From 79789a18de4afefcf7407cc24081f1cf4b27466b Mon Sep 17 00:00:00 2001
From: Daniel Hedlund <daniel@digitree.org>
Date: Sun, 8 Dec 2013 11:25:20 -0800
Subject: [PATCH] Implement font leading metric for linux platform

Fixes #76.
---
 src/components/gfx/platform/android/font.rs | 11 ++++++++++-
 src/components/gfx/platform/linux/font.rs   | 11 ++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/src/components/gfx/platform/android/font.rs b/src/components/gfx/platform/android/font.rs
index c350f8b820c..745157f5354 100644
--- a/src/components/gfx/platform/android/font.rs
+++ b/src/components/gfx/platform/android/font.rs
@@ -231,6 +231,15 @@ impl FontHandleMethods for FontHandle {
         let descent = self.font_units_to_au(face.descender as float);
         let max_advance = self.font_units_to_au(face.max_advance_width as float);
 
+        // 'leading' is supposed to be the vertical distance between two baselines,
+        // reflected by the height attibute in freetype.  On OS X (w/ CTFont),
+        // leading represents the distance between the bottom of a line descent to
+        // the top of the next line's ascent or: (line_height - ascent - descent),
+        // see http://stackoverflow.com/a/5635981 for CTFont implementation.
+        // Convert using a formular similar to what CTFont returns for consistency.
+        let height = self.font_units_to_au(face.height as float);
+        let leading = height - (ascent + descent);
+
         let mut strikeout_size = geometry::from_pt(0.0);
         let mut strikeout_offset = geometry::from_pt(0.0);
         let mut x_height = geometry::from_pt(0.0);
@@ -249,7 +258,7 @@ impl FontHandleMethods for FontHandle {
             underline_offset: underline_offset,
             strikeout_size:   strikeout_size,
             strikeout_offset: strikeout_offset,
-            leading:          geometry::from_pt(0.0), //FIXME
+            leading:          leading,
             x_height:         x_height,
             em_size:          em_size,
             ascent:           ascent,
diff --git a/src/components/gfx/platform/linux/font.rs b/src/components/gfx/platform/linux/font.rs
index ca01f2ee949..cb2573a9a13 100644
--- a/src/components/gfx/platform/linux/font.rs
+++ b/src/components/gfx/platform/linux/font.rs
@@ -230,6 +230,15 @@ impl FontHandleMethods for FontHandle {
         let descent = self.font_units_to_au(face.descender as f64);
         let max_advance = self.font_units_to_au(face.max_advance_width as f64);
 
+        // 'leading' is supposed to be the vertical distance between two baselines,
+        // reflected by the height attibute in freetype.  On OS X (w/ CTFont),
+        // leading represents the distance between the bottom of a line descent to
+        // the top of the next line's ascent or: (line_height - ascent - descent),
+        // see http://stackoverflow.com/a/5635981 for CTFont implementation.
+        // Convert using a formular similar to what CTFont returns for consistency.
+        let height = self.font_units_to_au(face.height as f64);
+        let leading = height - (ascent + descent);
+
         let mut strikeout_size = geometry::from_pt(0.0);
         let mut strikeout_offset = geometry::from_pt(0.0);
         let mut x_height = geometry::from_pt(0.0);
@@ -248,7 +257,7 @@ impl FontHandleMethods for FontHandle {
             underline_offset: underline_offset,
             strikeout_size:   strikeout_size,
             strikeout_offset: strikeout_offset,
-            leading:          geometry::from_pt(0.0), //FIXME
+            leading:          leading,
             x_height:         x_height,
             em_size:          em_size,
             ascent:           ascent,