Add _replyTo field to ComposerViewModel that can be set from a message

src/domain/session/room/RoomViewModel.js

@@ -44,6 +44,7 @@ export class RoomViewModel extends ViewModel {
             const timeline = await this._room.openTimeline();
             const timelineVM = this.track(new TimelineViewModel(this.childOptions({
                 room: this._room,
+                roomVM: this,
                 timeline,
             })));
             this._timelineVM = timelineVM;
@@ -294,12 +295,17 @@ export class RoomViewModel extends ViewModel {
         path = path.with(this.navigation.segment("details", true));
         this.navigation.applyPath(path);
     }
+
+    setReply(entry) {
+        this._composerVM.setReply(entry);
+    }
 }
 
 class ComposerViewModel extends ViewModel {
     constructor(roomVM) {
         super();
         this._roomVM = roomVM;
+        this._replyTo = null;
         this._isEmpty = true;
     }
 
@@ -307,6 +313,19 @@ class ComposerViewModel extends ViewModel {
         return this._roomVM.isEncrypted;
     }
 
+    setReply(entry) {
+        this._replyTo = entry;
+        this.emitChange("replyTo");
+    }
+
+    clearReply() {
+        this.setReply(null);
+    }
+
+    get replyTo() {
+        return this._replyTo;
+    }
+
     sendMessage(message) {
         const success = this._roomVM._sendMessage(message);
         if (success) {

src/domain/session/room/timeline/TimelineViewModel.js

@@ -38,9 +38,9 @@ import {ViewModel} from "../../../ViewModel.js";
 export class TimelineViewModel extends ViewModel {
     constructor(options) {
         super(options);
-        const {room, timeline} = options;
+        const {room, timeline, roomVM} = options;
         this._timeline = this.track(timeline);
-        this._tiles = new TilesCollection(timeline.entries, tilesCreator(this.childOptions({room, timeline})));
+        this._tiles = new TilesCollection(timeline.entries, tilesCreator(this.childOptions({room, timeline, roomVM})));
     }
 
     /**

src/domain/session/room/timeline/tiles/BaseMessageTile.js

@@ -106,6 +106,10 @@ export class BaseMessageTile extends SimpleTile {
         return action;
     }
 
+    setReply() {
+        this._roomVM.setReply(this._entry);
+    }
+
     redact(reason, log) {
         return this._room.sendRedaction(this._entry.id, reason, log);
     }

src/domain/session/room/timeline/tiles/SimpleTile.js

@@ -129,6 +129,10 @@ export class SimpleTile extends ViewModel {
         return this._options.room;
     }
 
+    get _roomVM() {
+        return this._options.roomVM;
+    }
+
     get _timeline() {
         return this._options.timeline;
     }

src/platform/web/ui/session/room/timeline/BaseMessageView.js

@@ -113,6 +113,7 @@ export class BaseMessageView extends TemplateView {
         if (vm.canReact && vm.shape !== "redacted") {
             options.push(new QuickReactionsMenuOption(vm));
         }
+        options.push(Menu.option(vm.i18n`Reply`, () => vm.setReply()));
         if (vm.canAbortSending) {
             options.push(Menu.option(vm.i18n`Cancel`, () => vm.abortSending()));
         } else if (vm.canRedact) {