Fix sign error in CoreText font rasterizer

Descent was being reported as a positive value instead of negative. This
caused the background and text alignment to be off dramatically.

Resolves #545

1 files changed, 1 insertions, 1 deletions

diff --git a/font/src/darwin/mod.rs b/font/src/darwin/mod.rs
index cd27c6e2..3ced7524 100644
--- a/font/src/darwin/mod.rs
+++ b/font/src/darwin/mod.rs
@@ -334,7 +334,7 @@ impl Font {
         Metrics {
             average_advance: average_advance,
             line_height: line_height,
-            descent: self.ct_font.descent() as f32,
+            descent: -(self.ct_font.descent() as f32),
         }
     }