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 embedder_traits::UntrustedNodeAddress;
9use euclid::Size2D;
10use fonts::FontContext;
11use layout_api::{
12    AnimatingImages, IFrameSizes, LayoutImageDestination, LayoutNode, PendingImage,
13    PendingImageState, PendingRasterizationImage,
14};
15use net_traits::image_cache::{
16    Image as CachedImage, ImageCache, ImageCacheResult, ImageOrMetadataAvailable, PendingImageId,
17};
18use net_traits::request::InternalRequest;
19use parking_lot::{Mutex, RwLock};
20use pixels::RasterImage;
21use script::layout_dom::ServoLayoutNode;
22use servo_base::id::PainterId;
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        is_internal_request: InternalRequest,
134    ) -> LayoutImageCacheResult {
135        // Check for available image or start tracking.
136        let cache_result =
137            self.image_cache
138                .get_cached_image_status(url.clone(), self.origin.clone(), None);
139
140        match cache_result {
141            ImageCacheResult::Available(img_or_meta) => {
142                LayoutImageCacheResult::DataAvailable(img_or_meta)
143            },
144            // Image has been requested, is still pending. Return no image for this paint loop.
145            // When the image loads it will trigger a reflow and/or repaint.
146            ImageCacheResult::Pending(id) => {
147                let image = PendingImage {
148                    state: PendingImageState::PendingResponse,
149                    node: node.into(),
150                    id,
151                    origin: self.origin.clone(),
152                    destination,
153                    is_internal_request,
154                };
155                self.pending_images.lock().push(image);
156                LayoutImageCacheResult::Pending
157            },
158            // Not yet requested - request image or metadata from the cache
159            ImageCacheResult::ReadyForRequest(id) => {
160                let image = PendingImage {
161                    state: PendingImageState::Unrequested(url),
162                    node: node.into(),
163                    id,
164                    origin: self.origin.clone(),
165                    destination,
166                    is_internal_request,
167                };
168                self.pending_images.lock().push(image);
169                LayoutImageCacheResult::Pending
170            },
171            // Image failed to load, so just return the same error.
172            ImageCacheResult::FailedToLoadOrDecode => LayoutImageCacheResult::LoadError,
173        }
174    }
175
176    pub(crate) fn handle_animated_image(&self, node: OpaqueNode, image: Arc<RasterImage>) {
177        let mut animating_images = self.animating_images.write();
178        if !image.should_animate() {
179            animating_images.remove(node);
180        } else {
181            animating_images.maybe_insert_or_update(node, image, self.animation_timeline_value);
182        }
183    }
184
185    pub(crate) fn get_cached_image_for_url(
186        &self,
187        node: OpaqueNode,
188        url: ServoUrl,
189        destination: LayoutImageDestination,
190        is_internal_request: InternalRequest,
191    ) -> Result<CachedImage, ResolveImageError> {
192        if let Some(cached_image) = self.resolved_images_cache.read().get(&url) {
193            return cached_image.clone();
194        }
195
196        let result =
197            self.get_or_request_image_or_meta(node, url.clone(), destination, is_internal_request);
198        match result {
199            LayoutImageCacheResult::DataAvailable(img_or_meta) => match img_or_meta {
200                ImageOrMetadataAvailable::ImageAvailable { image, .. } => {
201                    if let Some(image) = image.as_raster_image() {
202                        self.handle_animated_image(node, image);
203                    }
204
205                    let mut resolved_images_cache = self.resolved_images_cache.write();
206                    resolved_images_cache.insert(url, Ok(image.clone()));
207                    Ok(image)
208                },
209                ImageOrMetadataAvailable::MetadataAvailable(..) => {
210                    Result::Err(ResolveImageError::OnlyMetadata)
211                },
212            },
213            LayoutImageCacheResult::Pending => Result::Err(ResolveImageError::ImagePending),
214            LayoutImageCacheResult::LoadError => {
215                let error = Err(ResolveImageError::LoadError);
216                self.resolved_images_cache
217                    .write()
218                    .insert(url, error.clone());
219                error
220            },
221        }
222    }
223
224    pub(crate) fn rasterize_vector_image(
225        &self,
226        image_id: PendingImageId,
227        size: DeviceIntSize,
228        node: OpaqueNode,
229        svg_id: Option<String>,
