Split up PDF exporter

1 files changed, 491 insertions, 0 deletions

diff --git a/src/export/pdf/page.rs b/src/export/pdf/page.rs
new file mode 100644
index 00000000..7cd0f58f
--- /dev/null
+++ b/src/export/pdf/page.rs
@@ -0,0 +1,491 @@
+use pdf_writer::types::{ActionType, AnnotationType, ColorSpaceOperand};
+use pdf_writer::writers::ColorSpace;
+use pdf_writer::{Content, Filter, Finish, Name, Rect, Ref, Str};
+
+use super::{
+    deflate, EmExt, Heading, HeadingNode, LengthExt, PdfContext, RefExt, D65_GRAY, SRGB,
+};
+use crate::font::FaceId;
+use crate::frame::{Destination, Element, Frame, Group, Role, Text};
+use crate::geom::{
+    self, Color, Em, Geometry, Length, Numeric, Paint, Point, Ratio, Shape, Size, Stroke,
+    Transform,
+};
+use crate::image::ImageId;
+
+/// Construct page objects.
+pub fn construct_pages(ctx: &mut PdfContext, frames: &[Frame]) {
+    for frame in frames {
+        construct_page(ctx, frame);
+    }
+}
+
+/// Construct a page object.
+pub fn construct_page(ctx: &mut PdfContext, frame: &Frame) {
+    let page_ref = ctx.alloc.bump();
+    ctx.page_refs.push(page_ref);
+    ctx.page_heights.push(frame.height().to_f32());
+
+    let mut ctx = PageContext {
+        parent: ctx,
+        page_ref,
+        content: Content::new(),
+        state: State::default(),
+        saves: vec![],
+        bottom: 0.0,
+        links: vec![],
+    };
+
+    let size = frame.size();
+
+    // Make the coordinate system start at the top-left.
+    ctx.bottom = size.y.to_f32();
+    ctx.transform(Transform {
+        sx: Ratio::one(),
+        ky: Ratio::zero(),
+        kx: Ratio::zero(),
+        sy: Ratio::new(-1.0),
+        tx: Length::zero(),
+        ty: size.y,
+    });
+
+    // Encode the page into the content stream.
+    write_frame(&mut ctx, frame);
+
+    let page = Page {
+        size,
+        content: ctx.content,
+        id: ctx.page_ref,
+        links: ctx.links,
+    };
+
+    ctx.parent.pages.push(page);
+}
+
+/// Write the page tree.
+pub fn write_page_tree(ctx: &mut PdfContext) {
+    for page in std::mem::take(&mut ctx.pages).into_iter() {
+        write_page(ctx, page);
+    }
+
+    let mut pages = ctx.writer.pages(ctx.page_tree_ref);
+    pages
+        .count(ctx.page_refs.len() as i32)
+        .kids(ctx.page_refs.iter().copied());
+
+    let mut resources = pages.resources();
+    let mut spaces = resources.color_spaces();
+    spaces.insert(SRGB).start::<ColorSpace>().srgb();
+    spaces.insert(D65_GRAY).start::<ColorSpace>().d65_gray();
+    spaces.finish();
+
+    let mut fonts = resources.fonts();
+    for (font_ref, f) in ctx.face_map.pdf_indices(&ctx.face_refs) {
+        let name = format_eco!("F{}", f);
+        fonts.pair(Name(name.as_bytes()), font_ref);
+    }
+
+    fonts.finish();
+
+    let mut images = resources.x_objects();
+    for (image_ref, im) in ctx.image_map.pdf_indices(&ctx.image_refs) {
+        let name = format_eco!("Im{}", im);
+        images.pair(Name(name.as_bytes()), image_ref);
+    }
+
+    images.finish();
+    resources.finish();
+    pages.finish();
+}
+
+/// Write a page tree node.
