Crate alpha2_geometry 

Deterministic vector geometry for alpha2 shapes.

A shapes generator’s content tree, evaluated at one time (EvaluatedItem), becomes a VectorScene: fills and stroke outlines in device pixels, in drawing order, with the group layers that fade them. raster::rasterize turns one of its paths into tile coverage. Queries the editor needs (bounds, hit tests, lengths, trims) use the same code.

Every result is the same bits on every target. Geometry is f64, trigonometry is libm’s, arc lengths and flattening use only + - * / and sqrt, and coverage is accumulated in scalar f32 in a fixed order. Stroke expansion is kurbo’s, and its transcendental calls are libm’s too, unless another crate in the build turns on kurbo’s std: then outlines and scene keys can differ in the last bits, and the shared hash goldens compare coverage only.

Re-exports

pub use kurbo;

Modules

affine

Affine transforms built from libm, and lengths from sqrt alone, so they are the same bits on every target.

arclen

Arc lengths of path segments, from + - * / and sqrt alone.

query

What an editor asks of shapes: where items are, which one is under a point, how long a path is, and paths cut, resampled, or converted. Each answer comes from the code the renderer draws with.

raster

Coverage of a path: per pixel, the average winding number over the pixel’s area, mapped by the fill rule, in 16 by 16 pixel tiles.

shapes

Parametric shapes as Bezier paths in pixel space, with the start points and directions After Effects and Lottie give them, so a trim cuts them where it cuts there.

spatial

Motion along spatial curves: a position keyframed with tangents travels along the cubic Bezier between its keyframes at the speed its timing curve sets, along the curve’s length.

trim

Trim paths: keeping a span of geometry’s length.

Structs

CanvasSize

The size, in device pixels, of the picture a content tree is drawn on: normalized (1, 1) is (width, height), and lengths are fractions of the shorter side.

EvaluatedPath

A path evaluated at one time.

EvaluatedSubpath

A subpath evaluated at one time.

EvaluatedTransform

A group’s transform evaluated at one time, normalized.

EvaluatedVertex

A path vertex evaluated at one time, normalized.

IRect

A half-open rectangle of device pixels.

ItemPath

What item_paths reports of one item.

ScenePaint

The paint of a fill, as the generator pass reads a paint: points in the normalized coordinates of the paint’s space, and the transform from device pixels into that space’s pixels.

SceneStop

One stop of a scene paint: its offset and straight, sRGB-encoded color.

StableHash

Two FNV-style lanes over the bytes written, as the render graph keys its results.

StrokeStyle

A stroke’s style, in the pixels of the space it is drawn in.

VectorScene

Everything a content tree draws at one time and size.

Enums

EvaluatedGeometry

A geometry item evaluated at one time.

EvaluatedItem

One content-tree item evaluated at one time.

PaintKind

What kind of paint covers a fill.

VectorOp

One drawing operation of a VectorScene.

Constants

MAX_DEVICE

How far past the canvas, in device pixels, a path may reach and still be rasterized as it is.

Functions

build_scene

The scene items draw on a picture of size.

build_scene_in

The operations items draw on a picture of space whose top-left corner lies at origin on a canvas of canvas, as an SVG viewBox places its picture: positions are normalized to space, lengths are fractions of its shorter side, and paints are in it. What they cover is clipped to canvas. build_scene is the case space == canvas at the origin.

build_scene_with_items

The scene items draw, with the item each of its operations was drawn for (empty for a layer’s push and pop).

item_paths

Every item’s outline or painted area, in document order, for the editor’s queries.

project_far

path as it fills a width by height canvas: itself when it stays within MAX_DEVICE of the canvas, or projected onto the canvas and a 64-pixel margin around it. Every subpath of the projection is closed, as filling closes it. A non-finite coordinate leaves nothing.

scene_paint

paint as the scene paints it, through inverse from device pixels into a paint space of space pixels.

stroke_outline

The outline style covers along path, both in the space to_device takes to device pixels, there. The pen is round in path’s space, so a non-uniform transform makes it an ellipse, as After Effects draws it. Empty for a width of zero or less.