Links! (#43)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

src/eval/template.rs

@@ -20,7 +20,7 @@ pub struct Template(Rc<Vec<TemplateNode>>);
 #[derive(Clone)]
 enum TemplateNode {
     /// A word space.
-    Space,
+    Space(Vec<Decoration>),
     /// A line break.
     Linebreak,
     /// A paragraph break.
@@ -28,11 +28,11 @@ enum TemplateNode {
     /// A page break.
     Pagebreak(bool),
     /// Plain text.
-    Text(EcoString),
+    Text(EcoString, Vec<Decoration>),
     /// Spacing.
     Spacing(GenAxis, Linear),
     /// An inline node builder.
-    Inline(Rc<dyn Fn(&State) -> LayoutNode>),
+    Inline(Rc<dyn Fn(&State) -> LayoutNode>, Vec<Decoration>),
     /// An block node builder.
     Block(Rc<dyn Fn(&State) -> LayoutNode>),
     /// Save the current state.
@@ -43,6 +43,13 @@ enum TemplateNode {
     Modify(Rc<dyn Fn(&mut State)>),
 }
 
+/// A template node decoration.
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub enum Decoration {
+    /// A link.
+    Link(EcoString),
+}
+
 impl Template {
     /// Create a new, empty template.
     pub fn new() -> Self {
@@ -55,7 +62,7 @@ impl Template {
         F: Fn(&State) -> T + 'static,
         T: Into<LayoutNode>,
     {
-        let node = TemplateNode::Inline(Rc::new(move |s| f(s).into()));
+        let node = TemplateNode::Inline(Rc::new(move |s| f(s).into()), vec![]);
         Self(Rc::new(vec![node]))
     }
 
@@ -71,7 +78,7 @@ impl Template {
 
     /// Add a word space to the template.
     pub fn space(&mut self) {
-        self.make_mut().push(TemplateNode::Space);
+        self.make_mut().push(TemplateNode::Space(vec![]));
     }
 
     /// Add a line break to the template.
@@ -91,7 +98,7 @@ impl Template {
 
     /// Add text to the template.
     pub fn text(&mut self, text: impl Into<EcoString>) {
-        self.make_mut().push(TemplateNode::Text(text.into()));
+        self.make_mut().push(TemplateNode::Text(text.into(), vec![]));
     }
 
     /// Add text, but in monospace.
@@ -107,6 +114,19 @@ impl Template {
         self.make_mut().push(TemplateNode::Spacing(axis, spacing));
     }
 
+    /// Add a decoration to the last template node.
+    pub fn decorate(&mut self, deco: Decoration) {
+        for node in self.make_mut() {
+            let decos = match node {
+                TemplateNode::Space(decos) => decos,
+                TemplateNode::Text(_, decos) => decos,
+                TemplateNode::Inline(_, decos) => decos,
+                _ => continue,
+            };
+            decos.push(deco.clone());
+        }
+    }
+
     /// Register a restorable snapshot.
     pub fn save(&mut self) {
         self.make_mut().push(TemplateNode::Save);
@@ -201,7 +221,7 @@ impl Add<Str> for Template {
     type Output = Self;
 
     fn add(mut self, rhs: Str) -> Self::Output {
-        Rc::make_mut(&mut self.0).push(TemplateNode::Text(rhs.into()));
+        Rc::make_mut(&mut self.0).push(TemplateNode::Text(rhs.into(), vec![]));
         self
     }
 }
@@ -210,7 +230,7 @@ impl Add<Template> for Str {
     type Output = Template;
 
     fn add(self, mut rhs: Template) -> Self::Output {
-        Rc::make_mut(&mut rhs.0).insert(0, TemplateNode::Text(self.into()));
+        Rc::make_mut(&mut rhs.0).insert(0, TemplateNode::Text(self.into(), vec![]));
         rhs
     }
 }
@@ -261,26 +281,26 @@ impl Builder {
                     self.pagebreak(true, false);
                 }
             }
-            TemplateNode::Space => self.space(),
+            TemplateNode::Space(decos) => self.space(decos),
             TemplateNode::Linebreak => self.linebreak(),
             TemplateNode::Parbreak => self.parbreak(),
             TemplateNode::Pagebreak(keep) => self.pagebreak(*keep, true),
-            TemplateNode::Text(text) => self.text(text),
+            TemplateNode::Text(text, decos) => self.text(text, decos),
             TemplateNode::Spacing(axis, amount) => self.spacing(*axis, *amount),
-            TemplateNode::Inline(f) => self.inline(f(&self.state)),
+            TemplateNode::Inline(f, decos) => self.inline(f(&self.state), decos),
             TemplateNode::Block(f) => self.block(f(&self.state)),
             TemplateNode::Modify(f) => f(&mut self.state),
         }
     }
 
