last-n is set to 1 when entering PiP, isn't raised back when exiting PiP

[lultimouomo]

Description:

Both on Android and iOS, entering PiP sets last-n to 1, but exiting PiP doesn't raise it back, which causes a bunch of video-less rectangles to be shown in grid mode.
I think what is happening is the following: by entering PiP the window becomes smaller than REDUCED_UI_THRESHOLD, this causes the UI to toggle to reduced mode, which disables the filmstrip.
lastn middleware is listening for fimstrip changes, and calls _updateLastN, which finds that filmStrip is not enabled and sets last-n to 1.

When PiP is exited, the filmstrip is enabled again and _updateLastN is called; but since by default it will use the last selected value, it just sets last-n again to 1.

The only way to exit the impasse is enter audio-only mode; this sets last-n to 0, which is falsey and therefore is not considered when computing lastNSelected

This happens both when using the SDK in a 3rd party app and when using the official Jitsi app (at least on Android, on iOS I only tried the SDK)

Steps to reproduce:

1. Open Jitsi app on mobile
2. Join conference with at least two other participants
3. Enter PiP
4. Exit PiP

Expected behavior:

When exiting PiP, last-n is restored to the initial value and you can see multiple video streams

Actual behavior:

last-n is set again to 1 (as shown by android logcat), only your own video + one other participant is shown

Server information:

Happens both on self-hosted server and meet.jit.si

Client information:

• Browser / app version: Happens on Jitsi Meet for Android 21.4.1, Android SDK 3.10.2, iOS SDK 3.10.4
• Operating System:

Additional information:

A possible solution would be to store the requested last-n separately from the one that is applied, which could be lower because of audio-only, PiP, etc.

[saghul]

Great analysis! @tmoldovan8x8 can you PTAL when you get a chance?

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[lultimouomo]

Any chance someone can take a look at the open PR fixing this issue?

[saghul]

I just left a review.