Fix subpixel rendering for macOS

This adds a bunch of APIs to CGContext (and supporting types) that
aren't actually necessary to turn on subpixel rendering. The key for
subpixel rendering were the options passed to bitmap_context_create().
Specifically, kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host
are necessary to enable it.

5 files changed, 234 insertions, 31 deletions

diff --git a/font/Cargo.toml b/font/Cargo.toml
index 8345af73..d6cfcc38 100644
--- a/font/Cargo.toml
+++ b/font/Cargo.toml
@@ -7,11 +7,11 @@ license = "Apache-2.0"
 
 [dependencies]
 euclid = "0.6.8"
+libc = "0.2.11"
 
 [target.'cfg(not(target_os = "macos"))'.dependencies]
 servo-fontconfig = { git = "https://github.com/jwilm/rust-fontconfig" }
 freetype-rs = "0.9.0"
-libc = "0.2.11"
 
 [target.'cfg(target_os = "macos")'.dependencies]
 core-text = "1.1.1"
diff --git a/font/src/darwin/byte_order.rs b/font/src/darwin/byte_order.rs
new file mode 100644
index 00000000..5b696554
--- /dev/null
+++ b/font/src/darwin/byte_order.rs
@@ -0,0 +1,34 @@
+//! Constants for bitmap byte order
+#![allow(non_upper_case_globals)]
+pub const kCGBitmapByteOrder32Little: u32 = 2 << 12;
+pub const kCGBitmapByteOrder32Big: u32 = 4 << 12;
+
+#[cfg(target_endian = "little")]
+pub const kCGBitmapByteOrder32Host: u32 = kCGBitmapByteOrder32Little;
+
+#[cfg(target_endian = "big")]
+pub const kCGBitmapByteOrder32Host: u32 = kCGBitmapByteOrder32Big;
+
+#[cfg(target_endian = "little")]
+pub fn extract_rgb(bytes: Vec<u8>) -> Vec<u8> {
+    let pixels = bytes.len() / 4;
+    let mut rgb = Vec::with_capacity(pixels * 3);
+
+    for i in 0..pixels {
+        let offset = i * 4;
+        rgb.push(bytes[offset + 2]);
+        rgb.push(bytes[offset + 1]);
+        rgb.push(bytes[offset + 0]);
+    }
+
+    rgb
+}
+
+#[cfg(target_endian = "big")]
+pub fn extract_rgb(bytes: Vec<u8>) -> Vec<u8> {
+    bytes.into_iter()
+         .enumerate()
+         .filter(|&(index, _)| ((index) % 4) != 0)
+         .map(|(_, val)| val)
+         .collect::<Vec<_>>()
+}
diff --git a/font/src/darwin/cg_color.rs b/font/src/darwin/cg_color.rs
new file mode 100644
index 00000000..552137cc
--- /dev/null
+++ b/font/src/darwin/cg_color.rs
@@ -0,0 +1,79 @@
+use core_foundation::base::{CFRelease, CFRetain, CFTypeID, CFTypeRef, TCFType};
+use core_graphics::color_space::{CGColorSpace, CGColorSpaceRef};
+use core_graphics::base::CGFloat;
+use std::mem;
+
+#[repr(C)]
+pub struct __CGColor;
+
+pub type CGColorRef = *const __CGColor;
+
+pub struct CGColor {
+    obj: CGColorRef,
+}
+
+impl Drop for CGColor {
+    fn drop(&mut self) {
+        unsafe {
+            CFRelease(self.as_CFTypeRef())
+        }
+    }
+}
+
+impl Clone for CGColor {
+    fn clone(&self) -> CGColor {
+        unsafe {
+            TCFType::wrap_under_get_rule(self.as_concrete_TypeRef())
+        }
+    }
+}
+
+impl TCFType<CGColorRef> for CGColor {
+    #[inline]
+    fn as_concrete_TypeRef(&self) -> CGColorRef {
+        self.obj
+    }
+
+    #[inline]
+    unsafe fn wrap_under_get_rule(reference: CGColorRef) -> CGColor {
+        let reference: CGColorRef = mem::transmute(CFRetain(mem::transmute(reference)));
+        TCFType::wrap_under_create_rule(reference)
+    }
+
+    #[inline]
+    fn as_CFTypeRef(&self) -> CFTypeRef {
+        unsafe {
+            mem::transmute(self.as_concrete_TypeRef())
+        }
+    }
+
+    #[inline]
+    unsafe fn wrap_under_create_rule(obj: CGColorRef) -> CGColor {
+        CGColor {
+            obj: obj,
+        }
+    }
+
+    #[inline]
+    fn type_id() -> CFTypeID {
+        unsafe {
+            CGColorGetTypeID()
+        }
+    }
+}
+
+impl CGColor {
+    pub fn new(color_space: CGColorSpace, values: [CGFloat; 4]) -> CGColor {
+        unsafe {
+            let result = CGColorCreate(color_space.as_concrete_TypeRef(), values.as_ptr());
+            TCFType::wrap_under_create_rule(result)
+        }
+    }
+}
+
+#[link(name = "ApplicationServices", kind = "framework")]
+extern {
+    fn CGColorCreate(space: CGColorSpaceRef, vals: *const CGFloat) -> CGColorRef;
+    fn CGColorGetTypeID() -> CFTypeID;
+}
+
diff --git a/font/src/darwin/mod.rs b/font/src/darwin/mod.rs
index 844850e0..5e53abd5 100644
--- a/font/src/darwin/mod.rs
+++ b/font/src/darwin/mod.rs
@@ -1,20 +1,20 @@
 //! Font rendering based on CoreText
 //!
 //! TODO error handling... just search for unwrap.
+#![allow(improper_ctypes)]
 use std::collections::HashMap;
-use std::ops::Deref;
 use std::ptr;
 