     /// Push a word space into the active paragraph.
-    fn space(&mut self) {
+    fn space(&mut self, decos: &[Decoration]) {
-        self.stack.par.push_soft(self.make_text_node(' '));
+        self.stack.par.push_soft(self.make_text_node(' ', decos.to_vec()));
     }
 
     /// Apply a forced line break.
     fn linebreak(&mut self) {
-        self.stack.par.push_hard(self.make_text_node('\n'));
+        self.stack.par.push_hard(self.make_text_node('\n', vec![]));
     }
 
     /// Apply a forced paragraph break.
@@ -300,16 +320,14 @@ impl Builder {
     }
 
     /// Push text into the active paragraph.
-    ///
+    fn text(&mut self, text: impl Into<EcoString>, decos: &[Decoration]) {
-    /// The text is split into lines at newlines.
+        self.stack.par.push(self.make_text_node(text, decos.to_vec()));
-    fn text(&mut self, text: impl Into<EcoString>) {
-        self.stack.par.push(self.make_text_node(text));
     }
 
     /// Push an inline node into the active paragraph.
-    fn inline(&mut self, node: impl Into<LayoutNode>) {
+    fn inline(&mut self, node: impl Into<LayoutNode>, decos: &[Decoration]) {
         let align = self.state.aligns.inline;
-        self.stack.par.push(ParChild::Any(node.into(), align));
+        self.stack.par.push(ParChild::Any(node.into(), align, decos.to_vec()));
     }
 
     /// Push a block node into the active stack, finishing the active paragraph.
@@ -348,11 +366,16 @@ impl Builder {
 
     /// Construct a text node with the given text and settings from the active
     /// state.
-    fn make_text_node(&self, text: impl Into<EcoString>) -> ParChild {
+    fn make_text_node(
+        &self,
+        text: impl Into<EcoString>,
+        decos: Vec<Decoration>,
+    ) -> ParChild {
         ParChild::Text(
             text.into(),
             self.state.aligns.inline,
             Rc::clone(&self.state.font),
+            decos,
         )
     }
 }
@@ -465,11 +488,14 @@ impl ParBuilder {
     }
 
     fn push_inner(&mut self, child: ParChild) {
-        if let ParChild::Text(curr_text, curr_align, curr_props) = &child {
+        if let ParChild::Text(curr_text, curr_align, curr_props, curr_decos) = &child {
-            if let Some(ParChild::Text(prev_text, prev_align, prev_props)) =
+            if let Some(ParChild::Text(prev_text, prev_align, prev_props, prev_decos)) =
                 self.children.last_mut()
             {
-                if prev_align == curr_align && Rc::ptr_eq(prev_props, curr_props) {
+                if prev_align == curr_align
+                    && Rc::ptr_eq(prev_props, curr_props)
+                    && curr_decos == prev_decos
+                {
                     prev_text.push_str(&curr_text);
                     return;
                 }

src/eval/walk.rs

@@ -115,6 +115,7 @@ fn walk_item(ctx: &mut EvalContext, label: EcoString, body: Template) {
                 label.clone(),
                 state.aligns.inline,
                 Rc::clone(&state.font),
+                vec![],
             )],
         };
         StackNode {

src/export/pdf.rs

@@ -8,8 +8,8 @@ use std::rc::Rc;
 use image::{DynamicImage, GenericImageView, ImageFormat, ImageResult, Rgba};
 use miniz_oxide::deflate;
 use pdf_writer::{
-    CidFontType, ColorSpace, Content, Filter, FontFlags, Name, PdfWriter, Rect, Ref, Str,
+    ActionType, AnnotationType, CidFontType, ColorSpace, Content, Filter, FontFlags,
-    SystemInfo, UnicodeCmap,
+    Name, PdfWriter, Rect, Ref, Str, SystemInfo, UnicodeCmap,
 };
 use ttf_parser::{name_id, GlyphId};
 
