On bad connectivity, trying to upload a file will block. On cancelling the upload, the modal still appears (minutes later)

[ara4n]

Steps to reproduce

1. Simulate a bad network
2. In an e2ee room send some normal messages, which will probably stack up as we try to do e2ee with the server
3. Send an image
4. Watch an infinite fullscreen modal spinner; the thumbnail doesn't even appear (which is weird, as it shouldn't need to talk to the server to calculate a thumbnail)
5. Click in the background of the modal to cancel it
6. Move on with your life
7. Be very confused when ~30s later the thumbnail upload still suddenly pops up... even if you're now in an entirely different room.

Outcome

What did you expect?

You should be able to queue up images to be sent even when on bad connectivity. They certainly shouldn't pop up unexpectedly later.

What happened instead?

Much flakiness.

Operating system

macOS 12.3.1 on M1

Application version

nightly

How did you install the app?

nightly

Homeserver

matrix.org

Will you send logs?

No

[turt2live]

(which is weird, as it shouldn't need to talk to the server to calculate a thumbnail)

This sounds like it might be the /media/config request or possibly it trying to encrypt before determining size/thumbnail/whatever

[t3chguy]

That is exactly what it is, it only happens once per session

[t3chguy]

Not specific to E2EE rooms either, the media info is used to early-reject uploads that are too large for your HS's config

[ara4n]

(related: #7069)

[t3chguy]

Duplicate of #24667

[gaelledel]

We should use the Retry banner that appears above the composer when sending fails.
This currently works for messages that failed to send. We should therefore display the same banner for anything else including photos, videos, attachments etc...
As a second phase, we will probably modify this and adopt the same behaviour/style as EX. This will come with the timeline rework using Compound.