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::color::Color;
27use style::values::computed::image::{Gradient, Image};
28use style_traits::DevicePixel;
29use webrender_api::units::{DeviceIntSize, DeviceSize};
30
31pub(crate) type CachedImageOrError = Result<CachedImage, ResolveImageError>;
32
33pub(crate) struct LayoutContext<'a> {
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    /// Whether or not parallel layout should be allowed for this layout.
51    pub allow_parallel_layout: bool,
52
53    /// The minimum number of jobs that need to be larger than
54    /// [`Self::parallelism_job_size_minimum`] in order to enable parallelism.
55    pub parallelism_job_count_minimum: usize,
56
57    /// The minimum size a job needs to be to be counted when determining if the number of
58    /// jobs exceeds [`Self::parallelism_job_count_minimum`].
59    pub parallelism_job_size_minimum: usize,
60
61    /// The device dimensions on which this layout is running, in device pixels.
62    pub device_size: Size2D<f32, DevicePixel>,
63}
64
65impl LayoutContext<'_> {
66    pub(crate) fn should_parallelize(&self, number_of_jobs: usize) -> bool {
67        self.allow_parallel_layout && number_of_jobs >= self.parallelism_job_count_minimum
68    }
69
70    pub(crate) fn should_parallelize_layout(&self, jobs: impl Iterator<Item = usize>) -> bool {
71        self.allow_parallel_layout &&
72            jobs.filter(|job| *job >= self.parallelism_job_size_minimum)
73                .count() >=
74                self.parallelism_job_count_minimum
75    }
76}
77
78pub enum ResolvedImage<'a> {
79    Gradient(&'a Gradient),
80    Color(&'a Color),
81    // The size is tracked explicitly as image-set images can specify their
82    // natural resolution which affects the final size for raster images.
83    Image {
84        image: CachedImage,
85        size: DeviceSize,
86    },
87}
88
89#[derive(Clone, Copy, Debug)]
90pub enum ResolveImageError {
91    LoadError,
92    ImagePending,
93    OnlyMetadata,
94    InvalidUrl,
95    MissingNode,
96    ImageMissingFromImageSet,
97    NotImplementedYet,
98    None,
99}
100
101pub(crate) enum LayoutImageCacheResult {
102    Pending,
103    DataAvailable(ImageOrMetadataAvailable),
104    LoadError,
105}
106
107pub(crate) struct ImageResolver {
108    /// The origin of the `Document` that this [`ImageResolver`] resolves images for.
109    pub origin: ImmutableOrigin,
110
111    /// Reference to the script thread image cache.
112    pub image_cache: Arc<dyn ImageCache>,
113
114    /// A list of in-progress image loads to be shared with the script thread.
115    pub pending_images: Mutex<Vec<PendingImage>>,
116
117    /// A list of fully loaded vector images that need to be rasterized to a specific
118    /// size determined by layout. This will be shared with the script thread.
119    pub pending_rasterization_images: Mutex<Vec<PendingRasterizationImage>>,
120
121    /// A list of `SVGSVGElement`s encountered during layout that are not
122    /// serialized yet. This is needed to support inline SVGs as they are treated
123    /// as replaced elements and the layout is responsible for triggering the
124    /// network load for the corresponding serialized data: urls (similar to
125    /// background images).
126    pub pending_svg_elements_for_serialization: Mutex<Vec<UntrustedNodeAddress>>,
127
128    /// A shared reference to script's map of DOM nodes with animated images. This is used
129    /// to manage image animations in script and inform the script about newly animating
130    /// nodes.
131    pub animating_images: Arc<RwLock<AnimatingImages>>,
132
133    // A cache that maps image resources used in CSS (e.g as the `url()` value
134    // for `background-image` or `content` property) to the final resolved image data.
135    pub resolved_images_cache: Arc<RwLock<HashMap<ServoUrl, CachedImageOrError>>>,
136
137    /// The current animation timeline value used to properly initialize animating images.
