Implement a subset of FontTools Pens for write-fonts, leaning on kurbo for things like transform

font-types/src/lib.rs

@@ -30,7 +30,7 @@ pub use fword::{FWord, UfWord};
 pub use glyph_id::GlyphId;
 pub use longdatetime::LongDateTime;
 pub use offset::{Nullable, Offset16, Offset24, Offset32};
-pub use pen::Pen;
+pub use pen::{Pen, PenCommand};
 pub use point::Point;
 pub use raw::{BigEndian, FixedSize, ReadScalar, Scalar};
 pub use tag::{InvalidTag, Tag};

font-types/src/pen.rs

@@ -2,6 +2,10 @@
 ///
 /// This is a general abstraction to unify ouput for processes that decode and/or
 /// transform outlines.
+///
+/// /// AbstractPen in Python terms.
+/// <https://github.com/fonttools/fonttools/blob/78e10d8b42095b709cd4125e592d914d3ed1558e/Lib/fontTools/pens/basePen.py#L54>.
+/// Implementations
 pub trait Pen {
     /// Emit a command to begin a new subpath at (x, y).
     fn move_to(&mut self, x: f32, y: f32);
@@ -20,3 +24,50 @@ pub trait Pen {
     /// Emit a command to close the current subpath.
     fn close(&mut self);
 }
+
+/// Captures commands to [Pen] to facilitate implementations that buffer commands.
+#[derive(Debug, Copy, Clone)]
+pub enum PenCommand {
+    MoveTo {
+        x: f32,
+        y: f32,
+    },
+    LineTo {
+        x: f32,
+        y: f32,
+    },
+    QuadTo {
+        cx0: f32,
+        cy0: f32,
+        x: f32,
+        y: f32,
+    },
+    CurveTo {
+        cx0: f32,
+        cy0: f32,
+        cx1: f32,
+        cy1: f32,
+        x: f32,
+        y: f32,
+    },
+    Close,
+}
+
+impl PenCommand {
+    pub fn apply_to<T: Pen>(&self, pen: &mut T) {
+        match *self {
+            PenCommand::MoveTo { x, y } => pen.move_to(x, y),
+            PenCommand::LineTo { x, y } => pen.line_to(x, y),
+            PenCommand::QuadTo { cx0, cy0, x, y } => pen.quad_to(cx0, cy0, x, y),
+            PenCommand::CurveTo {
+                cx0,
+                cy0,
+                cx1,
+                cy1,
+                x,
+                y,
+            } => pen.curve_to(cx0, cy0, cx1, cy1, x, y),
+            PenCommand::Close => pen.close(),
+        }
+    }
+}

write-fonts/src/lib.rs

@@ -5,6 +5,7 @@ mod font_builder;
 pub mod from_obj;
 mod graph;
 mod offsets;
+pub mod pens;
 pub mod tables;
 pub mod validate;
 mod write;