tawasuyu/taffy

1mod common {
2    pub mod image;
3    pub mod text;
4}
5use common::image::{image_measure_function, ImageContext};
6use common::text::{text_measure_function, FontMetrics, TextContext, WritingMode, LOREM_IPSUM};
7use taffy::tree::Cache;
8use taffy::util::print_tree;
9use taffy::{
10    compute_cached_layout, compute_flexbox_layout, compute_grid_layout, compute_leaf_layout, compute_root_layout,
11    prelude::*, round_layout,
12};
13
14#[derive(Debug, Copy, Clone)]
15#[allow(dead_code)]
16enum NodeKind {
17    Flexbox,
18    Grid,
19    Text,
20    Image,
21}
22
23struct Node {
24    kind: NodeKind,
25    style: Style,
26    text_data: Option<TextContext>,
27    image_data: Option<ImageContext>,
28    cache: Cache,
29    unrounded_layout: Layout,
30    final_layout: Layout,
31    children: Vec<Node>,
32}
33
34impl Default for Node {
35    fn default() -> Self {
36        Node {
37            kind: NodeKind::Flexbox,
38            style: Style::default(),
39            text_data: None,
40            image_data: None,
41            cache: Cache::new(),
42            unrounded_layout: Layout::with_order(0),
43            final_layout: Layout::with_order(0),
44            children: Vec::new(),
45        }
46    }
47}
48
49#[allow(dead_code)]
50impl Node {
51    pub fn new_row(style: Style) -> Node {
52        Node {
53            kind: NodeKind::Flexbox,
54            style: Style { display: Display::Flex, flex_direction: FlexDirection::Row, ..style },
55            ..Node::default()
56        }
57    }
58    pub fn new_column(style: Style) -> Node {
59        Node {
60            kind: NodeKind::Flexbox,
61            style: Style { display: Display::Flex, flex_direction: FlexDirection::Column, ..style },
62            ..Node::default()
63        }
64    }
65    pub fn new_grid(style: Style) -> Node {
66        Node { kind: NodeKind::Grid, style: Style { display: Display::Grid, ..style }, ..Node::default() }
67    }
68    pub fn new_text(style: Style, text_data: TextContext) -> Node {
69        Node { kind: NodeKind::Text, style, text_data: Some(text_data), ..Node::default() }
70    }
71    pub fn new_image(style: Style, image_data: ImageContext) -> Node {
72        Node { kind: NodeKind::Image, style, image_data: Some(image_data), ..Node::default() }
73    }
74    pub fn append_child(&mut self, node: Node) {
75        self.children.push(node);
76    }
77
78    unsafe fn as_id(&self) -> NodeId {
79        NodeId::from(self as *const Node as usize)
80    }
81
82    pub fn compute_layout(&mut self, available_space: Size<AvailableSpace>, use_rounding: bool) {
83        let root_node_id = unsafe { self.as_id() };
84        compute_root_layout(&mut StatelessLayoutTree, root_node_id, available_space);
85        if use_rounding {
86            round_layout(&mut StatelessLayoutTree, root_node_id)
87        }
88    }
89
90    pub fn print_tree(&mut self) {
91        print_tree(&StatelessLayoutTree, unsafe { self.as_id() });
92    }
93}
94
95struct ChildIter<'a>(std::slice::Iter<'a, Node>);
96impl Iterator for ChildIter<'_> {
97    type Item = NodeId;
98    fn next(&mut self) -> Option<Self::Item> {
99        self.0.next().map(|c| NodeId::from(c as *const Node as usize))
100    }
101}
102
103#[inline(always)]
104unsafe fn node_from_id<'a>(node_id: NodeId) -> &'a Node {
105    &*(usize::from(node_id) as *const Node)
106}
107
108#[inline(always)]
109unsafe fn node_from_id_mut<'a>(node_id: NodeId) -> &'a mut Node {
110    &mut *(usize::from(node_id) as *mut Node)
111}
112
113struct StatelessLayoutTree;
114impl TraversePartialTree for StatelessLayoutTree {
115    type ChildIter<'a> = ChildIter<'a>;
116
117    fn child_ids(&self, node_id: NodeId) -> Self::ChildIter<'_> {
118        unsafe { ChildIter(node_from_id(node_id).children.iter()) }
119    }
120
121    fn child_count(&self, node_id: NodeId) -> usize {
122        unsafe { node_from_id(node_id).children.len() }
123    }
124
125    fn get_child_id(&self, node_id: NodeId, index: usize) -> NodeId {
126        unsafe { node_from_id(node_id).children[index].as_id() }
127    }
128}
129
130impl TraverseTree for StatelessLayoutTree {}
131
132impl LayoutPartialTree for StatelessLayoutTree {
133    type CoreContainerStyle<'a>
134        = &'a Style
135    where
136        Self: 'a;
137
138    type CacheMut<'b>
139        = &'b mut Cache
140    where