 use core_foundation::base::TCFType;
 use core_foundation::string::{CFString, CFStringRef};
 use core_foundation::array::CFIndex;
 use core_foundation_sys::string::UniChar;
-use core_graphics::base::kCGImageAlphaNoneSkipFirst;
-use core_graphics::base::kCGImageAlphaPremultipliedLast;
+use core_graphics::base::kCGImageAlphaPremultipliedFirst;
+use core_graphics::base::CGFloat;
 use core_graphics::color_space::CGColorSpace;
 use core_graphics::context::{CGContext, CGContextRef};
-use core_graphics::font::CGGlyph;
-use core_graphics::geometry::CGPoint;
+use core_graphics::font::{CGFont, CGFontRef, CGGlyph};
+use core_graphics::geometry::{CGPoint, CGRect, CGSize};
 use core_text::font::{CTFont, new_from_descriptor as ct_new_from_descriptor};
 use core_text::font_collection::create_for_family;
 use core_text::font_collection::get_family_names as ct_get_family_names;
@@ -23,12 +23,21 @@ use core_text::font_descriptor::kCTFontHorizontalOrientation;
 use core_text::font_descriptor::kCTFontVerticalOrientation;
 use core_text::font_descriptor::{CTFontDescriptor, CTFontDescriptorRef, CTFontOrientation};
 
+use libc::size_t;
+
 use euclid::point::Point2D;
 use euclid::rect::Rect;
 use euclid::size::Size2D;
 
 use super::{FontDesc, RasterizedGlyph, Metrics};
 
+pub mod cg_color;
+use self::cg_color::{CGColorRef, CGColor};
+
+pub mod byte_order;
+use self::byte_order::kCGBitmapByteOrder32Host;
+use self::byte_order::extract_rgb;
+
 /// Font descriptor
 ///
 /// The descriptor provides data about a font and supports creating a font.
@@ -52,7 +61,7 @@ pub struct Rasterizer {
 }
 
 impl Rasterizer {
-    pub fn new(dpi_x: f32, dpi_y: f32, device_pixel_ratio: f32) -> Rasterizer {
+    pub fn new(_dpi_x: f32, _dpi_y: f32, device_pixel_ratio: f32) -> Rasterizer {
         println!("device_pixel_ratio: {}", device_pixel_ratio);
         Rasterizer {
             fonts: HashMap::new(),
@@ -106,9 +115,10 @@ impl Default for FontOrientation {
 }
 
