Added a rudimentary undercurl to Alacritty. Currently does not support setting the color. That is the next task

6 files changed, 112 insertions, 15 deletions

diff --git a/alacritty/src/display/content.rs b/alacritty/src/display/content.rs
index 2deb3d3e..09116508 100644
--- a/alacritty/src/display/content.rs
+++ b/alacritty/src/display/content.rs
@@ -271,7 +271,7 @@ impl RenderableCell {
         self.bg_alpha == 0.
             && self.character == ' '
             && self.zerowidth.is_none()
-            && !self.flags.intersects(Flags::UNDERLINE | Flags::STRIKEOUT | Flags::DOUBLE_UNDERLINE)
+            && !self.flags.intersects(Flags::UNDERLINE | Flags::STRIKEOUT | Flags::DOUBLE_UNDERLINE | Flags::UNDERCURL)
     }
 
     /// Apply [`CellRgb`] colors to the cell's colors.
diff --git a/alacritty/src/renderer/rects.rs b/alacritty/src/renderer/rects.rs
index 77c22011..91a67c22 100644
--- a/alacritty/src/renderer/rects.rs
+++ b/alacritty/src/renderer/rects.rs
@@ -62,7 +62,7 @@ impl RenderLine {
         end: Point<usize>,
         color: Rgb,
     ) {
-        let (position, thickness) = match flag {
+        match flag {
             Flags::DOUBLE_UNDERLINE => {
                 // Position underlines so each one has 50% of descent available.
                 let top_pos = 0.25 * metrics.descent;
@@ -78,22 +78,93 @@ impl RenderLine {
                     color,
                 ));
 
-                (bottom_pos, metrics.underline_thickness)
+                rects.push(Self::create_rect(
+                    size,
+                    metrics.descent,
+                    start,
+                    end,
+                    bottom_pos,
+                    metrics.underline_thickness,
+                    color,
+                ));
+            },
+            Flags::UNDERLINE => {
+                rects.push(Self::create_rect(
+                    size,
+                    metrics.descent,
+                    start,
+                    end,
+                    metrics.underline_position,
+                    metrics.underline_thickness,
+                    color,
+                ));
             },
-            Flags::UNDERLINE => (metrics.underline_position, metrics.underline_thickness),
-            Flags::STRIKEOUT => (metrics.strikeout_position, metrics.strikeout_thickness),
+            Flags::STRIKEOUT => {
+                rects.push(Self::create_rect(
+                    size,
+                    metrics.descent,
+                    start,
+                    end,
+                    metrics.strikeout_position,
+                    metrics.strikeout_thickness,
+                    color,
+                ));
+            },
+            Flags::UNDERCURL => {
+                Self::push_undercurl_rects(
+                    rects,
+                    size,
+                    metrics.descent,
+                    start,
+                    end,
+                    metrics.underline_position,
+                    metrics.underline_thickness,
+                    color)
+            }
             _ => unimplemented!("Invalid flag for cell line drawing specified"),
         };
+    }
 
-        rects.push(Self::create_rect(
-            size,
-            metrics.descent,
-            start,
-            end,
-            position,
-            thickness,
-            color,
-        ));
+    fn push_undercurl_rects(
+        rects: &mut Vec<RenderRect>,
+        size: &SizeInfo,
+        descent: f32,
+        start: Point<usize>,
+        end: Point<usize>,
+        position: f32,
+        mut thickness: f32,
+        color: Rgb,
+    ) {
+        let start_x = start.column.0 as f32 * size.cell_width();
+        let end_x = (end.column.0 + 1) as f32 * size.cell_width();
+
+        // Make sure lines are always visible.
+        thickness = thickness.max(1.);
+
+        let line_bottom = (start.line as f32 + 1.) * size.cell_height();
+        let baseline = line_bottom + descent;
+
+        let mut y = (baseline - position - thickness / 2.).ceil();
+        let max_y = line_bottom - thickness;
+        if y > max_y {
+            y = max_y;
+        }
+
+        let mut x = start_x;
+        let mut idx = 0;
+        while x < end_x {
+            let rect = RenderRect::new(
+                x + size.padding_x(),
+                y + size.padding_y() + ((idx % 2) as f32) - 1.,
+                1.,
+                thickness + 1.,
+                color,
+                1.,
+            );
+            rects.push(rect);
+            x += 1.;
+            idx += 1;
+        }
     }
 
     /// Create a line's rect at a position relative to the baseline.
@@ -161,6 +232,7 @@ impl RenderLines {
         self.update_flag(cell, Flags::UNDERLINE);
         self.update_flag(cell, Flags::DOUBLE_UNDERLINE);
         self.update_flag(cell, Flags::STRIKEOUT);
+        self.update_flag(cell, Flags::UNDERCURL);
     }
 
     /// Update the lines for a specific flag.
diff --git a/alacritty_terminal/src/ansi.rs b/alacritty_terminal/src/ansi.rs
index 55492d36..35a46549 100644
--- a/alacritty_terminal/src/ansi.rs
+++ b/alacritty_terminal/src/ansi.rs
@@ -768,6 +768,8 @@ pub enum Attr {
     Underline,
     /// Underlined twice.
     DoubleUnderline,
+    /// Underlined twice.
+    Undercurl,
     /// Blink cursor slowly.
     BlinkSlow,
     /// Blink cursor fast.
@@ -798,6 +800,8 @@ pub enum Attr {
     Foreground(Color),
     /// Set indexed background color.
     Background(Color),
+    /// Set indexed special color (for underlines).
+    Special(Color),
 }
 
