Refactored loading and cache architecture

2 files changed, 591 insertions, 0 deletions

diff --git a/src/export/mod.rs b/src/export/mod.rs
new file mode 100644
index 00000000..5ed0abf9
--- /dev/null
+++ b/src/export/mod.rs
@@ -0,0 +1,5 @@
+//! Exporting into external formats.
+
+mod pdf;
+
+pub use pdf::*;
diff --git a/src/export/pdf.rs b/src/export/pdf.rs
new file mode 100644
index 00000000..0ca4df38
--- /dev/null
+++ b/src/export/pdf.rs
@@ -0,0 +1,586 @@
+//! Exporting into PDF documents.
+
+use std::cmp::Eq;
+use std::collections::HashMap;
+use std::hash::Hash;
+
+use image::{DynamicImage, GenericImageView, ImageFormat, ImageResult, Rgba};
+use miniz_oxide::deflate;
+use pdf_writer::{
+    CidFontType, ColorSpace, Content, Filter, FontFlags, Name, PdfWriter, Rect, Ref, Str,
+    SystemInfo, UnicodeCmap,
+};
+use ttf_parser::{name_id, GlyphId};
+
+use crate::cache::Cache;
+use crate::color::Color;
+use crate::font::{Em, FaceId, VerticalFontMetric};
+use crate::geom::{self, Length, Size};
+use crate::image::{Image, ImageId};
+use crate::layout::{Element, Fill, Frame, Shape};
+
+/// Export a collection of frames into a PDF document.
+///
+/// This creates one page per frame. In addition to the frames, you need to pass
+/// in the cache used during compilation such that things like fonts and images
+/// can be included in the PDF.
+///
+/// Returns the raw bytes making up the PDF document.
+pub fn pdf(cache: &Cache, frames: &[Frame]) -> Vec<u8> {
+    PdfExporter::new(cache, frames).write()
+}
+
+struct PdfExporter<'a> {
+    writer: PdfWriter,
+    frames: &'a [Frame],
+    cache: &'a Cache,
+    refs: Refs,
+    fonts: Remapper<FaceId>,
+    images: Remapper<ImageId>,
+}
+
+impl<'a> PdfExporter<'a> {
+    fn new(cache: &'a Cache, frames: &'a [Frame]) -> Self {
+        let mut writer = PdfWriter::new(1, 7);
+        writer.set_indent(2);
+
+        let mut fonts = Remapper::new();
+        let mut images = Remapper::new();
+        let mut alpha_masks = 0;
+
+        for frame in frames {
+            for (_, element) in &frame.elements {
+                match *element {
+                    Element::Text(ref shaped) => fonts.insert(shaped.face_id),
+                    Element::Geometry(_, _) => {}
+                    Element::Image(id, _) => {
+                        let img = cache.image.get(id);
+                        if img.buf.color().has_alpha() {
+                            alpha_masks += 1;
+                        }
+                        images.insert(id);
+                    }
+                }
+            }
+        }
+
+        let refs = Refs::new(frames.len(), fonts.len(), images.len(), alpha_masks);
+
+        Self {
+            writer,
+            frames,
+            cache,
+            refs,
+            fonts,
+            images,
+        }
+    }
+
+    fn write(mut self) -> Vec<u8> {
+        self.write_structure();
+        self.write_pages();
+        self.write_fonts();
+        self.write_images();
+        self.writer.finish(self.refs.catalog)
+    }
+
+    fn write_structure(&mut self) {
+        // The document catalog.
+        self.writer.catalog(self.refs.catalog).pages(self.refs.page_tree);
+
+        // The root page tree.
+        let mut pages = self.writer.pages(self.refs.page_tree);
+        pages.kids(self.refs.pages());
+
+        let mut resources = pages.resources();
+        let mut fonts = resources.fonts();
+        for (refs, f) in self.refs.fonts().zip(self.fonts.pdf_indices()) {
+            let name = format!("F{}", f);
+            fonts.pair(Name(name.as_bytes()), refs.type0_font);
+        }
+
+        drop(fonts);
+
+        let mut images = resources.x_objects();
+        for (id, im) in self.refs.images().zip(self.images.pdf_indices()) {
+            let name = format!("Im{}", im);
+            images.pair(Name(name.as_bytes()), id);
+        }
+
+        drop(images);
+        drop(resources);
+        drop(pages);
+
+        // The page objects (non-root nodes in the page tree).
