Module cosmic::widget::canvas::path::lyon_path::commands

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Expand description

A generic representation for paths that allow more control over how endpoints and control points are stored.

§Motivation

The default Path data structure in this crate is works well for the most common use cases. Sometimes, however, it is useful to be able to specify exactly how endpoints and control points are stored instead of relying on implicitly following the order of the events.

This module contains bricks to help with building custom path representations. The central piece is the PathCommands buffer and its PathCommandsBuilder, providing a compact representation for path events with IDs instead of positions.

§Examples

The following example shows how PathCommands can be used together with an external buffers for positions to implement features similar to the default Path type with a different data structure.

use lyon_path::{EndpointId, Event, IdEvent, commands::PathCommands};
let points = &[
    [0.0, 0.0],
    [1.0, 1.0],
    [0.0, 2.0],
];

let mut cmds = PathCommands::builder();
cmds.begin(EndpointId(0));
cmds.line_to(EndpointId(1));
cmds.line_to(EndpointId(2));
cmds.end(true);

let cmds = cmds.build();

for event in &cmds {
    match event {
        IdEvent::Begin { at } => { println!("move to {:?}", points[at.to_usize()]); }
        IdEvent::Line { to, .. } => { println!("line to {:?}", points[to.to_usize()]); }
        IdEvent::End { close: true, .. } => { println!("close"); }
        _ => { panic!("unexpected event!") }
    }
}

// Iterate over the points directly using CommandsPathSlice
for event in cmds.path_slice(points, points).events() {
    match event {
        Event::Begin { at } => { println!("move to {:?}", at); }
        Event::Line { to, .. } => { println!("line to {:?}", to); }
        Event::End { close: true, .. } => { println!("close"); }
        _ => { panic!("unexpected event!") }
    }
}

Structs§