timeline-item: Add unique ID accessor for debugging purposes

src/session/room/event/mod.rs

@@ -1,3 +1,5 @@
+use std::fmt;
+
 use gtk::{glib, prelude::*, subclass::prelude::*};
 use matrix_sdk::{
     media::MediaEventContent,
@@ -42,6 +44,15 @@ pub enum EventKey {
     EventId(OwnedEventId),
 }
 
+impl fmt::Display for EventKey {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            EventKey::TransactionId(txn_id) => write!(f, "transaction_id:{txn_id}"),
+            EventKey::EventId(event_id) => write!(f, "event_id:{event_id}"),
+        }
+    }
+}
+
 #[derive(Clone, Debug, glib::Boxed)]
 #[boxed_type(name = "BoxedEventTimelineItem")]
 pub struct BoxedEventTimelineItem(EventTimelineItem);
@@ -130,6 +141,10 @@ mod imp {
     }
 
     impl TimelineItemImpl for Event {
+        fn id(&self) -> String {
+            format!("Event::{}", self.obj().key())
+        }
+
         fn is_visible(&self) -> bool {
             match self.obj().content() {
                 TimelineItemContent::Message(message) => matches!(

src/session/room/timeline/timeline_day_divider.rs

@@ -58,7 +58,17 @@ mod imp {
         }
     }
 
-    impl TimelineItemImpl for TimelineDayDivider {}
+    impl TimelineItemImpl for TimelineDayDivider {
+        fn id(&self) -> String {
+            format!(
+                "TimelineDayDivider::{}",
+                self.obj()
+                    .date()
+                    .map(|d| d.format("%F").unwrap())
+                    .unwrap_or_default()
+            )
+        }
+    }
 }
 
 glib::wrapper! {

src/session/room/timeline/timeline_item.rs

@@ -17,6 +17,7 @@ mod imp {
     #[repr(C)]
     pub struct TimelineItemClass {
         pub parent_class: glib::object::ObjectClass,
+        pub id: fn(&super::TimelineItem) -> String,
         pub is_visible: fn(&super::TimelineItem) -> bool,
         pub selectable: fn(&super::TimelineItem) -> bool,
         pub can_hide_header: fn(&super::TimelineItem) -> bool,
@@ -27,6 +28,11 @@ mod imp {
         type Type = TimelineItem;
     }
 
+    pub(super) fn timeline_item_id(this: &super::TimelineItem) -> String {
+        let klass = this.class();
+        (klass.as_ref().id)(this)
+    }
+
     pub(super) fn timeline_item_is_visible(this: &super::TimelineItem) -> bool {
         let klass = this.class();
         (klass.as_ref().is_visible)(this)
@@ -161,6 +167,11 @@ impl TimelineItem {
 /// To override the behavior of these methods, override the corresponding method
 /// of `TimelineItemImpl`.
 pub trait TimelineItemExt: 'static {
+    /// A unique ID for this `TimelineItem`.
+    ///
+    /// For debugging purposes.
+    fn id(&self) -> String;
+
     /// Whether this `TimelineItem` is visible.
     ///
     /// Defaults to `true`.
@@ -191,6 +202,10 @@ pub trait TimelineItemExt: 'static {
 }
 
 impl<O: IsA<TimelineItem>> TimelineItemExt for O {
+    fn id(&self) -> String {
+        imp::timeline_item_id(self.upcast_ref())
+    }
+
     fn is_visible(&self) -> bool {
         imp::timeline_item_is_visible(self.upcast_ref())
     }
@@ -229,6 +244,8 @@ impl<O: IsA<TimelineItem>> TimelineItemExt for O {
 /// Overriding a method from this Trait overrides also its behavior in
 /// `TimelineItemExt`.
 pub trait TimelineItemImpl: ObjectImpl {
+    fn id(&self) -> String;
+
     fn is_visible(&self) -> bool {
         true
     }
@@ -257,6 +274,7 @@ where
 
         let klass = class.as_mut();
 
+        klass.id = id_trampoline::<T>;
         klass.is_visible = is_visible_trampoline::<T>;
         klass.selectable = selectable_trampoline::<T>;
         klass.can_hide_header = can_hide_header_trampoline::<T>;
@@ -265,6 +283,15 @@ where
 }
 
 // Virtual method implementation trampolines.
+fn id_trampoline<T>(this: &TimelineItem) -> String
+where
+    T: ObjectSubclass + TimelineItemImpl,
+    T::Type: IsA<TimelineItem>,
+{
+    let this = this.downcast_ref::<T::Type>().unwrap();
+    this.imp().id()
+}
+
 fn is_visible_trampoline<T>(this: &TimelineItem) -> bool
 where
     T: ObjectSubclass + TimelineItemImpl,

src/session/room/timeline/timeline_new_messages_divider.rs

@@ -16,7 +16,12 @@ mod imp {
     }
 
     impl ObjectImpl for TimelineNewMessagesDivider {}
-    impl TimelineItemImpl for TimelineNewMessagesDivider {}
+
+    impl TimelineItemImpl for TimelineNewMessagesDivider {
+        fn id(&self) -> String {
+            "TimelineNewMessagesDivider".to_owned()
+        }
+    }
 }
 
 glib::wrapper! {

src/session/room/timeline/timeline_placeholder.rs

@@ -58,7 +58,16 @@ mod imp {
         }
     }
 
-    impl TimelineItemImpl for TimelinePlaceholder {}
+    impl TimelineItemImpl for TimelinePlaceholder {
+        fn id(&self) -> String {
+            match self.obj().kind() {
+                PlaceholderKind::Spinner => "TimelinePlaceholder::Spinner",
+                PlaceholderKind::Typing => "TimelinePlaceholder::Typing",
+                PlaceholderKind::TimelineStart => "TimelinePlaceholder::TimelineStart",
+            }
+            .to_owned()
+        }
+    }
 }
 
 glib::wrapper! {