+        for ((page_id, content_id), page) in
+            self.refs.pages().zip(self.refs.contents()).zip(self.frames)
+        {
+            self.writer
+                .page(page_id)
+                .parent(self.refs.page_tree)
+                .media_box(Rect::new(
+                    0.0,
+                    0.0,
+                    page.size.width.to_pt() as f32,
+                    page.size.height.to_pt() as f32,
+                ))
+                .contents(content_id);
+        }
+    }
+
+    fn write_pages(&mut self) {
+        for (id, page) in self.refs.contents().zip(self.frames) {
+            self.write_page(id, &page);
+        }
+    }
+
+    fn write_page(&mut self, id: Ref, page: &'a Frame) {
+        let mut content = Content::new();
+
+        // We only write font switching actions when the used face changes. To
+        // do that, we need to remember the active face.
+        let mut face = FaceId::MAX;
+        let mut size = Length::zero();
+        let mut fill: Option<Fill> = None;
+
+        for (pos, element) in &page.elements {
+            let x = pos.x.to_pt() as f32;
+            let y = (page.size.height - pos.y).to_pt() as f32;
+
+            match *element {
+                Element::Text(ref shaped) => {
+                    if fill != Some(shaped.fill) {
+                        write_fill(&mut content, shaped.fill);
+                        fill = Some(shaped.fill);
+                    }
+
+                    let mut text = content.text();
+
+                    // Then, also check if we need to issue a font switching
+                    // action.
+                    if shaped.face_id != face || shaped.size != size {
+                        face = shaped.face_id;
+                        size = shaped.size;
+
+                        let name = format!("F{}", self.fonts.map(shaped.face_id));
+                        text.font(Name(name.as_bytes()), size.to_pt() as f32);
+                    }
+
+                    // TODO: Respect individual glyph offsets.
+                    text.matrix(1.0, 0.0, 0.0, 1.0, x, y);
+                    text.show(Str(&shaped.encode_glyphs_be()));
+                }
+
+                Element::Geometry(ref shape, fill) => {
+                    content.save_state();
+                    write_fill(&mut content, fill);
+
+                    match *shape {
+                        Shape::Rect(Size { width, height }) => {
+                            let w = width.to_pt() as f32;
+                            let h = height.to_pt() as f32;
+                            if w > 0.0 && h > 0.0 {
+                                content.rect(x, y - h, w, h, false, true);
+                            }
+                        }
+
+                        Shape::Ellipse(size) => {
+                            let path = geom::Path::ellipse(size);
+                            write_path(&mut content, x, y, &path, false, true);
+                        }
+
+                        Shape::Path(ref path) => {
+                            write_path(&mut content, x, y, path, false, true)
+                        }
+                    }
+
+                    content.restore_state();
+                }
+
+                Element::Image(id, Size { width, height }) => {
+                    let name = format!("Im{}", self.images.map(id));
+                    let w = width.to_pt() as f32;
+                    let h = height.to_pt() as f32;
+
+                    content.save_state();
+                    content.matrix(w, 0.0, 0.0, h, x, y - h);
+                    content.x_object(Name(name.as_bytes()));
+                    content.restore_state();
+                }
+            }
+        }
+
+        self.writer.stream(id, &content.finish());
+    }
+
+    fn write_fonts(&mut self) {
+        for (refs, face_id) in self.refs.fonts().zip(self.fonts.layout_indices()) {
+            let face = self.cache.font.get(face_id);
+            let ttf = face.ttf();
+
+            let name = ttf
+                .names()
+                .find(|entry| {
+                    entry.name_id() == name_id::POST_SCRIPT_NAME && entry.is_unicode()
+                })
+                .and_then(|entry| entry.to_string())
+                .unwrap_or_else(|| "unknown".to_string());
+
+            let base_font = format!("ABCDEF+{}", name);
+            let base_font = Name(base_font.as_bytes());
+            let cmap_name = Name(b"Custom");
+            let system_info = SystemInfo {
+                registry: Str(b"Adobe"),
+                ordering: Str(b"Identity"),
+                supplement: 0,
+            };
+
+            let mut flags = FontFlags::empty();
+            flags.set(FontFlags::SERIF, name.contains("Serif"));
+            flags.set(FontFlags::FIXED_PITCH, ttf.is_monospaced());
+            flags.set(FontFlags::ITALIC, ttf.is_italic());
+            flags.insert(FontFlags::SYMBOLIC);
+            flags.insert(FontFlags::SMALL_CAP);
+
+            let global_bbox = ttf.global_bounding_box();
+            let bbox = Rect::new(
+                face.to_em(global_bbox.x_min).to_pdf(),
+                face.to_em(global_bbox.y_min).to_pdf(),
+                face.to_em(global_bbox.x_max).to_pdf(),
+                face.to_em(global_bbox.y_max).to_pdf(),
+            );
+
+            let italic_angle = ttf.italic_angle().unwrap_or(0.0);
+            let ascender = face.vertical_metric(VerticalFontMetric::Ascender).to_pdf();
+            let descender = face.vertical_metric(VerticalFontMetric::Descender).to_pdf();
+            let cap_height = face.vertical_metric(VerticalFontMetric::CapHeight).to_pdf();
+            let stem_v = 10.0 + 0.244 * (f32::from(ttf.weight().to_number()) - 50.0);
+
+            // Write the base font object referencing the CID font.
