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, builder.context);
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
88                    .finish(
89                        builder.context,
90                        true,  /* has_first_formatted_line */
91                        false, /* is_single_line_text_box */
92                        builder.info.style.to_bidi_level(),
93                    )
94                    .expect("Did not expect document white space only text runs");
95
96                let block_formatting_context = BlockFormattingContext::from_block_container(
97                    BlockContainer::InlineFormattingContext(inline_formatting_context),
98                );
99
100                let info = builder.anonymous_info();
101                let formatting_context = IndependentFormattingContext::new(
102                    LayoutBoxBase::new(info.into(), info.style.clone()),
103                    IndependentFormattingContextContents::Flow(block_formatting_context),
104                    // This is just a series of anonymous text runs, so we don't need to worry
105                    // about what kind of PropagatedBoxTreeData is used here.
106                    Default::default(),
107                );
108
109                Some(ModernItem {
110                    kind: ModernItemKind::InFlow(formatting_context),
111                    order: 0,
112                    box_slot,
113                })
114            },
115            ModernContainerJob::ElementOrPseudoElement {
116                info,
117                display,
118                contents,
119                box_slot,
120            } => {
121                let is_abspos = info.style.get_box().position.is_absolutely_positioned();
122                let order = if is_abspos {
123                    0
124                } else {
125                    info.style.clone_order()
126                };
127
128                if let Some(layout_box) =
129                    box_slot
130                        .take_layout_box()
131                        .and_then(|layout_box| match &layout_box {
132                            LayoutBox::FlexLevel(_) | LayoutBox::TaffyItemBox(_) => {
133                                Some(layout_box)
134                            },
135                            _ => None,
136                        })
137                {
138                    return Some(ModernItem {
139                        kind: ModernItemKind::ReusedBox(layout_box),
140                        order,
141                        box_slot,
142                    });
143                }
144
145                // Text decorations are not propagated to any out-of-flow descendants. In addition,
146                // absolutes don't affect the size of ancestors so it is fine to allow descendent
147                // tables to resolve percentage columns.
148                let propagated_data = match is_abspos {
149                    false => builder.propagated_data,
150                    true => PropagatedBoxTreeData::default(),
151                };
152
153                let formatting_context = IndependentFormattingContext::construct(
154                    builder.context,
155                    &info,
156                    display.display_inside(),
157                    contents,
158                    propagated_data,
159                );
160
161                let kind = if is_abspos {
162                    ModernItemKind::OutOfFlow(formatting_context)
163                } else {
164                    ModernItemKind::InFlow(formatting_context)
165                };
166                Some(ModernItem {
167                    kind,
168                    order,
169                    box_slot,
170                })
171            },
172        }
173    }
174}
175
176struct ModernContainerTextRun<'dom> {
177    info: NodeAndStyleInfo<'dom>,
178    text: Cow<'dom, str>,
179    style_from_display_contents: Option<SharedInlineStyles>,
180}
181
182impl ModernContainerTextRun<'_> {
183    /// <https://drafts.csswg.org/css-flexbox/#flex-items>:
184    /// > However, if the entire text sequences contains only document white space characters (i.e.
185    /// > characters that can be affected by the white-space property) it is instead not rendered
186    /// > (just as if its text nodes were display:none).
187    fn is_only_document_white_space(&self) -> bool {
188        self.text
189            .bytes()
190            .all(|byte| InlineFormattingContextBuilder::is_document_white_space(byte.into()))
191    }
192}
193
194pub(crate) enum ModernItemKind {
195    InFlow(IndependentFormattingContext),
196    OutOfFlow(IndependentFormattingContext),
197    ReusedBox(LayoutBox),
198}
199
200pub(crate) struct ModernItem<'dom> {
201    pub kind: ModernItemKind,
202    pub order: i32,
203    pub box_slot: BoxSlot<'dom>,
204}
205
206impl<'dom> TraversalHandler<'dom> for ModernContainerBuilder<'_, 'dom> {
207    fn handle_text(&mut self, info: &NodeAndStyleInfo<'dom>, text: Cow<'dom, str>) {
208        self.contiguous_text_runs.push(ModernContainerTextRun {
209            info: info.clone(),
210            text,
211            style_from_display_contents: self.display_contents_shared_styles.last().cloned(),
212        })
213    }
214
215    fn enter_display_contents(&mut self, styles: SharedInlineStyles) {
216        self.display_contents_shared_styles.push(styles);
217    }
218
219    fn leave_display_contents(&mut self) {
220        self.display_contents_shared_styles.pop();
221    }
222
223    /// Or pseudo-element
224    fn handle_element(
225        &mut self,
226        info: &NodeAndStyleInfo<'dom>,
227        display: DisplayGeneratingBox,
228        contents: Contents,
229        box_slot: BoxSlot<'dom>,
230    ) {
231        self.wrap_any_text_in_anonymous_block_container();
232
233        self.jobs.push(ModernContainerJob::ElementOrPseudoElement {
234            info: info.clone(),
235            display,
236            contents,
237            box_slot,
238        })
239    }
240}
241
242impl<'a, 'dom> ModernContainerBuilder<'a, 'dom> {
243    pub fn new(
244        context: &'a LayoutContext<'a>,
245        info: &'a NodeAndStyleInfo<'dom>,
246        propagated_data: PropagatedBoxTreeData,
247    ) -> Self {
248        ModernContainerBuilder {
249            context,
250            info,
251            anonymous_info: Default::default(),
252            propagated_data: propagated_data.disallowing_percentage_table_columns(),
253            contiguous_text_runs: Vec::new(),
254            jobs: Vec::new(),
255            has_text_runs: false,
256            display_contents_shared_styles: Vec::new(),
257        }
258    }
259
260    fn anonymous_info(&self) -> &NodeAndStyleInfo<'dom> {
261        self.anonymous_info.get_or_init(|| {
262            self.info
263                .with_pseudo_element(self.context, PseudoElement::ServoAnonymousBox)
264                .expect("Should always be able to construct info for anonymous boxes.")
265        })
266    }
267
268    fn wrap_any_text_in_anonymous_block_container(&mut self) {
269        let runs = std::mem::take(&mut self.contiguous_text_runs);
270
271        // If there is no text run or they all only contain document white space
272        // characters, do nothing.
273        if runs
274            .iter()
275            .all(ModernContainerTextRun::is_only_document_white_space)
276        {
277            return;
278        }
279
280        let box_slot = self.anonymous_info().node.box_slot();
281        self.jobs.push(ModernContainerJob::TextRuns(runs, box_slot));
282        self.has_text_runs = true;
283    }
284
285    pub(crate) fn finish(mut self) -> Vec<ModernItem<'dom>> {
286        self.wrap_any_text_in_anonymous_block_container();
287
288        let jobs = std::mem::take(&mut self.jobs);
289        let mut children: Vec<_> = if self.context.use_rayon {
290            jobs.into_par_iter()
291                .filter_map(|job| job.finish(&self))
292                .collect()
293        } else {
294            jobs.into_iter()
295                .filter_map(|job| job.finish(&self))
296                .collect()
297        };
298
299        // https://drafts.csswg.org/css-flexbox/#order-modified-document-order
300        children.sort_by_key(|child| child.order);
301
302        children
303    }
304}
layout/construct_modern.rs

layout/
construct_modern.rs