 /// Identifiers which can be assigned to a graphic character set.
@@ -1316,6 +1320,7 @@ fn attrs_from_sgr_parameters(params: &mut ParamsIter<'_>) -> Vec<Option<Attr>> {
             [3] => Some(Attr::Italic),
             [4, 0] => Some(Attr::CancelUnderline),
             [4, 2] => Some(Attr::DoubleUnderline),
+            [4, 3] => Some(Attr::Undercurl),
             [4, ..] => Some(Attr::Underline),
             [5] => Some(Attr::BlinkSlow),
             [6] => Some(Attr::BlinkFast),
@@ -1370,6 +1375,14 @@ fn attrs_from_sgr_parameters(params: &mut ParamsIter<'_>) -> Vec<Option<Attr>> {
                 parse_sgr_color(&mut iter).map(Attr::Background)
             },
             [49] => Some(Attr::Background(Color::Named(NamedColor::Background))),
+            [58, params @ ..] => {
+                let rgb_start = if params.len() > 4 { 2 } else { 1 };
+                let rgb_iter = params[rgb_start..].iter().copied();
+                let mut iter = iter::once(params[0]).chain(rgb_iter);
+
+                parse_sgr_color(&mut iter).map(Attr::Special)
+            },
+            [59] => Some(Attr::Special(Color::Named(NamedColor::Foreground))),
             [90] => Some(Attr::Foreground(Color::Named(NamedColor::BrightBlack))),
             [91] => Some(Attr::Foreground(Color::Named(NamedColor::BrightRed))),
             [92] => Some(Attr::Foreground(Color::Named(NamedColor::BrightGreen))),
diff --git a/alacritty_terminal/src/config/mod.rs b/alacritty_terminal/src/config/mod.rs
index 0b313598..382314bd 100644
--- a/alacritty_terminal/src/config/mod.rs
+++ b/alacritty_terminal/src/config/mod.rs
@@ -66,6 +66,7 @@ pub struct Cursor {
     pub style: ConfigCursorStyle,
     pub vi_mode_style: Option<ConfigCursorStyle>,
     pub unfocused_hollow: bool,
+    pub cursor_crosshairs: bool,
 
     thickness: Percentage,
     blink_interval: u64,
@@ -79,6 +80,7 @@ impl Default for Cursor {
             blink_interval: 750,
             style: Default::default(),
             vi_mode_style: Default::default(),
+            cursor_crosshairs: false,
         }
     }
 }
diff --git a/alacritty_terminal/src/term/cell.rs b/alacritty_terminal/src/term/cell.rs
index 64de5492..2191ced2 100644
--- a/alacritty_terminal/src/term/cell.rs
+++ b/alacritty_terminal/src/term/cell.rs
@@ -24,6 +24,7 @@ bitflags! {
         const STRIKEOUT                 = 0b0000_0010_0000_0000;
         const LEADING_WIDE_CHAR_SPACER  = 0b0000_0100_0000_0000;
         const DOUBLE_UNDERLINE          = 0b0000_1000_0000_0000;
+        const UNDERCURL                 = 0b0001_0000_0000_0000;
     }
 }
 
@@ -119,6 +120,7 @@ impl GridCell for Cell {
                 Flags::INVERSE
                     | Flags::UNDERLINE
                     | Flags::DOUBLE_UNDERLINE
+                    | Flags::UNDERCURL
                     | Flags::STRIKEOUT
                     | Flags::WRAPLINE
                     | Flags::WIDE_CHAR_SPACER
diff --git a/alacritty_terminal/src/term/mod.rs b/alacritty_terminal/src/term/mod.rs
index 1808f3aa..367f39f9 100644
--- a/alacritty_terminal/src/term/mod.rs
+++ b/alacritty_terminal/src/term/mod.rs
@@ -1509,14 +1509,22 @@ impl<T: EventListener> Handler for Term<T> {
             Attr::CancelItalic => cursor.template.flags.remove(Flags::ITALIC),
             Attr::Underline => {
                 cursor.template.flags.remove(Flags::DOUBLE_UNDERLINE);
+                cursor.template.flags.remove(Flags::UNDERCURL);
                 cursor.template.flags.insert(Flags::UNDERLINE);
             },
             Attr::DoubleUnderline => {
                 cursor.template.flags.remove(Flags::UNDERLINE);
+                cursor.template.flags.remove(Flags::UNDERCURL);
                 cursor.template.flags.insert(Flags::DOUBLE_UNDERLINE);
             },
+            Attr::Undercurl => {
+                cursor.template.flags.remove(Flags::UNDERLINE);
+                cursor.template.flags.remove(Flags::DOUBLE_UNDERLINE);
+                cursor.template.flags.insert(Flags::UNDERCURL);
+            },
             Attr::CancelUnderline => {
-                cursor.template.flags.remove(Flags::UNDERLINE | Flags::DOUBLE_UNDERLINE);
+                cursor.template.flags.remove(
+                    Flags::UNDERLINE | Flags::DOUBLE_UNDERLINE | Flags::UNDERCURL);
             },
             Attr::Hidden => cursor.template.flags.insert(Flags::HIDDEN),
             Attr::CancelHidden => cursor.template.flags.remove(Flags::HIDDEN),