 /// A font
-#[derive(Debug, Clone)]
+#[derive(Clone)]
 pub struct Font {
-    ct_font: CTFont
+    ct_font: CTFont,
+    cg_font: CGFont,
 }
 
 unsafe impl Send for Font {}
@@ -159,21 +169,14 @@ impl Descriptor {
     /// Create a Font from this descriptor
     pub fn to_font(&self, pt_size: f64) -> Font {
         let ct_font = ct_new_from_descriptor(&self.ct_descriptor, pt_size);
+        let cg_font = ct_font.copy_to_CGFont();
         Font {
-            ct_font: ct_font
+            ct_font: ct_font,
+            cg_font: cg_font,
         }
     }
 }
 
-impl Deref for Font {
-    type Target = CTFont;
-
-    #[inline]
-    fn deref(&self) -> &Self::Target {
-        &self.ct_font
-    }
-}
-
 impl Font {
     /// The the bounding rect of a glyph
     pub fn bounding_rect_for_glyph(&self, orientation: FontOrientation, index: u32) -> Rect<f64> {
@@ -211,7 +214,7 @@ impl Font {
                                              1)
     }
 
-    pub fn get_glyph(&self, character: char, size: f64) -> RasterizedGlyph {
+    pub fn get_glyph(&self, character: char, _size: f64) -> RasterizedGlyph {
         let glyph_index = match self.glyph_index(character) {
             Some(i) => i,
             None => {
@@ -252,14 +255,27 @@ impl Font {
                                                               8, // bits per component
                                                               rasterized_width as usize * 4,
                                                               &CGColorSpace::create_device_rgb(),
-                                                              kCGImageAlphaNoneSkipFirst);
+                                                              kCGImageAlphaPremultipliedFirst |
+                                                              kCGBitmapByteOrder32Host);
+
+        // Give the context an opaque, black background
+        cg_context.set_rgb_fill_color(0.0, 0.0, 0.0, 1.0);
+        let context_rect = CGRect::new(&CGPoint::new(0.0, 0.0),
+                                       &CGSize::new(rasterized_width as f64,
+                                                    rasterized_height as f64));
+        cg_context.fill_rect(context_rect);
 
         cg_context.set_allows_font_smoothing(true);
         cg_context.set_should_smooth_fonts(true);
         cg_context.set_allows_font_subpixel_quantization(true);
         cg_context.set_should_subpixel_quantize_fonts(true);
-        cg_context.set_rgb_fill_color(1.0, 1.0, 1.0, 1.0);
+        cg_context.set_allows_font_subpixel_positioning(true);
+        cg_context.set_should_subpixel_position_fonts(true);
+        cg_context.set_allows_antialiasing(true);
+        cg_context.set_should_antialias(true);
 
+        // Set fill color to white for drawing the glyph
+        cg_context.set_rgb_fill_color(1.0, 1.0, 1.0, 1.0);
         let rasterization_origin = CGPoint {
             x: -rasterized_left as f64,
             y: rasterized_descent as f64,
@@ -269,13 +285,10 @@ impl Font {
                                  &[rasterization_origin],
                                  cg_context.clone());
 
-        let rasterized_area = (rasterized_width * rasterized_height) as usize;
         let rasterized_pixels = cg_context.data().to_vec();
-        let buf = rasterized_pixels.into_iter()
-                                   .enumerate()
-                                   .filter(|&(index, _)| (index % 4) != 0)
-                                   .map(|(_, val)| val)
-                                   .collect::<Vec<_>>();
+        println!("rasterized_pixels: {:?}", rasterized_pixels);
+
+        let buf = extract_rgb(rasterized_pixels);
 
         RasterizedGlyph {
             c: character,
@@ -304,9 +317,18 @@ impl Font {
 /// Additional methods needed to render fonts for Alacritty
 ///
 /// TODO upstream these into core_graphics crate
-trait CGContextExt {
+pub trait CGContextExt {
     fn set_allows_font_subpixel_quantization(&self, bool);
     fn set_should_subpixel_quantize_fonts(&self, bool);
+    fn set_allows_font_subpixel_positioning(&self, bool);
+    fn set_should_subpixel_position_fonts(&self, bool);
+    fn set_allows_antialiasing(&self, bool);
+    fn set_should_antialias(&self, bool);
+    fn fill_rect(&self, rect: CGRect);
+    fn set_font_smoothing_background_color(&self, color: CGColor);
+    fn show_glyphs_at_positions(&self, &[CGGlyph], &[CGPoint]);
+    fn set_font(&self, &CGFont);
+    fn set_font_size(&self, size: f64);
 }
 
