src/main.rs
@@ -836,6 +836,9 @@ impl App {
                     VirtualTimelineItem::ReadMarker => {
                         content.push("Read marker".to_owned());
                     }
+                    VirtualTimelineItem::TimelineStart => {
+                        content.push("🥳 Timeline start! 🥳".to_owned());
+                    }
                 },
             }
         }