Draft text support in `iced_tiny_skia`

4 files changed, 523 insertions, 112 deletions

diff --git a/tiny_skia/Cargo.toml b/tiny_skia/Cargo.toml
index 70b1f5e7..55f7f5b7 100644
--- a/tiny_skia/Cargo.toml
+++ b/tiny_skia/Cargo.toml
@@ -12,6 +12,8 @@ raw-window-handle = "0.5"
 softbuffer = "0.2"
 tiny-skia = "0.8"
 bytemuck = "1"
+rustc-hash = "1.1"
+ouroboros = "0.15"
 
 [dependencies.iced_native]
 version = "0.9"
@@ -20,3 +22,16 @@ path = "../native"
 [dependencies.iced_graphics]
 version = "0.7"
 path = "../graphics"
+
+[dependencies.cosmic-text]
+features = ["std", "swash"]
+git = "https://github.com/hecrj/cosmic-text"
+rev = "dc83efbf00a2efb4118403538e8a47bfd69c3e5e"
+
+[dependencies.twox-hash]
+version = "1.6"
+default-features = false
+
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies.twox-hash]
+version = "1.6.1"
+features = ["std"]
diff --git a/tiny_skia/src/backend.rs b/tiny_skia/src/backend.rs
index 9eea1a32..5e743479 100644
--- a/tiny_skia/src/backend.rs
+++ b/tiny_skia/src/backend.rs
@@ -9,6 +9,7 @@ use std::borrow::Cow;
 pub struct Backend {
     default_font: Font,
     default_text_size: f32,
+    text_pipeline: crate::text::Pipeline,
 }
 
 impl Backend {
@@ -16,6 +17,7 @@ impl Backend {
         Self {
             default_font: settings.default_font,
             default_text_size: settings.default_text_size,
+            text_pipeline: crate::text::Pipeline::new(),
         }
     }
 
@@ -32,123 +34,161 @@ impl Backend {
         let scale_factor = viewport.scale_factor() as f32;
 
         for primitive in primitives {
-            draw_primitive(primitive, pixels, None, scale_factor, Vector::ZERO);
+            self.draw_primitive(
+                primitive,
+                pixels,
+                None,
+                scale_factor,
+                Vector::ZERO,
+            );
         }
+
+        self.text_pipeline.end_frame();
     }
-}
 
-fn draw_primitive(
-    primitive: &Primitive,
-    pixels: &mut tiny_skia::PixmapMut<'_>,
-    clip_mask: Option<&tiny_skia::ClipMask>,
-    scale_factor: f32,
-    translation: Vector,
-) {
-    match primitive {
-        Primitive::None => {}
-        Primitive::Quad {
-            bounds,
-            background,
-            border_radius: _, // TODO
-            border_width,
-            border_color,
-        } => {
-            let transform = tiny_skia::Transform::from_translate(
-                translation.x,
-                translation.y,
-            )
-            .post_scale(scale_factor, scale_factor);
-
-            let path = tiny_skia::PathBuilder::from_rect(
-                tiny_skia::Rect::from_xywh(
-                    bounds.x,
-                    bounds.y,
-                    bounds.width,
-                    bounds.height,
+    fn draw_primitive(
+        &mut self,
+        primitive: &Primitive,
+        pixels: &mut tiny_skia::PixmapMut<'_>,
+        clip_mask: Option<&tiny_skia::ClipMask>,
+        scale_factor: f32,
+        translation: Vector,
+    ) {
+        match primitive {
+            Primitive::None => {}
+            Primitive::Quad {
+                bounds,
+                background,
+                border_radius: _, // TODO
+                border_width,
+                border_color,
+            } => {
+                let transform = tiny_skia::Transform::from_translate(
+                    translation.x,
+                    translation.y,
                 )
-                .expect("Create quad rectangle"),
-            );
+                .post_scale(scale_factor, scale_factor);
 
-            pixels.fill_path(
-                &path,
-                &tiny_skia::Paint {
-                    shader: match background {
-                        Background::Color(color) => {
-                            tiny_skia::Shader::SolidColor(into_color(*color))
-                        }
-                    },
-                    anti_alias: true,
-                    ..tiny_skia::Paint::default()
-                },
-                tiny_skia::FillRule::EvenOdd,
-                transform,
-                clip_mask,
-            );
+                let path = tiny_skia::PathBuilder::from_rect(
+                    tiny_skia::Rect::from_xywh(
+                        bounds.x,
+                        bounds.y,
+                        bounds.width,
+                        bounds.height,
+                    )
+                    .expect("Create quad rectangle"),
+                );
 
