layout/
construct_modern.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
5//! Layout construction code that is shared between modern layout modes (Flexbox and CSS Grid)
6
7use std::borrow::Cow;
8use std::sync::OnceLock;
9
10use rayon::iter::{IntoParallelIterator, ParallelIterator};
11use style::selector_parser::PseudoElement;
12
13use crate::PropagatedBoxTreeData;
14use crate::context::LayoutContext;
15use crate::dom::{BoxSlot, LayoutBox, NodeExt};
16use crate::dom_traversal::{Contents, NodeAndStyleInfo, TraversalHandler};
17use crate::flow::inline::SharedInlineStyles;
18use crate::flow::inline::construct::InlineFormattingContextBuilder;
19use crate::flow::{BlockContainer, BlockFormattingContext};
20use crate::formatting_contexts::{
21    IndependentFormattingContext, IndependentFormattingContextContents,
22};
23use crate::layout_box_base::LayoutBoxBase;
24use crate::style_ext::{ComputedValuesExt, DisplayGeneratingBox};
25
26/// A builder used for both flex and grid containers.
27pub(crate) struct ModernContainerBuilder<'a, 'dom> {
28    context: &'a LayoutContext<'a>,
29    info: &'a NodeAndStyleInfo<'dom>,
30    /// A [`NodeAndStyleInfo`] to use for anonymous box children. Only initialized if
31    /// there is such a child.
32    anonymous_info: OnceLock<NodeAndStyleInfo<'dom>>,
33    propagated_data: PropagatedBoxTreeData,
34    contiguous_text_runs: Vec<ModernContainerTextRun<'dom>>,
35    /// To be run in parallel with rayon in `finish`
36    jobs: Vec<ModernContainerJob<'dom>>,
37    has_text_runs: bool,
38    /// A stack of `display: contents` styles currently in scope. This matters because
39    /// `display: contents` elements do not generate boxes but still provide styling
40    /// for their children, and text runs which get different styles due to that can be
41    /// wrapped into the same anonymous flex/grid item.
42    display_contents_shared_styles: Vec<SharedInlineStyles>,
43}
44
45enum ModernContainerJob<'dom> {
46    ElementOrPseudoElement {
47        info: NodeAndStyleInfo<'dom>,
48        display: DisplayGeneratingBox,
49        contents: Contents,
50        box_slot: BoxSlot<'dom>,
51    },
52    TextRuns(Vec<ModernContainerTextRun<'dom>>, BoxSlot<'dom>),
53}
54
55impl<'dom> ModernContainerJob<'dom> {
56    fn finish(self, builder: &ModernContainerBuilder) -> Option<ModernItem<'dom>> {
57        match self {
58            ModernContainerJob::TextRuns(runs, box_slot) => {
59                let mut inline_formatting_context_builder =
60                    InlineFormattingContextBuilder::new(builder.info);
61                let mut last_style_from_display_contents: Option<SharedInlineStyles> = None;
62                for flex_text_run in runs.into_iter() {
63                    match (
64                        last_style_from_display_contents.as_ref(),
65                        flex_text_run.style_from_display_contents.as_ref(),
66                    ) {
67                        (None, None) => {},
68                        (Some(old_style), Some(new_style)) if old_style.ptr_eq(new_style) => {},
69                        _ => {
70                            // If we have nested `display: contents`, then this logic will leave the
71                            // outer one before entering the new one. This is fine, because the inline
72                            // formatting context builder only uses the last style on the stack.
73                            if last_style_from_display_contents.is_some() {
74                                inline_formatting_context_builder.leave_display_contents();
75                            }
76                            if let Some(ref new_style) = flex_text_run.style_from_display_contents {
77                                inline_formatting_context_builder
78                                    .enter_display_contents(new_style.clone());
79                            }
80                        },
81                    }
82                    last_style_from_display_contents = flex_text_run.style_from_display_contents;
83                    inline_formatting_context_builder
84                        .push_text(flex_text_run.text, &flex_text_run.info);
85                }
86
87                let inline_formatting_context = inline_formatting_context_builder.finish(
88                    builder.context,
89                    true,  /* has_first_formatted_line */
90                    false, /* is_single_line_text_box */
91                    builder.info.style.to_bidi_level(),
92                )?;
93
94                let block_formatting_context = BlockFormattingContext::from_block_container(
95                    BlockContainer::InlineFormattingContext(inline_formatting_context),
96                );
97
98                let info = builder.anonymous_info();
99                let formatting_context = IndependentFormattingContext::new(
100                    LayoutBoxBase::new(info.into(), info.style.clone()),
101                    IndependentFormattingContextContents::Flow(block_formatting_context),
102                );
103
104                Some(ModernItem {
105                    kind: ModernItemKind::InFlow(formatting_context),
106                    order: 0,
107                    box_slot,
108                })
109            },
110            ModernContainerJob::ElementOrPseudoElement {
111                info,
112                display,
113                contents,
114                box_slot,
115            } => {
116                let is_abspos = info.style.get_box().position.is_absolutely_positioned();
117                let order = if is_abspos {
118                    0
119                } else {
120                    info.style.clone_order()
121                };
122
123                if let Some(layout_box) = box_slot
124                    .take_layout_box_if_undamaged(info.damage)
125                    .and_then(|layout_box| match &layout_box {
126                        LayoutBox::FlexLevel(_) | LayoutBox::TaffyItemBox(_) => Some(layout_box),
127                        _ => None,
128                    })
129                {
130                    return Some(ModernItem {
131                        kind: ModernItemKind::ReusedBox(layout_box),
132                        order,
133                        box_slot,
134                    });
135                }
136
137                // Text decorations are not propagated to any out-of-flow descendants. In addition,
138                // absolutes don't affect the size of ancestors so it is fine to allow descendent
139                // tables to resolve percentage columns.
