layout/
dom.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::marker::PhantomData;
6
7use atomic_refcell::{AtomicRef, AtomicRefCell, AtomicRefMut};
8use base::id::{BrowsingContextId, PipelineId};
9use html5ever::{local_name, ns};
10use layout_api::wrapper_traits::{LayoutDataTrait, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
11use layout_api::{
12    GenericLayoutDataTrait, LayoutDamage, LayoutElementType,
13    LayoutNodeType as ScriptLayoutNodeType, SVGElementData,
14};
15use malloc_size_of_derive::MallocSizeOf;
16use net_traits::image_cache::Image;
17use script::layout_dom::ServoThreadSafeLayoutNode;
18use servo_arc::Arc as ServoArc;
19use smallvec::SmallVec;
20use style::context::SharedStyleContext;
21use style::properties::ComputedValues;
22use style::selector_parser::{PseudoElement, RestyleDamage};
23
24use crate::cell::ArcRefCell;
25use crate::flexbox::FlexLevelBox;
26use crate::flow::BlockLevelBox;
27use crate::flow::inline::{InlineItem, SharedInlineStyles};
28use crate::fragment_tree::Fragment;
29use crate::geom::PhysicalSize;
30use crate::layout_box_base::LayoutBoxBase;
31use crate::replaced::CanvasInfo;
32use crate::table::TableLevelBox;
33use crate::taffy::TaffyItemBox;
34
35#[derive(MallocSizeOf)]
36pub struct PseudoLayoutData {
37    pseudo: PseudoElement,
38    data: ArcRefCell<InnerDOMLayoutData>,
39}
40
41/// The data that is stored in each DOM node that is used by layout.
42#[derive(Default, MallocSizeOf)]
43pub struct InnerDOMLayoutData {
44    pub(super) self_box: ArcRefCell<Option<LayoutBox>>,
45    pub(super) pseudo_boxes: SmallVec<[PseudoLayoutData; 2]>,
46}
47
48impl InnerDOMLayoutData {
49    fn pseudo_layout_data(
50        &self,
51        pseudo_element: PseudoElement,
52    ) -> Option<ArcRefCell<InnerDOMLayoutData>> {
53        for pseudo_layout_data in self.pseudo_boxes.iter() {
54            if pseudo_element == pseudo_layout_data.pseudo {
55                return Some(pseudo_layout_data.data.clone());
56            }
57        }
58        None
59    }
60
61    fn create_pseudo_layout_data(
62        &mut self,
63        pseudo_element: PseudoElement,
64    ) -> ArcRefCell<InnerDOMLayoutData> {
65        let data: ArcRefCell<InnerDOMLayoutData> = Default::default();
66        self.pseudo_boxes.push(PseudoLayoutData {
67            pseudo: pseudo_element,
68            data: data.clone(),
69        });
70        data
71    }
72
73    fn fragments(&self) -> Vec<Fragment> {
74        self.self_box
75            .borrow()
76            .as_ref()
77            .map(|layout_box| layout_box.with_base_flat(LayoutBoxBase::fragments))
78            .unwrap_or_default()
79    }
80
81    fn repair_style(&self, node: &ServoThreadSafeLayoutNode, context: &SharedStyleContext) {
82        if let Some(layout_object) = &*self.self_box.borrow() {
83            layout_object.repair_style(context, node, &node.style(context));
84        }
85
86        for pseudo_layout_data in self.pseudo_boxes.iter() {
87            let Some(node_with_pseudo) = node.with_pseudo(pseudo_layout_data.pseudo) else {
88                continue;
89            };
90            pseudo_layout_data
91                .data
92                .borrow()
93                .repair_style(&node_with_pseudo, context);
94        }
95    }
96
97    fn clear_fragment_layout_cache(&self) {
98        if let Some(data) = self.self_box.borrow().as_ref() {
99            data.with_each_base(LayoutBoxBase::clear_fragment_layout_cache);
100        }
101        for pseudo_layout_data in self.pseudo_boxes.iter() {
102            pseudo_layout_data
103                .data
104                .borrow()
105                .clear_fragment_layout_cache();
106        }
107    }
108}
109
110/// A box that is stored in one of the `DOMLayoutData` slots.
