Part of #2271. The native targets took ONE colour from a layer (`first_fill`: the bottom visible solid, or a gradient's first stop) and dropped every other fill, so a frame with white, a gradient and 50% black came out as flat white.
Now SwiftUI, Compose and Flutter write every visible solid and gradient fill of a frame, group, rectangle or ellipse, in paint order, and a gradient as a gradient. A shared `visible_fills` gives each target the same list (document order, bottom first); each target only formats it.
- SwiftUI: chained `.background(...)`, top fill first, since each one goes behind the ones before it. A rectangle or ellipse fills with the bottom paint and lays a copy of the shape over it (`.overlay`) for each paint above, bottom first.
- Compose: chained `Modifier.background(...)`, bottom fill first, since each one draws over the ones before it. A linear gradient snaps to one of eight directions (a modifier doesn't know pixels); radial and angular ones sit at the box's centre.
- Flutter: a `BoxDecoration` paints one colour or gradient, so the Container keeps the top fill and each fill under it becomes a `DecoratedBox` around the widget, the bottom fill outermost. The drop shadow goes on the outermost box so it never lies over a lower fill. An instance's call is now made once, in `flutter_placed`.
A layer with one solid fill gives the same code as before, variable names included (only the paint at index 0, when solid, takes the `fill` variable's name). A lone gradient used to come out as its first stop's colour and is now a gradient.
Still not written: image and pattern fills in the native targets, ArkUI (one background and one gradient per component, so a stack needs extra nodes) and text with several fills. Figma's iOS and Android output was not measured: the order follows how each platform paints.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Model-Effort: Opus 5.5 drove; Fable 5.2 briefed; Sonnet 5.5 wrote at medium
Trevor BrownandClaude Sonnet 5.5
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