Large documents stay interactive: the canvas re-renders only what a pan uncovers or an edit
touches, the layers panel lays out only the rows in view, and per-frame work no longer walks the
whole page.
- Benchmark: `cargo xtask bench [SIZES]` builds synthetic pages (`figcraft_engine::synthetic`:
screens with an auto layout header, a card group, button instances and shapes/text) at
1k/10k/50k layers and prints engine/render timings (`figcraft-cli perf --layers 1000,10000`) and
headless whole-UI frame timings (an ignored ui-egui test).
- Retained canvas rendering (`figcraft_render::Retained`, used by the render worker): views snap
to whole device pixels, so a pan shifts the previous image in place and renders only the
uncovered strips; an edit renders only where changed layers were and are
(`Document::changed_ids` diffs the two versions skipping shared structure; ancestors that paint
from their children's pixels - booleans, effects, masks - count whole; background blur reach
and noise are allowed for). Zoom, page, options, font or page-level changes, or large changes,
render the whole view as before. `ui.inspect` reports `canvas.renderWork`.
- The texture image is converted on the render thread, not the UI thread.
- Layers panel: only visible rows are laid out (stable ids while scrolling); rows are cached per
document version, page, expanded set and filter.
- Frame labels and layout grids of off-screen top-level frames are skipped; the Prototype tab's
connection sources are cached per document version.
- Text: the layout cache keys by a cheap fingerprint confirmed by `TextData` equality (no Debug
formatting per lookup, 32k entries) and hands out shared layouts; a layout generation marks
renders stale when fonts arrive. Overflowing text is culled by its glyphs, so it no longer
vanishes while its box is off screen.
Before -> after (release, Windows, 1440x900 view, ms; 10k / 50k layers):
- move one layer, re-render @100%: 7.65 / 6.49 -> 0.18 / 0.81
- move one layer, re-render zoomed out: 11.95 / 24.10 -> 0.16 / 0.77
- pan 40 px @100%: 7.53 / 6.82 -> 0.69 / 0.81
- pan 40 px zoomed out: 12.07 / 24.30 -> 1.62 / 4.17
- full render @100% / zoomed to fit: 7.78 / 44.22 -> 6.56 / 38.83 (10k @100%, 50k fit)
- UI frame, every screen expanded in layers: 6.16 / 39.07 -> 0.24 / 0.57
- UI frame, scrolling that panel: 6.11 / 40.18 -> 0.43 / 0.40
- UI frame, layers filtered by name: 1.03 / 6.92 -> 0.17 / 0.36
- UI frame, Prototype tab: 0.89 / 6.45 -> 0.18 / 0.80
- UI frame, idle: 0.31 / 1.43 -> 0.11 / 0.39
Unchanged and within budget: single-layer edits through the engine ~0.01 ms, normalize after a
one-node edit < 0.01 ms, hit test 26 / 93 us. Left: save/load at 50k (~0.7 s each), zoomed-out
renders at 50k (~40 ms).
Tests: retained renders match full renders after pans, moves, recolours, hide/remove/add, undo,
masks, overflowing text, edits under a background blur and an inner-shadow/noise layer, a drop-
shadowed group, and a blur panned in from the view's edge; zoom/page/options/page background
render full; junk views don't panic. Layer-row and prototype-source caches follow edits, undo,
page switches, expansion and the filter. `changed_ids`, the text cache, and the perf CLI.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
The canvas renders large views in parallel horizontal bands, and each band crops a layer to its
own rows. Three effects went wrong at those crops:
- Inner shadow (the reported bug): the padded shadow buffer treated everything beyond the cropped
layer as outside the shape, so every band edge cast shadow inwards, drawing dark bands across
the layer (any shape and fill; also at the view's edge when a layer was partly off screen). The
shape itself is now rasterised over the padded buffer at the shadow's offset (sub-pixel
accurate), so only its real edges cast shadow.
- Layers starting above or left of the pixmap (inside the blur margin) were sized from the
clamped origin and came out short by the margin: a drop-shadowed or background-blurred layer
crossing a band edge lost a strip at its far side.
- Background blur read a backdrop that stopped at the band's edge (streaks at band edges). Bands
now overlap by what background blurs read (3 sigma + box rounding) and keep only their own
rows; a blur wider than a band renders the view in one piece.
Regression tests (crates/render/src/band_tests.rs): an image-filled ellipse and a rotated solid
rectangle with inner shadows (spread, offsets) under a background-blurred panel, at 1x and 2x,
rendered in 2, 3 and 7 bands, must match the one-piece render row by row; the ellipse's interior
far from its edge must equal the render without the shadow on every row; a huge backdrop blur
falls back to one piece.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
- Layers gain `maskType` (alpha by default, so files are unchanged): a vector mask clips by the
mask layer's outline whatever its fills and opacity; a luminance mask shows content where the
mask is bright and hides it where it is dark.
- `node.set {maskType}` (validated), `node.get` reports it, and the Appearance section shows a
Mask dropdown when the selection is masks.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
