PrintTree and RoundTree: use Layout instead of &Layout (#849)
1//! Low-level access to the layout algorithms themselves. For a higher-level API, see the [`TaffyTree`](crate::TaffyTree) struct.
2//!
3//! ### Layout functions
4//!
5//! The layout functions all take an [`&mut impl LayoutPartialTree`](crate::LayoutPartialTree) parameter, which represents a single container node and it's direct children.
6//!
7//! | Function | Purpose |
8//! | --- | --- |
9//! | [`compute_flexbox_layout`] | Layout a Flexbox container and it's direct children |
10//! | [`compute_grid_layout`] | Layout a CSS Grid container and it's direct children |
11//! | [`compute_block_layout`] | Layout a Block container and it's direct children |
12//! | [`compute_leaf_layout`] | Applies common properties like padding/border/aspect-ratio to a node before deferring to a passed closure to determine it's size. Can be applied to nodes like text or image nodes. |
13//! | [`compute_root_layout`] | Layout the root node of a tree (regardless of it's layout mode). This function is typically called once to begin a layout run. | |
14//! | [`compute_hidden_layout`] | Mark a node as hidden during layout (like `Display::None`) |
15//! | [`compute_cached_layout`] | Attempts to find a cached layout for the specified node and layout inputs. Uses the provided closure to compute the layout (and then stores the result in the cache) if no cached layout is found. |
16//!
17//! ### Other functions
18//!
19//! | Function | Requires | Purpose |
20//! | --- | --- | --- |
21//! | [`round_layout`] | [`RoundTree`] | Round a tree of float-valued layouts to integer pixels |
22//! | [`print_tree`](crate::print_tree) | [`PrintTree`](crate::PrintTree) | Print a debug representation of a node tree and it's computed layout |
23//!
24pub(crate) mod common;
25pub(crate) mod leaf;
26
27#[cfg(feature = "block_layout")]
28pub(crate) mod block;
29
30#[cfg(feature = "flexbox")]
31pub(crate) mod flexbox;
32
33#[cfg(feature = "grid")]
34pub(crate) mod grid;
35
36pub use leaf::compute_leaf_layout;
37
38#[cfg(feature = "block_layout")]
39pub use self::block::compute_block_layout;
40
41#[cfg(feature = "flexbox")]
42pub use self::flexbox::compute_flexbox_layout;
43
44#[cfg(feature = "grid")]
45pub use self::grid::compute_grid_layout;
46
47use crate::geometry::{Line, Point, Size};
48use crate::style::{AvailableSpace, CoreStyle, Overflow};
49use crate::tree::{
50 Layout, LayoutInput, LayoutOutput, LayoutPartialTree, LayoutPartialTreeExt, NodeId, RoundTree, SizingMode,
51};
52use crate::util::debug::{debug_log, debug_log_node, debug_pop_node, debug_push_node};
53use crate::util::sys::round;
54use crate::util::ResolveOrZero;
55use crate::{CacheTree, MaybeMath, MaybeResolve};
56
57/// Compute layout for the root node in the tree
58pub fn compute_root_layout(tree: &mut impl LayoutPartialTree, root: NodeId, available_space: Size<AvailableSpace>) {
59 let mut known_dimensions = Size::NONE;
60
61 #[cfg(feature = "block_layout")]
62 {
63 use crate::BoxSizing;
64
65 let parent_size = available_space.into_options();
66 let style = tree.get_core_container_style(root);
67
68 if style.is_block() {
69 // Pull these out earlier to avoid borrowing issues
70 let aspect_ratio = style.aspect_ratio();
71 let margin = style.margin().resolve_or_zero(parent_size.width, |val, basis| tree.calc(val, basis));
72 let padding = style.padding().resolve_or_zero(parent_size.width, |val, basis| tree.calc(val, basis));
73 let border = style.border().resolve_or_zero(parent_size.width, |val, basis| tree.calc(val, basis));
74 let padding_border_size = (padding + border).sum_axes();
75 let box_sizing_adjustment =
76 if style.box_sizing() == BoxSizing::ContentBox { padding_border_size } else { Size::ZERO };
77
78 let min_size = style
79 .min_size()
80 .maybe_resolve(parent_size, |val, basis| tree.calc(val, basis))
81 .maybe_apply_aspect_ratio(aspect_ratio)
82 .maybe_add(box_sizing_adjustment);
83 let max_size = style
84 .max_size()
85 .maybe_resolve(parent_size, |val, basis| tree.calc(val, basis))
86 .maybe_apply_aspect_ratio(aspect_ratio)
87 .maybe_add(box_sizing_adjustment);
88 let clamped_style_size = style
89 .size()
90 .maybe_resolve(parent_size, |val, basis| tree.calc(val, basis))
91 .maybe_apply_aspect_ratio(aspect_ratio)
92 .maybe_add(box_sizing_adjustment)
