1use crate::{AssetSource, DevicePixels, IsZero, Result, SharedString, Size};
2use resvg::tiny_skia::Pixmap;
3use std::{
4 hash::Hash,
5 sync::{Arc, LazyLock},
6};
7
8/// When rendering SVGs, we render them at twice the size to get a higher-quality result.
9pub const SMOOTH_SVG_SCALE_FACTOR: f32 = 2.;
10
11#[derive(Clone, PartialEq, Hash, Eq)]
12pub(crate) struct RenderSvgParams {
13 pub(crate) path: SharedString,
14 pub(crate) size: Size<DevicePixels>,
15}
16
17#[derive(Clone)]
18pub struct SvgRenderer {
19 asset_source: Arc<dyn AssetSource>,
20 usvg_options: Arc<usvg::Options<'static>>,
21}
22
23pub enum SvgSize {
24 Size(Size<DevicePixels>),
25 ScaleFactor(f32),
26}
27
28impl SvgRenderer {
29 pub fn new(asset_source: Arc<dyn AssetSource>) -> Self {
30 static FONT_DB: LazyLock<Arc<usvg::fontdb::Database>> = LazyLock::new(|| {
31 let mut db = usvg::fontdb::Database::new();
32 db.load_system_fonts();
33 Arc::new(db)
34 });
35 let default_font_resolver = usvg::FontResolver::default_font_selector();
36 let font_resolver = Box::new(
37 move |font: &usvg::Font, db: &mut Arc<usvg::fontdb::Database>| {
38 if db.is_empty() {
39 *db = FONT_DB.clone();
40 }
41 default_font_resolver(font, db)
42 },
43 );
44 let options = usvg::Options {
45 font_resolver: usvg::FontResolver {
46 select_font: font_resolver,
47 select_fallback: usvg::FontResolver::default_fallback_selector(),
48 },
49 ..Default::default()
50 };
51 Self {
52 asset_source,
53 usvg_options: Arc::new(options),
54 }
55 }
56
57 pub(crate) fn render(
58 &self,
59 params: &RenderSvgParams,
60 ) -> Result<Option<(Size<DevicePixels>, Vec<u8>)>> {
61 anyhow::ensure!(!params.size.is_zero(), "can't render at a zero size");
62
63 // Load the tree.
64 let Some(bytes) = self.asset_source.load(¶ms.path)? else {
65 return Ok(None);
66 };
67
68 let pixmap = self.render_pixmap(&bytes, SvgSize::Size(params.size))?;
69
70 // Convert the pixmap's pixels into an alpha mask.
71 let size = Size::new(
72 DevicePixels(pixmap.width() as i32),
73 DevicePixels(pixmap.height() as i32),
74 );
75 let alpha_mask = pixmap
76 .pixels()
77 .iter()
78 .map(|p| p.alpha())
79 .collect::<Vec<_>>();
80 Ok(Some((size, alpha_mask)))
81 }
82
83 pub fn render_pixmap(&self, bytes: &[u8], size: SvgSize) -> Result<Pixmap, usvg::Error> {
84 let tree = usvg::Tree::from_data(bytes, &self.usvg_options)?;
85 let svg_size = tree.size();
86 let scale = match size {
87 SvgSize::Size(size) => size.width.0 as f32 / svg_size.width(),
88 SvgSize::ScaleFactor(scale) => scale,
89 };
90
91 // Render the SVG to a pixmap with the specified width and height.
92 let mut pixmap = resvg::tiny_skia::Pixmap::new(
93 (svg_size.width() * scale) as u32,
94 (svg_size.height() * scale) as u32,
95 )
96 .ok_or(usvg::Error::InvalidSize)?;
97
98 let transform = resvg::tiny_skia::Transform::from_scale(scale, scale);
99
100 resvg::render(&tree, transform, &mut pixmap.as_mut());
101
102 Ok(pixmap)
103 }
104}