Add the gallery timeline item rendered as a placeholder

Introduces the GalleryRoomTimelineItem and its typed GalleryItem model (reusing the existing per-message content types), builds it in the RoomTimelineItemFactory and routes it through RoomTimelineItemView. For now it renders as a placeholder; the grid/list media views and the full-screen preview land in follow-up PRs.

Co-authored-by: svetoslav.mitov <svetoslav.mitov@sportinno.com>

ElementX.xcodeproj/project.pbxproj

@@ -197,6 +197,7 @@
 		1C8BC70A18060677E295A846 /* ShareToMapsAppActivity.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4481799F455B3DA243BDA2AC /* ShareToMapsAppActivity.swift */; };
 		1C9BB74711E5F24C77B7FED0 /* RoomMembersListScreenCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 5AEA0B743847CFA5B3C38EE4 /* RoomMembersListScreenCoordinator.swift */; };
 		1CA094038D4D036A6F0A1314 /* VoiceMessageTrashButton.swift in Sources */ = {isa = PBXBuildFile; fileRef = ABF84AA68B2B7584D9275769 /* VoiceMessageTrashButton.swift */; };
+		1CA6E1843E1B3680544EB584 /* GalleryRoomTimelineItemContent.swift in Sources */ = {isa = PBXBuildFile; fileRef = 35A5AB4E2E5CA98F99BFC552 /* GalleryRoomTimelineItemContent.swift */; };
 		1D2D713A5A269072D103AE37 /* CLLocationManagerProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = DA46D6DD4B4AB17E1D45092E /* CLLocationManagerProtocol.swift */; };
 		1D5DC685CED904386C89B7DA /* NSRegularExpresion.swift in Sources */ = {isa = PBXBuildFile; fileRef = 95BAC0F6C9644336E9567EE6 /* NSRegularExpresion.swift */; };
 		1D623953F970D11F6F38499C /* AppLockService.swift in Sources */ = {isa = PBXBuildFile; fileRef = 851B95BB98649B8E773D6790 /* AppLockService.swift */; };
@@ -307,6 +308,7 @@
 		3042527CB344A9EF1157FC26 /* AudioRecorderStateTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C55CC239AE12339C565F6C9A /* AudioRecorderStateTests.swift */; };
 		308BD9343B95657FAA583FB7 /* GZIP in Frameworks */ = {isa = PBXBuildFile; productRef = 2B788C81F6369D164ADEB917 /* GZIP */; };
 		30CC1DB7CE357659C82AA115 /* MediaProviderProtocol.swift in Sources */ = {isa = PBXBuildFile; fileRef = 85EB16E7FE59A947CA441531 /* MediaProviderProtocol.swift */; };
+		30DA1A668482E5B95E8F1F2B /* GalleryRoomTimelineView.swift in Sources */ = {isa = PBXBuildFile; fileRef = A04EFA0E3139C01E1CFDC93B /* GalleryRoomTimelineView.swift */; };
 		30E5628F74AD3C27A061BF25 /* QRCodeLoginScreenViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3BC1B7CB061C9865B2B91B56 /* QRCodeLoginScreenViewModel.swift */; };
 		311868F5E65BA61AFA6CCC2C /* CompoundHook.swift in Sources */ = {isa = PBXBuildFile; fileRef = 8B89D6C760E8CAE29CA28FB1 /* CompoundHook.swift */; };
 		3118D9ABFD4BE5A3492FF88A /* ElementCallConfiguration.swift in Sources */ = {isa = PBXBuildFile; fileRef = CC437C491EA6996513B1CEAB /* ElementCallConfiguration.swift */; };
@@ -1362,6 +1364,7 @@
 		DFF7D6A6C26DDD40D00AE579 /* target.yml in Resources */ = {isa = PBXBuildFile; fileRef = F012CB5EE3F2B67359F6CC52 /* target.yml */; };
