added the strings for the pin banner, the room list and the notification content builder

ElementX/Sources/Services/Room/RoomSummary/RoomMessageEventStringBuilder.swift

@@ -66,7 +66,7 @@ nonisolated struct RoomMessageEventStringBuilder {
                 message = AttributedString(content.body)
             }
         case .gallery(let content):
-            message = AttributedString(content.body)
+            message = buildGalleryMessage(for: style, content: content)
         case .other(_, let body):
             message = AttributedString(body)
         }
@@ -91,6 +91,21 @@ nonisolated struct RoomMessageEventStringBuilder {
         }
     }
     
+    /// A gallery's body is its caption. Notifications fall back to counting the attachments when
+    /// there isn't one, whilst elsewhere it is treated as any other media's caption.
+    private func buildGalleryMessage(for style: Style, content: GalleryMessageContent) -> AttributedString {
+        switch style {
+        case .plain:
+            if content.body.isBlank {
+                AttributedString(L10n.notificationGalleryBody(content.itemtypes.count))
+            } else {
+                AttributedString(content.body)
+            }
+        case .senderPrefixed, .typeBolded:
+            buildMessage(for: style, caption: content.body, type: L10n.commonGallery)
+        }
+    }
+    
     private func buildMessage(for style: Style, caption: String?, type: String) -> AttributedString {
         guard let caption else {
             return AttributedString(type)

NSE/Sources/NotificationContentBuilder.swift

@@ -207,6 +207,13 @@ nonisolated struct NotificationContentBuilder {
                                      using: mediaProvider,
                                      mediaSource: .init(source: content.source,
                                                         mimeType: content.info?.mimetype))
+        case .gallery(content: let content):
+            // A notification can only show one attachment, so the gallery is represented by its first.
+            if let mediaSource = content.itemtypes.firstPreviewableMediaSource {
+                await addMediaAttachment(notificationContent: &notificationContent,
+                                         using: mediaProvider,
+                                         mediaSource: mediaSource)
+            }
         default:
             break
         }
@@ -362,3 +369,24 @@ private nonisolated struct NotificationIcon {
         groupInfo != nil
     }
 }
+
+private nonisolated extension [GalleryItemType] {
+    /// The media source of the first attachment that a notification is able to show, skipping the
+    /// types that it can't such as documents.
+    var firstPreviewableMediaSource: MediaSourceProxy? {
+        for itemType in self {
+            switch itemType {
+            case .image(let content):
+                return .init(source: content.source, mimeType: content.info?.mimetype)
+            case .video(let content):
+                return .init(source: content.source, mimeType: content.info?.mimetype)
+            case .audio(let content):
+                return .init(source: content.source, mimeType: content.info?.mimetype)
+            case .file, .other:
+                continue
+            }
+        }
+        
+        return nil
+    }
+}