230    ) -> Option<RasterImage> {
231        let result = self
232            .image_cache
233            .rasterize_vector_image(image_id, size, svg_id);
234        if result.is_none() {
235            self.pending_rasterization_images
236                .lock()
237                .push(PendingRasterizationImage {
238                    id: image_id,
239                    node: node.into(),
240                    size,
241                });
242        }
243        result
244    }
245
246    pub(crate) fn queue_svg_element_for_serialization(&self, element: ServoLayoutNode<'_>) {
247        self.pending_svg_elements_for_serialization
248            .lock()
249            .push(element.opaque().into())
250    }
251
252    pub(crate) fn resolve_image<'a>(
253        &self,
254        node: Option<OpaqueNode>,
255        image: &'a Image,
256    ) -> Result<ResolvedImage<'a>, ResolveImageError> {
257        match image {
258            // TODO: Add support for PaintWorklet and CrossFade rendering.
259            Image::None => Result::Err(ResolveImageError::None),
260            Image::CrossFade(_) => Result::Err(ResolveImageError::NotImplementedYet),
261            Image::PaintWorklet(_) => Result::Err(ResolveImageError::NotImplementedYet),
262            Image::Gradient(gradient) => Ok(ResolvedImage::Gradient(gradient)),
263            Image::Url(image_url) => {
264                // FIXME: images won’t always have in intrinsic width or
265                // height when support for SVG is added, or a WebRender
266                // `ImageKey`, for that matter.
267                //
268                // FIXME: It feels like this should take into account the pseudo
269                // element and not just the node.
270                let image_url = image_url.url().ok_or(ResolveImageError::InvalidUrl)?;
271                let node = node.ok_or(ResolveImageError::MissingNode)?;
272                let image = self.get_cached_image_for_url(
273                    node,
274                    image_url.clone().into(),
275                    LayoutImageDestination::DisplayListBuilding,
276                    InternalRequest::No,
277                )?;
278                let metadata = image.metadata();
279                let size = Size2D::new(metadata.width, metadata.height).to_f32();
280                Ok(ResolvedImage::Image { image, size })
281            },
282            Image::ImageSet(image_set) => {
283                image_set
284                    .items
285                    .get(image_set.selected_index)
286                    .ok_or(ResolveImageError::ImageMissingFromImageSet)
287                    .and_then(|image| {
288                        self.resolve_image(node, &image.image)
289                            .map(|info| match info {
290                                ResolvedImage::Image {
291                                    image: cached_image,
292                                    ..
293                                } => {
294                                    // From <https://drafts.csswg.org/css-images-4/#image-set-notation>:
295                                    // > A <resolution> (optional). This is used to help the UA decide
296                                    // > which <image-set-option> to choose. If the image reference is
297                                    // > for a raster image, it also specifies the image’s natural
298                                    // > resolution, overriding any other source of data that might
299                                    // > supply a natural resolution.
300                                    let image_metadata = cached_image.metadata();
301                                    let size = if cached_image.as_raster_image().is_some() {
302                                        let scale_factor = image.resolution.dppx();
303                                        Size2D::new(
304                                            image_metadata.width as f32 / scale_factor,
305                                            image_metadata.height as f32 / scale_factor,
306                                        )
307                                    } else {
308                                        Size2D::new(image_metadata.width, image_metadata.height)
309                                            .to_f32()
310                                    };
311
312                                    ResolvedImage::Image {
313                                        image: cached_image,
314                                        size,
315                                    }
316                                },
317                                _ => info,
318                            })
319                    })
320            },
321            Image::LightDark(..) => unreachable!("light-dark() should be disabled"),
322        }
323    }
324}
layout/context.rs

layout/
context.rs