111#[derive(MallocSizeOf)]
112pub(super) enum LayoutBox {
113    DisplayContents(SharedInlineStyles),
114    BlockLevel(ArcRefCell<BlockLevelBox>),
115    InlineLevel(Vec<ArcRefCell<InlineItem>>),
116    FlexLevel(ArcRefCell<FlexLevelBox>),
117    TableLevelBox(TableLevelBox),
118    TaffyItemBox(ArcRefCell<TaffyItemBox>),
119}
120
121impl LayoutBox {
122    pub(crate) fn with_each_base(&self, callback: impl Fn(&LayoutBoxBase)) {
123        self.with_base_fold((), |_, base| callback(base))
124    }
125
126    pub(crate) fn with_first_base<T>(
127        &self,
128        callback: impl FnOnce(&LayoutBoxBase) -> T,
129    ) -> Option<T> {
130        Some(match self {
131            LayoutBox::DisplayContents(..) => return None,
132            LayoutBox::BlockLevel(block_level_box) => block_level_box.borrow().with_base(callback),
133            LayoutBox::InlineLevel(inline_items) => {
134                inline_items.first()?.borrow().with_base(callback)
135            },
136            LayoutBox::FlexLevel(flex_level_box) => flex_level_box.borrow().with_base(callback),
137            LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box.borrow().with_base(callback),
138            LayoutBox::TableLevelBox(table_box) => table_box.with_base(callback),
139        })
140    }
141
142    pub(crate) fn with_base_flat<T>(&self, callback: impl Fn(&LayoutBoxBase) -> Vec<T>) -> Vec<T> {
143        match self {
144            LayoutBox::DisplayContents(..) => vec![],
145            LayoutBox::BlockLevel(block_level_box) => block_level_box.borrow().with_base(callback),
146            LayoutBox::InlineLevel(inline_items) => inline_items
147                .iter()
148                .flat_map(|inline_item| inline_item.borrow().with_base(&callback))
149                .collect(),
150            LayoutBox::FlexLevel(flex_level_box) => flex_level_box.borrow().with_base(callback),
151            LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box.borrow().with_base(callback),
152            LayoutBox::TableLevelBox(table_box) => table_box.with_base(callback),
153        }
154    }
155
156    pub(crate) fn with_base_fold<T>(
157        &self,
158        init: T,
159        callback: impl Fn(T, &LayoutBoxBase) -> T,
160    ) -> T {
161        match self {
162            LayoutBox::DisplayContents(..) => init,
163            LayoutBox::BlockLevel(block_level_box) => block_level_box
164                .borrow()
165                .with_base(|base| callback(init, base)),
166            LayoutBox::InlineLevel(inline_items) => inline_items.iter().fold(init, |acc, item| {
167                item.borrow().with_base(|base| callback(acc, base))
168            }),
169            LayoutBox::FlexLevel(flex_level_box) => flex_level_box
170                .borrow()
171                .with_base(|base| callback(init, base)),
172            LayoutBox::TableLevelBox(table_level_box) => {
173                table_level_box.with_base(|base| callback(init, base))
174            },
175            LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box
176                .borrow()
177                .with_base(|base| callback(init, base)),
178        }
179    }
180
181    pub(crate) fn with_base_mut_fold<T>(
182        &mut self,
183        init: T,
184        callback: impl Fn(T, &mut LayoutBoxBase) -> T,
185    ) -> T {
186        match self {
187            LayoutBox::DisplayContents(..) => init,
188            LayoutBox::BlockLevel(block_level_box) => block_level_box
189                .borrow_mut()
190                .with_base_mut(|base| callback(init, base)),
191            LayoutBox::InlineLevel(inline_items) => inline_items.iter().fold(init, |acc, item| {
192                item.borrow_mut().with_base_mut(|base| callback(acc, base))
193            }),
194            LayoutBox::FlexLevel(flex_level_box) => flex_level_box
195                .borrow_mut()
196                .with_base_mut(|base| callback(init, base)),
197            LayoutBox::TableLevelBox(table_level_box) => {
198                table_level_box.with_base_mut(|base| callback(init, base))
199            },
200            LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box
201                .borrow_mut()
