[read-fonts] Add scaler for CFF/CFF2

read-fonts/src/tables/postscript.rs

@@ -34,6 +34,8 @@ pub enum Error {
     CharstringNestingDepthLimitExceeded,
     MissingSubroutines,
     MissingBlendState,
+    MissingPrivateDict,
+    MissingCharstrings,
     Read(ReadError),
 }
 
@@ -98,7 +100,12 @@ impl fmt::Display for Error {
                     "encountered a blend operator but no blend state was provided"
                 )
             }
-
+            Self::MissingPrivateDict => {
+                write!(f, "CFF table does not contain a private dictionary")
+            }
+            Self::MissingCharstrings => {
+                write!(f, "CFF table does not contain a charstrings index")
+            }
             Self::Read(err) => write!(f, "{err}"),
         }
     }

read-fonts/src/tables/postscript/charstring.rs

@@ -55,21 +55,21 @@ where
     P: Pen,
 {
     fn move_to(&mut self, x: Fixed, y: Fixed) {
-        self.0.move_to(x.to_f64() as f32, y.to_f64() as f32);
+        self.0.move_to(x.to_f32(), y.to_f32());
     }
 
     fn line_to(&mut self, x: Fixed, y: Fixed) {
-        self.0.line_to(x.to_f64() as f32, y.to_f64() as f32);
+        self.0.line_to(x.to_f32(), y.to_f32());
     }
 
     fn curve_to(&mut self, cx0: Fixed, cy0: Fixed, cx1: Fixed, cy1: Fixed, x: Fixed, y: Fixed) {
         self.0.curve_to(
-            cx0.to_f64() as f32,
-            cy0.to_f64() as f32,
-            cx1.to_f64() as f32,
-            cy1.to_f64() as f32,
-            x.to_f64() as f32,
-            y.to_f64() as f32,
+            cx0.to_f32(),
+            cy0.to_f32(),
+            cx1.to_f32(),
+            cy1.to_f32(),
+            x.to_f32(),
+            y.to_f32(),
         );
     }
 

skrifa/src/scale/cff/hint.rs

@@ -0,0 +1,49 @@
+//! CFF hinting.
+
+use read_fonts::{tables::postscript::dict::Blues, types::Fixed};
+
+/// Parameters used to generate the stem and counter zones for the hinting
+/// algorithm.
+#[derive(Clone)]
+pub(crate) struct HintParams {
+    pub blues: Blues,
+    pub family_blues: Blues,
+    pub other_blues: Blues,
+    pub family_other_blues: Blues,
+    pub blue_scale: Fixed,
+    pub blue_shift: Fixed,
+    pub blue_fuzz: Fixed,
+    pub language_group: i32,
+}
+
+impl Default for HintParams {
+    fn default() -> Self {
+        Self {
+            blues: Blues::default(),
+            other_blues: Blues::default(),
+            family_blues: Blues::default(),
+            family_other_blues: Blues::default(),
+            // See <https://learn.microsoft.com/en-us/typography/opentype/spec/cff2#table-16-private-dict-operators>
+            blue_scale: Fixed::from_f64(0.039625),
+            blue_shift: Fixed::from_i32(7),
+            blue_fuzz: Fixed::ONE,
+            language_group: 0,
+        }
+    }
+}
+
+/// Hinting state for a PostScript subfont.
+///
+/// Note that hinter states depend on the scale, subfont index and
+/// variation coordinates of a glyph. They can be retained and reused
+/// if those values remain the same.
+#[derive(Copy, Clone)]
+pub(crate) struct HintState {
+    // TODO
+}
+
+impl HintState {
+    pub fn new(_params: &HintParams, _scale: Fixed) -> Self {
+        Self {}
+    }
+}

skrifa/src/scale/cff/mod.rs

@@ -0,0 +1,9 @@
+//! Support for scaling CFF outlines.
+
+// Temporary until new scaler API is done.
+#![allow(dead_code)]
+
+mod hint;
+mod scaler;
+
+pub(crate) use scaler::{Scaler, Subfont};