Move image/svg handling into iced_graphics

The `TextureStore` trait is implemented by the atlas, and can also be
implemented in the glow renderer or in a software renderer.

The API here may be improved in the future, but API stability is
presumably not a huge issue since these types will only be used by
renderer backends.

graphics/src/image/vector.rs

@@ -0,0 +1,183 @@
+//! Vector image loading and caching
+
+use iced_native::svg;
+
+use std::collections::{HashMap, HashSet};
+use std::fs;
+
+use super::TextureStore;
+
+/// Entry in cache corresponding to an svg handle
+pub enum Svg {
+    /// Parsed svg
+    Loaded(usvg::Tree),
+    /// Svg not found or failed to parse
+    NotFound,
+}
+
+impl Svg {
+    /// Viewport width and height
+    pub fn viewport_dimensions(&self) -> (u32, u32) {
+        match self {
+            Svg::Loaded(tree) => {
+                let size = tree.svg_node().size;
+
+                (size.width() as u32, size.height() as u32)
+            }
+            Svg::NotFound => (1, 1),
+        }
+    }
+}
+
+/// Caches svg vector and raster data
+#[derive(Debug)]
+pub struct Cache<T: TextureStore> {
+    svgs: HashMap<u64, Svg>,
+    rasterized: HashMap<(u64, u32, u32), T::Entry>,
+    svg_hits: HashSet<u64>,
+    rasterized_hits: HashSet<(u64, u32, u32)>,
+}
+
+impl<T: TextureStore> Cache<T> {
+    /// Load svg
+    pub fn load(&mut self, handle: &svg::Handle) -> &Svg {
+        if self.svgs.contains_key(&handle.id()) {
+            return self.svgs.get(&handle.id()).unwrap();
+        }
+
+        let svg = match handle.data() {
+            svg::Data::Path(path) => {
+                let tree = fs::read_to_string(path).ok().and_then(|contents| {
+                    usvg::Tree::from_str(
+                        &contents,
+                        &usvg::Options::default().to_ref(),
+                    )
+                    .ok()
+                });
+
+                tree.map(Svg::Loaded).unwrap_or(Svg::NotFound)
+            }
+            svg::Data::Bytes(bytes) => {
+                match usvg::Tree::from_data(
+                    bytes,
+                    &usvg::Options::default().to_ref(),
+                ) {
+                    Ok(tree) => Svg::Loaded(tree),
+                    Err(_) => Svg::NotFound,
+                }
+            }
+        };
+
+        let _ = self.svgs.insert(handle.id(), svg);
+        self.svgs.get(&handle.id()).unwrap()
+    }
+
+    /// Load svg and upload raster data
+    pub fn upload(
+        &mut self,
+        handle: &svg::Handle,
+        [width, height]: [f32; 2],
+        scale: f32,
+        state: &mut T::State<'_>,
+        texture_store: &mut T,
+    ) -> Option<&T::Entry> {
+        let id = handle.id();
+
+        let (width, height) = (
+            (scale * width).ceil() as u32,
+            (scale * height).ceil() as u32,
+        );
+
+        // TODO: Optimize!
+        // We currently rerasterize the SVG when its size changes. This is slow
+        // as heck. A GPU rasterizer like `pathfinder` may perform better.
+        // It would be cool to be able to smooth resize the `svg` example.
+        if self.rasterized.contains_key(&(id, width, height)) {
+            let _ = self.svg_hits.insert(id);
+            let _ = self.rasterized_hits.insert((id, width, height));
+
+            return self.rasterized.get(&(id, width, height));
+        }
+
+        match self.load(handle) {
+            Svg::Loaded(tree) => {
+                if width == 0 || height == 0 {
+                    return None;
+                }
+
+                // TODO: Optimize!
+                // We currently rerasterize the SVG when its size changes. This is slow
+                // as heck. A GPU rasterizer like `pathfinder` may perform better.
+                // It would be cool to be able to smooth resize the `svg` example.
+                let mut img = tiny_skia::Pixmap::new(width, height)?;
+
+                resvg::render(
+                    tree,
+                    if width > height {
+                        usvg::FitTo::Width(width)
+                    } else {
+                        usvg::FitTo::Height(height)
+                    },
+                    img.as_mut(),
+                )?;
+
+                let mut rgba = img.take();
+                rgba.chunks_exact_mut(4).for_each(|rgba| rgba.swap(0, 2));
+
+                let allocation = texture_store.upload(
+                    width,
+                    height,
+                    bytemuck::cast_slice(rgba.as_slice()),
+                    state,
+                )?;
+                log::debug!("allocating {} {}x{}", id, width, height);
+
+                let _ = self.svg_hits.insert(id);
+                let _ = self.rasterized_hits.insert((id, width, height));
+                let _ = self.rasterized.insert((id, width, height), allocation);
+
+                self.rasterized.get(&(id, width, height))
+            }
+            Svg::NotFound => None,
+        }
+    }
+
+    /// Load svg and upload raster data
+    pub fn trim(&mut self, texture_store: &mut T, state: &mut T::State<'_>) {
+        let svg_hits = &self.svg_hits;
+        let rasterized_hits = &self.rasterized_hits;
+
+        self.svgs.retain(|k, _| svg_hits.contains(k));
+        self.rasterized.retain(|k, entry| {
+            let retain = rasterized_hits.contains(k);
+
+            if !retain {
+                texture_store.remove(entry, state);
+            }
+
+            retain
+        });
+        self.svg_hits.clear();
+        self.rasterized_hits.clear();
+    }
+}
+
+impl<T: TextureStore> Default for Cache<T> {
+    fn default() -> Self {
+        Self {
+            svgs: HashMap::new(),
+            rasterized: HashMap::new(),
+            svg_hits: HashSet::new(),
+            rasterized_hits: HashSet::new(),
+        }
+    }
+}
+
+impl std::fmt::Debug for Svg {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Svg::Loaded(_) => write!(f, "Svg::Loaded"),
+            Svg::NotFound => write!(f, "Svg::NotFound"),
+        }
+    }
+}