Add subpixel anti-aliasing support on macOS 10.14+

2 files changed, 29 insertions, 0 deletions

diff --git a/font/Cargo.toml b/font/Cargo.toml
index 1c546f40..6b5825c4 100644
--- a/font/Cargo.toml
+++ b/font/Cargo.toml
@@ -17,6 +17,7 @@ servo-fontconfig = "0.5.0"
 freetype-rs = "0.25"
 
 [target.'cfg(target_os = "macos")'.dependencies]
+cocoa = "0.20.1"
 core-foundation = "0.7"
 core-text = "15"
 core-graphics = "0.19"
diff --git a/font/src/darwin/mod.rs b/font/src/darwin/mod.rs
index 19371c9b..f7bf6c82 100644
--- a/font/src/darwin/mod.rs
+++ b/font/src/darwin/mod.rs
@@ -38,6 +38,9 @@ use core_text::font_descriptor::kCTFontVerticalOrientation;
 use core_text::font_descriptor::SymbolicTraitAccessors;
 use core_text::font_descriptor::{CTFontDescriptor, CTFontOrientation};
 
+use cocoa::base::{id, nil, NO};
+use cocoa::foundation::{NSOperatingSystemVersion, NSProcessInfo, NSString, NSUserDefaults};
+
 use euclid::{Point2D, Rect, Size2D};
 
 use log::{trace, warn};
@@ -278,6 +281,31 @@ pub struct Font {
 
 unsafe impl Send for Font {}
 
+
+/// Set subpixel anti-aliasing on macOS.
+///
+/// Sub-pixel anti-aliasing has been disabled since macOS Mojave by default. This function allows
+/// overriding the global `CGFontRenderingFontSmoothingDisabled` setting on a per-application basis
+/// to re-enable it.
+///
+/// This is a no-op on systems running High Sierra or earlier (< 10.14.0).
+pub fn set_font_smoothing(enable: bool) {
+    let min_macos_version = NSOperatingSystemVersion::new(10, 14, 0);
+    unsafe {
+        // Check that we're running at least Mojave (10.14.0+).
+        if !NSProcessInfo::processInfo(nil).isOperatingSystemAtLeastVersion(min_macos_version) {
+            return
+        }
+
+        let key = NSString::alloc(nil).init_str("CGFontRenderingFontSmoothingDisabled");
+        if enable {
+            id::standardUserDefaults().setBool_forKey_(NO, key);
+        } else {
+            id::standardUserDefaults().removeObject_forKey_(key);
+        }
+    }
+}
+
 /// List all family names.
 pub fn get_family_names() -> Vec<String> {
     // CFArray of CFStringRef.