`RasterStrokeAction`/`RasterFillAction` stored the whole before+after RGBA frame
(~16 MB/action at 1080p → up to ~1.6 GB at the 100-action cap). They now store a
`RasterDiff` — only the changed bounding box's pixels before and after — computed
once in `new()` from the full buffers, which are then dropped. A brush dab shrinks
from ~16 MB to tens of KB; a full-canvas fill is unchanged (its bbox is the frame).
Paging interaction: a diff overwrites just the bbox, so the keyframe's pixels must
be resident when undo/redo applies. A clean evicted frame's container bytes equal
its current logical state, so the editor faults the target frame in (synchronously)
before undo/redo via a new `Action::raster_resident_hint` + `peek_undo/redo_raster_hint`.
Dirty frames are never evicted, so they're already resident. If a base is somehow
not resident the apply is skipped (logged), never resized-and-corrupted.
Unit tests cover exact before/after round-trip, blank-first-stroke, no-op, and the
non-resident-base skip.
Scrubbing a large paint project no longer accumulates every visited frame in RAM.
A fault-in-recency LRU keeps the most-recently-paged-in RASTER_RESIDENT_MAX (12)
keyframes resident and drops the pixels of older *clean* ones (re-arming their
fault-in so they re-page on revisit). The shown frame is always the most-recent
fault-in, so it's never evicted.
Data-loss safety: a new `dirty` flag marks any keyframe whose `raw_pixels` were
mutated by editing (stroke/fill/paint-bucket/floating-lift + their undo/redo) and
is NOT yet in the container. Dirty keyframes are NEVER evicted — they're only
unpinned from the LRU. The flag is cleared on a successful save, which also re-arms
the LRU for the now-clean resident frames so the bound still applies to frames
edited this session.
Also: the save loop now walks all layers (incl. nested) to match the load path's
recursive fault-in arming — evicted frames keep their existing container row
(media_exists), and nested raster keyframes are persisted + covered by live_media.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Skyler Lehmkuhl