Remove skrifa from vello's public API (#747)

The motivation for this is two-fold:

- To align vello's representation of "normalized coordinates" with that
of swash/parley (avoiding a boilerplatey conversion when integrating
parley with vello)
- To make skrifa version bumps in vello non-breaking changes.

---------

Signed-off-by: Nico Burns <nico@nicoburns.com>
Co-authored-by: Daniel McNab <36049421+DJMcNab@users.noreply.github.com>

CHANGELOG.md

@@ -27,6 +27,7 @@ This is the first step towards providing richer color functionality, better hand
 - Breaking: The `full` feature is no longer present as the full pipeline is now always built ([#754][] by [@waywardmonkeys])
 - The `r8` permutation of the shaders is no longer available ([#756][] by [@waywardmonkeys])
 - Breaking: The `buffer_labels` feature is no longer present as the labels are always configured ([#757][] by [@waywardmonkeys])
+- Breaking: Use a type alias for `i16` rather than `skrifa::NormalizedCoord` in the public API ([#747][] by [@nicoburns][])
 
 ### Fixed
 
@@ -142,15 +143,16 @@ This release has an [MSRV][] of 1.75.
 [@dfrg]: https://github.com/drfg
 [@DJMcNab]: https://github.com/DJMcNab
 [@kmoon2437]: https://github.com/kmoon2437
+[@LaurenzV]: https://github.com/LaurenzV
 [@msiglreith]: https://github.com/msiglreith
+[@nicoburns]: https://github.com/nicoburns
+[@ratmice]: https://github.com/ratmice
 [@simbleau]: https://github.com/simbleau
 [@TheNachoBIT]: https://github.com/TheNachoBIT
 [@timtom-dev]: https://github.com/timtom-dev
 [@TrueDoctor]: https://github.com/TrueDoctor
 [@waywardmonkeys]: https://github.com/waywardmonkeys
 [@yutannihilation]: https://github.com/yutannihilation
-[@LaurenzV]: https://github.com/LaurenzV
-[@ratmice]: https://github.com/ratmice
 
 [#416]: https://github.com/linebender/vello/pull/416
 [#435]: https://github.com/linebender/vello/pull/435
@@ -213,6 +215,7 @@ This release has an [MSRV][] of 1.75.
 [#740]: https://github.com/linebender/vello/pull/740
 [#742]: https://github.com/linebender/vello/pull/742
 [#743]: https://github.com/linebender/vello/pull/743
+[#747]: https://github.com/linebender/vello/pull/747
 [#754]: https://github.com/linebender/vello/pull/754
 [#756]: https://github.com/linebender/vello/pull/756
 

examples/scenes/Cargo.toml

@@ -11,13 +11,15 @@ workspace = true
 
 [dependencies]
 vello = { workspace = true }
+skrifa = { workspace = true }
 anyhow = { workspace = true }
 clap = { workspace = true, features = ["derive"] }
 image = { workspace = true, features = ["jpeg"] }
 rand = "0.8.5"
 
 # for pico_svg
 roxmltree = "0.20.0"
+bytemuck.workspace = true
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 web-time = { workspace = true }

examples/scenes/src/simple_text.rs

@@ -3,9 +3,12 @@
 
 use std::sync::Arc;
 
+use skrifa::{
+    raw::{FileRef, FontRef},
+    MetadataProvider,
+};
 use vello::kurbo::Affine;
-use vello::peniko::{color::palette, Blob, Brush, BrushRef, Font, StyleRef};
-use vello::skrifa::{raw::FontRef, MetadataProvider};
+use vello::peniko::{color::palette, Blob, Brush, BrushRef, Fill, Font, StyleRef};
 use vello::{Glyph, Scene};
 
 // This is very much a hack to get things working.
@@ -144,7 +147,7 @@ impl SimpleText {
         let brush = brush.into();
         let style = style.into();
         let axes = font_ref.axes();
-        let font_size = vello::skrifa::instance::Size::new(size);
+        let font_size = skrifa::instance::Size::new(size);
         let var_loc = axes.location(variations.iter().copied());
         let charmap = font_ref.charmap();
         let metrics = font_ref.metrics(font_size, &var_loc);
@@ -157,7 +160,7 @@ impl SimpleText {
             .font_size(size)
             .transform(transform)
             .glyph_transform(glyph_transform)
-            .normalized_coords(var_loc.coords())
+            .normalized_coords(bytemuck::cast_slice(var_loc.coords()))
             .brush(brush)
             .hint(false)
             .draw(
@@ -190,7 +193,6 @@ impl SimpleText {
         transform: Affine,
         text: &str,
     ) {
-        use vello::peniko::Fill;
         let brush = brush.unwrap_or(&Brush::Solid(palette::css::WHITE));
         self.add_run(
             scene,
@@ -206,7 +208,6 @@ impl SimpleText {
 }
 
 fn to_font_ref(font: &Font) -> Option<FontRef<'_>> {
-    use vello::skrifa::raw::FileRef;
     let file_ref = FileRef::new(font.data.as_ref()).ok()?;
     match file_ref {
         FileRef::Font(font) => Some(font),

vello/src/lib.rs

@@ -147,13 +147,12 @@ pub mod low_level {
 pub use peniko;
 /// 2D geometry, with a focus on curves.
 pub use peniko::kurbo;
-pub use skrifa;
 
