**A paint and effects behaviour suite written from the public documentation, and fixes for every divergence it found.** Each documented rule (fill stacking and opacity, paint vs layer opacity, every blend mode per paint and per layer, pass-through and Normal containers, the four gradient kinds and their handles, stops, image scale modes, rotation and adjustments, the colour models and hex entry, the document colour profile, drop and inner shadows, showing shadows behind transparent areas, layer and background blurs, effects on groups, effect order, what exports include) is a table-driven case with a one-line derivation; where the documentation is silent the case says so and pins today's behaviour. Scenes are small and synthetic; pixel cases use tolerances (blurs are checked against the normal distribution with sigma = radius / 2).
**Fixes (13 render cases and 8 command/export cases fail on the old code)**
- **Pass-through and Normal containers**: a group or frame set to Normal now blends its children among themselves first (it never isolated), and a **clipping frame no longer isolates** its children: they were drawn on a fresh layer, so a Multiply child inside a frame (frames clip by default) met neither the frame's fill nor what is behind it. The clipped layer now starts as a copy of what lies under it and goes back in its place through the clip (a memcpy for rectangular clips, so no slower); backdrop effects see the right composite, also for a clipping frame inside a faded group. Same in exports: SVG gives Normal groups `isolation:isolate` and puts a clipping frame's clip on what blends instead of a clipped `<g>` (a clipped group is a stacking context, which isolates); PDF wraps Normal groups in an isolated group (`Node::isolates_children`, shared).
- **Plus darker** (linear burn) is drawn by its formula on the canvas and in pixel exports for paints, layers, shadows and noise (it was multiply); tiny-skia lacks the mode, so `fx::plus_darker` composites it and `paint::composite` routes every layer, shadow and noise composite through it.
- **Shadows hidden behind the layer**: a drop shadow that doesn't show behind transparent areas is now hidden behind what the layer covers, translucent and 0% fills included (it was cut out by the layer's alpha, so it showed through a 50% fill anyway); groups and layers whose pixels a layer blur or texture moves still hide it behind their pixels. One `shadow::Caster::new` serves the canvas, PNG and the PDF's shadow rasters. **SVG** never cut shadows out: its filters now composite them `out` of an image of the layer's outline (or `SourceAlpha` for groups), and the filter region reaches as far as the effects (a fixed 200% box cut off a small layer's long shadow).
- **Fill images cover the box to its edges**: an upscaled Fill (or covering Crop) image faded to transparent over a source pixel at the box's edge.
- **"Normal" meant pass-through** when named: `BlendMode::from_name("normal")` found pass-through first (its CSS keyword is also `normal`), so `node.set {blend: "normal"}` and the blend menu's Normal set pass-through. Labels now win, and the menu sends labels.
**Added**
- A blend mode menu for each paint in the colour picker (no pass-through for paints), sharing `right::blend_menu` with the Design panel's layer menu; strings already translated.
- Inspect (`node.get`, MCP) reports a solid paint's `blend` when it isn't normal.
A 64-case behaviour suite derived from public documentation (sizing, padding, strokes, gaps, alignment, wrap, absolute position, grid, stacking) plus command-level tests. Fixes: frames never shrink below their padding, only the frame's own inside stroke counts when strokes are included (now the default for new auto layout), auto gaps stop at 0, grid fr tracks never go below their content, and canvas stacking (reverseZ) now drives drawing, exports and hit testing. New settings: evenly/around auto gaps, vertical wrap with a column gap, per-child grid cell alignment, strokes included/excluded and canvas stacking in the Design panel.
- Inner shadows paint over the fills and under the children and strokes, as documented (canvas,
PNG, PDF and SVG alike; text fills every run before the inner shadow and the strokes).
- Layer and background blur gain a progressive type: the radius ramps linearly from a start radius
at a start point to the end radius at an end point (unit-box points, like gradient handles).
Rendered by blending a few geometric blur levels, each blurred only around the pixels that use
it; bands and partial renders match one piece. Design panel type menu and Start/End fields,
on-canvas handles while the settings are open, effect.add/effect.set params, startRadius
variable bindings, scale tool, REST import (blurType, startRadius, startOffset, endOffset),
Inspect row; CSS leaves progressive blurs out.
- SVG export embeds renders for what filters can't match: noise grains over the vector layer
(crisp, blended), texture and progressive layer blur whole, background blur and glass from what
lies under the layer among the exported layers. PDF and SVG share the renderer's helpers.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
- Background blur sees the whole backdrop under the layer: the renderer keeps the stack of
isolated surfaces it draws into (clipping frames, rounded clips, faded groups, masks) and
flattens it for the layer's area, reading past the layer's own box. A blur inside a clipping
frame now shows the frame's fill instead of the sharp layers below, on the canvas and in PNG
exports. The PDF export draws background blur and glass through the same code from a render of
what lies under the node (`backdrop::render_beneath`, which the PDF's backdrop now shares), and
its images match the PNG's pixels.
- Shadow spread offsets the outline: the shape filled and stroked twice the spread wide with
mitred joins (grow) or cut away (shrink), the stroked bands cached per outline. Ellipses stay
ellipses, stars keep sharp points, text keeps its letterforms, rounded corners grow their
radius. Inner shadows shrink the outline the same way. Canvas, PNG and PDF share the shadow
code; SVG writes spread shadows as the same geometry and now exports inner shadows.
- Glass effect (light angle and intensity, refraction, depth, dispersion, frost, splay): the
frosted backdrop bent towards the inside within `depth` of the edge, colour fringes, light on
the rim, from an exact distance transform with smoothed normals.
- Noise: mono, duo and multi colour modes, grain size, density, opacity and blend mode; grains
live in the layer's coordinates (stable when panning and zooming). Texture is now drawn
(pixels scattered by the radius, grain size, clip to shape).
- Design panel rows for noise mode/colours/opacity, texture clip to shape and every glass value;
`effect.add` takes `glass`; REST import of NOISE, TEXTURE and GLASS; Inspect rows and CSS;
the scale tool scales grain sizes, texture radius, glass depth and frost.
- Tests in new modules: render backdrop/spread/grain tests, PDF backdrop tests, SVG, doc,
engine and REST effect tests.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
bflatastic