202                .with_base_mut(|base| callback(init, base)),
203        }
204    }
205
206    fn repair_style(
207        &self,
208        context: &SharedStyleContext,
209        node: &ServoThreadSafeLayoutNode,
210        new_style: &ServoArc<ComputedValues>,
211    ) {
212        match self {
213            LayoutBox::DisplayContents(inline_shared_styles) => {
214                *inline_shared_styles.style.borrow_mut() = new_style.clone();
215                *inline_shared_styles.selected.borrow_mut() = node.selected_style();
216            },
217            LayoutBox::BlockLevel(block_level_box) => {
218                block_level_box
219                    .borrow_mut()
220                    .repair_style(context, node, new_style);
221            },
222            LayoutBox::InlineLevel(inline_items) => {
223                for inline_item in inline_items {
224                    inline_item
225                        .borrow_mut()
226                        .repair_style(context, node, new_style);
227                }
228            },
229            LayoutBox::FlexLevel(flex_level_box) => flex_level_box
230                .borrow_mut()
231                .repair_style(context, node, new_style),
232            LayoutBox::TableLevelBox(table_level_box) => {
233                table_level_box.repair_style(context, node, new_style)
234            },
235            LayoutBox::TaffyItemBox(taffy_item_box) => taffy_item_box
236                .borrow_mut()
237                .repair_style(context, node, new_style),
238        }
239    }
240
241    /// If this [`LayoutBox`] represents an unsplit (due to inline-block splits) inline
242    /// level item, unwrap and return it. If not, return `None`.
243    pub(crate) fn unsplit_inline_level_layout_box(self) -> Option<ArcRefCell<InlineItem>> {
244        let LayoutBox::InlineLevel(inline_level_boxes) = self else {
245            return None;
246        };
247        // If this element box has been subject to inline-block splitting, ignore it. It's
248        // not useful currently for incremental box tree construction.
249        if inline_level_boxes.len() != 1 {
250            return None;
251        }
252        inline_level_boxes.into_iter().next()
253    }
254}
255
256/// A wrapper for [`InnerDOMLayoutData`]. This is necessary to give the entire data
257/// structure interior mutability, as we will need to mutate the layout data of
258/// non-mutable DOM nodes.
259#[derive(Default, MallocSizeOf)]
260pub struct DOMLayoutData(AtomicRefCell<InnerDOMLayoutData>);
261
262// The implementation of this trait allows the data to be stored in the DOM.
263impl LayoutDataTrait for DOMLayoutData {}
264impl GenericLayoutDataTrait for DOMLayoutData {
265    fn as_any(&self) -> &dyn std::any::Any {
266        self
267    }
268}
269
270pub struct BoxSlot<'dom> {
271    pub(crate) slot: Option<ArcRefCell<Option<LayoutBox>>>,
272    pub(crate) marker: PhantomData<&'dom ()>,
273}
274
275impl From<ArcRefCell<Option<LayoutBox>>> for BoxSlot<'_> {
276    fn from(layout_box_slot: ArcRefCell<Option<LayoutBox>>) -> Self {
277        let slot = Some(layout_box_slot);
278        Self {
279            slot,
280            marker: PhantomData,
281        }
282    }
283}
284
285/// A mutable reference to a `LayoutBox` stored in a DOM element.
286impl BoxSlot<'_> {
287    pub(crate) fn set(mut self, box_: LayoutBox) {
288        if let Some(slot) = &mut self.slot {
289            *slot.borrow_mut() = Some(box_);
290        }
291    }
292
293    pub(crate) fn take_layout_box_if_undamaged(&self, damage: LayoutDamage) -> Option<LayoutBox> {
294        if damage.has_box_damage() {
295            return None;
296        }
297        self.slot.as_ref().and_then(|slot| slot.borrow_mut().take())
298    }
299}
300
301impl Drop for BoxSlot<'_> {
302    fn drop(&mut self) {
303        if !std::thread::panicking() {
304            if let Some(slot) = &mut self.slot {
305                assert!(slot.borrow().is_some(), "failed to set a layout box");
306            }
307        }
308    }
309}
310
311pub(crate) trait NodeExt<'dom> {
312    /// Returns the image if it’s loaded, and its size in image pixels
313    /// adjusted for `image_density`.