 		E010DDE938032D3B8E84CC35 /* TracingHook.swift in Sources */ = {isa = PBXBuildFile; fileRef = 2A95C9B8299A36A6495DECA6 /* TracingHook.swift */; };
 		E02DAD9FD8D62587049FFFEC /* LinkNewDeviceTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 80F04B12FA231E797B7151A8 /* LinkNewDeviceTests.swift */; };
+		E08DFC18E97623B5C91C5025 /* GalleryRoomTimelineItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = E994322F10D20ECE68683683 /* GalleryRoomTimelineItem.swift */; };
 		E0B6A569AC3E81D233B43D60 /* SettingsScreenViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4E625B0EB2F86B37C14EF7E6 /* SettingsScreenViewModel.swift */; };
 		E0C167D41A48EDB30B447DE3 /* VoiceMessageRecordingComposer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 73A5C3F7C9C1DA10CAEC6A98 /* VoiceMessageRecordingComposer.swift */; };
 		E1428612B08ED3030EC1FEC3 /* SpacesScreen.swift in Sources */ = {isa = PBXBuildFile; fileRef = 104B7747499487538483FEAF /* SpacesScreen.swift */; };
@@ -1980,6 +1983,7 @@
 		3558A15CFB934F9229301527 /* RestorationToken.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RestorationToken.swift; sourceTree = "<group>"; };
 		358528B29FA72ACFD0D9644B /* SpacesScreenCoordinator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SpacesScreenCoordinator.swift; sourceTree = "<group>"; };
 		35A057BA9BE0F079784CD061 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist; path = Info.plist; sourceTree = "<group>"; };
+		35A5AB4E2E5CA98F99BFC552 /* GalleryRoomTimelineItemContent.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GalleryRoomTimelineItemContent.swift; sourceTree = "<group>"; };
 		35AFCF4C05DEED04E3DB1A16 /* de */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = de; path = de.lproj/Localizable.strings; sourceTree = "<group>"; };
 		36DA824791172B9821EACBED /* PrivacyInfo.xcprivacy */ = {isa = PBXFileReference; path = PrivacyInfo.xcprivacy; sourceTree = "<group>"; };
 		36FD673E24FBFCFDF398716A /* RoomMemberProxyMock.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RoomMemberProxyMock.swift; sourceTree = "<group>"; };
@@ -2579,6 +2583,7 @@
 		A010B8EAD1A9F6B4686DF2F4 /* BlockedUsersScreenViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BlockedUsersScreenViewModel.swift; sourceTree = "<group>"; };
 		A019A12C866D64CF072024B9 /* AppLockSetupPINScreenViewModel.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppLockSetupPINScreenViewModel.swift; sourceTree = "<group>"; };
 		A02D1A490944BF01A37586E1 /* sk */ = {isa = PBXFileReference; lastKnownFileType = text.plist.strings; name = sk; path = sk.lproj/SAS.strings; sourceTree = "<group>"; };
+		A04EFA0E3139C01E1CFDC93B /* GalleryRoomTimelineView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GalleryRoomTimelineView.swift; sourceTree = "<group>"; };
 		A057F2FDC14866C3026A89A4 /* NotificationManagerProtocol.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotificationManagerProtocol.swift; sourceTree = "<group>"; };
 		A07B011547B201A836C03052 /* EncryptionResetFlowCoordinator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = EncryptionResetFlowCoordinator.swift; sourceTree = "<group>"; };