-            if *border_width > 0.0 {
-                pixels.stroke_path(
+                pixels.fill_path(
                     &path,
                     &tiny_skia::Paint {
-                        shader: tiny_skia::Shader::SolidColor(into_color(
-                            *border_color,
-                        )),
+                        shader: match background {
+                            Background::Color(color) => {
+                                tiny_skia::Shader::SolidColor(into_color(
+                                    *color,
+                                ))
+                            }
+                        },
                         anti_alias: true,
                         ..tiny_skia::Paint::default()
                     },
-                    &tiny_skia::Stroke {
-                        width: *border_width,
-                        ..tiny_skia::Stroke::default()
-                    },
+                    tiny_skia::FillRule::EvenOdd,
                     transform,
                     clip_mask,
                 );
+
+                if *border_width > 0.0 {
+                    pixels.stroke_path(
+                        &path,
+                        &tiny_skia::Paint {
+                            shader: tiny_skia::Shader::SolidColor(into_color(
+                                *border_color,
+                            )),
+                            anti_alias: true,
+                            ..tiny_skia::Paint::default()
+                        },
+                        &tiny_skia::Stroke {
+                            width: *border_width,
+                            ..tiny_skia::Stroke::default()
+                        },
+                        transform,
+                        clip_mask,
+                    );
+                }
             }
-        }
-        Primitive::Text { .. } => {
-            // TODO
-        }
-        Primitive::Image { .. } => {
-            // TODO
-        }
-        Primitive::Svg { .. } => {
-            // TODO
-        }
-        Primitive::Group { primitives } => {
-            for primitive in primitives {
-                draw_primitive(
-                    primitive,
+            Primitive::Text {
+                content,
+                bounds,
+                color,
+                size,
+                font,
+                horizontal_alignment,
+                vertical_alignment,
+            } => {
+                self.text_pipeline.draw(
+                    content,
+                    (*bounds + translation) * scale_factor,
+                    *color,
+                    *size * scale_factor,
+                    *font,
+                    *horizontal_alignment,
+                    *vertical_alignment,
+                    pixels,
+                    clip_mask,
+                );
+            }
+            Primitive::Image { .. } => {
+                // TODO
+            }
+            Primitive::Svg { .. } => {
+                // TODO
+            }
+            Primitive::Group { primitives } => {
+                for primitive in primitives {
+                    self.draw_primitive(
+                        primitive,
+                        pixels,
+                        clip_mask,
+                        scale_factor,
+                        translation,
+                    );
+                }
+            }
+            Primitive::Translate {
+                translation: offset,
+                content,
+            } => {
+                self.draw_primitive(
+                    content,
                     pixels,
                     clip_mask,
                     scale_factor,
+                    translation + *offset,
+                );
+            }
+            Primitive::Clip { bounds, content } => {
+                self.draw_primitive(
+                    content,
+                    pixels,
+                    Some(&rectangular_clip_mask(
+                        pixels,
+                        *bounds * scale_factor,
+                    )),
+                    scale_factor,
                     translation,
                 );
             }
+            Primitive::Cached { cache } => {
+                self.draw_primitive(
+                    cache,
+                    pixels,
+                    clip_mask,
+                    scale_factor,
+                    translation,
+                );
+            }
+            Primitive::SolidMesh { .. } | Primitive::GradientMesh { .. } => {}
         }
-        Primitive::Translate {
-            translation: offset,
-            content,
-        } => {
-            draw_primitive(
-                content,
-                pixels,
-                clip_mask,
-                scale_factor,
-                translation + *offset,
-            );
-        }
-        Primitive::Clip { bounds, content } => {
-            draw_primitive(
-                content,
-                pixels,
-                Some(&rectangular_clip_mask(pixels, *bounds * scale_factor)),
-                scale_factor,
-                translation,
-            );
-        }
-        Primitive::Cached { cache } => {
-            draw_primitive(cache, pixels, clip_mask, scale_factor, translation);
-        }
-        Primitive::SolidMesh { .. } | Primitive::GradientMesh { .. } => {}
     }
 }
 