@@ -59,6 +59,7 @@ impl<'a> PdfExporter<'a> {
                         }
                         image_map.insert(id);
                     }
+                    Element::Link(_, _) => {}
                 }
             }
         }
@@ -116,16 +117,34 @@ impl<'a> PdfExporter<'a> {
         for ((page_id, content_id), page) in
             self.refs.pages().zip(self.refs.contents()).zip(self.frames)
         {
-            self.writer
+            let w = page.size.w.to_pt() as f32;
-                .page(page_id)
+            let h = page.size.h.to_pt() as f32;
+
+            let mut page_writer = self.writer.page(page_id);
+            page_writer
                 .parent(self.refs.page_tree)
-                .media_box(Rect::new(
+                .media_box(Rect::new(0.0, 0.0, w, h));
-                    0.0,
+
-                    0.0,
+            let mut annotations = page_writer.annotations();
-                    page.size.w.to_pt() as f32,
+            for (pos, element) in page.elements() {
-                    page.size.h.to_pt() as f32,
+                if let Element::Link(href, size) = element {
-                ))
+                    let x = pos.x.to_pt() as f32;
-                .contents(content_id);
+                    let y = (page.size.h - pos.y).to_pt() as f32;
+                    let w = size.w.to_pt() as f32;
+                    let h = size.h.to_pt() as f32;
+
+                    annotations
+                        .push()
+                        .subtype(AnnotationType::Link)
+                        .rect(Rect::new(x, y - h, x + w, y))
+                        .action()
+                        .action_type(ActionType::Uri)
+                        .uri(Str(href.as_bytes()));
+                }
+            }
+
+            drop(annotations);
+            page_writer.contents(content_id);
         }
     }
 
@@ -248,6 +267,8 @@ impl<'a> PdfExporter<'a> {
                     content.x_object(Name(name.as_bytes()));
                     content.restore_state();
                 }
+
+                Element::Link(_, _) => {}
             }
         }
 

src/layout/frame.rs

@@ -16,17 +16,17 @@ pub struct Frame {
     /// The baseline of the frame measured from the top.
     pub baseline: Length,
     /// The elements composing this layout.
-    children: Vec<(Point, Child)>,
+    pub children: Vec<(Point, FrameChild)>,
 }
 
 /// A frame can contain two different kinds of children: a leaf element or a
 /// nested frame.
 #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
-enum Child {
+pub enum FrameChild {
     /// A leaf node in the frame tree.
     Element(Element),
-    /// An interior node.
+    /// An interior node with an optional index.
-    Frame(Rc<Frame>),
+    Frame(Option<usize>, Rc<Frame>),
 }
 
 impl Frame {
@@ -38,17 +38,22 @@ impl Frame {
 
     /// Add an element at a position in the foreground.
     pub fn push(&mut self, pos: Point, element: Element) {
-        self.children.push((pos, Child::Element(element)));
+        self.children.push((pos, FrameChild::Element(element)));
     }
 
     /// Add an element at a position in the background.
     pub fn prepend(&mut self, pos: Point, element: Element) {
-        self.children.insert(0, (pos, Child::Element(element)))
+        self.children.insert(0, (pos, FrameChild::Element(element)));
     }
 
     /// Add a frame element.
     pub fn push_frame(&mut self, pos: Point, subframe: Rc<Self>) {
-        self.children.push((pos, Child::Frame(subframe)))
+        self.children.push((pos, FrameChild::Frame(None, subframe)))
+    }
+
+    /// Add a frame element with an index of arbitrary use.
+    pub fn push_indexed_frame(&mut self, pos: Point, index: usize, subframe: Rc<Self>) {
+        self.children.push((pos, FrameChild::Frame(Some(index), subframe)));
     }
 