 		A0E7B059E84E7E374D3322A2 /* SpaceRoomCell.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SpaceRoomCell.swift; sourceTree = "<group>"; };
@@ -3000,6 +3005,7 @@
 		E8AE4B3273BA189FDCD4055C /* UserIndicator.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = UserIndicator.swift; sourceTree = "<group>"; };
 		E944F717FC10A428D027074D /* RoomPowerLevelsProxyMock.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = RoomPowerLevelsProxyMock.swift; sourceTree = "<group>"; };
 		E992D7B8BE54B2AB454613AF /* XCUIElement.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = XCUIElement.swift; sourceTree = "<group>"; };
+		E994322F10D20ECE68683683 /* GalleryRoomTimelineItem.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = GalleryRoomTimelineItem.swift; sourceTree = "<group>"; };
 		E9A3D3CFA199FA7897364547 /* CallInviteRoomTimelineItem.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CallInviteRoomTimelineItem.swift; sourceTree = "<group>"; };
 		E9B796D347E53631576F631C /* PreviewTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = PreviewTests.swift; sourceTree = "<group>"; };
 		E9D059BFE329BE09B6D96A9F /* ro */ = {isa = PBXFileReference; lastKnownFileType = text.plist.stringsdict; name = ro; path = ro.lproj/Localizable.stringsdict; sourceTree = "<group>"; };
@@ -5500,6 +5506,8 @@
 				EE378083653EF0C9B5E9D580 /* EmoteRoomTimelineItemContent.swift */,
 				5098DA7799946A61E34A2373 /* FileRoomTimelineItem.swift */,
 				216F0DDC98F2A2C162D09C28 /* FileRoomTimelineItemContent.swift */,
+				E994322F10D20ECE68683683 /* GalleryRoomTimelineItem.swift */,
+				35A5AB4E2E5CA98F99BFC552 /* GalleryRoomTimelineItemContent.swift */,
 				3DFE4453AB0B34C203447162 /* ImageRoomTimelineItem.swift */,
 				B2B5EDCD05D50BA9B815C66C /* ImageRoomTimelineItemContent.swift */,
 				8A8DCBD0ABAADFDE5AF17E1F /* LiveLocationRoomTimelineItem.swift */,
@@ -6572,6 +6580,7 @@
 				2F06F70B9C433BAD4BC6B9F5 /* EncryptedRoomTimelineView.swift */,
 				4F75EF13F49DD2204E760910 /* FileRoomTimelineView.swift */,
 				C258C9C815272911A5B132C3 /* FormattedBodyText.swift */,
+				A04EFA0E3139C01E1CFDC93B /* GalleryRoomTimelineView.swift */,
 				59B7CC77B82C6C67DE3AD869 /* HighlightedTimelineItemModifier.swift */,
 				C5599255A6C98EBDA77B76E6 /* ImageRoomTimelineView.swift */,
 				52947F8F356F0BA5B1F50912 /* LiveLocationRoomTimelineView.swift */,
@@ -8544,6 +8553,9 @@
 				7807B1DEE32617896886A8E5 /* FormattingToolbar.swift in Sources */,
 				5705511EBE083295EF98F998 /* FrequentlyUsedEmoji.swift in Sources */,
 				46BA7F4B4D3A7164DED44B88 /* FullscreenDialog.swift in Sources */,
+				E08DFC18E97623B5C91C5025 /* GalleryRoomTimelineItem.swift in Sources */,
+				1CA6E1843E1B3680544EB584 /* GalleryRoomTimelineItemContent.swift in Sources */,
+				30DA1A668482E5B95E8F1F2B /* GalleryRoomTimelineView.swift in Sources */,
 				F18CA61A58C77C84F551B8E7 /* GeneratedMocks.swift in Sources */,
 				4295E5F850897710A51AE114 /* GeoURI.swift in Sources */,
 				F3C9CAD26FD4D7D6EBACF501 /* HTMLFixtures.swift in Sources */,

