Add a developer option to duplicate tiles

This is useful for testing how the UI behaves with different numbers of participants.

public/locales/en-GB/app.json

@@ -132,6 +132,7 @@
     "developer_settings_label": "Developer Settings",
     "developer_settings_label_description": "Expose developer settings in the settings window.",
     "developer_tab_title": "Developer",
+    "duplicate_tiles_label": "Number of duplicate tiles",
     "feedback_tab_body": "If you are experiencing issues or simply would like to provide some feedback, please send us a short description below.",
     "feedback_tab_description_label": "Your feedback",
     "feedback_tab_h4": "Submit feedback",

src/settings/SettingsModal.tsx

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { ChangeEvent, FC, Key, ReactNode } from "react";
+import { ChangeEvent, FC, Key, ReactNode, useCallback } from "react";
 import { Item } from "@react-stately/collections";
 import { Trans, useTranslation } from "react-i18next";
 import { MatrixClient } from "matrix-js-sdk";
@@ -44,6 +44,7 @@ import {
   useSetting,
   optInAnalytics as optInAnalyticsSetting,
   developerSettingsTab as developerSettingsTabSetting,
+  duplicateTiles as duplicateTilesSetting,
 } from "./settings";
 import { isFirefox } from "../Platform";
 
@@ -80,6 +81,7 @@ export const SettingsModal: FC<Props> = ({
   const [developerSettingsTab, setDeveloperSettingsTab] = useSetting(
     developerSettingsTabSetting,
   );
+  const [duplicateTiles, setDuplicateTiles] = useSetting(duplicateTilesSetting);
 
   // Generate a `SelectInput` with a list of devices for a given device kind.
   const generateDeviceSelection = (
@@ -244,6 +246,20 @@ export const SettingsModal: FC<Props> = ({
           })}
         </Body>
       </FieldRow>
+      <FieldRow>
+        <InputField
+          id="duplicateTiles"
+          type="number"
+          label={t("settings.duplicate_tiles_label")}
+          value={duplicateTiles.toString()}
+          onChange={useCallback(
+            (event: ChangeEvent<HTMLInputElement>): void => {
+              setDuplicateTiles(event.target.valueAsNumber);
+            },
+            [setDuplicateTiles],
+          )}
+        />
+      </FieldRow>
     </TabItem>
   );
 

src/settings/settings.ts

@@ -76,6 +76,8 @@ export const developerSettingsTab = new Setting(
   false,
 );
 
+export const duplicateTiles = new Setting("duplicate-tiles", 0);
+
 export const audioInput = new Setting<string | undefined>(
   "audio-input",
   undefined,

src/state/CallViewModel.ts

@@ -67,6 +67,7 @@ import {
 } from "./MediaViewModel";
 import { finalizeValue } from "../observable-utils";
 import { ObservableScope } from "./ObservableScope";
+import { duplicateTiles } from "../settings/settings";
 
 // How long we wait after a focus switch before showing the real participant
 // list again
@@ -308,11 +309,16 @@ export class CallViewModel extends ViewModel {
     combineLatest([
       this.remoteParticipants,
       observeParticipantMedia(this.livekitRoom.localParticipant),
+      duplicateTiles.value,
     ]).pipe(
       scan(
         (
           prevItems,
-          [remoteParticipants, { participant: localParticipant }],
+          [
+            remoteParticipants,
+            { participant: localParticipant },
+            duplicateTiles,
+          ],
         ) => {
           let allGhosts = true;
 
@@ -330,20 +336,29 @@ export class CallViewModel extends ViewModel {
                   );
                 }
 
-                const userMediaId = p.identity;
-                yield [
-                  userMediaId,
-                  prevItems.get(userMediaId) ??
-                    new UserMedia(userMediaId, member, p, this.encrypted),
-                ];
-
-                if (p.isScreenShareEnabled) {
-                  const screenShareId = `${userMediaId}:screen-share`;
+                // Create as many tiles for this participant as called for by
+                // the duplicateTiles option
+                for (let i = 0; i < 1 + duplicateTiles; i++) {
+                  const userMediaId = `${p.identity}:${i}`;
                   yield [
-                    screenShareId,
-                    prevItems.get(screenShareId) ??
-                      new ScreenShare(screenShareId, member, p, this.encrypted),
+                    userMediaId,
+                    prevItems.get(userMediaId) ??
+                      new UserMedia(userMediaId, member, p, this.encrypted),
                   ];
+
+                  if (p.isScreenShareEnabled) {
+                    const screenShareId = `${userMediaId}:screen-share`;
+                    yield [
+                      screenShareId,
+                      prevItems.get(screenShareId) ??
+                        new ScreenShare(
+                          screenShareId,
+                          member,
+                          p,
+                          this.encrypted,
+                        ),
+                    ];
+                  }
                 }
               }
             }.bind(this)(),