feat: add TextDecoration rendering

src/buffer.rs

@@ -10,9 +10,9 @@ use core_maths::CoreFloat;
 use unicode_segmentation::UnicodeSegmentation;
 
 use crate::{
-    Affinity, Align, Attrs, AttrsList, BidiParagraphs, BorrowedWithFontSystem, BufferLine, Color,
-    Cursor, Ellipsize, FontSystem, Hinting, LayoutCursor, LayoutGlyph, LayoutLine, LineEnding,
-    LineIter, Motion, Renderer, Scroll, ShapeLine, Shaping, Wrap,
+    render_decoration, Affinity, Align, Attrs, AttrsList, BidiParagraphs, BorrowedWithFontSystem,
+    BufferLine, Color, Cursor, Ellipsize, FontSystem, Hinting, LayoutCursor, LayoutGlyph,
+    LayoutLine, LineEnding, LineIter, Motion, Renderer, Scroll, ShapeLine, Shaping, Wrap,
 };
 
 /// A line of visible text for rendering
@@ -1385,6 +1385,8 @@ impl Buffer {
 
     pub fn render<R: Renderer>(&self, renderer: &mut R, color: Color) {
         for run in self.layout_runs() {
+            // draw decorations before glyphs so text renders on top
+            render_decoration(renderer, &run, color);
             for glyph in run.glyphs {
                 let physical_glyph = glyph.physical((0., run.line_y), 1.0);
                 let glyph_color = glyph.color_opt.map_or(color, |some| some);

src/edit/editor.rs

@@ -10,8 +10,9 @@ use core::cmp;
 use unicode_segmentation::UnicodeSegmentation;
 
 use crate::{
-    Action, Attrs, AttrsList, BorrowedWithFontSystem, BufferLine, BufferRef, Change, ChangeItem,
-    Color, Cursor, Edit, FontSystem, LayoutRun, LineEnding, LineIter, Renderer, Selection, Shaping,
+    render_decoration, Action, Attrs, AttrsList, BorrowedWithFontSystem, BufferLine, BufferRef,
+    Change, ChangeItem, Color, Cursor, Edit, FontSystem, LayoutRun, LineEnding, LineIter, Renderer,
+    Selection, Shaping,
 };
 
 /// A wrapper of [`Buffer`] for easy editing
@@ -211,6 +212,7 @@ impl<'buffer> Editor<'buffer> {
                     renderer.rectangle(x, y, 1, line_height as u32, cursor_color);
                 }
 
+                render_decoration(renderer, &run, text_color);
                 for glyph in run.glyphs {
                     let physical_glyph = glyph.physical((0., line_y), 1.0);
 

src/edit/syntect.rs

@@ -9,7 +9,7 @@ use syntect::parsing::{ParseState, ScopeStack, SyntaxReference, SyntaxSet};
 
 use crate::{
     Action, AttrsList, BorrowedWithFontSystem, BufferRef, Change, Color, Cursor, Edit, Editor,
-    FontSystem, Renderer, Selection, Shaping, Style, Weight,
+    FontSystem, Renderer, Selection, Shaping, Style, UnderlineStyle, Weight,
 };
 
 pub use syntect::highlighting::Theme as SyntaxTheme;
@@ -366,7 +366,12 @@ impl<'buffer> Edit<'buffer> for SyntaxEditor<'_, 'buffer> {
                             Weight::BOLD
                         } else {
                             Weight::NORMAL
-                        }); //TODO: underline
+                        })
+                        .underline(if style.font_style.contains(FontStyle::UNDERLINE) {
+                            UnderlineStyle::Single
+                        } else {
+                            UnderlineStyle::None
+                        });
                     if span_attrs != original_attrs {
                         attrs_list.add_span(range, &span_attrs);
                     }

src/layout.rs

@@ -2,7 +2,7 @@
 
 use core::fmt::Display;
 
-use crate::{math, CacheKey, CacheKeyFlags, Color};
+use crate::{math, CacheKey, CacheKeyFlags, Color, TextDecoration};
 #[cfg(not(feature = "std"))]
 use alloc::vec::Vec;
 
@@ -58,6 +58,8 @@ pub struct LayoutGlyph {
     pub metadata: usize,
     /// [`CacheKeyFlags`]
     pub cache_key_flags: CacheKeyFlags,
+    /// Text decoration (underline, strikethough, overline)
+    pub text_decoration: TextDecoration,
 }
 
 #[derive(Clone, Debug)]

src/render.rs

@@ -1,6 +1,6 @@
 //! Helpers for rendering buffers and editors
 
-use crate::{Color, PhysicalGlyph};
+use crate::{Color, LayoutGlyph, LayoutRun, PhysicalGlyph, TextDecoration, UnderlineStyle};
 #[cfg(feature = "swash")]
 use crate::{FontSystem, SwashCache};
 
@@ -14,6 +14,117 @@ pub trait Renderer {
     fn glyph(&mut self, physical_glyph: PhysicalGlyph, color: Color);
 }
 