141        Self: 'b;
142
143    fn get_core_container_style(&self, node_id: NodeId) -> Self::CoreContainerStyle<'_> {
144        unsafe { &node_from_id(node_id).style }
145    }
146
147    fn set_unrounded_layout(&mut self, node_id: NodeId, layout: &Layout) {
148        unsafe { node_from_id_mut(node_id).unrounded_layout = *layout };
149    }
150
151    fn get_cache_mut(&mut self, node_id: NodeId) -> &mut Cache {
152        unsafe { &mut node_from_id_mut(node_id).cache }
153    }
154
155    fn compute_child_layout(&mut self, node_id: NodeId, inputs: taffy::tree::LayoutInput) -> taffy::tree::LayoutOutput {
156        compute_cached_layout(self, node_id, inputs, |tree, node_id, inputs| {
157            let node = unsafe { node_from_id_mut(node_id) };
158            let font_metrics = FontMetrics { char_width: 10.0, char_height: 10.0 };
159
160            match node.kind {
161                NodeKind::Flexbox => compute_flexbox_layout(tree, node_id, inputs),
162                NodeKind::Grid => compute_grid_layout(tree, node_id, inputs),
163                NodeKind::Text => compute_leaf_layout(inputs, &node.style, |known_dimensions, available_space| {
164                    text_measure_function(
165                        known_dimensions,
166                        available_space,
167                        node.text_data.as_ref().unwrap(),
168                        &font_metrics,
169                    )
170                }),
171                NodeKind::Image => compute_leaf_layout(inputs, &node.style, |known_dimensions, _available_space| {
172                    image_measure_function(known_dimensions, node.image_data.as_ref().unwrap())
173                }),
174            }
175        })
176    }
177}
178
179impl taffy::LayoutFlexboxContainer for StatelessLayoutTree {
180    type FlexboxContainerStyle<'a>
181        = &'a Style
182    where
183        Self: 'a;
184
185    type FlexboxItemStyle<'a>
186        = &'a Style
187    where
188        Self: 'a;
189
190    fn get_flexbox_container_style(&self, node_id: NodeId) -> Self::FlexboxContainerStyle<'_> {
191        unsafe { &node_from_id(node_id).style }
192    }
193
194    fn get_flexbox_child_style(&self, child_node_id: NodeId) -> Self::FlexboxItemStyle<'_> {
195        unsafe { &node_from_id(child_node_id).style }
196    }
197}
198
199impl taffy::LayoutGridContainer for StatelessLayoutTree {
200    type GridContainerStyle<'a>
201        = &'a Style
202    where
203        Self: 'a;
204
205    type GridItemStyle<'a>
206        = &'a Style
207    where
208        Self: 'a;
209
210    fn get_grid_container_style(&self, node_id: NodeId) -> Self::GridContainerStyle<'_> {
211        unsafe { &node_from_id(node_id).style }
212    }
213
214    fn get_grid_child_style(&self, child_node_id: NodeId) -> Self::GridItemStyle<'_> {
215        unsafe { &node_from_id(child_node_id).style }
216    }
217}
218
219impl RoundTree for StatelessLayoutTree {
220    fn get_unrounded_layout(&self, node_id: NodeId) -> &Layout {
221        unsafe { &node_from_id_mut(node_id).unrounded_layout }
222    }
223
224    fn set_final_layout(&mut self, node_id: NodeId, layout: &Layout) {
225        unsafe { node_from_id_mut(node_id).final_layout = *layout }
226    }
227}
228
229impl PrintTree for StatelessLayoutTree {
230    fn get_debug_label(&self, node_id: NodeId) -> &'static str {
231        match unsafe { node_from_id(node_id).kind } {
232            NodeKind::Flexbox => "FLEX",
233            NodeKind::Grid => "GRID",
234            NodeKind::Text => "TEXT",
235            NodeKind::Image => "IMAGE",
236        }
237    }
238
239    fn get_final_layout(&self, node_id: NodeId) -> &Layout {
240        unsafe { &node_from_id(node_id).final_layout }
241    }
242}
243
244fn main() -> Result<(), taffy::TaffyError> {
245    let mut root = Node::new_column(Style::DEFAULT);
246
247    let text_node = Node::new_text(
248        Style::default(),
249        TextContext { text_content: LOREM_IPSUM.into(), writing_mode: WritingMode::Horizontal },
250    );
251    root.append_child(text_node);
252
253    let image_node = Node::new_image(Style::default(), ImageContext { width: 400.0, height: 300.0 });
254    root.append_child(image_node);
255
256    // Compute layout and print result
257    root.compute_layout(Size::MAX_CONTENT, true);
258    root.print_tree();
259
260    Ok(())
261}