Take the orientation of a path into account when computing normals

demo/client/html/mesh-debugger.html.hbs

@@ -41,6 +41,7 @@
                                     <option value="font-open-sans">Font: Open Sans</option>
                                     <option value="font-nimbus-sans">Font: Nimbus Sans</option>
                                     <option value="font-inter-ui">Font: Inter UI</option>
+                                    <option value="font-custom">Font: Custom…</option>
                                     <option value="svg-tiger">SVG: Ghostscript Tiger</option>
                                     <option value="svg-logo">SVG: Pathfinder Logo</option>
                                     <option value="svg-custom">SVG: Custom…</option>

demo/server/src/main.rs

@@ -77,7 +77,7 @@ const SUGGESTED_JSON_SIZE_LIMIT: u64 = 32 * 1024 * 1024;
 
 const MESH_LIBRARY_CACHE_SIZE: usize = 16;
 
-const CUBIC_TO_QUADRATIC_APPROX_TOLERANCE: f32 = 1.0;
+const CUBIC_TO_QUADRATIC_APPROX_TOLERANCE: f32 = 5.0;
 
 static NEXT_FONT_KEY: AtomicUsize = ATOMIC_USIZE_INIT;
 

partitioner/src/mesh_library.rs

@@ -176,10 +176,10 @@ impl MeshLibrary {
 
         let mut b_quad_vertex_positions = BQuadVertexPositions {
             upper_left_vertex_position: ul,
-            upper_control_point_position: ul,
+            upper_control_point_position: ul.lerp(ur, 0.5),
             upper_right_vertex_position: ur,
             lower_left_vertex_position: ll,
-            lower_control_point_position: lr,
+            lower_control_point_position: ll.lerp(lr, 0.5),
             lower_right_vertex_position: lr,
         };
 

path-utils/src/lib.rs

@@ -19,6 +19,7 @@ extern crate lyon_path;
 
 pub mod cubic_to_quadratic;
 pub mod normals;
+pub mod orientation;
 pub mod segments;
 pub mod stroke;
 pub mod transform;

path-utils/src/normals.rs

@@ -10,6 +10,7 @@
 
 use euclid::{Point2D, Vector2D};
 use lyon_path::PathEvent;
+use orientation::Orientation;
 
 #[derive(Clone, Copy, Debug)]
 pub struct SegmentNormals {
@@ -40,8 +41,12 @@ impl PathNormals {
         self.normals.clear()
     }
 
-    pub fn add_path<I>(&mut self, mut stream: I) where I: Iterator<Item = PathEvent> {
+    pub fn add_path<I>(&mut self, stream: I) where I: Iterator<Item = PathEvent> {
+        let events: Vec<_> = stream.collect();
+        let orientation = Orientation::from_path(events.iter().cloned());
+
         let (mut path_ops, mut path_points) = (vec![], vec![]);
+        let mut stream = events.iter().cloned();
         while let Some(event) = stream.next() {
             path_ops.push(PathOp::from_path_event(&event));
             match event {
@@ -54,40 +59,49 @@ impl PathNormals {
                 PathEvent::Arc(..) => {
                     panic!("PathNormals::add_path(): Convert arcs to quadratics first!")
                 }
-                PathEvent::Close => self.flush(path_ops.drain(..), &mut path_points),
+                PathEvent::Close => self.flush(orientation, path_ops.drain(..), &mut path_points),
             }
         }
 
-        self.flush(path_ops.into_iter(), &mut path_points);
+        self.flush(orientation, path_ops.into_iter(), &mut path_points);
     }
 
-    fn flush<I>(&mut self, path_stream: I, path_points: &mut Vec<Point2D<f32>>)
+    fn flush<I>(&mut self,
+                orientation: Orientation,
+                path_stream: I,
+                path_points: &mut Vec<Point2D<f32>>)
                 where I: Iterator<Item = PathOp> {
         match path_points.len() {
             0 | 1 => path_points.clear(),
             2 => {
+                let orientation = -(orientation as i32 as f32);
                 self.normals.push(SegmentNormals {
-                    from: path_points[1] - path_points[0],
+                    from: (path_points[1] - path_points[0]) * orientation,
                     ctrl: Vector2D::zero(),
-                    to: path_points[0] - path_points[1],
+                    to: (path_points[0] - path_points[1]) * orientation,
                 });
                 path_points.clear();
             }
-            _ => self.flush_slow(path_stream, path_points),
+            _ => self.flush_slow(orientation, path_stream, path_points),
         }
     }
 