314    fn as_image(&self) -> Option<(Option<Image>, PhysicalSize<f64>)>;
315    fn as_canvas(&self) -> Option<(CanvasInfo, PhysicalSize<f64>)>;
316    fn as_iframe(&self) -> Option<(PipelineId, BrowsingContextId)>;
317    fn as_video(&self) -> Option<(Option<webrender_api::ImageKey>, Option<PhysicalSize<f64>>)>;
318    fn as_svg(&self) -> Option<SVGElementData>;
319    fn as_typeless_object_with_data_attribute(&self) -> Option<String>;
320
321    fn ensure_inner_layout_data(&self) -> AtomicRefMut<'dom, InnerDOMLayoutData>;
322    fn inner_layout_data(&self) -> Option<AtomicRef<'dom, InnerDOMLayoutData>>;
323    fn box_slot(&self) -> BoxSlot<'dom>;
324
325    /// Remove boxes for the element itself, and all of its pseudo-element boxes.
326    fn unset_all_boxes(&self);
327
328    /// Remove all pseudo-element boxes for this element.
329    fn unset_all_pseudo_boxes(&self);
330
331    fn fragments_for_pseudo(&self, pseudo_element: Option<PseudoElement>) -> Vec<Fragment>;
332    fn clear_fragment_layout_cache(&self);
333
334    fn repair_style(&self, context: &SharedStyleContext);
335    fn take_restyle_damage(&self) -> LayoutDamage;
336}
337
338impl<'dom> NodeExt<'dom> for ServoThreadSafeLayoutNode<'dom> {
339    fn as_image(&self) -> Option<(Option<Image>, PhysicalSize<f64>)> {
340        let (resource, metadata) = self.image_data()?;
341        let width = metadata.map(|metadata| metadata.width).unwrap_or_default();
342        let height = metadata.map(|metadata| metadata.height).unwrap_or_default();
343        let (mut width, mut height) = (width as f64, height as f64);
344        if let Some(density) = self.image_density().filter(|density| *density != 1.) {
345            width /= density;
346            height /= density;
347        }
348        Some((resource, PhysicalSize::new(width, height)))
349    }
350
351    fn as_svg(&self) -> Option<SVGElementData> {
352        self.svg_data()
353    }
354
355    fn as_video(&self) -> Option<(Option<webrender_api::ImageKey>, Option<PhysicalSize<f64>>)> {
356        let data = self.media_data()?;
357        let natural_size = if let Some(frame) = data.current_frame {
358            Some(PhysicalSize::new(frame.width.into(), frame.height.into()))
359        } else {
360            data.metadata
361                .map(|meta| PhysicalSize::new(meta.width.into(), meta.height.into()))
362        };
363        Some((
364            data.current_frame.map(|frame| frame.image_key),
365            natural_size,
366        ))
367    }
368
369    fn as_canvas(&self) -> Option<(CanvasInfo, PhysicalSize<f64>)> {
370        let canvas_data = self.canvas_data()?;
371        let source = canvas_data.image_key;
372        Some((
373            CanvasInfo { source },
374            PhysicalSize::new(canvas_data.width.into(), canvas_data.height.into()),
375        ))
376    }
377
378    fn as_iframe(&self) -> Option<(PipelineId, BrowsingContextId)> {
379        match (self.iframe_pipeline_id(), self.iframe_browsing_context_id()) {
380            (Some(pipeline_id), Some(browsing_context_id)) => {
381                Some((pipeline_id, browsing_context_id))
382            },
383            _ => None,
384        }
385    }
386
387    fn as_typeless_object_with_data_attribute(&self) -> Option<String> {
388        if self.type_id() !=
389            Some(ScriptLayoutNodeType::Element(
390                LayoutElementType::HTMLObjectElement,
391            ))
392        {
393            return None;
394        }
395
396        // TODO: This is the what the legacy layout system did, but really if Servo
397        // supports any `<object>` that's an image, it should support those with URLs
398        // and `type` attributes with image mime types.
