layout/
context.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5use std::collections::HashMap;
6use std::sync::Arc;
7
8use base::id::PainterId;
9use embedder_traits::UntrustedNodeAddress;
10use euclid::Size2D;
11use fonts::FontContext;
12use layout_api::wrapper_traits::ThreadSafeLayoutNode;
13use layout_api::{
14    AnimatingImages, IFrameSizes, LayoutImageDestination, PendingImage, PendingImageState,
15    PendingRasterizationImage,
16};
17use net_traits::image_cache::{
18    Image as CachedImage, ImageCache, ImageCacheResult, ImageOrMetadataAvailable, PendingImageId,
19};
20use parking_lot::{Mutex, RwLock};
21use pixels::RasterImage;
22use script::layout_dom::ServoThreadSafeLayoutNode;
23use servo_url::{ImmutableOrigin, ServoUrl};
24use style::context::SharedStyleContext;
25use style::dom::OpaqueNode;
26use style::values::computed::image::{Gradient, Image};
27use webrender_api::units::{DeviceIntSize, DeviceSize};
28
29pub(crate) type CachedImageOrError = Result<CachedImage, ResolveImageError>;
30
31pub(crate) struct LayoutContext<'a> {
32    pub use_rayon: bool,
33
34    /// Bits shared by the layout and style system.
35    pub style_context: SharedStyleContext<'a>,
36
37    /// A FontContext to be used during layout.
38    pub font_context: Arc<FontContext>,
39
40    /// A collection of `<iframe>` sizes to send back to script.
41    pub iframe_sizes: Mutex<IFrameSizes>,
42
43    /// An [`ImageResolver`] used for resolving images during box and fragment
44    /// tree construction. Later passed to display list construction.
45    pub image_resolver: Arc<ImageResolver>,
46
47    /// The [`PainterId`] that identifies which `RenderingContext` that this layout targets.
48    pub painter_id: PainterId,
49}
50
51pub enum ResolvedImage<'a> {
52    Gradient(&'a Gradient),
53    // The size is tracked explicitly as image-set images can specify their
54    // natural resolution which affects the final size for raster images.
55    Image {
56        image: CachedImage,
57        size: DeviceSize,
58    },
59}
60
61#[derive(Clone, Copy, Debug)]
62pub enum ResolveImageError {
63    LoadError,
64    ImagePending,
65    OnlyMetadata,
66    InvalidUrl,
67    MissingNode,
68    ImageMissingFromImageSet,
69    NotImplementedYet,
70    None,
71}
72
73pub(crate) enum LayoutImageCacheResult {
74    Pending,
75    DataAvailable(ImageOrMetadataAvailable),
76    LoadError,
77}
78
79pub(crate) struct ImageResolver {
80    /// The origin of the `Document` that this [`ImageResolver`] resolves images for.
81    pub origin: ImmutableOrigin,
82
83    /// Reference to the script thread image cache.
84    pub image_cache: Arc<dyn ImageCache>,
85
86    /// A list of in-progress image loads to be shared with the script thread.
87    pub pending_images: Mutex<Vec<PendingImage>>,
88
89    /// A list of fully loaded vector images that need to be rasterized to a specific
90    /// size determined by layout. This will be shared with the script thread.
91    pub pending_rasterization_images: Mutex<Vec<PendingRasterizationImage>>,
92
93    /// A list of `SVGSVGElement`s encountered during layout that are not
94    /// serialized yet. This is needed to support inline SVGs as they are treated
95    /// as replaced elements and the layout is responsible for triggering the
96    /// network load for the corresponding serialized data: urls (similar to
97    /// background images).
98    pub pending_svg_elements_for_serialization: Mutex<Vec<UntrustedNodeAddress>>,
99
100    /// A shared reference to script's map of DOM nodes with animated images. This is used
101    /// to manage image animations in script and inform the script about newly animating
102    /// nodes.
103    pub animating_images: Arc<RwLock<AnimatingImages>>,
104
105    // A cache that maps image resources used in CSS (e.g as the `url()` value
106    // for `background-image` or `content` property) to the final resolved image data.