93 .maybe_clamp(min_size, max_size);
94
95 // If both min and max in a given axis are set and max <= min then this determines the size in that axis
96 let min_max_definite_size = min_size.zip_map(max_size, |min, max| match (min, max) {
97 (Some(min), Some(max)) if max <= min => Some(min),
98 _ => None,
99 });
100
101 // Block nodes automatically stretch fit their width to fit available space if available space is definite
102 let available_space_based_size = Size {
103 width: available_space.width.into_option().maybe_sub(margin.horizontal_axis_sum()),
104 height: None,
105 };
106
107 let styled_based_known_dimensions = known_dimensions
108 .or(min_max_definite_size)
109 .or(clamped_style_size)
110 .or(available_space_based_size)
111 .maybe_max(padding_border_size);
112
113 known_dimensions = styled_based_known_dimensions;
114 }
115 }
116
117 // Recursively compute node layout
118 let output = tree.perform_child_layout(
119 root,
120 known_dimensions,
121 available_space.into_options(),
122 available_space,
123 SizingMode::InherentSize,
124 Line::FALSE,
125 );
126
127 let style = tree.get_core_container_style(root);
128 let padding =
129 style.padding().resolve_or_zero(available_space.width.into_option(), |val, basis| tree.calc(val, basis));
130 let border =
131 style.border().resolve_or_zero(available_space.width.into_option(), |val, basis| tree.calc(val, basis));
132 let margin =
133 style.margin().resolve_or_zero(available_space.width.into_option(), |val, basis| tree.calc(val, basis));
134 let scrollbar_size = Size {
135 width: if style.overflow().y == Overflow::Scroll { style.scrollbar_width() } else { 0.0 },
136 height: if style.overflow().x == Overflow::Scroll { style.scrollbar_width() } else { 0.0 },
137 };
138 drop(style);
139
140 tree.set_unrounded_layout(
141 root,
142 &Layout {
143 order: 0,
144 location: Point::ZERO,
145 size: output.size,
146 #[cfg(feature = "content_size")]
147 content_size: output.content_size,
148 scrollbar_size,
149 padding,
150 border,
151 // TODO: support auto margins for root node?
152 margin,
153 },
154 );
155}
156
157/// Attempts to find a cached layout for the specified node and layout inputs.
158///
159/// Uses the provided closure to compute the layout (and then stores the result in the cache) if no cached layout is found.
160#[inline(always)]
161pub fn compute_cached_layout<Tree: CacheTree + ?Sized, ComputeFunction>(
162 tree: &mut Tree,
163 node: NodeId,
164 inputs: LayoutInput,
165 mut compute_uncached: ComputeFunction,
166) -> LayoutOutput
167where
168 ComputeFunction: FnMut(&mut Tree, NodeId, LayoutInput) -> LayoutOutput,
169{
170 debug_push_node!(node);
171 let LayoutInput { known_dimensions, available_space, run_mode, .. } = inputs;
172
173 // First we check if we have a cached result for the given input
174 let cache_entry = tree.cache_get(node, known_dimensions, available_space, run_mode);
175 if let Some(cached_size_and_baselines) = cache_entry {
176 debug_log_node!(known_dimensions, inputs.parent_size, available_space, run_mode, inputs.sizing_mode);
177 debug_log!("RESULT (CACHED)", dbg:cached_size_and_baselines.size);
178 debug_pop_node!();
179 return cached_size_and_baselines;
180 }
181
182 debug_log_node!(known_dimensions, inputs.parent_size, available_space, run_mode, inputs.sizing_mode);
183
184 let computed_size_and_baselines = compute_uncached(tree, node, inputs);
185
186 // Cache result
187 tree.cache_store(node, known_dimensions, available_space, run_mode, computed_size_and_baselines);
188
189 debug_log!("RESULT", dbg:computed_size_and_baselines.size);
190 debug_pop_node!();
191
192 computed_size_and_baselines
193}
194
195/// Rounds the calculated layout to exact pixel values
196///
197/// In order to ensure that no gaps in the layout are introduced we:
198/// - Always round based on the cumulative x/y coordinates (relative to the viewport) rather than
199/// parent-relative coordinates
200/// - Compute width/height by first rounding the top/bottom/left/right and then computing the difference
201/// rather than rounding the width/height directly
202///
203/// See <https://github.com/facebook/yoga/commit/aa5b296ac78f7a22e1aeaf4891243c6bb76488e2> for more context
204///
205/// In order to prevent innacuracies caused by rounding already-rounded values, we read from `unrounded_layout`
206/// and write to `final_layout`.