@@ -185,7 +225,7 @@ fn rectangular_clip_mask(
 
 impl iced_graphics::Backend for Backend {
     fn trim_measurements(&mut self) {
-        // TODO
+        self.text_pipeline.trim_measurement_cache();
     }
 }
 
@@ -204,30 +244,35 @@ impl backend::Text for Backend {
 
     fn measure(
         &self,
-        _contents: &str,
-        _size: f32,
-        _font: Font,
-        _bounds: Size,
+        contents: &str,
+        size: f32,
+        font: Font,
+        bounds: Size,
     ) -> (f32, f32) {
-        // TODO
-        (0.0, 0.0)
+        self.text_pipeline.measure(contents, size, font, bounds)
     }
 
     fn hit_test(
         &self,
-        _contents: &str,
-        _size: f32,
-        _font: Font,
-        _bounds: Size,
-        _point: iced_native::Point,
-        _nearest_only: bool,
+        contents: &str,
+        size: f32,
+        font: Font,
+        bounds: Size,
+        point: iced_native::Point,
+        nearest_only: bool,
     ) -> Option<text::Hit> {
-        // TODO
-        None
+        self.text_pipeline.hit_test(
+            contents,
+            size,
+            font,
+            bounds,
+            point,
+            nearest_only,
+        )
     }
 
-    fn load_font(&mut self, _font: Cow<'static, [u8]>) {
-        // TODO
+    fn load_font(&mut self, font: Cow<'static, [u8]>) {
+        self.text_pipeline.load_font(font);
     }
 }
 
diff --git a/tiny_skia/src/lib.rs b/tiny_skia/src/lib.rs
index fce44e9e..420a1ffb 100644
--- a/tiny_skia/src/lib.rs
+++ b/tiny_skia/src/lib.rs
@@ -2,6 +2,7 @@ pub mod window;
 
 mod backend;
 mod settings;
+mod text;
 