+            self.writer
+                .type0_font(refs.type0_font)
+                .base_font(base_font)
+                .encoding_predefined(Name(b"Identity-H"))
+                .descendant_font(refs.cid_font)
+                .to_unicode(refs.cmap);
+
+            // Write the CID font referencing the font descriptor.
+            self.writer
+                .cid_font(refs.cid_font, CidFontType::Type2)
+                .base_font(base_font)
+                .system_info(system_info)
+                .font_descriptor(refs.font_descriptor)
+                .widths()
+                .individual(0, {
+                    let num_glyphs = ttf.number_of_glyphs();
+                    (0 .. num_glyphs).map(|g| {
+                        let x = ttf.glyph_hor_advance(GlyphId(g)).unwrap_or(0);
+                        face.to_em(x).to_pdf()
+                    })
+                });
+
+            // Write the font descriptor (contains metrics about the font).
+            self.writer
+                .font_descriptor(refs.font_descriptor)
+                .font_name(base_font)
+                .font_flags(flags)
+                .font_bbox(bbox)
+                .italic_angle(italic_angle)
+                .ascent(ascender)
+                .descent(descender)
+                .cap_height(cap_height)
+                .stem_v(stem_v)
+                .font_file2(refs.data);
+
+            // Write the to-unicode character map, which maps glyph ids back to
+            // unicode codepoints to enable copying out of the PDF.
+            self.writer
+                .cmap(refs.cmap, &{
+                    let mut cmap = UnicodeCmap::new(cmap_name, system_info);
+                    for subtable in ttf.character_mapping_subtables() {
+                        subtable.codepoints(|n| {
+                            if let Some(c) = std::char::from_u32(n) {
+                                if let Some(g) = ttf.glyph_index(c) {
+                                    cmap.pair(g.0, c);
+                                }
+                            }
+                        })
+                    }
+                    cmap.finish()
+                })
+                .name(cmap_name)
+                .system_info(system_info);
+
+            // Write the face's bytes.
+            self.writer.stream(refs.data, face.buffer());
+        }
+    }
+
+    fn write_images(&mut self) {
+        let mut masks_seen = 0;
+
+        for (id, image_id) in self.refs.images().zip(self.images.layout_indices()) {
+            let img = self.cache.image.get(image_id);
+            let (width, height) = img.buf.dimensions();
+
+            // Add the primary image.
+            if let Ok((data, filter, color_space)) = encode_image(img) {
+                let mut image = self.writer.image(id, &data);
+                image.filter(filter);
+                image.width(width as i32);
+                image.height(height as i32);
+                image.color_space(color_space);
+                image.bits_per_component(8);
+
+                // Add a second gray-scale image containing the alpha values if
+                // this image has an alpha channel.