     /// Add all elements of another frame, placing them relative to the given
@@ -85,12 +90,12 @@ impl<'a> Iterator for Elements<'a> {
     fn next(&mut self) -> Option<Self::Item> {
         let (cursor, offset, frame) = self.stack.last_mut()?;
         match frame.children.get(*cursor) {
-            Some((pos, Child::Frame(f))) => {
+            Some((pos, FrameChild::Frame(_, f))) => {
                 let new_offset = *offset + *pos;
                 self.stack.push((0, new_offset, f.as_ref()));
                 self.next()
             }
-            Some((pos, Child::Element(e))) => {
+            Some((pos, FrameChild::Element(e))) => {
                 *cursor += 1;
                 Some((*offset + *pos, e))
             }
@@ -115,6 +120,8 @@ pub enum Element {
     Geometry(Geometry, Paint),
     /// A raster image.
     Image(ImageId, Size),
+    /// A link to an external resource.
+    Link(String, Size),
 }
 
 /// A run of shaped text.

src/layout/par.rs

@@ -4,7 +4,7 @@ use unicode_bidi::{BidiInfo, Level};
 use xi_unicode::LineBreakIterator;
 
 use super::*;
-use crate::eval::FontState;
+use crate::eval::{Decoration, FontState};
 use crate::util::{EcoString, RangeExt, SliceExt};
 
 type Range = std::ops::Range<usize>;
@@ -26,9 +26,9 @@ pub enum ParChild {
     /// Spacing between other nodes.
     Spacing(Linear),
     /// A run of text and how to align it in its line.
-    Text(EcoString, Align, Rc<FontState>),
+    Text(EcoString, Align, Rc<FontState>, Vec<Decoration>),
     /// Any child node and how to align it in its line.
-    Any(LayoutNode, Align),
+    Any(LayoutNode, Align, Vec<Decoration>),
 }
 
 impl Layout for ParNode {
@@ -48,7 +48,7 @@ impl Layout for ParNode {
         let layouter = ParLayouter::new(self, ctx, regions, bidi);
 
         // Find suitable linebreaks.
-        layouter.layout(ctx, regions.clone())
+        layouter.layout(ctx, &self.children, regions.clone())
     }
 }
 
@@ -79,8 +79,8 @@ impl ParNode {
     fn strings(&self) -> impl Iterator<Item = &str> {
         self.children.iter().map(|child| match child {
             ParChild::Spacing(_) => " ",
-            ParChild::Text(ref piece, _, _) => piece,
+            ParChild::Text(ref piece, ..) => piece,
-            ParChild::Any(_, _) => "\u{FFFC}",
+            ParChild::Any(..) => "\u{FFFC}",
         })
     }
 }
@@ -119,25 +119,25 @@ impl<'a> ParLayouter<'a> {
         let mut ranges = vec![];
 
         // Layout the children and collect them into items.
-        for (range, child) in par.ranges().zip(&par.children) {
+        for (i, (range, child)) in par.ranges().zip(&par.children).enumerate() {
             match *child {
                 ParChild::Spacing(amount) => {
                     let resolved = amount.resolve(regions.current.w);
                     items.push(ParItem::Spacing(resolved));
                     ranges.push(range);
                 }
-                ParChild::Text(_, align, ref state) => {
+                ParChild::Text(_, align, ref state, _) => {
                     // TODO: Also split by language and script.
                     for (subrange, dir) in split_runs(&bidi, range) {
                         let text = &bidi.text[subrange.clone()];
                         let shaped = shape(ctx, text, dir, state);
-                        items.push(ParItem::Text(shaped, align));
+                        items.push(ParItem::Text(shaped, align, i));
                         ranges.push(subrange);
                     }
                 }
-                ParChild::Any(ref node, align) => {
+                ParChild::Any(ref node, align, _) => {
                     let frame = node.layout(ctx, regions).remove(0);
-                    items.push(ParItem::Frame(frame.item, align));
+                    items.push(ParItem::Frame(frame.item, align, i));
                     ranges.push(range);
                 }
             }
@@ -156,9 +156,10 @@ impl<'a> ParLayouter<'a> {
     fn layout(
         self,
         ctx: &mut LayoutContext,
+        children: &[ParChild],
         regions: Regions,
     ) -> Vec<Constrained<Rc<Frame>>> {
-        let mut stack = LineStack::new(self.line_spacing, regions);
+        let mut stack = LineStack::new(self.line_spacing, children, regions);
 
