Module transform 

Mapping user space onto clip space.

Three coordinate systems meet here, and confusing any two of them produces output that is mirrored or off by a scale factor rather than obviously broken:

• Path space — whatever units a path was authored in.
• Device space — pixels on the target. Origin top-left, X right, Y down, which is the convention 2D UI works in.
• Clip space — what the vertex shader emits. Both axes in [-1, 1], and Y runs up, following the WGSL convention that shader translation normalizes to. This is the axis that flips.

Tolerance is a device-space quantity, so flattening a path that will be scaled up has to happen more finely in path space. max_scale is what that adjustment is computed from.

Structs

Transform2D

A transform of the plane that may carry perspective.

Functions

invert_to_local

Invert a paint’s placement into the form a shader’s to_local takes.

max_scale

The largest factor by which a transform can stretch a direction.

preserves_axis_alignment

Whether a transform maps axis-aligned rectangles to axis-aligned rectangles.

to_local_columns

The same packing, for a mapping already stated in the direction the shader reads it.

transform_points

Apply a transform to every point in place.

transformed_bounds

The bounds of a rectangle’s corners after a transform, if there are any.

unbounded

Bounds standing in for “anywhere”, where a mapping gives none.

viewport_projection

Map device pixels onto clip space for a target of the given size.