Add a background without putting it on, before joining too

- Added to the backgrounds on offer and in force once chosen, in the lobby
  exactly as in a call. Choosing a file and choosing to wear it are two
  decisions, and one rule for both places is one less thing to know.
- The footer's before-joining flag existed only for the other rule, so it
  goes, from both view models and the story.
- The edge-fade story waits longer for a scroll to settle: under the full
  parallel run a wait could outlast the default second.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/components/CallFooter.stories.tsx

@@ -136,7 +136,6 @@ export const Default: Story = {
     videoBlurEnabled: true,
     backgroundEffect: "none",
     selectBackgroundEffect: fn(),
-    beforeJoining: false,
     hangup: fn(),
     buttonSize: "lg",
     showFooter: true,

src/components/CallFooter.tsx

@@ -99,12 +99,6 @@ export interface FooterState {
   videoBlurEnabled: boolean;
   /** The chosen background effect, in its stored form. */
   backgroundEffect: string;
-  /**
-   * Whether this footer is shown before joining. An image added there becomes
-   * the background at once; one added in a call waits to be chosen, because
-   * putting it on would change what everyone sees with no further word.
-   */
-  beforeJoining: boolean;
   showFooter: boolean;
 
   /* This is needed for WindowMode = "flat" */
@@ -189,7 +183,6 @@ export const CallFooter: FC<FooterProps> = ({
   const selectVideoButtonOption = useBehavior(vm.selectVideoButtonOption$);
   const backgroundEffect = useBehavior(vm.backgroundEffect$);
   const selectBackgroundEffect = useBehavior(vm.selectBackgroundEffect$);
-  const beforeJoining = useBehavior(vm.beforeJoining$);
   const { added, addBackground, removeBackground } = useAddedBackgrounds();
   const { settling, cameraTrack } = useBackgroundProcessing();
 
@@ -241,26 +234,21 @@ export const CallFooter: FC<FooterProps> = ({
   const onAddBackgroundImage = useCallback(
     (file: File): void => {
       setBackgroundEffectError(undefined);
-      addBackground(file)
-        .then((id) => {
-          // Before joining, nobody sees the change, so the picture goes on at
-          // once. In a call it waits to be chosen: otherwise choosing a file
-          // would change what everyone sees, with no further word from the
-          // user. Teams draws the line in the same place.
-          if (beforeJoining)
-            selectBackgroundEffect?.(serializeEffect({ kind: "added", id }));
-        })
-        .catch((e) => {
-          setBackgroundEffectError(whyRefused(e));
-          logger.warn(
-            e instanceof UnusableImage
-              ? `Cannot use that file as a background: ${e.reason}`
-              : "Could not keep that background",
-            e,
-          );
-        });
+      // Added, not put on — before joining and during a call alike. It joins
+      // the backgrounds on offer and is in force once the user chooses it:
+      // choosing a file and choosing to wear it are two decisions, and one
+      // rule for both places is one less thing to know.
+      addBackground(file).catch((e) => {
+        setBackgroundEffectError(whyRefused(e));
+        logger.warn(
+          e instanceof UnusableImage
+            ? `Cannot use that file as a background: ${e.reason}`
+            : "Could not keep that background",
+          e,
+        );
+      });
     },
-    [addBackground, beforeJoining, selectBackgroundEffect, whyRefused],
+    [addBackground, whyRefused],
   );
 
   // The catalogue is named here rather than in the view model: the names are

src/components/CallFooterViewModel.tsx

@@ -181,7 +181,6 @@ export function createCallFooterViewModel(
   return {
     ...buildMuteBehaviors(scope, muteStates),
     ...buildDeviceBehaviors(scope, mediaDevices, disableDeviceSwitcher$),
-    beforeJoining$: constant(false),
     // candidat to move into the FooterViewModel
     showFooter$: callModel.showFooter$,
     hideControls$: constant(!showControls),
@@ -295,6 +294,5 @@ export function createLobbyFooterViewModel(
     }),
     ...buildMuteBehaviors(scope, muteStates),
     ...buildDeviceBehaviors(scope, mediaDevices, constant(false)),
-    beforeJoining$: constant(true),
   };
 }

src/components/MediaMuteAndSwitchButton.stories.tsx

@@ -1097,7 +1097,9 @@ export const BackgroundEffectsShowThereIsMore: Story = {
       edge.classList.contains(styles.scrollEdgeShown);
 
     // Opened at the top: more below, nothing above.
-    await waitFor(async () => expect(shown(bottom)).toBe(true));
+    await waitFor(async () => expect(shown(bottom)).toBe(true), {
+      timeout: 4000,
+    });
     await expect(shown(top)).toBe(false);
     // And the fade is at the foot of what is in view, not of the content.
     await expect(
@@ -1109,8 +1111,12 @@ export const BackgroundEffectsShowThereIsMore: Story = {
 
     // At the end: nothing below, more above.
     list.scrollTop = list.scrollHeight;
-    await waitFor(async () => expect(shown(bottom)).toBe(false));
-    await waitFor(async () => expect(shown(top)).toBe(true));
+    await waitFor(async () => expect(shown(bottom)).toBe(false), {
+      timeout: 4000,
+    });
+    await waitFor(async () => expect(shown(top)).toBe(true), {
+      timeout: 4000,
+    });
 
     // Standing just below the heading holding the top, where the content comes
     // out from under it — not behind the heading, where it could not be seen.
@@ -1124,13 +1130,15 @@ export const BackgroundEffectsShowThereIsMore: Story = {
         ) < 2,
     )!;
     await expect(stuck).toBeDefined();
-    await waitFor(async () =>
-      expect(
-        Math.round(
-          top.getBoundingClientRect().top -
-            stuck.getBoundingClientRect().bottom,
-        ),
-      ).toBe(0),
+    await waitFor(
+      async () =>
+        expect(
+          Math.round(
+            top.getBoundingClientRect().top -
+              stuck.getBoundingClientRect().bottom,
+          ),
+        ).toBe(0),
+      { timeout: 4000 },
     );
   },
 };