ElementX/Sources/Screens/SearchScreen/SearchScreenModels.swift

@@ -95,7 +95,7 @@ struct SearchScreenMessage: Identifiable, Equatable {
                 content.formattedBody ?? AttributedString(content.body)
             case .emote(let content):
                 content.formattedBody ?? AttributedString(content.body)
-            case .audio, .file, .image, .video:
+            case .audio, .file, .image, .video, .gallery:
                 nil
             case .voice:
                 AttributedString(L10n.commonVoiceMessage)
@@ -130,7 +130,7 @@ struct SearchScreenMessage: Identifiable, Equatable {
             return .init(title: content.caption ?? content.filename,
                          details: mediaDetails(filename: content.filename, fileSize: content.videoInfo.fileSize),
                          kind: .video(thumbnail: content.thumbnailInfo, blurhash: content.blurhash))
-        case .text, .notice, .emote, .voice, .location:
+        case .text, .notice, .emote, .voice, .location, .gallery:
             return nil
         }
     }

ElementX/Sources/Screens/Timeline/View/Replies/TimelineReplyView.swift

@@ -129,6 +129,13 @@ struct TimelineReplyView: View {
                                   plainBody: L10n.commonSharedLocation,
                                   formattedBody: nil,
                                   icon: .init(kind: .icon(\.locationPin)))
+                    case .gallery(let content):
+                        ReplyView(sender: sender,
+                                  plainBody: content.caption ?? content.body,
+                                  formattedBody: content.formattedCaption,
+                                  icon: content.items.first?.thumbnailSource.map { .init(kind: .mediaSource($0)) }
+                                      ?? content.items.first?.mediaSource.map { .init(kind: .mediaSource($0)) }
+                                      ?? .init(kind: .icon(\.attachment)))
                     }
                 case .poll(let question):
                     ReplyView(sender: sender,

ElementX/Sources/Screens/Timeline/View/Threads/TimelineThreadSummaryView.swift

@@ -82,6 +82,12 @@ struct TimelineThreadSummaryView: View {
                                plainBody: L10n.commonSharedLocation,
                                formattedBody: nil,
                                numberOfReplies: numberOfReplies)
+                case .gallery(let content):
+                    ThreadView(senderID: senderID,
+                               sender: sender,
+                               plainBody: content.caption ?? content.body,
+                               formattedBody: content.formattedCaption,
+                               numberOfReplies: numberOfReplies)
                 }
             case .poll(let question):
                 ThreadView(senderID: senderID,

ElementX/Sources/Screens/Timeline/View/TimelineItemViews/GalleryRoomTimelineView.swift

@@ -0,0 +1,22 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Compound
+import SwiftUI
+
+struct GalleryRoomTimelineView: View {
+    let timelineItem: GalleryRoomTimelineItem
+    
+    var body: some View {
+        TimelineStyler(timelineItem: timelineItem) {
+            // Placeholder rendering — the grid/list media views land in a follow-up.
+            FormattedBodyText(text: timelineItem.content.caption ?? timelineItem.content.body,
+                              trailingReservedSize: timelineItem.trailingReservedSize,
+                              boostFontSize: timelineItem.shouldBoost)
+        }
+    }
+}

ElementX/Sources/Services/Timeline/TimelineItems/EventBasedMessageTimelineItemProtocol.swift

@@ -18,6 +18,7 @@ nonisolated enum EventBasedMessageTimelineItemContentType: Hashable {
     case video(VideoRoomTimelineItemContent)
     case location(LocationRoomTimelineItemContent)
     case voice(AudioRoomTimelineItemContent)
+    case gallery(GalleryRoomTimelineItemContent)
 }
 
 nonisolated protocol EventBasedMessageTimelineItemProtocol: EventBasedTimelineItemProtocol {
@@ -27,7 +28,7 @@ nonisolated protocol EventBasedMessageTimelineItemProtocol: EventBasedTimelineIt
 nonisolated extension EventBasedMessageTimelineItemProtocol {
     var supportsMediaCaption: Bool {
         switch contentType {
-        case .audio, .file, .image, .video:
+        case .audio, .file, .image, .video, .gallery:
             true
         case .emote, .notice, .text, .location, .voice:
             false
@@ -48,6 +49,8 @@ nonisolated extension EventBasedMessageTimelineItemProtocol {
             content.caption
         case .video(let content):
             content.caption
+        case .gallery(let content):
+            content.caption
         case .emote, .notice, .text, .location, .voice:
             nil
         }
@@ -63,6 +66,8 @@ nonisolated extension EventBasedMessageTimelineItemProtocol {
             content.formattedCaption
         case .video(let content):
             content.formattedCaption
+        case .gallery(let content):
+            content.formattedCaption
         case .emote, .notice, .text, .location, .voice:
             nil
         }

ElementX/Sources/Services/Timeline/TimelineItems/EventBasedTimelineItemProtocol.swift

@@ -103,7 +103,7 @@ nonisolated extension EventBasedTimelineItemProtocol {
         }
         
         switch messageBasedItem.contentType {
-        case .audio, .file, .image, .video, .location, .voice:
+        case .audio, .file, .image, .video, .location, .voice, .gallery:
             return false
         case .text, .emote, .notice:
             return true

ElementX/Sources/Services/Timeline/TimelineItems/Items/Messages/GalleryRoomTimelineItem.swift