138    pub animation_timeline_value: f64,
139}
140
141impl Drop for ImageResolver {
142    fn drop(&mut self) {
143        if !std::thread::panicking() {
144            assert!(self.pending_images.lock().is_empty());
145            assert!(self.pending_rasterization_images.lock().is_empty());
146            assert!(
147                self.pending_svg_elements_for_serialization
148                    .lock()
149                    .is_empty()
150            );
151        }
152    }
153}
154
155impl ImageResolver {
156    pub(crate) fn get_or_request_image_or_meta(
157        &self,
158        node: OpaqueNode,
159        url: ServoUrl,
160        destination: LayoutImageDestination,
161        is_internal_request: InternalRequest,
162    ) -> LayoutImageCacheResult {
163        // Check for available image or start tracking.
164        let cache_result =
165            self.image_cache
166                .get_cached_image_status(url.clone(), self.origin.clone(), None);
167
168        match cache_result {
169            ImageCacheResult::Available(img_or_meta) => {
170                LayoutImageCacheResult::DataAvailable(img_or_meta)
171            },
172            // Image has been requested, is still pending. Return no image for this paint loop.
173            // When the image loads it will trigger a reflow and/or repaint.
174            ImageCacheResult::Pending(id) => {
175                let image = PendingImage {
176                    state: PendingImageState::PendingResponse,
177                    node: node.into(),
178                    id,
179                    origin: self.origin.clone(),
180                    destination,
181                    is_internal_request,
182                };
183                self.pending_images.lock().push(image);
184                LayoutImageCacheResult::Pending
185            },
186            // Not yet requested - request image or metadata from the cache
187            ImageCacheResult::ReadyForRequest(id) => {
188                let image = PendingImage {
189                    state: PendingImageState::Unrequested(url),
190                    node: node.into(),
191                    id,
192                    origin: self.origin.clone(),
193                    destination,
194                    is_internal_request,
195                };
196                self.pending_images.lock().push(image);
197                LayoutImageCacheResult::Pending
198            },
199            // Image failed to load, so just return the same error.
200            ImageCacheResult::FailedToLoadOrDecode => LayoutImageCacheResult::LoadError,
201        }
202    }
203
204    pub(crate) fn handle_animated_image(&self, node: OpaqueNode, image: Arc<RasterImage>) {
205        let mut animating_images = self.animating_images.write();
206        if !image.should_animate() {
207            animating_images.remove(node);
208        } else {
209            animating_images.maybe_insert_or_update(node, image, self.animation_timeline_value);
210        }
211    }
212
213    pub(crate) fn get_cached_image_for_url(
214        &self,
215        node: OpaqueNode,
216        url: ServoUrl,
217        destination: LayoutImageDestination,
218        is_internal_request: InternalRequest,
219    ) -> Result<CachedImage, ResolveImageError> {
220        if let Some(cached_image) = self.resolved_images_cache.read().get(&url) {
221            return cached_image.clone();
222        }
223
224        let result =
225            self.get_or_request_image_or_meta(node, url.clone(), destination, is_internal_request);
226        match result {
227            LayoutImageCacheResult::DataAvailable(img_or_meta) => match img_or_meta {
228                ImageOrMetadataAvailable::ImageAvailable { image, .. } => {
229                    if let Some(image) = image.as_raster_image() {
230                        self.handle_animated_image(node, image);
231                    }
232
233                    let mut resolved_images_cache = self.resolved_images_cache.write();
234                    resolved_images_cache.insert(url, Ok(image.clone()));
235                    Ok(image)
236                },
237                ImageOrMetadataAvailable::MetadataAvailable(..) => {
238                    Result::Err(ResolveImageError::OnlyMetadata)
239                },
240            },
241            LayoutImageCacheResult::Pending => Result::Err(ResolveImageError::ImagePending),
242            LayoutImageCacheResult::LoadError => {
243                let error = Err(ResolveImageError::LoadError);
244                self.resolved_images_cache
245                    .write()
246                    .insert(url, error.clone());
247                error
248            },
249        }
250    }
251
252    pub(crate) fn rasterize_vector_image(
253        &self,
254        image_id: PendingImageId,
255        size: DeviceIntSize,
256        node: OpaqueNode,
257        svg_id: Option<String>,
258    ) -> Option<RasterImage> {
259        let result = self
260            .image_cache
261            .rasterize_vector_image(image_id, size, svg_id);
262        if result.is_none() {
263            self.pending_rasterization_images
264                .lock()
265                .push(PendingRasterizationImage {
266                    id: image_id,
267                    node: node.into(),
268                    size,
269                });
270        }
271        result
272    }
273
274    pub(crate) fn queue_svg_element_for_serialization(&self, element: ServoLayoutNode<'_>) {
275        self.pending_svg_elements_for_serialization
276            .lock()
277            .push(element.opaque().into())
278    }
279
280    pub(crate) fn resolve_image<'a>(
281        &self,
282        node: Option<OpaqueNode>,
283        image: &'a Image,
284    ) -> Result<ResolvedImage<'a>, ResolveImageError> {
285        match image {
286            // TODO: Add support for PaintWorklet and CrossFade rendering.