+fn write_page(ctx: &mut PdfContext, page: Page) {
+    let content_id = ctx.alloc.bump();
+
+    let mut page_writer = ctx.writer.page(page.id);
+    page_writer.parent(ctx.page_tree_ref);
+
+    let w = page.size.x.to_f32();
+    let h = page.size.y.to_f32();
+    page_writer.media_box(Rect::new(0.0, 0.0, w, h));
+    page_writer.contents(content_id);
+
+    let mut annotations = page_writer.annotations();
+    for (dest, rect) in page.links {
+        let mut link = annotations.push();
+        link.subtype(AnnotationType::Link).rect(rect);
+        match dest {
+            Destination::Url(uri) => {
+                link.action()
+                    .action_type(ActionType::Uri)
+                    .uri(Str(uri.as_str().as_bytes()));
+            }
+            Destination::Internal(loc) => {
+                let index = loc.page.get() - 1;
+                if let Some(&height) = ctx.page_heights.get(index) {
+                    link.action()
+                        .action_type(ActionType::GoTo)
+                        .destination_direct()
+                        .page(ctx.page_refs[index])
+                        .xyz(loc.pos.x.to_f32(), height - loc.pos.y.to_f32(), None);
+                }
+            }
+        }
+    }
+
+    annotations.finish();
+    page_writer.finish();
+
+    let data = page.content.finish();
+    let data = deflate(&data);
+    ctx.writer.stream(content_id, &data).filter(Filter::FlateDecode);
+}
+
+/// Data for an exported page.
+pub struct Page {
+    /// The indirect object id of the page.
+    pub id: Ref,
+    /// The page's dimensions.
+    pub size: Size,
+    /// The page's content stream.
+    pub content: Content,
+    /// Links in the PDF coordinate system.
+    pub links: Vec<(Destination, Rect)>,
+}
+
+/// An exporter for the contents of a single PDF page.
+struct PageContext<'a, 'b> {
+    parent: &'a mut PdfContext<'b>,
+    page_ref: Ref,
+    content: Content,
+    state: State,
+    saves: Vec<State>,
+    bottom: f32,
+    links: Vec<(Destination, Rect)>,
+}
+
+/// A simulated graphics state used to deduplicate graphics state changes and
+/// keep track of the current transformation matrix for link annotations.
+#[derive(Debug, Default, Clone)]
+struct State {
+    transform: Transform,
+    font: Option<(FaceId, Length)>,
+    fill: Option<Paint>,
+    fill_space: Option<Name<'static>>,
+    stroke: Option<Stroke>,
+    stroke_space: Option<Name<'static>>,
+}
+
+impl<'a, 'b> PageContext<'a, 'b> {
+    fn save_state(&mut self) {
+        self.saves.push(self.state.clone());
+        self.content.save_state();
+    }
+
+    fn restore_state(&mut self) {
+        self.content.restore_state();
+        self.state = self.saves.pop().expect("missing state save");
+    }
+
+    fn transform(&mut self, transform: Transform) {
+        let Transform { sx, ky, kx, sy, tx, ty } = transform;
+        self.state.transform = self.state.transform.pre_concat(transform);
+        self.content.transform([
+            sx.get() as _,
+            ky.get() as _,
+            kx.get() as _,
+            sy.get() as _,
+            tx.to_f32(),
+            ty.to_f32(),
+        ]);
+    }
+
+    fn set_font(&mut self, face_id: FaceId, size: Length) {
+        if self.state.font != Some((face_id, size)) {
+            self.parent.face_map.insert(face_id);
+            let name = format_eco!("F{}", self.parent.face_map.map(face_id));
+            self.content.set_font(Name(name.as_bytes()), size.to_f32());
+            self.state.font = Some((face_id, size));
+        }
+    }
+
+    fn set_fill(&mut self, fill: Paint) {
+        if self.state.fill != Some(fill) {
+            let f = |c| c as f32 / 255.0;
+            let Paint::Solid(color) = fill;
+            match color {
+                Color::Luma(c) => {
+                    self.set_fill_color_space(D65_GRAY);
+                    self.content.set_fill_gray(f(c.0));
+                }
+                Color::Rgba(c) => {
+                    self.set_fill_color_space(SRGB);
+                    self.content.set_fill_color([f(c.r), f(c.g), f(c.b)]);
+                }
+                Color::Cmyk(c) => {
+                    self.content.set_fill_cmyk(f(c.c), f(c.m), f(c.y), f(c.k));
+                }
+            }
+            self.state.fill = Some(fill);
+        }
+    }
+
+    fn set_fill_color_space(&mut self, space: Name<'static>) {
+        if self.state.fill_space != Some(space) {
+            self.content.set_fill_color_space(ColorSpaceOperand::Named(space));
+            self.state.fill_space = Some(space);
+        }
+    }
+
+    fn set_stroke(&mut self, stroke: Stroke) {
+        if self.state.stroke != Some(stroke) {
+            let f = |c| c as f32 / 255.0;
+            let Paint::Solid(color) = stroke.paint;
+            match color {
+                Color::Luma(c) => {
+                    self.set_stroke_color_space(D65_GRAY);
+                    self.content.set_stroke_gray(f(c.0));
+                }
+                Color::Rgba(c) => {
+                    self.set_stroke_color_space(SRGB);
+                    self.content.set_stroke_color([f(c.r), f(c.g), f(c.b)]);
+                }
+                Color::Cmyk(c) => {
+                    self.content.set_stroke_cmyk(f(c.c), f(c.m), f(c.y), f(c.k));
+                }
+            }
+
+            self.content.set_line_width(stroke.thickness.to_f32());
+            self.state.stroke = Some(stroke);
+        }
+    }
+
+    fn set_stroke_color_space(&mut self, space: Name<'static>) {
+        if self.state.stroke_space != Some(space) {
+            self.content.set_stroke_color_space(ColorSpaceOperand::Named(space));
+            self.state.stroke_space = Some(space);
+        }
+    }
+}
+
+/// Encode a frame into the content stream.