@@ -0,0 +1,31 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import UIKit
+
+nonisolated struct GalleryRoomTimelineItem: EventBasedMessageTimelineItemProtocol, Equatable {
+    let id: TimelineItemIdentifier
+    let timestamp: Date
+    let isOutgoing: Bool
+    let isEditable: Bool
+    let canBeRepliedTo: Bool
+    var shouldBoost = false
+    
+    let sender: TimelineItemSender
+    
+    let content: GalleryRoomTimelineItemContent
+    
+    var properties = RoomTimelineItemProperties()
+    
+    var body: String {
+        content.caption ?? content.body
+    }
+    
+    var contentType: EventBasedMessageTimelineItemContentType {
+        .gallery(content)
+    }
+}

ElementX/Sources/Services/Timeline/TimelineItems/Items/Messages/GalleryRoomTimelineItemContent.swift

@@ -0,0 +1,145 @@
+//
+// Copyright 2026 Element Creations Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Foundation
+import UniformTypeIdentifiers
+
+nonisolated struct GalleryRoomTimelineItemContent: Hashable {
+    let body: String
+    var caption: String?
+    var formattedCaption: AttributedString?
+    /// The original textual representation of the formatted caption directly from the event (usually HTML code)
+    var formattedCaptionHTMLString: String?
+    let items: [GalleryItem]
+}
+
+/// Identifies a single attachment within a gallery message.
+nonisolated struct GalleryItemID: Hashable {
+    /// The unique ID of the parent gallery timeline item.
+    let timelineItemUniqueID: TimelineItemIdentifier.UniqueID
+    /// The item's position within the gallery.
+    let mediaIndex: Int
+}
+
+/// A single attachment of a gallery message. The SDK hands back the same content types it uses for
+/// individual messages, so we reuse them here rather than duplicating their fields.
+nonisolated enum GalleryItem: Hashable, Identifiable {
+    case image(id: GalleryItemID, ImageRoomTimelineItemContent)
+    case video(id: GalleryItemID, VideoRoomTimelineItemContent)
+    case audio(id: GalleryItemID, AudioRoomTimelineItemContent)
+    case file(id: GalleryItemID, FileRoomTimelineItemContent)
+    /// An item of an unknown type. It has no media source, so there's nothing to preview.
+    case other(id: GalleryItemID, filename: String)
+    
+    var id: GalleryItemID {
+        switch self {
+        case .image(let id, _), .video(let id, _), .audio(let id, _), .file(let id, _), .other(let id, _):
+            id
+        }
+    }
+    
+    var isImage: Bool {
+        if case .image = self {
+            true
+        } else {
+            false
+        }
+    }
+    
+    var isVideo: Bool {
+        if case .video = self {
+            true
+        } else {
+            false
+        }
+    }
+    
+    var isAudio: Bool {
+        if case .audio = self {
+            true
+        } else {
+            false
+        }
+    }
+    
+    var isFile: Bool {
+        if case .file = self {
+            true
+        } else {
+            false
+        }
+    }
+    
+    var filename: String {
+        switch self {
+        case .image(_, let content): content.filename
+        case .video(_, let content): content.filename
+        case .audio(_, let content): content.filename
+        case .file(_, let content): content.filename
+        case .other(_, let filename): filename
+        }
+    }
+    
+    var mediaSource: MediaSourceProxy? {
+        switch self {
+        case .image(_, let content): content.imageInfo.source
+        case .video(_, let content): content.videoInfo.source
+        case .audio(_, let content): content.source
+        case .file(_, let content): content.source
+        case .other: nil
+        }
+    }
+    
+    var thumbnailSource: MediaSourceProxy? {
+        switch self {
+        case .image(_, let content): content.thumbnailInfo?.source
+        case .video(_, let content): content.thumbnailInfo?.source
+        case .file(_, let content): content.thumbnailSource
+        case .audio, .other: nil
+        }
+    }
+    
+    var size: CGSize? {
+        switch self {
+        case .image(_, let content): content.imageInfo.size
+        case .video(_, let content): content.videoInfo.size
+        case .audio, .file, .other: nil
+        }
+    }
+    
+    var blurhash: String? {
+        switch self {
+        case .image(_, let content): content.blurhash
+        case .video(_, let content): content.blurhash
+        case .audio, .file, .other: nil
+        }
+    }
+    
+    var duration: TimeInterval? {
+        switch self {
+        case .video(_, let content): content.videoInfo.duration
+        case .audio(_, let content): content.duration
+        case .image, .file, .other: nil
+        }
+    }
+    
+    var contentType: UTType? {
+        switch self {
+        case .image(_, let content): content.contentType
+        case .video(_, let content): content.contentType
+        case .audio(_, let content): content.contentType
+        case .file(_, let content): content.contentType
+        case .other: nil
+        }
+    }
+    
+    /// Whether the item can render a visible thumbnail. Images always can (their media source
+    /// IS the image); for everything else we need an explicit thumbnail source.
+    var hasThumbnail: Bool {
+        isImage || thumbnailSource != nil
+    }
+}

