Add proper underline and strikeout support

This makes use of the new rectangle rendering methods used to display
the colored visual bell to add proper underline and strikeout support to
Alacritty.

1 files changed, 36 insertions, 0 deletions

diff --git a/font/src/ft/mod.rs b/font/src/ft/mod.rs
index 1d3f64bd..03e8bb31 100644
--- a/font/src/ft/mod.rs
+++ b/font/src/ft/mod.rs
@@ -18,6 +18,7 @@ use std::cmp::min;
 use std::path::PathBuf;
 use std::fmt;
 
+use freetype::tt_os2::TrueTypeOS2Table;
 use freetype::{self, Library};
 use libc::c_uint;
 
@@ -86,15 +87,50 @@ impl ::Rasterize for FreeTypeRasterizer {
     }
 
     fn metrics(&self, key: FontKey, _size: Size) -> Result<Metrics, Error> {
+        let face = self.faces
+            .get(&key)
+            .ok_or(Error::FontNotLoaded)?;
         let full = self.full_metrics(key)?;
 
         let height = (full.size_metrics.height / 64) as f64;
         let descent = (full.size_metrics.descender / 64) as f32;
 
+        // Get underline position and thickness in device pixels
+        let x_scale = full.size_metrics.x_scale as f32 / 65536.0;
+        let underline_position =
+            (f32::from(face.ft_face.underline_position()) * x_scale / 64.).round();
+        let underline_thickness =
+            (f32::from(face.ft_face.underline_thickness()) * x_scale / 64.)
+            .round()
+            .max(1.);
+
+        // Get strikeout position and thickness in device pixels
+        let (strikeout_position, strikeout_thickness) =
+            match TrueTypeOS2Table::from_face(&mut face.ft_face.clone())
+        {
+            Some(os2) => {
+                let strikeout_position =
+                    (f32::from(os2.y_strikeout_position()) * x_scale / 64.).round();
+                let strikeout_thickness =
+                    (f32::from(os2.y_strikeout_size()) * x_scale / 64.).round();
+                (strikeout_position, strikeout_thickness)
+            },
+            _ => {
+                // Fallback if font doesn't provide info about strikeout
+                trace!("No strikeout data available for font, using fallback.");
+                let strikeout_position = height as f32 / 2. + descent;
+                (strikeout_position, underline_thickness)
+            },
+        };
+
         Ok(Metrics {
             average_advance: full.cell_width,
             line_height: height,
             descent,
+            underline_position,
+            underline_thickness,
+            strikeout_position,
+            strikeout_thickness,
         })
     }