107    pub resolved_images_cache: Arc<RwLock<HashMap<ServoUrl, CachedImageOrError>>>,
108
109    /// The current animation timeline value used to properly initialize animating images.
110    pub animation_timeline_value: f64,
111}
112
113impl Drop for ImageResolver {
114    fn drop(&mut self) {
115        if !std::thread::panicking() {
116            assert!(self.pending_images.lock().is_empty());
117            assert!(self.pending_rasterization_images.lock().is_empty());
118            assert!(
119                self.pending_svg_elements_for_serialization
120                    .lock()
121                    .is_empty()
122            );
123        }
124    }
125}
126
127impl ImageResolver {
128    pub(crate) fn get_or_request_image_or_meta(
129        &self,
130        node: OpaqueNode,
131        url: ServoUrl,
132        destination: LayoutImageDestination,
133    ) -> LayoutImageCacheResult {
134        // Check for available image or start tracking.
135        let cache_result =
136            self.image_cache
137                .get_cached_image_status(url.clone(), self.origin.clone(), None);
138
139        match cache_result {
140            ImageCacheResult::Available(img_or_meta) => {
141                LayoutImageCacheResult::DataAvailable(img_or_meta)
142            },
143            // Image has been requested, is still pending. Return no image for this paint loop.
144            // When the image loads it will trigger a reflow and/or repaint.
145            ImageCacheResult::Pending(id) => {
146                let image = PendingImage {
147                    state: PendingImageState::PendingResponse,
148                    node: node.into(),
149                    id,
150                    origin: self.origin.clone(),
151                    destination,
152                };
153                self.pending_images.lock().push(image);
154                LayoutImageCacheResult::Pending
155            },
156            // Not yet requested - request image or metadata from the cache
157            ImageCacheResult::ReadyForRequest(id) => {
158                let image = PendingImage {
159                    state: PendingImageState::Unrequested(url),
160                    node: node.into(),
161                    id,
162                    origin: self.origin.clone(),
163                    destination,
164                };
165                self.pending_images.lock().push(image);
166                LayoutImageCacheResult::Pending
167            },
168            // Image failed to load, so just return the same error.
169            ImageCacheResult::FailedToLoadOrDecode => LayoutImageCacheResult::LoadError,
170        }
171    }
172
173    pub(crate) fn handle_animated_image(&self, node: OpaqueNode, image: Arc<RasterImage>) {
174        let mut animating_images = self.animating_images.write();
175        if !image.should_animate() {
176            animating_images.remove(node);
177        } else {
178            animating_images.maybe_insert_or_update(node, image, self.animation_timeline_value);
179        }
180    }
181
182    pub(crate) fn get_cached_image_for_url(
183        &self,
184        node: OpaqueNode,
185        url: ServoUrl,
186        destination: LayoutImageDestination,
187    ) -> Result<CachedImage, ResolveImageError> {
188        if let Some(cached_image) = self.resolved_images_cache.read().get(&url) {
189            return cached_image.clone();
190        }
191
192        let result = self.get_or_request_image_or_meta(node, url.clone(), destination);
193        match result {
194            LayoutImageCacheResult::DataAvailable(img_or_meta) => match img_or_meta {
195                ImageOrMetadataAvailable::ImageAvailable { image, .. } => {
196                    if let Some(image) = image.as_raster_image() {
197                        self.handle_animated_image(node, image.clone());
198                    }
199
200                    let mut resolved_images_cache = self.resolved_images_cache.write();
201                    resolved_images_cache.insert(url, Ok(image.clone()));
202                    Ok(image)
203                },
204                ImageOrMetadataAvailable::MetadataAvailable(..) => {
205                    Result::Err(ResolveImageError::OnlyMetadata)
206                },
207            },
208            LayoutImageCacheResult::Pending => Result::Err(ResolveImageError::ImagePending),
209            LayoutImageCacheResult::LoadError => {
210                let error = Err(ResolveImageError::LoadError);
211                self.resolved_images_cache
212                    .write()
213                    .insert(url, error.clone());
214                error
215            },
216        }
217    }
218
219    pub(crate) fn rasterize_vector_image(
220        &self,
221        image_id: PendingImageId,
222        size: DeviceIntSize,
223        node: OpaqueNode,
