investigate: why do we capture screenshot separate from events #2643

Follow-up issue to #2641

There might be a good pre-existing reason to it, but this isn't clear from the code/docs. The rendering order compared to Unreal is different (so screenshots are only available at EndOfFrame), but maybe there is a possibility of delaying the event capture until after the screenshot was captured?

The (broken as reported in #2641) flow is currently

SentrySdk.CaptureMessage("...") → SentryClient.cs:316 — DoSendEvent(@event) begins
SentryClient.cs:356 — ProcessEvent calls ScreenshotEventProcessor.Process(@event)
ScreenshotEventProcessor.cs:30 — queues coroutine with @event in closure
SentryMonoBehaviour.cs:69 — StartCoroutine → coroutine runs until yield return WaitForEndOfFrame() → pauses
SentryClient.cs:362 — BeforeSend runs → returns null → event dropped
SentryClient.cs:365 — returns SentryId.Empty
End of frame:

ScreenshotEventProcessor.cs:54 — coroutine resumes, BeforeCaptureScreenshot callback runs
ScreenshotEventProcessor.cs:59 — captures screenshot
ScreenshotEventProcessor.cs:95 — CaptureAttachment(@event.EventId, attachment) — sends orphaned envelope

Other Questions

• UserFeedback -> why can we capture screenshot synchronously here but not in CaptureEvent