63 lines
1.9 KiB
Rust
63 lines
1.9 KiB
Rust
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// pathfinder/path-utils/src/orientation.rs
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//
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// Copyright © 2018 The Pathfinder Project Developers.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use euclid::Point2D;
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use lyon_path::PathEvent;
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#[derive(Clone, Copy, Debug, PartialEq)]
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pub enum Orientation {
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Ccw = -1,
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Cw = 1,
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}
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impl Orientation {
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/// This follows the FreeType algorithm.
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pub fn from_path<I>(stream: I) -> Orientation where I: Iterator<Item = PathEvent> {
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let (mut from, mut subpath_start) = (Point2D::zero(), Point2D::zero());
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let mut area = 0.0;
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for event in stream {
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match event {
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PathEvent::MoveTo(to) => {
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from = to;
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subpath_start = to;
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}
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PathEvent::LineTo(to) => {
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area += det(&from, &to);
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from = to;
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}
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PathEvent::QuadraticTo(ctrl, to) => {
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area += det(&from, &ctrl) + det(&ctrl, &to);
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from = to;
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}
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PathEvent::CubicTo(ctrl0, ctrl1, to) => {
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area += det(&from, &ctrl0) + det(&ctrl0, &ctrl1) + det(&ctrl1, &to);
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from = to;
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}
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PathEvent::Arc(..) => {
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// TODO(pcwalton)
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}
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PathEvent::Close => {
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area += det(&from, &subpath_start);
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from = subpath_start;
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}
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}
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}
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if area <= 0.0 {
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Orientation::Ccw
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} else {
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Orientation::Cw
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}
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}
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}
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fn det(a: &Point2D<f32>, b: &Point2D<f32>) -> f32 {
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a.x * b.y - a.y * b.x
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}
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