207pub fn round_layout(tree: &mut impl RoundTree, node_id: NodeId) {
208 return round_layout_inner(tree, node_id, 0.0, 0.0);
209
210 /// Recursive function to apply rounding to all descendents
211 fn round_layout_inner(tree: &mut impl RoundTree, node_id: NodeId, cumulative_x: f32, cumulative_y: f32) {
212 let unrounded_layout = tree.get_unrounded_layout(node_id);
213 let mut layout = unrounded_layout;
214
215 let cumulative_x = cumulative_x + unrounded_layout.location.x;
216 let cumulative_y = cumulative_y + unrounded_layout.location.y;
217
218 layout.location.x = round(unrounded_layout.location.x);
219 layout.location.y = round(unrounded_layout.location.y);
220 layout.size.width = round(cumulative_x + unrounded_layout.size.width) - round(cumulative_x);
221 layout.size.height = round(cumulative_y + unrounded_layout.size.height) - round(cumulative_y);
222 layout.scrollbar_size.width = round(unrounded_layout.scrollbar_size.width);
223 layout.scrollbar_size.height = round(unrounded_layout.scrollbar_size.height);
224 layout.border.left = round(cumulative_x + unrounded_layout.border.left) - round(cumulative_x);
225 layout.border.right = round(cumulative_x + unrounded_layout.size.width)
226 - round(cumulative_x + unrounded_layout.size.width - unrounded_layout.border.right);
227 layout.border.top = round(cumulative_y + unrounded_layout.border.top) - round(cumulative_y);
228 layout.border.bottom = round(cumulative_y + unrounded_layout.size.height)
229 - round(cumulative_y + unrounded_layout.size.height - unrounded_layout.border.bottom);
230 layout.padding.left = round(cumulative_x + unrounded_layout.padding.left) - round(cumulative_x);
231 layout.padding.right = round(cumulative_x + unrounded_layout.size.width)
232 - round(cumulative_x + unrounded_layout.size.width - unrounded_layout.padding.right);
233 layout.padding.top = round(cumulative_y + unrounded_layout.padding.top) - round(cumulative_y);
234 layout.padding.bottom = round(cumulative_y + unrounded_layout.size.height)
235 - round(cumulative_y + unrounded_layout.size.height - unrounded_layout.padding.bottom);
236
237 #[cfg(feature = "content_size")]
238 round_content_size(&mut layout, unrounded_layout.content_size, cumulative_x, cumulative_y);
239
240 tree.set_final_layout(node_id, &layout);
241
242 let child_count = tree.child_count(node_id);
243 for index in 0..child_count {
244 let child = tree.get_child_id(node_id, index);
245 round_layout_inner(tree, child, cumulative_x, cumulative_y);
246 }
247 }
248
249 #[cfg(feature = "content_size")]
250 #[inline(always)]
251 /// Round content size variables.
252 /// This is split into a separate function to make it easier to feature flag.
253 fn round_content_size(
254 layout: &mut Layout,
255 unrounded_content_size: Size<f32>,
256 cumulative_x: f32,
257 cumulative_y: f32,
258 ) {
259 layout.content_size.width = round(cumulative_x + unrounded_content_size.width) - round(cumulative_x);
260 layout.content_size.height = round(cumulative_y + unrounded_content_size.height) - round(cumulative_y);
261 }
262}
263
264/// Creates a layout for this node and its children, recursively.
265/// Each hidden node has zero size and is placed at the origin
266pub fn compute_hidden_layout(tree: &mut (impl LayoutPartialTree + CacheTree), node: NodeId) -> LayoutOutput {
267 // Clear cache and set zeroed-out layout for the node
268 tree.cache_clear(node);
269 tree.set_unrounded_layout(node, &Layout::with_order(0));
270
271 // Perform hidden layout on all children
272 for index in 0..tree.child_count(node) {
273 let child_id = tree.get_child_id(node, index);
274 tree.compute_child_layout(child_id, LayoutInput::HIDDEN);
275 }
276
277 LayoutOutput::HIDDEN
278}
279
280/// A module for unified re-exports of detailed layout info structs, used by low level API
281#[cfg(feature = "detailed_layout_info")]
282pub mod detailed_info {
283 #[cfg(feature = "grid")]
284 pub use super::grid::{DetailedGridInfo, DetailedGridTracksInfo};
285}
286
287#[cfg(test)]
288mod tests {
289 use super::compute_hidden_layout;
290 use crate::geometry::{Point, Size};
291 use crate::style::{Display, Style};
292 use crate::TaffyTree;
293
294 #[test]
295 fn hidden_layout_should_hide_recursively() {
296 let mut taffy: TaffyTree<()> = TaffyTree::new();
297
298 let style: Style = Style { display: Display::Flex, size: Size::from_lengths(50.0, 50.0), ..Default::default() };
299
300 let grandchild_00 = taffy.new_leaf(style.clone()).unwrap();
301 let grandchild_01 = taffy.new_leaf(style.clone()).unwrap();
302 let child_00 = taffy.new_with_children(style.clone(), &[grandchild_00, grandchild_01]).unwrap();
303
304 let grandchild_02 = taffy.new_leaf(style.clone()).unwrap();
305 let child_01 = taffy.new_with_children(style.clone(), &[grandchild_02]).unwrap();
306
307 let root = taffy
308 .new_with_children(
309 Style { display: Display::None, size: Size::from_lengths(50.0, 50.0), ..Default::default() },
310 &[child_00, child_01],
311 )
312 .unwrap();
313
314 compute_hidden_layout(&mut taffy.as_layout_tree(), root);
315
316 // Whatever size and display-mode the nodes had previously,
317 // all layouts should resolve to ZERO due to the root's DISPLAY::NONE
318
319 for node in [root, child_00, child_01, grandchild_00, grandchild_01, grandchild_02] {
320 let layout = taffy.layout(node).unwrap();
321 assert_eq!(layout.size, Size::zero());
322 assert_eq!(layout.location, Point::zero());
323 }
324 }
325}