A user's live wallpaper reached "started" with zero errors (Cogl and
GStreamer both loading fine, actor added to _backgroundGroup) but
never actually appeared on screen, and no code path here could tell
us why: the bus handler only looked at EOS/ERROR, silently discarding
WARNING and STATE_CHANGED messages where a stalled negotiation or
preroll would actually show up.
Adds: WARNING message logging, PLAYING/PAUSED/etc. state-changed
logging for the playbin itself, a frame counter with first-frame and
periodic debug logs, and a one-shot watchdog that logs an explicit
warning if zero frames arrive within 4s of set_state(PLAYING). Also
switched appsink's pull-sample from an emitted action signal to the
plain pull_sample() method, which is the more directly supported
GstApp.AppSink API and one less variable while debugging.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019RDqbdjsiisSU7CbQke4g8
Claude
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