Draft implementation of wasm shaper

.gitignore

@@ -3,3 +3,4 @@ Cargo.lock
 .directory
 .DS_Store
 /src/complex/*.ri
+.vscode

Cargo.toml

@@ -21,6 +21,7 @@ unicode-bidi-mirroring = "0.3.0"
 unicode-ccc = "0.3.0"
 unicode-properties = { version = "0.1.0", default-features = false, features = ["general-category"] }
 unicode-script = "0.5.2"
+wasmi = { version = "0.34.0", optional = true }
 
 [dependencies.ttf-parser]
 version = "0.24.0"
@@ -37,6 +38,9 @@ features = [
 default = ["std"]
 std = ["ttf-parser/std"]
 
+# experimental features live here.
+wasm-shaper = ["std", "dep:wasmi"]
+
 [dev-dependencies]
 pico-args = { version = "0.5", features = ["eq-separator"] }
 libc = "0.2"

src/hb/buffer.rs

@@ -120,7 +120,7 @@ pub struct GlyphPosition {
     /// How much the glyph moves on the Y-axis before drawing it, this should
     /// not affect how much the line advances.
     pub y_offset: i32,
-    var: u32,
+    pub(crate) var: u32,
 }
 
 unsafe impl bytemuck::Zeroable for GlyphPosition {}
@@ -337,6 +337,7 @@ pub const HB_BUFFER_CLUSTER_LEVEL_MONOTONE_CHARACTERS: u32 = 1;
 pub const HB_BUFFER_CLUSTER_LEVEL_CHARACTERS: u32 = 2;
 pub const HB_BUFFER_CLUSTER_LEVEL_DEFAULT: u32 = HB_BUFFER_CLUSTER_LEVEL_MONOTONE_GRAPHEMES;
 
+#[cfg_attr(feature = "wasm-shaper", derive(Default, Clone))]
 pub struct hb_buffer_t {
     // Information about how the text in the buffer should be treated.
     pub flags: BufferFlags,
@@ -1556,6 +1557,7 @@ pub const HB_BUFFER_SCRATCH_FLAG_SHAPER0: u32 = 0x01000000;
 // pub const HB_BUFFER_SCRATCH_FLAG_SHAPER3: u32 = 0x08000000;
 
 /// A buffer that contains an input string ready for shaping.
+#[cfg_attr(feature = "wasm-shaper", derive(Clone))]
 pub struct UnicodeBuffer(pub(crate) hb_buffer_t);
 
 impl UnicodeBuffer {

src/hb/face.rs

@@ -369,13 +369,17 @@ impl<'a> hb_font_t<'a> {
 }
 
 #[derive(Clone, Copy, Default)]
+#[repr(C)]
 pub struct hb_glyph_extents_t {
     pub x_bearing: i32,
     pub y_bearing: i32,
     pub width: i32,
     pub height: i32,
 }
 
+unsafe impl bytemuck::Zeroable for hb_glyph_extents_t {}
+unsafe impl bytemuck::Pod for hb_glyph_extents_t {}
+
 fn find_best_cmap_subtable(face: &ttf_parser::Face) -> Option<u16> {
     use ttf_parser::PlatformId;
 

src/hb/mod.rs

@@ -50,6 +50,8 @@ mod ot_shaper_vowel_constraints;
 mod paint_extents;
 mod set_digest;
 pub mod shape;
+#[cfg(feature = "wasm-shaper")]
+mod shape_wasm;
 mod tag;
 mod tag_table;
 mod text_parser;

src/hb/shape.rs

@@ -20,7 +20,16 @@ pub fn shape(face: &hb_font_t, features: &[Feature], mut buffer: UnicodeBuffer)
         buffer.0.language.as_ref(),
         features,
     );
-    shape_with_plan(face, &plan, buffer)
+    #[cfg(not(feature = "wasm-shaper"))]
+    {
+        shape_with_plan(face, &plan, buffer)
+    }
+    #[cfg(feature = "wasm-shaper")]
+    {
+        // is there a way around the clone here?
+        super::shape_wasm::shape_with_wasm(face, &plan, buffer.clone())
+            .unwrap_or_else(|| shape_with_plan(face, &plan, buffer))
+    }
 }
 
 /// Shapes the buffer content using the provided font and plan.