 pub use backend::Backend;
 pub use settings::Settings;
diff --git a/tiny_skia/src/text.rs b/tiny_skia/src/text.rs
new file mode 100644
index 00000000..5bd6eff1
--- /dev/null
+++ b/tiny_skia/src/text.rs
@@ -0,0 +1,350 @@
+pub use iced_native::text::Hit;
+
+use iced_native::alignment;
+use iced_native::{Color, Font, Rectangle, Size};
+
+use rustc_hash::{FxHashMap, FxHashSet};
+use std::borrow::Cow;
+use std::cell::RefCell;
+use std::collections::hash_map;
+use std::hash::{BuildHasher, Hash, Hasher};
+use std::sync::Arc;
+
+#[allow(missing_debug_implementations)]
+pub struct Pipeline {
+    system: Option<System>,
+}
+
+#[ouroboros::self_referencing]
+struct System {
+    fonts: cosmic_text::FontSystem,
+
+    #[borrows(fonts)]
+    #[not_covariant]
+    measurement_cache: RefCell<Cache<'this>>,
+
+    #[borrows(fonts)]
+    #[not_covariant]
+    render_cache: Cache<'this>,
+}
+
+impl Pipeline {
+    pub fn new() -> Self {
+        Pipeline {
+            system: Some(
+                SystemBuilder {
+                    fonts: cosmic_text::FontSystem::new_with_fonts(
+                        [cosmic_text::fontdb::Source::Binary(Arc::new(
+                            include_bytes!("../../wgpu/fonts/Iced-Icons.ttf")
+                                .as_slice(),
+                        ))]
+                        .into_iter(),
+                    ),
+                    measurement_cache_builder: |_| RefCell::new(Cache::new()),
+                    render_cache_builder: |_| Cache::new(),
+                }
+                .build(),
+            ),
+        }
+    }
+
+    pub fn load_font(&mut self, bytes: Cow<'static, [u8]>) {
+        let heads = self.system.take().unwrap().into_heads();
+
+        let (locale, mut db) = heads.fonts.into_locale_and_db();
+
+        db.load_font_source(cosmic_text::fontdb::Source::Binary(Arc::new(
+            bytes.into_owned(),
+        )));
+
+        self.system = Some(
+            SystemBuilder {
+                fonts: cosmic_text::FontSystem::new_with_locale_and_db(
+                    locale, db,
+                ),
+                measurement_cache_builder: |_| RefCell::new(Cache::new()),
+                render_cache_builder: |_| Cache::new(),
+            }
+            .build(),
+        );
+    }
+
+    pub fn draw(
+        &mut self,
+        content: &str,
+        bounds: Rectangle,
+        color: Color,
+        size: f32,
+        font: Font,
+        _horizontal_alignment: alignment::Horizontal, // TODO
+        _vertical_alignment: alignment::Vertical,     // TODO
+        pixels: &mut tiny_skia::PixmapMut<'_>,
+        clip_mask: Option<&tiny_skia::ClipMask>,
+    ) {
+        self.system.as_mut().unwrap().with_mut(|fields| {
+            let key = Key {
+                bounds: bounds.size(),
+                content,
+                font,
+                size,
+            };
+
+            let (_, buffer) = fields.render_cache.allocate(&fields.fonts, key);
+
+            let mut swash = cosmic_text::SwashCache::new(&fields.fonts);
+
+            for run in buffer.layout_runs() {
+                for glyph in run.glyphs {
+                    // TODO: Outline support
+                    if let Some(image) = swash.get_image(glyph.cache_key) {
+                        let glyph_size = image.placement.width as usize
+                            * image.placement.height as usize;
+
+                        if glyph_size == 0 {
+                            continue;
+                        }
+
+                        // TODO: Cache glyph rasterization
+                        let mut buffer = vec![0u32; glyph_size];
+
+                        match image.content {
+                            cosmic_text::SwashContent::Mask => {
+                                let mut i = 0;
+
+                                // TODO: Blend alpha
+                                let [r, g, b, _a] = color.into_rgba8();
+
+                                for _y in 0..image.placement.height {
+                                    for _x in 0..image.placement.width {
+                                        buffer[i] =
+                                            tiny_skia::ColorU8::from_rgba(
+                                                b,
+                                                g,
+                                                r,
+                                                image.data[i],
+                                            )
+                                            .premultiply()
+                                            .get();
+
+                                        i += 1;
+                                    }
+                                }
+                            }
+                            cosmic_text::SwashContent::Color => {
+                                let mut i = 0;
+
+                                for _y in 0..image.placement.height {
+                                    for _x in 0..image.placement.width {
+                                        // TODO: Blend alpha
+                                        buffer[i] = (image.data[i + 3] as u32)
+                                            << 24
+                                            | (image.data[i + 2] as u32) << 16
+                                            | (image.data[i + 1] as u32) << 8
+                                            | image.data[i] as u32;
+
+                                        i += 1;
+                                    }
+                                }
+                            }
+                            cosmic_text::SwashContent::SubpixelMask => {
+                                // TODO
+                            }
+                        }
+
+                        let pixmap = tiny_skia::PixmapRef::from_bytes(