-    fn flush_slow<I>(&mut self, path_stream: I, path_points: &mut Vec<Point2D<f32>>)
+    fn flush_slow<I>(&mut self,
+                     orientation: Orientation,
+                     path_stream: I,
+                     path_points: &mut Vec<Point2D<f32>>)
                      where I: Iterator<Item = PathOp> {
         let mut normals = vec![Vector2D::zero(); path_points.len()];
-        *normals.last_mut().unwrap() = compute_normal(&path_points[path_points.len() - 2],
+        *normals.last_mut().unwrap() = compute_normal(orientation,
+                                                      &path_points[path_points.len() - 2],
                                                       &path_points[path_points.len() - 1],
                                                       &path_points[0]);
-        normals[0] = compute_normal(&path_points[path_points.len() - 1],
+        normals[0] = compute_normal(orientation,
+                                    &path_points[path_points.len() - 1],
                                     &path_points[0],
                                     &path_points[1]);
         for (index, window) in path_points.windows(3).enumerate() {
-            normals[index + 1] = compute_normal(&window[0], &window[1], &window[2]);
+            normals[index + 1] = compute_normal(orientation, &window[0], &window[1], &window[2])
         }
 
         path_points.clear();
@@ -125,10 +139,13 @@ impl PathNormals {
     }
 }
 
-fn compute_normal(prev: &Point2D<f32>, current: &Point2D<f32>, next: &Point2D<f32>)
+fn compute_normal(orientation: Orientation,
+                  prev: &Point2D<f32>,
+                  current: &Point2D<f32>,
+                  next: &Point2D<f32>)
                   -> Vector2D<f32> {
     let vector = ((*current - *prev) + (*next - *current)).normalize();
-    Vector2D::new(vector.y, -vector.x)
+    Vector2D::new(vector.y, -vector.x) * -(orientation as i32 as f32)
 }
 
 #[derive(Clone, Copy, PartialEq, Debug)]

path-utils/src/orientation.rs

@@ -0,0 +1,62 @@
+// pathfinder/path-utils/src/orientation.rs
+//
+// Copyright © 2018 The Pathfinder Project Developers.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use euclid::Point2D;
+use lyon_path::PathEvent;
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum Orientation {
+    Ccw = -1,
+    Cw = 1,
+}
+
+impl Orientation {
+    /// This follows the FreeType algorithm.
+    pub fn from_path<I>(stream: I) -> Orientation where I: Iterator<Item = PathEvent> {
+        let (mut from, mut subpath_start) = (Point2D::zero(), Point2D::zero());
+        let mut area = 0.0;
+        for event in stream {
+            match event {
+                PathEvent::MoveTo(to) => {
+                    from = to;
+                    subpath_start = to;
+                }
+                PathEvent::LineTo(to) => {
+                    area += det(&from, &to);
+                    from = to;
+                }
+                PathEvent::QuadraticTo(ctrl, to) => {
+                    area += det(&from, &ctrl) + det(&ctrl, &to);
+                    from = to;
+                }
+                PathEvent::CubicTo(ctrl0, ctrl1, to) => {
+                    area += det(&from, &ctrl0) + det(&ctrl0, &ctrl1) + det(&ctrl1, &to);
+                    from = to;
+                }
+                PathEvent::Arc(..) => {
+                    // TODO(pcwalton)
+                }
+                PathEvent::Close => {
+                    area += det(&from, &subpath_start);
+                    from = subpath_start;
+                }
+            }
+        }
+        if area <= 0.0 {
+            Orientation::Ccw
+        } else {
+            Orientation::Cw
+        }
+    }
+}
+
+fn det(a: &Point2D<f32>, b: &Point2D<f32>) -> f32 {
+    a.x * b.y - a.y * b.x
+}

shaders/gles2/common.inc.glsl

@@ -101,7 +101,7 @@ vec2 hintPosition(vec2 position, vec4 pathHints) {
 }
 
 vec2 quantize(vec2 position) {
-    return (floor(position * 10000.0 + 0.5) - 0.5) / 10000.0;
+    return (floor(position * 20000.0 + 0.5) - 0.5) / 20000.0;
 }
 
 /// Converts the given 2D position in clip space to device pixel space (with origin in the lower