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemFactory.swift

@@ -149,7 +149,7 @@ nonisolated struct RoomTimelineItemFactory: RoomTimelineItemFactoryProtocol {
         case .location(let content):
             .location(buildLocationTimelineItemContent(content))
         case .gallery(let content):
-            .text(.init(body: content.body))
+            .gallery(buildGalleryTimelineItemContent(content, uniqueID: .init(senderID)))
         case .other(_, let body):
             .text(.init(body: body))
         case .none:
@@ -410,23 +410,54 @@ nonisolated struct RoomTimelineItemFactory: RoomTimelineItemFactoryProtocol {
                                           _ messageContent: MessageContent,
                                           _ galleryMessageContent: GalleryMessageContent,
                                           _ isOutgoing: Bool) -> RoomTimelineItemProtocol {
-        TextRoomTimelineItem(id: eventItemProxy.id,
+        GalleryRoomTimelineItem(id: eventItemProxy.id,
-                             timestamp: eventItemProxy.timestamp,
+                                timestamp: eventItemProxy.timestamp,
-                             isOutgoing: isOutgoing,
+                                isOutgoing: isOutgoing,
-                             isEditable: eventItemProxy.isEditable,
+                                isEditable: eventItemProxy.isEditable,
-                             canBeRepliedTo: eventItemProxy.canBeRepliedTo,
+                                canBeRepliedTo: eventItemProxy.canBeRepliedTo,
-                             shouldBoost: eventItemProxy.shouldBoost,
+                                shouldBoost: eventItemProxy.shouldBoost,
-                             sender: eventItemProxy.sender,
+                                sender: eventItemProxy.sender,
-                             content: .init(body: galleryMessageContent.body),
+                                content: buildGalleryTimelineItemContent(galleryMessageContent, uniqueID: eventItemProxy.id.uniqueID),
-                             properties: .init(replyDetails: buildTimelineItemReplyDetails(messageLikeContent.inReplyTo),
+                                properties: .init(replyDetails: buildTimelineItemReplyDetails(messageLikeContent.inReplyTo),
-                                               isThreaded: messageLikeContent.threadRoot != nil,
+                                                  isThreaded: messageLikeContent.threadRoot != nil,
-                                               threadSummary: buildTimelineItemThreadSummary(messageLikeContent.threadSummary),
+                                                  threadSummary: buildTimelineItemThreadSummary(messageLikeContent.threadSummary),
-                                               isEdited: messageContent.isEdited,
+                                                  isEdited: messageContent.isEdited,
-                                               reactions: buildAggregatedReactions(messageLikeContent.reactions),
+                                                  reactions: buildAggregatedReactions(messageLikeContent.reactions),
-                                               deliveryStatus: eventItemProxy.deliveryStatus,
+                                                  deliveryStatus: eventItemProxy.deliveryStatus,
-                                               orderedReadReceipts: buildOrderedReadReceipts(eventItemProxy.readReceipts),
+                                                  orderedReadReceipts: buildOrderedReadReceipts(eventItemProxy.readReceipts),
-                                               encryptionAuthenticity: buildEncryptionAuthenticity(eventItemProxy.shieldState),
+                                                  encryptionAuthenticity: buildEncryptionAuthenticity(eventItemProxy.shieldState),
-                                               encryptionForwarder: eventItemProxy.forwarder))
+                                                  encryptionForwarder: eventItemProxy.forwarder))
+    }
+    
+    private func buildGalleryTimelineItemContent(_ messageContent: GalleryMessageContent, uniqueID: TimelineItemIdentifier.UniqueID) -> GalleryRoomTimelineItemContent {
+        let htmlCaption = messageContent.formatted?.format == .html ? messageContent.formatted?.body : nil
+        let plainCaption = messageContent.formatted?.format != .html ? messageContent.formatted?.body : nil
+        let formattedCaption = htmlCaption != nil ? attributedStringBuilder.fromHTML(htmlCaption) : (plainCaption.flatMap(attributedStringBuilder.fromPlain))
+        
+        let items = messageContent.itemtypes.enumerated().map { index, itemType in
+            buildGalleryItem(itemType, id: GalleryItemID(timelineItemUniqueID: uniqueID, mediaIndex: index))
+        }
+        
+        return GalleryRoomTimelineItemContent(body: messageContent.body,
+                                              caption: plainCaption ?? messageContent.body,
+                                              formattedCaption: formattedCaption,
+                                              formattedCaptionHTMLString: htmlCaption,
+                                              items: items)
+    }
+    
+    private func buildGalleryItem(_ itemType: GalleryItemType, id: GalleryItemID) -> GalleryItem {
+        switch itemType {
+        case .image(let content):
+            .image(id: id, buildImageTimelineItemContent(content))
+        case .video(let content):
+            .video(id: id, buildVideoTimelineItemContent(content))
+        case .audio(let content):
+            .audio(id: id, buildAudioTimelineItemContent(content))
+        case .file(let content):
+            .file(id: id, buildFileTimelineItemContent(content))
+        case .other(_, let body):
+            .other(id: id, filename: body)
+        }
     }
     
