hook it up

src/domain/session/room/RoomViewModel.js

@@ -169,6 +169,7 @@ class ComposerViewModel extends ViewModel {
         super();
         this._roomVM = roomVM;
         this._isEmpty = true;
+        this._ensureKeyPromise = null;
     }
 
     get isEncrypted() {
@@ -188,8 +189,16 @@ class ComposerViewModel extends ViewModel {
         return !this._isEmpty;
     }
 
-    setInput(text) {
+    async setInput(text) {
+        const wasEmpty = this._isEmpty;
         this._isEmpty = text.length === 0;
-        this.emitChange("canSend");
+        if (wasEmpty && !this._isEmpty && !this._ensureKeyPromise) {
+            this._ensureKeyPromise = this._roomVM._room.ensureMessageKeyIsShared().then(() => {
+                this._ensureKeyPromise = null;
+            });
+        }
+        if (wasEmpty !== this._isEmpty) {
+            this.emitChange("canSend");
+        }
     }
 }

src/matrix/e2ee/RoomEncryption.js

@@ -247,9 +247,10 @@ export class RoomEncryption {
     }
 
     /** shares the encryption key for the next message if needed */
-    async ensureNextMessageKeyIsShared(hsApi) {
+    async ensureMessageKeyIsShared(hsApi) {
         const roomKeyMessage = await this._megolmEncryption.ensureOutboundSession(this._room.id, this._encryptionParams);
         if (roomKeyMessage) {
+            await this._deviceTracker.trackRoom(this._room);
             await this._shareNewRoomKey(roomKeyMessage, hsApi);
         }
     }

src/matrix/room/Room.js

@@ -354,6 +354,10 @@ export class Room extends EventEmitter {
         return this._sendQueue.enqueueEvent(eventType, content);
     }
 
+    async ensureMessageKeyIsShared() {
+        return this._roomEncryption?.ensureMessageKeyIsShared(this._hsApi);
+    }
+
     /** @public */
     async loadMemberList() {
         if (this._memberList) {