287            Image::None => Result::Err(ResolveImageError::None),
288            Image::CrossFade(_) => Result::Err(ResolveImageError::NotImplementedYet),
289            Image::PaintWorklet(_) => Result::Err(ResolveImageError::NotImplementedYet),
290            Image::Gradient(gradient) => Ok(ResolvedImage::Gradient(gradient)),
291            Image::Image(color) => Ok(ResolvedImage::Color(color)),
292            Image::Url(image_url) => {
293                // FIXME: images won’t always have in intrinsic width or
294                // height when support for SVG is added, or a WebRender
295                // `ImageKey`, for that matter.
296                //
297                // FIXME: It feels like this should take into account the pseudo
298                // element and not just the node.
299                let image_url = image_url.url().ok_or(ResolveImageError::InvalidUrl)?;
300                let node = node.ok_or(ResolveImageError::MissingNode)?;
301                let image = self.get_cached_image_for_url(
302                    node,
303                    image_url.clone().into(),
304                    LayoutImageDestination::DisplayListBuilding,
305                    InternalRequest::No,
306                )?;
307                let metadata = image.metadata();
308                let size = Size2D::new(metadata.width, metadata.height).to_f32();
309                Ok(ResolvedImage::Image { image, size })
310            },
311            Image::ImageSet(image_set) => {
312                image_set
313                    .items
314                    .get(image_set.selected_index)
315                    .ok_or(ResolveImageError::ImageMissingFromImageSet)
316                    .and_then(|image| {
317                        self.resolve_image(node, &image.image)
318                            .map(|info| match info {
319                                ResolvedImage::Image {
320                                    image: cached_image,
321                                    ..
322                                } => {
323                                    // From <https://drafts.csswg.org/css-images-4/#image-set-notation>:
324                                    // > A <resolution> (optional). This is used to help the UA decide
325                                    // > which <image-set-option> to choose. If the image reference is
326                                    // > for a raster image, it also specifies the image’s natural
327                                    // > resolution, overriding any other source of data that might
328                                    // > supply a natural resolution.
329                                    let image_metadata = cached_image.metadata();
330                                    let size = if cached_image.as_raster_image().is_some() {
331                                        let scale_factor = image.resolution.dppx();
332                                        Size2D::new(
333                                            image_metadata.width as f32 / scale_factor,
334                                            image_metadata.height as f32 / scale_factor,
335                                        )
336                                    } else {
337                                        Size2D::new(image_metadata.width, image_metadata.height)
338                                            .to_f32()
339                                    };
340
341                                    ResolvedImage::Image {
342                                        image: cached_image,
343                                        size,
344                                    }
345                                },
346                                _ => info,
347                            })
348                    })
349            },
350            Image::LightDark(..) => unreachable!("light-dark() should be disabled"),
351        }
352    }
353}
layout/context.rs

layout/
context.rs