399        let element = self.as_element()?;
400        if element.get_attr(&ns!(), &local_name!("type")).is_some() {
401            return None;
402        }
403        element
404            .get_attr(&ns!(), &local_name!("data"))
405            .map(|string| string.to_owned())
406    }
407
408    fn ensure_inner_layout_data(&self) -> AtomicRefMut<'dom, InnerDOMLayoutData> {
409        if self.layout_data().is_none() {
410            self.initialize_layout_data::<DOMLayoutData>();
411        }
412        self.layout_data()
413            .unwrap()
414            .as_any()
415            .downcast_ref::<DOMLayoutData>()
416            .unwrap()
417            .0
418            .borrow_mut()
419    }
420
421    fn inner_layout_data(&self) -> Option<AtomicRef<'dom, InnerDOMLayoutData>> {
422        self.layout_data().map(|data| {
423            data.as_any()
424                .downcast_ref::<DOMLayoutData>()
425                .unwrap()
426                .0
427                .borrow()
428        })
429    }
430
431    fn box_slot(&self) -> BoxSlot<'dom> {
432        let pseudo_element_chain = self.pseudo_element_chain();
433        let Some(primary) = pseudo_element_chain.primary else {
434            return self.ensure_inner_layout_data().self_box.clone().into();
435        };
436
437        let Some(secondary) = pseudo_element_chain.secondary else {
438            let primary_layout_data = self
439                .ensure_inner_layout_data()
440                .create_pseudo_layout_data(primary);
441            return primary_layout_data.borrow().self_box.clone().into();
442        };
443
444        // It's *very* important that this not borrow the element's main
445        // `InnerLayoutData`. Primary pseudo-elements are processed at the same recursion
446        // level as the main data, so the `BoxSlot` is created sequentially with other
447        // primary pseudo-elements and the element itself. The secondary pseudo-element is
448        // one level deep, so could be happening in parallel with the primary
449        // pseudo-elements or main element layout.
450        let primary_layout_data = self
451            .inner_layout_data()
452            .expect("Should already have element InnerLayoutData here.")
453            .pseudo_layout_data(primary)
454            .expect("Should already have primary pseudo-element InnerLayoutData here");
455        let secondary_layout_data = primary_layout_data
456            .borrow_mut()
457            .create_pseudo_layout_data(secondary);
458        secondary_layout_data.borrow().self_box.clone().into()
459    }
460
461    fn unset_all_boxes(&self) {
462        let mut layout_data = self.ensure_inner_layout_data();
463        *layout_data.self_box.borrow_mut() = None;
464        layout_data.pseudo_boxes.clear();
465
466        // Stylo already takes care of removing all layout data
467        // for DOM descendants of elements with `display: none`.
468    }
469
470    fn unset_all_pseudo_boxes(&self) {
471        self.ensure_inner_layout_data().pseudo_boxes.clear();
472    }
473
474    fn clear_fragment_layout_cache(&self) {
475        if let Some(inner_layout_data) = self.inner_layout_data() {
476            inner_layout_data.clear_fragment_layout_cache();
477        }
478    }
479
480    fn fragments_for_pseudo(&self, pseudo_element: Option<PseudoElement>) -> Vec<Fragment> {
481        let Some(layout_data) = self.inner_layout_data() else {
482            return vec![];
483        };
484        match pseudo_element {
485            Some(pseudo_element) => layout_data
486                .pseudo_layout_data(pseudo_element)
487                .map(|pseudo_layout_data| pseudo_layout_data.borrow().fragments())
488                .unwrap_or_default(),
489            None => layout_data.fragments(),
490        }
491    }
492
493    fn repair_style(&self, context: &SharedStyleContext) {
494        if let Some(layout_data) = self.inner_layout_data() {
495            layout_data.repair_style(self, context);
496        }
497    }
498
499    fn take_restyle_damage(&self) -> LayoutDamage {
500        let damage = self
501            .style_data()
502            .map(|style_data| std::mem::take(&mut style_data.element_data.borrow_mut().damage))
503            .unwrap_or_else(RestyleDamage::reconstruct);
504        LayoutDamage::from_bits_retain(damage.bits())
505    }
506}
layout/dom.rs

layout/
dom.rs