+                if img.buf.color().has_alpha() {
+                    let (alpha_data, alpha_filter) = encode_alpha(img);
+                    let mask_id = self.refs.alpha_mask(masks_seen);
+                    image.s_mask(mask_id);
+                    drop(image);
+
+                    let mut mask = self.writer.image(mask_id, &alpha_data);
+                    mask.filter(alpha_filter);
+                    mask.width(width as i32);
+                    mask.height(height as i32);
+                    mask.color_space(ColorSpace::DeviceGray);
+                    mask.bits_per_component(8);
+
+                    masks_seen += 1;
+                }
+            } else {
+                // TODO: Warn that image could not be encoded.
+                self.writer
+                    .image(id, &[])
+                    .width(0)
+                    .height(0)
+                    .color_space(ColorSpace::DeviceGray)
+                    .bits_per_component(1);
+            }
+        }
+    }
+}
+
+/// Write a fill change into a content stream.
+fn write_fill(content: &mut Content, fill: Fill) {
+    match fill {
+        Fill::Color(Color::Rgba(c)) => {
+            content.fill_rgb(c.r as f32 / 255.0, c.g as f32 / 255.0, c.b as f32 / 255.0);
+        }
+    }
+}
+
+/// Write a path into a content stream.
+fn write_path(
+    content: &mut Content,
+    x: f32,
+    y: f32,
+    path: &geom::Path,
+    stroke: bool,
+    fill: bool,
+) {
+    let f = |length: Length| length.to_pt() as f32;
+    let mut builder = content.path(stroke, fill);
+    for elem in &path.0 {
+        match elem {
+            geom::PathElement::MoveTo(p) => builder.move_to(x + f(p.x), y + f(p.y)),
+            geom::PathElement::LineTo(p) => builder.line_to(x + f(p.x), y + f(p.y)),
+            geom::PathElement::CubicTo(p1, p2, p3) => builder.cubic_to(
+                x + f(p1.x),
+                y + f(p1.y),
+                x + f(p2.x),
+                y + f(p2.y),
+                x + f(p3.x),
+                y + f(p3.y),
+            ),
+            geom::PathElement::ClosePath => builder.close_path(),
+        };
+    }
+}
+
+/// The compression level for the deflating.
+const DEFLATE_LEVEL: u8 = 6;
+
+/// Encode an image with a suitable filter.
+///
+/// Skips the alpha channel as that's encoded separately.
+fn encode_image(img: &Image) -> ImageResult<(Vec<u8>, Filter, ColorSpace)> {
+    let mut data = vec![];
+    let (filter, space) = match (img.format, &img.buf) {
+        // 8-bit gray JPEG.
+        (ImageFormat::Jpeg, DynamicImage::ImageLuma8(_)) => {
+            img.buf.write_to(&mut data, img.format)?;
+            (Filter::DctDecode, ColorSpace::DeviceGray)
+        }
+
+        // 8-bit Rgb JPEG (Cmyk JPEGs get converted to Rgb earlier).
+        (ImageFormat::Jpeg, DynamicImage::ImageRgb8(_)) => {
+            img.buf.write_to(&mut data, img.format)?;
+            (Filter::DctDecode, ColorSpace::DeviceRgb)
+        }
+
+        // TODO: Encode flate streams with PNG-predictor?
+
+        // 8-bit gray PNG.
+        (ImageFormat::Png, DynamicImage::ImageLuma8(luma)) => {
+            data = deflate::compress_to_vec_zlib(&luma.as_raw(), DEFLATE_LEVEL);
+            (Filter::FlateDecode, ColorSpace::DeviceGray)
+        }
+
+        // Anything else (including Rgb(a) PNGs).
+        (_, buf) => {
+            let (width, height) = buf.dimensions();
+            let mut pixels = Vec::with_capacity(3 * width as usize * height as usize);
+            for (_, _, Rgba([r, g, b, _])) in buf.pixels() {
+                pixels.push(r);
+                pixels.push(g);
+                pixels.push(b);
+            }
+
+            data = deflate::compress_to_vec_zlib(&pixels, DEFLATE_LEVEL);
+            (Filter::FlateDecode, ColorSpace::DeviceRgb)
+        }
+    };
+    Ok((data, filter, space))
+}
+
+/// Encode an image's alpha channel if present.
+fn encode_alpha(img: &Image) -> (Vec<u8>, Filter) {
+    let pixels: Vec<_> = img.buf.pixels().map(|(_, _, Rgba([_, _, _, a]))| a).collect();
+    let data = deflate::compress_to_vec_zlib(&pixels, DEFLATE_LEVEL);
+    (data, Filter::FlateDecode)
+}
+
+/// We need to know exactly which indirect reference id will be used for which
+/// objects up-front to correctly declare the document catalogue, page tree and
+/// so on. These offsets are computed in the beginning and stored here.
