cosmic::widget::canvas::path::lyon_path

Module builder

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Path building utilities.

§PathBuilder or SvgPathBuilder

Path can be built via either of two abstractions:

  • PathBuilder is a simple and efficient interface which does not deal with any ambiguous cases.
  • SvgPathBuilder is a higher-level interface that follows SVG’s specification, removing the the burden of dealing with special cases from the user at a run-time cost.

SvgPathBuilder may be a better choice when interactive with SVG, or dealing with arbitrary input. PathBuilder. PathBuilder is probably a more useful trait to implement when creating a new path data structure since all PathBuilder implementations automatically get an SvgPathBuilder adapter (see the with_svg method). It may also make sense to use the PathBuilder API when following a specification that behaves like SVG paths or when no performance can be traded for convenience.

§Examples

The following example shows how to create a simple path using the PathBuilder interface.

use lyon_path::{Path, geom::point};

let mut builder = Path::builder();

// All sub-paths *must* have be contained in a begin/end pair.
builder.begin(point(0.0, 0.0));
builder.line_to(point(1.0, 0.0));
builder.quadratic_bezier_to(point(2.0, 0.0), point(2.0, 1.0));
builder.end(false);

builder.begin(point(10.0, 0.0));
builder.cubic_bezier_to(point(12.0, 2.0), point(11.0, 2.0), point(5.0, 0.0));
builder.close(); // close() is equivalent to end(true).

let path = builder.build();

The same path can be built using the SvgPathBuilder API:

use lyon_path::{Path, geom::{point, vector}, builder::SvgPathBuilder};

// Use the SVG adapter.
let mut builder = Path::builder().with_svg();

// All sub-paths *must* have be contained in a begin/end pair.
builder.move_to(point(0.0, 0.0));
builder.line_to(point(1.0, 0.0));
builder.quadratic_bezier_to(point(2.0, 0.0), point(2.0, 1.0));
// No need to explicitly end a sub-path.

builder.move_to(point(10.0, 0.0));
builder.relative_cubic_bezier_to(vector(2.0, 2.0), vector(1.0, 2.0), vector(-5.0, 0.0));
builder.close();

let path = builder.build();

Implementors of the PathBuilder trait automatically gain access to a few other adapters. For example a builder that approximates curves with a sequence of line segments:

use lyon_path::{Path, geom::point};

let tolerance = 0.05;// maximum distance between a curve and its approximation.
let mut builder = Path::builder().flattened(tolerance);

builder.begin(point(0.0, 0.0));
builder.quadratic_bezier_to(point(1.0, 0.0), point(1.0, 1.0));
builder.end(true);

// The resulting path contains only Begin, Line and End events.
let path = builder.build();

Structs§

  • BorderRadii
    The radius of each corner of a rounded rectangle.
  • Flattened
    A Builder that approximates curves with successions of line segments.
  • NoAttributes
    A convenience wrapper for PathBuilder without custom attributes.
  • Transformed
    Builds a path with a transformation applied.
  • WithSvg
    Implements an SVG-like building interface on top of a PathBuilder.

Traits§