+fn write_frame(ctx: &mut PageContext, frame: &Frame) {
+    if let Some(Role::Heading { level, outlined: true }) = frame.role() {
+        let heading = Heading {
+            position: Point::new(ctx.state.transform.tx, ctx.state.transform.ty),
+            content: frame.text(),
+            page: ctx.page_ref,
+            level: level.get(),
+        };
+
+        if let Some(last) = ctx.parent.heading_tree.last_mut() {
+            if !last.insert(heading.clone(), 1) {
+                ctx.parent.heading_tree.push(HeadingNode::leaf(heading))
+            }
+        } else {
+            ctx.parent.heading_tree.push(HeadingNode::leaf(heading))
+        }
+    }
+
+    for &(pos, ref element) in frame.elements() {
+        let x = pos.x.to_f32();
+        let y = pos.y.to_f32();
+        match *element {
+            Element::Group(ref group) => write_group(ctx, pos, group),
+            Element::Text(ref text) => write_text(ctx, x, y, text),
+            Element::Shape(ref shape) => write_shape(ctx, x, y, shape),
+            Element::Image(id, size) => write_image(ctx, x, y, id, size),
+            Element::Link(ref dest, size) => write_link(ctx, pos, dest, size),
+            Element::Pin(_) => {}
+        }
+    }
+}
+
+/// Encode a group into the content stream.
+fn write_group(ctx: &mut PageContext, pos: Point, group: &Group) {
+    let translation = Transform::translate(pos.x, pos.y);
+
+    ctx.save_state();
+    ctx.transform(translation.pre_concat(group.transform));
+
+    if group.clips {
+        let size = group.frame.size();
+        let w = size.x.to_f32();
+        let h = size.y.to_f32();
+        ctx.content.move_to(0.0, 0.0);
+        ctx.content.line_to(w, 0.0);
+        ctx.content.line_to(w, h);
+        ctx.content.line_to(0.0, h);
+        ctx.content.clip_nonzero();
+        ctx.content.end_path();
+    }
+
+    write_frame(ctx, &group.frame);
+    ctx.restore_state();
+}
+
+/// Encode a text run into the content stream.
+fn write_text(ctx: &mut PageContext, x: f32, y: f32, text: &Text) {
+    *ctx.parent.languages.entry(text.lang).or_insert(0) += text.glyphs.len();
+    ctx.parent
+        .glyph_sets
+        .entry(text.face_id)
+        .or_default()
+        .extend(text.glyphs.iter().map(|g| g.id));
+
+    let face = ctx.parent.fonts.get(text.face_id);
+
+    ctx.set_fill(text.fill);
+    ctx.set_font(text.face_id, text.size);
+    ctx.content.begin_text();
+
+    // Position the text.
+    ctx.content.set_text_matrix([1.0, 0.0, 0.0, -1.0, x, y]);
+
+    let mut positioned = ctx.content.show_positioned();
+    let mut items = positioned.items();
+    let mut adjustment = Em::zero();
+    let mut encoded = vec![];
+
+    // Write the glyphs with kerning adjustments.
+    for glyph in &text.glyphs {
+        adjustment += glyph.x_offset;
+
+        if !adjustment.is_zero() {
+            if !encoded.is_empty() {
+                items.show(Str(&encoded));
+                encoded.clear();
+            }
+
+            items.adjust(-adjustment.to_font_units());
+            adjustment = Em::zero();
+        }
+
+        encoded.push((glyph.id >> 8) as u8);
+        encoded.push((glyph.id & 0xff) as u8);
+
+        if let Some(advance) = face.advance(glyph.id) {
+            adjustment += glyph.x_advance - advance;
+        }
+
+        adjustment -= glyph.x_offset;
+    }
+
+    if !encoded.is_empty() {
+        items.show(Str(&encoded));
+    }
+
+    items.finish();
+    positioned.finish();
+    ctx.content.end_text();
+}
+
+/// Encode a geometrical shape into the content stream.