+struct Refs {
+    catalog: Ref,
+    page_tree: Ref,
+    pages_start: i32,
+    contents_start: i32,
+    fonts_start: i32,
+    images_start: i32,
+    alpha_masks_start: i32,
+    end: i32,
+}
+
+struct FontRefs {
+    type0_font: Ref,
+    cid_font: Ref,
+    font_descriptor: Ref,
+    cmap: Ref,
+    data: Ref,
+}
+
+impl Refs {
+    const OBJECTS_PER_FONT: usize = 5;
+
+    fn new(frames: usize, fonts: usize, images: usize, alpha_masks: usize) -> Self {
+        let catalog = 1;
+        let page_tree = catalog + 1;
+        let pages_start = page_tree + 1;
+        let contents_start = pages_start + frames as i32;
+        let fonts_start = contents_start + frames as i32;
+        let images_start = fonts_start + (Self::OBJECTS_PER_FONT * fonts) as i32;
+        let alpha_masks_start = images_start + images as i32;
+        let end = alpha_masks_start + alpha_masks as i32;
+
+        Self {
+            catalog: Ref::new(catalog),
+            page_tree: Ref::new(page_tree),
+            pages_start,
+            contents_start,
+            fonts_start,
+            images_start,
+            alpha_masks_start,
+            end,
+        }
+    }
+
+    fn pages(&self) -> impl Iterator<Item = Ref> {
+        (self.pages_start .. self.contents_start).map(Ref::new)
+    }
+
+    fn contents(&self) -> impl Iterator<Item = Ref> {
+        (self.contents_start .. self.images_start).map(Ref::new)
+    }
+
+    fn fonts(&self) -> impl Iterator<Item = FontRefs> {
+        (self.fonts_start .. self.images_start)
+            .step_by(Self::OBJECTS_PER_FONT)
+            .map(|id| FontRefs {
+                type0_font: Ref::new(id),
+                cid_font: Ref::new(id + 1),
+                font_descriptor: Ref::new(id + 2),
+                cmap: Ref::new(id + 3),
+                data: Ref::new(id + 4),
+            })
+    }
+
+    fn images(&self) -> impl Iterator<Item = Ref> {
+        (self.images_start .. self.end).map(Ref::new)
+    }
+
+    fn alpha_mask(&self, i: usize) -> Ref {
+        Ref::new(self.alpha_masks_start + i as i32)
+    }
+}
+
+/// Used to assign new, consecutive PDF-internal indices to things.
+struct Remapper<Index> {
+    /// Forwards from the old indices to the new pdf indices.
+    to_pdf: HashMap<Index, usize>,
+    /// Backwards from the pdf indices to the old indices.
+    to_layout: Vec<Index>,
+}
+
+impl<Index> Remapper<Index>
+where
+    Index: Copy + Eq + Hash,
+{
+    fn new() -> Self {
+        Self {
+            to_pdf: HashMap::new(),
+            to_layout: vec![],
+        }
+    }
+
+    fn len(&self) -> usize {
+        self.to_layout.len()
+    }
+
+    fn insert(&mut self, index: Index) {
+        let to_layout = &mut self.to_layout;
+        self.to_pdf.entry(index).or_insert_with(|| {
+            let pdf_index = to_layout.len();
+            to_layout.push(index);
+            pdf_index
+        });
+    }
+
+    fn map(&self, index: Index) -> usize {
+        self.to_pdf[&index]
+    }
+
+    fn pdf_indices(&self) -> impl Iterator<Item = usize> {
+        0 .. self.to_pdf.len()
+    }
+
+    fn layout_indices(&self) -> impl Iterator<Item = Index> + '_ {
+        self.to_layout.iter().copied()
+    }
+}
+
+/// Additional methods for [`Em`].
+trait EmExt {
+    /// Convert an em length to a number of PDF font units.
+    fn to_pdf(self) -> f32;
+}
+
+impl EmExt for Em {
+    fn to_pdf(self) -> f32 {
+        1000.0 * self.get() as f32
+    }
+}