         // The current line attempt.
         // Invariant: Always fits into `stack.regions.current`.
@@ -273,9 +274,9 @@ enum ParItem<'a> {
     /// Spacing between other items.
     Spacing(Length),
     /// A shaped text run with consistent direction.
-    Text(ShapedText<'a>, Align),
+    Text(ShapedText<'a>, Align, usize),
     /// A layouted child node.
-    Frame(Rc<Frame>, Align),
+    Frame(Rc<Frame>, Align, usize),
 }
 
 impl ParItem<'_> {
@@ -283,8 +284,8 @@ impl ParItem<'_> {
     pub fn size(&self) -> Size {
         match self {
             Self::Spacing(amount) => Size::new(*amount, Length::zero()),
-            Self::Text(shaped, _) => shaped.size,
+            Self::Text(shaped, ..) => shaped.size,
-            Self::Frame(frame, _) => frame.size,
+            Self::Frame(frame, ..) => frame.size,
         }
     }
 
@@ -292,8 +293,17 @@ impl ParItem<'_> {
     pub fn baseline(&self) -> Length {
         match self {
             Self::Spacing(_) => Length::zero(),
-            Self::Text(shaped, _) => shaped.baseline,
+            Self::Text(shaped, ..) => shaped.baseline,
-            Self::Frame(frame, _) => frame.baseline,
+            Self::Frame(frame, ..) => frame.baseline,
+        }
+    }
+
+    /// The index of the `ParChild` that this item belongs to.
+    pub fn index(&self) -> Option<usize> {
+        match *self {
+            Self::Spacing(_) => None,
+            Self::Text(.., index) => Some(index),
+            Self::Frame(.., index) => Some(index),
         }
     }
 }
@@ -301,6 +311,7 @@ impl ParItem<'_> {
 /// Stacks lines on top of each other.
 struct LineStack<'a> {
     line_spacing: Length,
+    children: &'a [ParChild],
     full: Size,
     regions: Regions,
     size: Size,
@@ -312,11 +323,12 @@ struct LineStack<'a> {
 
 impl<'a> LineStack<'a> {
     /// Create an empty line stack.
-    fn new(line_spacing: Length, regions: Regions) -> Self {
+    fn new(line_spacing: Length, children: &'a [ParChild], regions: Regions) -> Self {
         Self {
             line_spacing,
-            constraints: Constraints::new(regions.expand),
+            children,
             full: regions.current,
+            constraints: Constraints::new(regions.expand),
             regions,
             size: Size::zero(),
             lines: vec![],
@@ -368,6 +380,25 @@ impl<'a> LineStack<'a> {
             output.merge_frame(pos, frame);
         }
 
+        // For each frame, we look if any decorations apply.
+        for i in 0 .. output.children.len() {
+            let &(point, ref child) = &output.children[i];
+            if let &FrameChild::Frame(Some(frame_idx), ref frame) = child {
+                let size = frame.size;
+                for deco in match &self.children[frame_idx] {
+                    ParChild::Spacing(_) => continue,
+                    ParChild::Text(.., decos) => decos,
+                    ParChild::Any(.., decos) => decos,
+                } {
+                    match deco {
+                        Decoration::Link(href) => {
+                            output.push(point, Element::Link(href.to_string(), size));
+                        }
+                    }
+                }
+            }
+        }
+
         self.finished.push(output.constrain(self.constraints));
         self.regions.next();
         self.full = self.regions.current;
@@ -426,7 +457,7 @@ impl<'a> LineLayout<'a> {
 
         // Reshape the last item if it's split in half.
         let mut last = None;
-        if let Some((ParItem::Text(shaped, align), rest)) = items.split_last() {
+        if let Some((ParItem::Text(shaped, align, i), rest)) = items.split_last() {
             // Compute the range we want to shape, trimming whitespace at the
             // end of the line.
             let base = par.ranges[last_idx].start;
@@ -442,7 +473,7 @@ impl<'a> LineLayout<'a> {
                 if !range.is_empty() || rest.is_empty() {
                     // Reshape that part.
                     let reshaped = shaped.reshape(ctx, range);
-                    last = Some(ParItem::Text(reshaped, *align));
+                    last = Some(ParItem::Text(reshaped, *align, *i));
                 }
 