140                let propagated_data = match is_abspos {
141                    false => builder.propagated_data,
142                    true => PropagatedBoxTreeData::default(),
143                };
144
145                let formatting_context = IndependentFormattingContext::construct(
146                    builder.context,
147                    &info,
148                    display.display_inside(),
149                    contents,
150                    propagated_data,
151                );
152
153                let kind = if is_abspos {
154                    ModernItemKind::OutOfFlow(formatting_context)
155                } else {
156                    ModernItemKind::InFlow(formatting_context)
157                };
158                Some(ModernItem {
159                    kind,
160                    order,
161                    box_slot,
162                })
163            },
164        }
165    }
166}
167
168struct ModernContainerTextRun<'dom> {
169    info: NodeAndStyleInfo<'dom>,
170    text: Cow<'dom, str>,
171    style_from_display_contents: Option<SharedInlineStyles>,
172}
173
174impl ModernContainerTextRun<'_> {
175    /// <https://drafts.csswg.org/css-text/#white-space>
176    fn is_only_document_white_space(&self) -> bool {
177        // FIXME: is this the right definition? See
178        // https://github.com/w3c/csswg-drafts/issues/5146
179        // https://github.com/w3c/csswg-drafts/issues/5147
180        self.text
181            .bytes()
182            .all(|byte| matches!(byte, b' ' | b'\n' | b'\t'))
183    }
184}
185
186pub(crate) enum ModernItemKind {
187    InFlow(IndependentFormattingContext),
188    OutOfFlow(IndependentFormattingContext),
189    ReusedBox(LayoutBox),
190}
191
192pub(crate) struct ModernItem<'dom> {
193    pub kind: ModernItemKind,
194    pub order: i32,
195    pub box_slot: BoxSlot<'dom>,
196}
197
198impl<'dom> TraversalHandler<'dom> for ModernContainerBuilder<'_, 'dom> {
199    fn handle_text(&mut self, info: &NodeAndStyleInfo<'dom>, text: Cow<'dom, str>) {
200        self.contiguous_text_runs.push(ModernContainerTextRun {
201            info: info.clone(),
202            text,
203            style_from_display_contents: self.display_contents_shared_styles.last().cloned(),
204        })
205    }
206
207    fn enter_display_contents(&mut self, styles: SharedInlineStyles) {
208        self.display_contents_shared_styles.push(styles);
209    }
210
211    fn leave_display_contents(&mut self) {
212        self.display_contents_shared_styles.pop();
213    }
214
215    /// Or pseudo-element
216    fn handle_element(
217        &mut self,
218        info: &NodeAndStyleInfo<'dom>,
219        display: DisplayGeneratingBox,
220        contents: Contents,
221        box_slot: BoxSlot<'dom>,
222    ) {
223        self.wrap_any_text_in_anonymous_block_container();
224
225        self.jobs.push(ModernContainerJob::ElementOrPseudoElement {
226            info: info.clone(),
227            display,
228            contents,
229            box_slot,
230        })
231    }
232}
233
234impl<'a, 'dom> ModernContainerBuilder<'a, 'dom> {
235    pub fn new(
236        context: &'a LayoutContext<'a>,
237        info: &'a NodeAndStyleInfo<'dom>,
238        propagated_data: PropagatedBoxTreeData,
239    ) -> Self {
240        ModernContainerBuilder {
241            context,
242            info,
243            anonymous_info: Default::default(),
244            propagated_data: propagated_data.disallowing_percentage_table_columns(),
245            contiguous_text_runs: Vec::new(),
246            jobs: Vec::new(),
247            has_text_runs: false,
248            display_contents_shared_styles: Vec::new(),
249        }
250    }
251
252    fn anonymous_info(&self) -> &NodeAndStyleInfo<'dom> {
253        self.anonymous_info.get_or_init(|| {
254            self.info
255                .with_pseudo_element(self.context, PseudoElement::ServoAnonymousBox)
256                .expect("Should always be able to construct info for anonymous boxes.")
257        })
258    }
259
260    fn wrap_any_text_in_anonymous_block_container(&mut self) {
261        let runs = std::mem::take(&mut self.contiguous_text_runs);
262
263        // If there is no text run or they all only contain document white space
264        // characters, do nothing.
265        if runs
266            .iter()
267            .all(ModernContainerTextRun::is_only_document_white_space)
268        {
269            return;
270        }
271
272        let box_slot = self.anonymous_info().node.box_slot();
273        self.jobs.push(ModernContainerJob::TextRuns(runs, box_slot));
274        self.has_text_runs = true;
275    }
276
277    pub(crate) fn finish(mut self) -> Vec<ModernItem<'dom>> {
278        self.wrap_any_text_in_anonymous_block_container();
279
280        let jobs = std::mem::take(&mut self.jobs);
281        let mut children: Vec<_> = if self.context.use_rayon {
282            jobs.into_par_iter()
283                .filter_map(|job| job.finish(&self))
284                .collect()
285        } else {
286            jobs.into_iter()
287                .filter_map(|job| job.finish(&self))
288                .collect()
289        };
290
291        // https://drafts.csswg.org/css-flexbox/#order-modified-document-order
292        children.sort_by_key(|child| child.order);
293
294        children
295    }
296}
layout/construct_modern.rs

layout/
construct_modern.rs