     private func buildStickerTimelineItem(_ eventItemProxy: EventTimelineItemProxy,

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemView.swift

@@ -40,6 +40,8 @@ struct RoomTimelineItemView: View {
             AudioRoomTimelineView(timelineItem: item)
         case .file(let item):
             FileRoomTimelineView(timelineItem: item)
+        case .gallery(let item):
+            GalleryRoomTimelineView(timelineItem: item)
         case .emote(let item):
             EmoteRoomTimelineView(timelineItem: item)
         case .notice(let item):

ElementX/Sources/Services/Timeline/TimelineItems/RoomTimelineItemViewState.swift

@@ -53,6 +53,7 @@ enum RoomTimelineItemType: Equatable {
     case video(VideoRoomTimelineItem)
     case audio(AudioRoomTimelineItem)
     case file(FileRoomTimelineItem)
+    case gallery(GalleryRoomTimelineItem)
     case emote(EmoteRoomTimelineItem)
     case notice(NoticeRoomTimelineItem)
     case redacted(RedactedRoomTimelineItem)
@@ -83,6 +84,8 @@ enum RoomTimelineItemType: Equatable {
             self = .audio(item)
         case let item as FileRoomTimelineItem:
             self = .file(item)
+        case let item as GalleryRoomTimelineItem:
+            self = .gallery(item)
         case let item as SeparatorRoomTimelineItem:
             self = .separator(item)
         case let item as NoticeRoomTimelineItem:
@@ -132,6 +135,7 @@ enum RoomTimelineItemType: Equatable {
              .video(let item as RoomTimelineItemProtocol),
              .audio(let item as RoomTimelineItemProtocol),
              .file(let item as RoomTimelineItemProtocol),
+             .gallery(let item as RoomTimelineItemProtocol),
              .emote(let item as RoomTimelineItemProtocol),
              .notice(let item as RoomTimelineItemProtocol),
              .redacted(let item as RoomTimelineItemProtocol),
@@ -171,6 +175,8 @@ enum RoomTimelineItemType: Equatable {
             return item.timestamp
         case .file(let item):
             return item.timestamp
+        case .gallery(let item):
+            return item.timestamp
         case .emote(let item):
             return item.timestamp
         case .notice(let item):