                 items = rest;
@@ -452,7 +483,7 @@ impl<'a> LineLayout<'a> {
 
         // Reshape the start item if it's split in half.
         let mut first = None;
-        if let Some((ParItem::Text(shaped, align), rest)) = items.split_first() {
+        if let Some((ParItem::Text(shaped, align, i), rest)) = items.split_first() {
             // Compute the range we want to shape.
             let Range { start: base, end: first_end } = par.ranges[first_idx];
             let start = line.start;
@@ -463,7 +494,7 @@ impl<'a> LineLayout<'a> {
             if range.len() < shaped.text.len() {
                 if !range.is_empty() {
                     let reshaped = shaped.reshape(ctx, range);
-                    first = Some(ParItem::Text(reshaped, *align));
+                    first = Some(ParItem::Text(reshaped, *align, *i));
                 }
 
                 items = rest;
@@ -511,11 +542,11 @@ impl<'a> LineLayout<'a> {
                     offset += amount;
                     return;
                 }
-                ParItem::Text(ref shaped, align) => {
+                ParItem::Text(ref shaped, align, _) => {
                     ruler = ruler.max(align);
                     Rc::new(shaped.build(ctx))
                 }
-                ParItem::Frame(ref frame, align) => {
+                ParItem::Frame(ref frame, align, _) => {
                     ruler = ruler.max(align);
                     frame.clone()
                 }
@@ -528,7 +559,11 @@ impl<'a> LineLayout<'a> {
             );
 
             offset += frame.size.w;
-            output.push_frame(pos, frame);
+
+            match item.index() {
+                Some(idx) => output.push_indexed_frame(pos, idx, frame),
+                None => output.push_frame(pos, frame),
+            }
         });
 
         output

src/library/mod.rs

@@ -35,6 +35,7 @@ pub fn new() -> Scope {
     std.def_func("strike", strike);
     std.def_func("underline", underline);
     std.def_func("overline", overline);
+    std.def_func("link", link);
 
     // Layout.
     std.def_func("page", page);

src/library/text.rs

@@ -1,4 +1,4 @@
-use crate::eval::{FontState, LineState};
+use crate::eval::{Decoration, FontState, LineState};
 use crate::layout::Paint;
 
 use super::*;
@@ -197,3 +197,18 @@ fn line_impl(
 
     Ok(Value::Template(template))
 }
+
+/// `link`: Set a link.
+pub fn link(_: &mut EvalContext, args: &mut Arguments) -> TypResult<Value> {
+    let url = args.expect::<Str>("url")?;
+
+    let mut body = args.eat().unwrap_or_else(|| {
+        let mut template = Template::new();
+        template.text(&url);
+        template
+    });
+
+    body.decorate(Decoration::Link(url.into()));
+
+    Ok(Value::Template(body))
+}

tests/typ/text/links.typ

@@ -0,0 +1,12 @@
+// Link without body.
+#link("https://example.com/")
+
+// Link with body.
+#link("https://typst.app/")[Some text text text]
+
+// With line break.
+This link appears #link("https://google.com/")[in the middle of] a paragraph.
+
+// Styled with underline and color.
+#let link(url, body) = link(url, [#font(fill: rgb("283663")) #underline(body)])
+You could also make the #link("https://html5zombo.com/")[link look way more typical.]

tests/typeset.rs

@@ -9,7 +9,7 @@ use tiny_skia as sk;
 use ttf_parser::{GlyphId, OutlineBuilder};
 use walkdir::WalkDir;
 
-use typst::color::Color;
+use typst::color::{Color, RgbaColor};
 use typst::diag::Error;
 use typst::eval::{State, Value};
 use typst::geom::{self, Length, PathElement, Point, Sides, Size};
@@ -428,6 +428,11 @@ fn draw(ctx: &Context, frames: &[Rc<Frame>], dpi: f32) -> sk::Pixmap {
                 Element::Image(id, size) => {
                     draw_image(&mut canvas, ts, ctx, id, size);
                 }
+                Element::Link(_, s) => {
+                    let outline = Geometry::Rect(s);
+                    let paint = Paint::Color(Color::Rgba(RgbaColor::new(40, 54, 99, 40)));
+                    draw_geometry(&mut canvas, ts, &outline, paint);
+                }
             }
         }