+fn write_shape(ctx: &mut PageContext, x: f32, y: f32, shape: &Shape) {
+    if shape.fill.is_none() && shape.stroke.is_none() {
+        return;
+    }
+
+    if let Some(fill) = shape.fill {
+        ctx.set_fill(fill);
+    }
+
+    if let Some(stroke) = shape.stroke {
+        ctx.set_stroke(stroke);
+    }
+
+    match shape.geometry {
+        Geometry::Rect(size) => {
+            let w = size.x.to_f32();
+            let h = size.y.to_f32();
+            if w > 0.0 && h > 0.0 {
+                ctx.content.rect(x, y, w, h);
+            }
+        }
+        Geometry::Ellipse(size) => {
+            let approx = geom::Path::ellipse(size);
+            write_path(ctx, x, y, &approx);
+        }
+        Geometry::Line(target) => {
+            let dx = target.x.to_f32();
+            let dy = target.y.to_f32();
+            ctx.content.move_to(x, y);
+            ctx.content.line_to(x + dx, y + dy);
+        }
+        Geometry::Path(ref path) => {
+            write_path(ctx, x, y, path);
+        }
+    }
+
+    match (shape.fill, shape.stroke) {
+        (None, None) => unreachable!(),
+        (Some(_), None) => ctx.content.fill_nonzero(),
+        (None, Some(_)) => ctx.content.stroke(),
+        (Some(_), Some(_)) => ctx.content.fill_nonzero_and_stroke(),
+    };
+}
+
+/// Encode a bezier path into the content stream.
+fn write_path(ctx: &mut PageContext, x: f32, y: f32, path: &geom::Path) {
+    for elem in &path.0 {
+        match elem {
+            geom::PathElement::MoveTo(p) => {
+                ctx.content.move_to(x + p.x.to_f32(), y + p.y.to_f32())
+            }
+            geom::PathElement::LineTo(p) => {
+                ctx.content.line_to(x + p.x.to_f32(), y + p.y.to_f32())
+            }
+            geom::PathElement::CubicTo(p1, p2, p3) => ctx.content.cubic_to(
+                x + p1.x.to_f32(),
+                y + p1.y.to_f32(),
+                x + p2.x.to_f32(),
+                y + p2.y.to_f32(),
+                x + p3.x.to_f32(),
+                y + p3.y.to_f32(),
+            ),
+            geom::PathElement::ClosePath => ctx.content.close_path(),
+        };
+    }
+}
+
+/// Encode a vector or raster image into the content stream.
+fn write_image(ctx: &mut PageContext, x: f32, y: f32, id: ImageId, size: Size) {
+    ctx.parent.image_map.insert(id);
+    let name = format_eco!("Im{}", ctx.parent.image_map.map(id));
+    let w = size.x.to_f32();
+    let h = size.y.to_f32();
+    ctx.content.save_state();
+    ctx.content.transform([w, 0.0, 0.0, -h, x, y + h]);
+    ctx.content.x_object(Name(name.as_bytes()));
+    ctx.content.restore_state();
+}
+
+/// Save a link for later writing in the annotations dictionary.
+fn write_link(ctx: &mut PageContext, pos: Point, dest: &Destination, size: Size) {
+    let mut min_x = Length::inf();
+    let mut min_y = Length::inf();
+    let mut max_x = -Length::inf();
+    let mut max_y = -Length::inf();
+
+    // Compute the bounding box of the transformed link.
+    for point in [
+        pos,
+        pos + Point::with_x(size.x),
+        pos + Point::with_y(size.y),
+        pos + size.to_point(),
+    ] {
+        let t = point.transform(ctx.state.transform);
+        min_x.set_min(t.x);
+        min_y.set_min(t.y);
+        max_x.set_max(t.x);
+        max_y.set_max(t.y);
+    }
+
+    let x1 = min_x.to_f32();
+    let x2 = max_x.to_f32();
+    let y1 = max_y.to_f32();
+    let y2 = min_y.to_f32();
+    let rect = Rect::new(x1, y1, x2, y2);
+
+    ctx.links.push((dest.clone(), rect));
+}