 #[cfg(feature = "wgpu")]
 pub use wgpu;
 
 pub use scene::{DrawGlyphs, Scene};
-pub use vello_encoding::Glyph;
+pub use vello_encoding::{Glyph, NormalizedCoord};
 
 use low_level::ShaderId;
 #[cfg(feature = "wgpu")]

vello/src/scene.rs

@@ -14,15 +14,15 @@ use peniko::{
 use png::{BitDepth, ColorType, Transformations};
 use skrifa::{
     color::{ColorGlyph, ColorPainter},
-    instance::{LocationRef, NormalizedCoord},
+    instance::LocationRef,
     outline::{DrawSettings, OutlinePen},
     prelude::Size,
     raw::{tables::cpal::Cpal, TableProvider},
     GlyphId, MetadataProvider, OutlineGlyphCollection,
 };
 #[cfg(feature = "bump_estimate")]
 use vello_encoding::BumpAllocatorMemory;
-use vello_encoding::{Encoding, Glyph, GlyphRun, Patch, Transform};
+use vello_encoding::{Encoding, Glyph, GlyphRun, NormalizedCoord, Patch, Transform};
 
 // TODO - Document invariants and edge cases (#470)
 // - What happens when we pass a transform matrix with NaN values to the Scene?
@@ -508,10 +508,11 @@ impl<'a> DrawGlyphs<'a> {
         let mut final_glyph = None;
         let mut outline_count = 0;
         // We copy out of the variable font coords here because we need to call an exclusive self method
-        let coords = &self.scene.encoding.resources.normalized_coords
-            [self.run.normalized_coords.clone()]
+        let coords = bytemuck::cast_slice(
+            &self.scene.encoding.resources.normalized_coords[self.run.normalized_coords.clone()],
+        )
         .to_vec();
-        let location = LocationRef::new(coords);
+        let location = LocationRef::new(&coords);
         loop {
             let ppem = self.run.font_size;
             let outline_glyphs = (&mut glyphs).take_while(|glyph| {

vello_encoding/src/encoding.rs

@@ -3,13 +3,13 @@
 
 use super::{
     DrawBlurRoundedRect, DrawColor, DrawImage, DrawLinearGradient, DrawRadialGradient,
-    DrawSweepGradient, DrawTag, Glyph, GlyphRun, Patch, PathEncoder, PathTag, Style, Transform,
+    DrawSweepGradient, DrawTag, Glyph, GlyphRun, NormalizedCoord, Patch, PathEncoder, PathTag,
+    Style, Transform,
 };
 
 use peniko::color::{palette, DynamicColor};
 use peniko::kurbo::{Shape, Stroke};
 use peniko::{BlendMode, BrushRef, ColorStop, Extend, Fill, GradientKind, Image};
-use skrifa::instance::NormalizedCoord;
 
 /// Encoded data streams for a scene.
 ///

vello_encoding/src/lib.rs

@@ -76,3 +76,21 @@ pub use resolve::{resolve_solid_paths_only, Layout, Patch, Resolver};
 
 #[cfg(feature = "bump_estimate")]
 pub use estimate::BumpEstimator;
+
+/// A normalized variation coordinate (for variable fonts) in 2.14 fixed point format.
+///
+/// In most cases, this can be [cast](bytemuck::cast_slice) from the
+/// normalised coords provided by your text layout library.
+///
+/// Equivalent to [`skrifa::instance::NormalizedCoord`], but defined
+/// in Vello so that Skrifa is not part of Vello's public API.
+/// This allows Vello to update its Skrifa in a patch release, and limits
+/// the need for updates only to align Skrifa versions.
+pub type NormalizedCoord = i16;
+
+#[cfg(test)]
+mod tests {
+    const _NORMALISED_COORD_SIZE_MATCHES: () = assert!(
+        size_of::<skrifa::prelude::NormalizedCoord>() == size_of::<crate::NormalizedCoord>()
+    );
+}

vello_encoding/src/resolve.rs

@@ -422,10 +422,13 @@ impl Resolver {
                             hint = false;
                         }
                     }
-                    let Some(mut session) = self
-                        .glyph_cache
-                        .session(&run.font, coords, font_size, hint, &run.style)
-                    else {
+                    let Some(mut session) = self.glyph_cache.session(
+                        &run.font,
+                        bytemuck::cast_slice(coords),
+                        font_size,
+                        hint,
+                        &run.style,
+                    ) else {
                         continue;
                     };
                     let glyph_start = self.glyphs.len();