Add support for strikethrough formatting on text.

piet-coregraphics/src/text.rs

@@ -323,6 +323,8 @@ impl Attributes {
             TextAttribute::Weight(w) => self.weight = Some(Span::new(w, range)),
             TextAttribute::FontSize(s) => self.size = Some(Span::new(s, range)),
             TextAttribute::Style(s) => self.style = Some(Span::new(s, range)),
+            TextAttribute::Strikethrough(_) => { /* Unimplemented for now as coregraphics doesn't have native strikethrough support. */
+            }
             _ => unreachable!(),
         }
     }

piet-direct2d/src/dwrite.rs

@@ -374,6 +374,13 @@ impl TextLayout {
         }
     }
 
+    pub(crate) fn set_strikethrough(&mut self, range: Utf16Range, flag: bool) {
+        let flag = if flag { TRUE } else { FALSE };
+        unsafe {
+            self.0.SetStrikethrough(flag, range.into());
+        }
+    }
+
     pub(crate) fn set_size(&mut self, range: Utf16Range, size: f32) {
         unsafe {
             self.0.SetFontSize(size, range.into());

piet-direct2d/src/text.rs

@@ -234,6 +234,7 @@ impl D2DTextLayoutBuilder {
                 TextAttribute::Weight(weight) => layout.set_weight(utf16_range, weight),
                 TextAttribute::Style(style) => layout.set_style(utf16_range, style),
                 TextAttribute::Underline(flag) => layout.set_underline(utf16_range, flag),
+                TextAttribute::Strikethrough(flag) => layout.set_strikethrough(utf16_range, flag),
                 TextAttribute::ForegroundColor(color) => self.colors.push((utf16_range, color)),
             }
         }

piet/src/samples/picture_5.rs

@@ -29,6 +29,7 @@ pub fn draw<R: RenderContext>(rc: &mut R) -> Result<(), Error> {
         .default_attribute(FontWeight::BOLD)
         .range_attribute(..200, TextAttribute::ForegroundColor(BLUE))
         .range_attribute(10..100, FontWeight::NORMAL)
+        .range_attribute(20..50, TextAttribute::Strikethrough(true))
         .range_attribute(40..300, TextAttribute::Underline(false))
         .range_attribute(60..160, FontStyle::Regular)
         .range_attribute(140..220, FontWeight::NORMAL)

piet/src/samples/picture_8.rs

@@ -40,6 +40,7 @@ pub fn draw<R: RenderContext>(rc: &mut R) -> Result<(), Error> {
         .range_attribute(220.., TextAttribute::FontSize(18.0))
         .range_attribute(240.., FontStyle::Italic)
         .range_attribute(280.., TextAttribute::Underline(true))
+        .range_attribute(320.., TextAttribute::Strikethrough(true))
         .build()?;
 
     rc.draw_text(&en_leading, (0., 0.));

piet/src/text.rs

@@ -123,6 +123,8 @@ pub enum TextAttribute {
     Style(FontStyle),
     /// Underline.
     Underline(bool),
+    /// Strikethrough.
+    Strikethrough(bool),
 }
 
 /// A trait for laying out text.

piet/src/util.rs

@@ -136,6 +136,7 @@ pub struct LayoutDefaults {
     pub fg_color: Color,
     pub style: FontStyle,
     pub underline: bool,
+    pub strikethrough: bool,
 }
 
 impl LayoutDefaults {
@@ -148,6 +149,7 @@ impl LayoutDefaults {
             TextAttribute::Style(style) => self.style = style,
             TextAttribute::Underline(flag) => self.underline = flag,
             TextAttribute::ForegroundColor(color) => self.fg_color = color,
+            TextAttribute::Strikethrough(flag) => self.strikethrough = flag,
         }
     }
 }
@@ -161,6 +163,7 @@ impl Default for LayoutDefaults {
             fg_color: DEFAULT_TEXT_COLOR,
             style: FontStyle::default(),
             underline: false,
+            strikethrough: false,
         }
     }
 }