 impl CGContextExt for CGContext {
@@ -321,12 +343,81 @@ impl CGContextExt for CGContext {
             CGContextSetShouldSubpixelQuantizeFonts(self.as_concrete_TypeRef(), should);
         }
     }
+
+    fn set_should_subpixel_position_fonts(&self, should: bool) {
+        unsafe {
+            CGContextSetShouldSubpixelPositionFonts(self.as_concrete_TypeRef(), should);
+        }
+    }
+
+    fn set_allows_font_subpixel_positioning(&self, allows: bool) {
+        unsafe {
+            CGContextSetAllowsFontSubpixelPositioning(self.as_concrete_TypeRef(), allows);
+        }
+    }
+
+    fn set_should_antialias(&self, should: bool) {
+        unsafe {
+            CGContextSetShouldAntialias(self.as_concrete_TypeRef(), should);
+        }
+    }
+
+    fn set_allows_antialiasing(&self, allows: bool) {
+        unsafe {
+            CGContextSetAllowsAntialiasing(self.as_concrete_TypeRef(), allows);
+        }
+    }
+
+    fn fill_rect(&self, rect: CGRect) {
+        unsafe {
+            CGContextFillRect(self.as_concrete_TypeRef(), rect);
+        }
+    }
+
+    fn set_font_smoothing_background_color(&self, color: CGColor) {
+        unsafe {
+            CGContextSetFontSmoothingBackgroundColor(self.as_concrete_TypeRef(),
+                                                     color.as_concrete_TypeRef());
+        }
+    }
+
+    fn show_glyphs_at_positions(&self, glyphs: &[CGGlyph], positions: &[CGPoint]) {
+        assert_eq!(glyphs.len(), positions.len());
+        unsafe {
+            CGContextShowGlyphsAtPositions(self.as_concrete_TypeRef(),
+                                           glyphs.as_ptr(),
+                                           positions.as_ptr(),
+                                           glyphs.len());
+        }
+    }
+
+    fn set_font(&self, font: &CGFont) {
+        unsafe {
+            CGContextSetFont(self.as_concrete_TypeRef(), font.as_concrete_TypeRef());
+        }
+    }
+
+    fn set_font_size(&self, size: f64) {
+        unsafe {
+            CGContextSetFontSize(self.as_concrete_TypeRef(), size as CGFloat);
+        }
+    }
 }
 
 #[link(name = "ApplicationServices", kind = "framework")]
 extern {
     fn CGContextSetAllowsFontSubpixelQuantization(c: CGContextRef, allows: bool);
     fn CGContextSetShouldSubpixelQuantizeFonts(c: CGContextRef, should: bool);
+    fn CGContextSetAllowsFontSubpixelPositioning(c: CGContextRef, allows: bool);
+    fn CGContextSetShouldSubpixelPositionFonts(c: CGContextRef, should: bool);
+    fn CGContextSetAllowsAntialiasing(c: CGContextRef, allows: bool);
+    fn CGContextSetShouldAntialias(c: CGContextRef, should: bool);
+    fn CGContextFillRect(c: CGContextRef, r: CGRect);
+    fn CGContextSetFontSmoothingBackgroundColor(c: CGContextRef, color: CGColorRef);
+    fn CGContextShowGlyphsAtPositions(c: CGContextRef, glyphs: *const CGGlyph,
+                                      positions: *const CGPoint, count: size_t);
+    fn CGContextSetFont(c: CGContextRef, font: CGFontRef);
+    fn CGContextSetFontSize(c: CGContextRef, size: CGFloat);
 }
 
 #[cfg(test)]
diff --git a/font/src/lib.rs b/font/src/lib.rs
index ba632bee..bd485ff0 100644
--- a/font/src/lib.rs
+++ b/font/src/lib.rs
@@ -10,8 +10,6 @@
 extern crate fontconfig;
 #[cfg(not(target_os = "macos"))]
 extern crate freetype;
-#[cfg(not(target_os = "macos"))]
-extern crate libc;
 
 #[cfg(target_os = "macos")]
 extern crate core_text;
@@ -23,6 +21,7 @@ extern crate core_foundation_sys;
 extern crate core_graphics;
 
 extern crate euclid;
+extern crate libc;
 
 use std::fmt;