+pub fn render_decoration<R: Renderer>(renderer: &mut R, run: &LayoutRun, default_color: Color) {
+    if run.glyphs.is_empty() {
+        return;
+    }
+
+    let mut group_start: Option<usize> = None;
+
+    for (i, glyph) in run.glyphs.iter().enumerate() {
+        let start_new_group = match group_start {
+            None => true,
+            Some(_) => {
+                let prev = &run.glyphs[i - 1];
+                glyph.text_decoration != prev.text_decoration
+            }
+        };
+
+        if start_new_group {
+            if let Some(gs) = group_start {
+                draw_decoration_group(renderer, run, &run.glyphs[gs..i], default_color);
+            }
+            group_start = if has_any_decoration(&glyph.text_decoration) {
+                Some(i)
+            } else {
+                None
+            };
+        }
+    }
+
+    if let Some(gs) = group_start {
+        draw_decoration_group(renderer, run, &run.glyphs[gs..], default_color);
+    }
+}
+
+fn has_any_decoration(td: &TextDecoration) -> bool {
+    td.underline != UnderlineStyle::None || td.overline || td.strikethrough
+}
+
+fn draw_decoration_group<R: Renderer>(
+    renderer: &mut R,
+    run: &LayoutRun,
+    glyphs: &[LayoutGlyph],
+    default_color: Color,
+) {
+    if glyphs.is_empty() {
+        return;
+    }
+
+    let first = &glyphs[0];
+    let last = &glyphs[glyphs.len() - 1];
+    let td = &glyphs[0].text_decoration;
+    let font_size = first.font_size;
+    let x_start = first.x;
+    let x_end = last.x + last.w;
+    let width = (x_end - x_start) as u32;
+    if width <= 0 {
+        return;
+    }
+    // Underline
+    match td.underline {
+        UnderlineStyle::None => {}
+        UnderlineStyle::Single => {
+            let color = td
+                .underline_color_opt
+                .or(first.color_opt)
+                .unwrap_or(default_color);
+            let thickness = (font_size * 14.0).max(1.0);
+            let y = run.line_y + font_size * 0.125;
+            renderer.rectangle(x_start as i32, y as i32, width, thickness as u32, color);
+        }
+        UnderlineStyle::Double => {
+            let color = td
+                .underline_color_opt
+                .or(first.color_opt)
+                .unwrap_or(default_color);
+            let thickness = (font_size * 14.0).max(1.0);
+            let gap = thickness;
+            let y = run.line_y + font_size * 0.125;
+            renderer.rectangle(x_start as i32, y as i32, width, thickness as u32, color);
+            renderer.rectangle(
+                x_start as i32,
+                (y + thickness + gap) as i32,
+                width,
+                thickness as u32,
+                color,
+            );
+        }
+    }
+
+    // Strikethrough
+    if td.strikethrough {
+        let color = td
+            .strikethrough_color_opt
+            .or(first.color_opt)
+            .unwrap_or(default_color);
+        let thickness = (font_size / 14.0).max(1.0);
+        let y = run.line_y - font_size * 0.3;
+        renderer.rectangle(x_start as i32, y as i32, width, thickness as u32, color);
+    }
+
+    // Overline
+    if td.overline {
+        let color = td
+            .overline_color_opt
+            .or(first.color_opt)
+            .unwrap_or(default_color);
+        let thickness = (font_size / 14.0).max(1.0);
+        let y = run.line_top;
+        renderer.rectangle(x_start as i32, y as i32, width, thickness as u32, color);
+    }
+}
+
 /// Helper to migrate from old renderer
 //TODO: remove in future version
 #[cfg(feature = "swash")]

src/shape.rs

@@ -5,7 +5,7 @@
 use crate::fallback::FontFallbackIter;
 use crate::{
     math, Align, Attrs, AttrsList, CacheKeyFlags, Color, Ellipsize, EllipsizeHeightLimit, Font,
-    FontSystem, Hinting, LayoutGlyph, LayoutLine, Metrics, Wrap,
+    FontSystem, Hinting, LayoutGlyph, LayoutLine, Metrics, TextDecoration, Wrap,
 };
 #[cfg(not(feature = "std"))]
 use alloc::{format, vec, vec::Vec};
@@ -236,6 +236,7 @@ fn shape_fallback(
             metadata: attrs.metadata,
             cache_key_flags: override_fake_italic(attrs.cache_key_flags, font, &attrs),
             metrics_opt: attrs.metrics_opt.map(Into::into),
+            text_decoration: attrs.text_decoration,
         });
     }
 
@@ -536,6 +537,7 @@ fn shape_skip(
                         &attrs,
                     ),
                     metrics_opt: attrs.metrics_opt.map(Into::into),
+                    text_decoration: attrs.text_decoration,
                 }
             }),
     );
@@ -572,6 +574,7 @@ pub struct ShapeGlyph {
     pub metadata: usize,
     pub cache_key_flags: CacheKeyFlags,
     pub metrics_opt: Option<Metrics>,
+    pub text_decoration: TextDecoration,
 }
 
 impl ShapeGlyph {
@@ -601,6 +604,7 @@ impl ShapeGlyph {
             color_opt: self.color_opt,
             metadata: self.metadata,
             cache_key_flags: self.cache_key_flags,
+            text_decoration: self.text_decoration,
         }
     }