Simplify decorations

1 files changed, 92 insertions, 0 deletions

diff --git a/src/layout/deco.rs b/src/layout/deco.rs
new file mode 100644
index 00000000..669bf404
--- /dev/null
+++ b/src/layout/deco.rs
@@ -0,0 +1,92 @@
+use super::*;
+use crate::util::EcoString;
+
+/// A decoration for a frame.
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub enum Decoration {
+    /// A link to an external resource.
+    Link(EcoString),
+    /// An underline/strikethrough/overline decoration.
+    Line(LineDecoration),
+}
+
+impl Decoration {
+    /// Apply a decoration to a child's frame.
+    pub fn apply(&self, ctx: &LayoutContext, frame: &mut Frame) {
+        match self {
+            Decoration::Link(href) => {
+                let link = Element::Link(href.to_string(), frame.size);
+                frame.push(Point::zero(), link);
+            }
+            Decoration::Line(line) => {
+                line.apply(ctx, frame);
+            }
+        }
+    }
+}
+
+/// Defines a line that is positioned over, under or on top of text.
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub struct LineDecoration {
+    /// The kind of line.
+    pub kind: LineKind,
+    /// Stroke color of the line, defaults to the text color if `None`.
+    pub stroke: Option<Paint>,
+    /// Thickness of the line's strokes (dependent on scaled font size), read
+    /// from the font tables if `None`.
+    pub thickness: Option<Linear>,
+    /// Position of the line relative to the baseline (dependent on scaled font
+    /// size), read from the font tables if `None`.
+    pub offset: Option<Linear>,
+    /// Amount that the line will be longer or shorter than its associated text
+    /// (dependent on scaled font size).
+    pub extent: Linear,
+}
+
+/// The kind of line decoration.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub enum LineKind {
+    /// A line under text.
+    Underline,
+    /// A line through text.
+    Strikethrough,
+    /// A line over text.
+    Overline,
+}
+
+impl LineDecoration {
+    /// Apply a line decoration to a all text elements in a frame.
+    pub fn apply(&self, ctx: &LayoutContext, frame: &mut Frame) {
+        for i in 0 .. frame.children.len() {
+            let (pos, child) = &frame.children[i];
+            if let FrameChild::Element(Element::Text(text)) = child {
+                let face = ctx.fonts.get(text.face_id);
+                let metrics = match self.kind {
+                    LineKind::Underline => face.underline,
+                    LineKind::Strikethrough => face.strikethrough,
+                    LineKind::Overline => face.overline,
+                };
+
+                let stroke = self.stroke.unwrap_or(text.fill);
+
+                let thickness = self
+                    .thickness
+                    .map(|s| s.resolve(text.size))
+                    .unwrap_or(metrics.strength.to_length(text.size));
+
+                let offset = self
+                    .offset
+                    .map(|s| s.resolve(text.size))
+                    .unwrap_or(-metrics.position.to_length(text.size));
+
+                let extent = self.extent.resolve(text.size);
+
+                let subpos = Point::new(pos.x - extent, pos.y + offset);
+                let vector = Point::new(text.width + 2.0 * extent, Length::zero());
+                let line = Geometry::Line(vector, thickness);
+
+                frame.push(subpos, Element::Geometry(line, stroke));
+            }
+        }
+    }
+}