Switch PDF backend to `krilla` (#5420)

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

1 files changed, 135 insertions, 0 deletions

diff --git a/crates/typst-pdf/src/text.rs b/crates/typst-pdf/src/text.rs
new file mode 100644
index 00000000..8d532e08
--- /dev/null
+++ b/crates/typst-pdf/src/text.rs
@@ -0,0 +1,135 @@
+use std::ops::Range;
+use std::sync::Arc;
+
+use bytemuck::TransparentWrapper;
+use krilla::surface::{Location, Surface};
+use krilla::text::GlyphId;
+use typst_library::diag::{bail, SourceResult};
+use typst_library::layout::Size;
+use typst_library::text::{Font, Glyph, TextItem};
+use typst_library::visualize::FillRule;
+use typst_syntax::Span;
+
+use crate::convert::{FrameContext, GlobalContext};
+use crate::paint;
+use crate::util::{display_font, AbsExt, TransformExt};
+
+#[typst_macros::time(name = "handle text")]
+pub(crate) fn handle_text(
+    fc: &mut FrameContext,
+    t: &TextItem,
+    surface: &mut Surface,
+    gc: &mut GlobalContext,
+) -> SourceResult<()> {
+    *gc.languages.entry(t.lang).or_insert(0) += t.glyphs.len();
+
+    let font = convert_font(gc, t.font.clone())?;
+    let fill = paint::convert_fill(
+        gc,
+        &t.fill,
+        FillRule::NonZero,
+        true,
+        surface,
+        fc.state(),
+        Size::zero(),
+    )?;
+    let stroke =
+        if let Some(stroke) = t.stroke.as_ref().map(|s| {
+            paint::convert_stroke(gc, s, true, surface, fc.state(), Size::zero())
+        }) {
+            Some(stroke?)
+        } else {
+            None
+        };
+    let text = t.text.as_str();
+    let size = t.size;
+    let glyphs: &[PdfGlyph] = TransparentWrapper::wrap_slice(t.glyphs.as_slice());
+
+    surface.push_transform(&fc.state().transform().to_krilla());
+    surface.set_fill(Some(fill));
+    surface.set_stroke(stroke);
+    surface.draw_glyphs(
+        krilla::geom::Point::from_xy(0.0, 0.0),
+        glyphs,
+        font.clone(),
+        text,
+        size.to_f32(),
+        false,
+    );
+
+    surface.pop();
+
+    Ok(())
+}
+
+fn convert_font(
+    gc: &mut GlobalContext,
+    typst_font: Font,
+) -> SourceResult<krilla::text::Font> {
+    if let Some(font) = gc.fonts_forward.get(&typst_font) {
+        Ok(font.clone())
+    } else {
+        let font = build_font(typst_font.clone())?;
+
+        gc.fonts_forward.insert(typst_font.clone(), font.clone());
+        gc.fonts_backward.insert(font.clone(), typst_font.clone());
+
+        Ok(font)
+    }
+}
+
+#[comemo::memoize]
+fn build_font(typst_font: Font) -> SourceResult<krilla::text::Font> {
+    let font_data: Arc<dyn AsRef<[u8]> + Send + Sync> =
+        Arc::new(typst_font.data().clone());
+
+    match krilla::text::Font::new(font_data.into(), typst_font.index()) {
+        None => {
+            let font_str = display_font(&typst_font);
+            bail!(Span::detached(), "failed to process font {font_str}");
+        }
+        Some(f) => Ok(f),
+    }
+}
+
+#[derive(TransparentWrapper, Debug)]
+#[repr(transparent)]
+struct PdfGlyph(Glyph);
+
+impl krilla::text::Glyph for PdfGlyph {
+    #[inline(always)]
+    fn glyph_id(&self) -> GlyphId {
+        GlyphId::new(self.0.id as u32)
+    }
+
+    #[inline(always)]
+    fn text_range(&self) -> Range<usize> {
+        self.0.range.start as usize..self.0.range.end as usize
+    }
+
+    #[inline(always)]
+    fn x_advance(&self, size: f32) -> f32 {
+        // Don't use `Em::at`, because it contains an expensive check whether the result is finite.
+        self.0.x_advance.get() as f32 * size
+    }
+
+    #[inline(always)]
+    fn x_offset(&self, size: f32) -> f32 {
+        // Don't use `Em::at`, because it contains an expensive check whether the result is finite.
+        self.0.x_offset.get() as f32 * size
+    }
+
+    #[inline(always)]
+    fn y_offset(&self, _: f32) -> f32 {
+        0.0
+    }
+
+    #[inline(always)]
+    fn y_advance(&self, _: f32) -> f32 {
+        0.0
+    }
+
+    fn location(&self) -> Option<Location> {
+        Some(self.0.span.0.into_raw().get())
+    }
+}