Handle glyph outlines in which the first point is off-curve correctly.

These show up in Helvetica.dfont and Times.dfont.

examples/generate-atlas.rs

@@ -25,10 +25,9 @@ use pathfinder::rasterizer::{Rasterizer, RasterizerOptions};
 use std::env;
 use std::os::raw::c_void;
 
-const POINT_SIZE: f32 = 24.0;
+const DEFAULT_POINT_SIZE: f32 = 24.0;
 const WIDTH: u32 = 512;
 const HEIGHT: u32 = 384;
-const SHELF_HEIGHT: u32 = 32;
 
 fn main() {
     let mut glfw = glfw::init(glfw::LOG_ERRORS).unwrap();
@@ -49,10 +48,19 @@ fn main() {
     let rasterizer_options = RasterizerOptions::from_env().unwrap();
     let rasterizer = Rasterizer::new(&instance, device, queue, rasterizer_options).unwrap();
 
-    let mut glyph_buffer_builder = GlyphBufferBuilder::new();
-    let mut batch_builder = BatchBuilder::new(device_pixel_width as GLuint, SHELF_HEIGHT);
-
     let file = Mmap::open_path(env::args().nth(1).unwrap(), Protection::Read).unwrap();
+
+    let point_size = match env::args().nth(2) {
+        None => DEFAULT_POINT_SIZE,
+        Some(point_size) => point_size.parse().unwrap()
+    };
+
+    // FIXME(pcwalton)
+    let shelf_height = (point_size * 2.0).ceil() as u32;
+
+    let mut glyph_buffer_builder = GlyphBufferBuilder::new();
+    let mut batch_builder = BatchBuilder::new(device_pixel_width as GLuint, shelf_height);
+
     unsafe {
         let font = Font::new(file.as_slice()).unwrap();
         let codepoint_ranges = [CodepointRange::new(' ' as u32, '~' as u32)];
@@ -60,7 +68,7 @@ fn main() {
         let glyph_ranges = font.glyph_ranges_for_codepoint_ranges(&codepoint_ranges).unwrap();
         for (glyph_index, glyph_id) in glyph_ranges.iter().enumerate() {
             glyph_buffer_builder.add_glyph(&font, glyph_id).unwrap();
-            batch_builder.add_glyph(&glyph_buffer_builder, glyph_index as u32, POINT_SIZE).unwrap()
+            batch_builder.add_glyph(&glyph_buffer_builder, glyph_index as u32, point_size).unwrap()
         }
     }
 

src/glyph_buffer.rs

@@ -52,11 +52,11 @@ impl GlyphBufferBuilder {
                 glyph_index: glyph_index,
             });
 
-            if !point.first_point_in_contour && point.on_curve {
-                let indices = if last_point_on_curve {
-                    [point_index - 1, 0, point_index]
-                } else {
+            if point.index_in_contour > 0 && point.on_curve {
+                let indices = if !last_point_on_curve {
                     [point_index - 2, point_index - 1, point_index]
+                } else {
+                    [point_index - 1, 0, point_index]
                 };
                 self.indices.extend(indices.iter().cloned());
             }

src/otf/glyf.rs

@@ -28,11 +28,11 @@ bitflags! {
     }
 }
 
-#[derive(Clone, Copy, PartialEq)]
+#[derive(Clone, Copy, PartialEq, Debug)]
 pub struct Point {
     pub position: Point2D<i16>,
+    pub index_in_contour: u16,
     pub on_curve: bool,
-    pub first_point_in_contour: bool,
 }
 
 /// TODO(pcwalton): Add some caching so we don't keep going to the `loca` table all the time.
@@ -97,7 +97,12 @@ impl<'a> GlyfTable<'a> {
         for _ in 0..number_of_contours {
             let contour_point_count =
                 try!(endpoints_reader.read_u16::<BigEndian>().map_err(drop)) - point_index + 1;
-            let (mut starting_point, mut last_point_was_off_curve) = (Point2D::new(0, 0), false);
+
+            let mut first_on_curve_point = None;
+            let mut initial_off_curve_point = None;
+            let mut last_point_was_off_curve = false;
+            let mut point_index_in_contour = 0;
+
             for contour_point_index in 0..contour_point_count {
                 let flags = Flags::from_bits_truncate(*flag_parser.current);
                 try!(flag_parser.next());
@@ -121,37 +126,64 @@ impl<'a> GlyfTable<'a> {
                 }
 
                 if last_point_was_off_curve && !flags.contains(ON_CURVE) {
-                    callback(&Point {
-                        position: position + delta / 2,
-                        on_curve: true,
-                        first_point_in_contour: false,
-                    })
-                }
+                    let position = position + delta / 2;
 
-                position = position + delta;
-
-                let first_point_in_contour = contour_point_index == 0;
-                if first_point_in_contour {
-                    starting_point = position
+                    // An important edge case!
+                    if first_on_curve_point.is_none() {
+                        first_on_curve_point = Some(position)
                     }
 
                     callback(&Point {
                         position: position,
-                    on_curve: flags.contains(ON_CURVE),
-                    first_point_in_contour: first_point_in_contour,
+                        index_in_contour: point_index_in_contour,
+                        on_curve: true,
                     });
+                    point_index_in_contour += 1
+                }
+
+                position = position + delta;
+
+                if flags.contains(ON_CURVE) && first_on_curve_point.is_none() {
+                    first_on_curve_point = Some(position)
+                }
+
+                // Sometimes the initial point is an off curve point. In that case, save it so we
+                // can emit it later when closing the path.
+                if !flags.contains(ON_CURVE) && first_on_curve_point.is_none() {
+                    debug_assert!(initial_off_curve_point.is_none());
+                    initial_off_curve_point = Some(position)
+                } else {
+                    callback(&Point {
+                        position: position,
+                        on_curve: flags.contains(ON_CURVE),
+                        index_in_contour: point_index_in_contour,
+                    });
+                    point_index_in_contour += 1
+                }
 
                 last_point_was_off_curve = !flags.contains(ON_CURVE);
-                point_index += 1
+                point_index += 1;
+            }
+
+            // We're about to close the path. Emit the initial off curve point if there was one.
+            if let Some(initial_off_curve_point) = initial_off_curve_point {
+                callback(&Point {
+                    position: initial_off_curve_point,
+                    on_curve: false,
+                    index_in_contour: point_index_in_contour,
+                });
+                point_index_in_contour += 1
             }
 
             // Close the path.
+            if let Some(first_on_curve_point) = first_on_curve_point {
                 callback(&Point {
-                position: starting_point,
+                    position: first_on_curve_point,
                     on_curve: true,
-                first_point_in_contour: false,
+                    index_in_contour: point_index_in_contour,
                 })
             }
+        }
 
         Ok(())
     }