Add optional freetype integration

Cargo.toml

@@ -23,11 +23,15 @@ appveyor = { repository = "manuel-rhdt/harfbuzz_rs", branch = "master", service
 [features]
 default = ["build-native-harfbuzz"]
 build-native-harfbuzz = []
+freetype = ["dep:freetype-rs", "dep:freetype-sys"]
 
 [dependencies]
 rusttype = { version = "0.9", optional = true }
+freetype-rs = { version = "0.36", optional = true }
+freetype-sys = { version = "0.20.1", optional = true }
 bitflags = "^1"
 
 [build-dependencies]
 cc = "1.0"
 pkg-config = "0.3.24"
+

src/freetype.rs

@@ -0,0 +1,33 @@
+//! This module allows you to create a harfbuzz font from freetype faces
+
+use crate::Font;
+use crate::bindings::hb_font_t;
+use crate::common::Owned;
+
+use freetype as ft;
+
+extern "C" {
+    fn hb_ft_font_create_referenced(face: freetype_sys::FT_Face) -> *mut hb_font_t;
+}
+
+impl<'a> Font<'a> {
+    /// Create a font from a freetype face.
+    ///
+    /// ```
+    /// let font_data = include_bytes!("../Inter-Regular.otf") as &[u8];
+    /// let face = harfbuzz_rs::Face::from_bytes(font_data, 0);
+    ///
+    /// let ftlib = ft::Library::init().unwrap();
+    /// let ft_face = ftlib.new_memory_face2(font_data, 0).unwrap();
+    ///
+    /// let hb_font = harfbuzz_rs::Font::from_freetype_face(ft_face.clone());
+    /// ```
+    pub fn from_freetype_face(mut ft_face: ft::Face<&'a [u8]>) -> Owned<Font<'a>> {
+        let hb_face = unsafe {
+            let ft_face_ptr: freetype_sys::FT_Face = ft_face.raw_mut();
+            hb_ft_font_create_referenced(ft_face_ptr)
+        };
+        unsafe { Owned::from_raw(hb_face) }
+    }
+}
+

src/lib.rs

@@ -89,6 +89,9 @@ mod face;
 mod font;
 pub mod font_funcs;
 
+#[cfg(feature = "freetype")]
+pub mod freetype;
+
 #[cfg(feature = "rusttype")]
 pub mod rusttype;