+                            bytemuck::cast_slice(&buffer),
+                            image.placement.width,
+                            image.placement.height,
+                        )
+                        .expect("Create glyph pixel map");
+
+                        pixels.draw_pixmap(
+                            bounds.x as i32
+                                + glyph.x_int
+                                + image.placement.left,
+                            bounds.y as i32 - glyph.y_int - image.placement.top
+                                + run.line_y as i32,
+                            pixmap,
+                            &tiny_skia::PixmapPaint::default(),
+                            tiny_skia::Transform::identity(),
+                            clip_mask,
+                        );
+                    }
+                }
+            }
+        });
+    }
+
+    pub fn end_frame(&mut self) {
+        self.system
+            .as_mut()
+            .unwrap()
+            .with_render_cache_mut(|cache| cache.trim());
+    }
+
+    pub fn measure(
+        &self,
+        content: &str,
+        size: f32,
+        font: Font,
+        bounds: Size,
+    ) -> (f32, f32) {
+        self.system.as_ref().unwrap().with(|fields| {
+            let mut measurement_cache = fields.measurement_cache.borrow_mut();
+
+            let (_, paragraph) = measurement_cache.allocate(
+                fields.fonts,
+                Key {
+                    content,
+                    size,
+                    font,
+                    bounds,
+                },
+            );
+
+            let (total_lines, max_width) = paragraph
+                .layout_runs()
+                .enumerate()
+                .fold((0, 0.0), |(_, max), (i, buffer)| {
+                    (i + 1, buffer.line_w.max(max))
+                });
+
+            (max_width, size * 1.2 * total_lines as f32)
+        })
+    }
+
+    pub fn hit_test(
+        &self,
+        content: &str,
+        size: f32,
+        font: iced_native::Font,
+        bounds: iced_native::Size,
+        point: iced_native::Point,
+        _nearest_only: bool,
+    ) -> Option<Hit> {
+        self.system.as_ref().unwrap().with(|fields| {
+            let mut measurement_cache = fields.measurement_cache.borrow_mut();
+
+            let (_, paragraph) = measurement_cache.allocate(
+                fields.fonts,
+                Key {
+                    content,
+                    size,
+                    font,
+                    bounds,
+                },
+            );
+
+            let cursor = paragraph.hit(point.x, point.y)?;
+
+            Some(Hit::CharOffset(cursor.index))
+        })
+    }
+
+    pub fn trim_measurement_cache(&mut self) {
+        self.system
+            .as_mut()
+            .unwrap()
+            .with_measurement_cache_mut(|cache| cache.borrow_mut().trim());
+    }
+}
+
+fn to_family(font: Font) -> cosmic_text::Family<'static> {
+    match font {
+        Font::Name(name) => cosmic_text::Family::Name(name),
+        Font::SansSerif => cosmic_text::Family::SansSerif,
+        Font::Serif => cosmic_text::Family::Serif,
+        Font::Cursive => cosmic_text::Family::Cursive,
+        Font::Fantasy => cosmic_text::Family::Fantasy,
+        Font::Monospace => cosmic_text::Family::Monospace,
+    }
+}
+
+struct Cache<'a> {
+    entries: FxHashMap<KeyHash, cosmic_text::Buffer<'a>>,
+    recently_used: FxHashSet<KeyHash>,
+    hasher: HashBuilder,
+    trim_count: usize,
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+type HashBuilder = twox_hash::RandomXxHashBuilder64;
+
+#[cfg(target_arch = "wasm32")]
+type HashBuilder = std::hash::BuildHasherDefault<twox_hash::XxHash64>;
+
+impl<'a> Cache<'a> {
+    const TRIM_INTERVAL: usize = 300;
+
+    fn new() -> Self {
+        Self {
+            entries: FxHashMap::default(),
+            recently_used: FxHashSet::default(),
+            hasher: HashBuilder::default(),
+            trim_count: 0,
+        }
+    }
+
+    fn allocate(
+        &mut self,
+        fonts: &'a cosmic_text::FontSystem,
+        key: Key<'_>,
+    ) -> (KeyHash, &mut cosmic_text::Buffer<'a>) {
+        let hash = {
+            let mut hasher = self.hasher.build_hasher();
+
+            key.content.hash(&mut hasher);
+            key.size.to_bits().hash(&mut hasher);
+            key.font.hash(&mut hasher);
+            key.bounds.width.to_bits().hash(&mut hasher);
+            key.bounds.height.to_bits().hash(&mut hasher);
+
+            hasher.finish()
+        };
+
+        if let hash_map::Entry::Vacant(entry) = self.entries.entry(hash) {
+            let metrics = cosmic_text::Metrics::new(key.size, key.size * 1.2);
+            let mut buffer = cosmic_text::Buffer::new(fonts, metrics);
+
+            buffer.set_size(
+                key.bounds.width,
+                key.bounds.height.max(key.size * 1.2),
+            );
+            buffer.set_text(
+                key.content,
+                cosmic_text::Attrs::new()
+                    .family(to_family(key.font))
+                    .monospaced(matches!(key.font, Font::Monospace)),
+            );
+
+            let _ = entry.insert(buffer);
+        }
+
+        let _ = self.recently_used.insert(hash);
+
+        (hash, self.entries.get_mut(&hash).unwrap())
+    }
+
+    fn trim(&mut self) {
+        if self.trim_count >= Self::TRIM_INTERVAL {
+            self.entries
+                .retain(|key, _| self.recently_used.contains(key));
+
+            self.recently_used.clear();
+
+            self.trim_count = 0;
+        } else {
+            self.trim_count += 1;
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+struct Key<'a> {
+    content: &'a str,
+    size: f32,
+    font: Font,
+    bounds: Size,
+}
+
+type KeyHash = u64;