The native content path only entered capture_mode when it was also narrowing
the canvas, so at full width — which is every plugin without a vegas_width_pct
override, i.e. most of them — a plugin calling update_display() while building
its Vegas content wrote straight to the hardware. That is a visible flash
mid-scroll, and it lines up with the flash reported at cycle transitions, when
several plugins are fetched back to back.
Suppression is now unconditional; the narrowing context stays separate because
it is already a no-op at full width.
Both contexts are reached through helpers that degrade to nullcontext when the
display manager lacks them. That matters more than it looks: the adapter's
handlers are deliberately broad, so an AttributeError from a missing context
does not surface as an error — it surfaces as the plugin contributing nothing.
Making the call unconditional without this turned 44 tests red for exactly that
reason, all of them reporting lost content rather than the real cause.
The test double now provides capture_mode and render_size too, so tests
exercise the real contexts instead of silently taking the degraded path.
Co-Authored-By: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KEZK1P1Q1fu5pcuVrkrCFZ
