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pdfcraft/crates/render
d415749556 Heavy pages: cull off-tile images, cache decodes, preview backdrops, calmer queues (#1117)
* Heavy pages: cull off-tile images, cache decodes, preview backdrops, calmer queues

A large CAD sheet (page 24 of the benchmark file: ~5050 pt wide, 2104
images, 9 MB of content) cost a full page interpret per tile: 4.3 s for a
1024 px tile at 1000%, 10.5 s for the whole page, and a storm of renders on
every pan frame. Tiles now cost 0.6 s, the sheet is covered by a handful of
large tiles, and gestures no longer queue work faster than workers finish it.

- Vendored hayro patch (10): skip images whose stream-size box misses the
  canvas before decoding them, so a tile no longer decodes, resamples and
  rasterizes every image on its page. Pixel-identical; the skip regression
  test now covers images too.
- Vendored hayro-interpret patch (23): decoded image pixels shared across
  renders through the interpreter cache, keyed by stream and decode target
  size within a 64 MiB budget.
- Preview renders (hayro patch 11, RenderRequest::preview through to the
  device): backdrops, thumbnails, grid cells and signature-drag backgrounds
  skip images under 16 device px. Tiles, whole pages, print and export always
  draw everything. Previews may differ by those pixels; finals don't.
- Viewer: zoom/pan settle holds apply only to pages whose raster proved slow
  (slow_pages, 500 ms), so fast pages render with no added latency; tile sides
  grow with zoom and page size (giant sheets need ~8 tiles, not ~28), queued
  center-first and keyed by exact coordinates; Edit-text outlines capped.
- vendor/README.md records the new patches with their tests.

Co-Authored-By: Muse Spark <[email protected]>

* Decoded-image cache: key every decode input, survive a poisoned lock

The key was the dictionary's bytes and the target size, so two images with byte-identical
dictionaries (uncompressed, one size) shared pixels, and an image drawn under a transfer
function reused pixels decoded without it. DecodedImageKey now holds the dictionary's place
in the document (its data follows it), its bytes and object, mask/stencil/raster output,
interpolation, the target size and preview or final quality; images under a transfer
function and inline images (named colour spaces, dictionaries in content streams) are not
cached, and an image over the budget is never kept. A poisoned lock decodes uncached
instead of panicking. Soft masks: the per-renderer cache can't carry a preview mask into a
final render (documented). Regression tests for identical dictionaries, preview then final
through one cache, and transfer functions.

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Co-authored-by: Muse Spark <[email protected]>
Co-authored-by: Brandon Thomas <[email protected]>
2026-10-11 17:42:48 -04:00
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