224    ) -> Option<RasterImage> {
225        let result = self.image_cache.rasterize_vector_image(image_id, size);
226        if result.is_none() {
227            self.pending_rasterization_images
228                .lock()
229                .push(PendingRasterizationImage {
230                    id: image_id,
231                    node: node.into(),
232                    size,
233                });
234        }
235        result
236    }
237
238    pub(crate) fn queue_svg_element_for_serialization(
239        &self,
240        element: ServoThreadSafeLayoutNode<'_>,
241    ) {
242        self.pending_svg_elements_for_serialization
243            .lock()
244            .push(element.opaque().into())
245    }
246
247    pub(crate) fn resolve_image<'a>(
248        &self,
249        node: Option<OpaqueNode>,
250        image: &'a Image,
251    ) -> Result<ResolvedImage<'a>, ResolveImageError> {
252        match image {
253            // TODO: Add support for PaintWorklet and CrossFade rendering.
254            Image::None => Result::Err(ResolveImageError::None),
255            Image::CrossFade(_) => Result::Err(ResolveImageError::NotImplementedYet),
256            Image::PaintWorklet(_) => Result::Err(ResolveImageError::NotImplementedYet),
257            Image::Gradient(gradient) => Ok(ResolvedImage::Gradient(gradient)),
258            Image::Url(image_url) => {
259                // FIXME: images won’t always have in intrinsic width or
260                // height when support for SVG is added, or a WebRender
261                // `ImageKey`, for that matter.
262                //
263                // FIXME: It feels like this should take into account the pseudo
264                // element and not just the node.
265                let image_url = image_url.url().ok_or(ResolveImageError::InvalidUrl)?;
266                let node = node.ok_or(ResolveImageError::MissingNode)?;
267                let image = self.get_cached_image_for_url(
268                    node,
269                    image_url.clone().into(),
270                    LayoutImageDestination::DisplayListBuilding,
271                )?;
272                let metadata = image.metadata();
273                let size = Size2D::new(metadata.width, metadata.height).to_f32();
274                Ok(ResolvedImage::Image { image, size })
275            },
276            Image::ImageSet(image_set) => {
277                image_set
278                    .items
279                    .get(image_set.selected_index)
280                    .ok_or(ResolveImageError::ImageMissingFromImageSet)
281                    .and_then(|image| {
282                        self.resolve_image(node, &image.image)
283                            .map(|info| match info {
284                                ResolvedImage::Image {
285                                    image: cached_image,
286                                    ..
287                                } => {
288                                    // From <https://drafts.csswg.org/css-images-4/#image-set-notation>:
289                                    // > A <resolution> (optional). This is used to help the UA decide
290                                    // > which <image-set-option> to choose. If the image reference is
291                                    // > for a raster image, it also specifies the image’s natural
292                                    // > resolution, overriding any other source of data that might
293                                    // > supply a natural resolution.
294                                    let image_metadata = cached_image.metadata();
295                                    let size = if cached_image.as_raster_image().is_some() {
296                                        let scale_factor = image.resolution.dppx();
297                                        Size2D::new(
298                                            image_metadata.width as f32 / scale_factor,
299                                            image_metadata.height as f32 / scale_factor,
300                                        )
301                                    } else {
302                                        Size2D::new(image_metadata.width, image_metadata.height)
303                                            .to_f32()
304                                    };
305
306                                    ResolvedImage::Image {
307                                        image: cached_image,
308                                        size,
309                                    }
310                                },
311                                _ => info,
312                            })
313                    })
314            },
315            Image::LightDark(..) => unreachable!("light-dark() should be disabled"),
316        }
317    }
318}
layout/context.rs

layout/
context.rs
