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, PartialLayoutTree};
8use taffy::util::print_tree;
9use taffy::{
10    compute_cached_layout, compute_flexbox_layout, compute_grid_layout, compute_layout, compute_leaf_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_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(&mut StatelessLayoutTree, unsafe { self.as_id() });
92    }
93}
94
95struct ChildIter<'a>(std::slice::Iter<'a, Node>);
96impl<'a> Iterator for ChildIter<'a> {
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 PartialLayoutTree 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    fn get_style(&self, node_id: NodeId) -> &Style {
130        unsafe { &node_from_id(node_id).style }
131    }
132
133    fn get_unrounded_layout_mut(&mut self, node_id: NodeId) -> &mut Layout {
134        unsafe { &mut node_from_id_mut(node_id).unrounded_layout }
135    }
136
137    fn get_cache_mut(&mut self, node_id: NodeId) -> &mut Cache {
138        unsafe { &mut node_from_id_mut(node_id).cache }
139    }
140
141    fn compute_child_layout(&mut self, node_id: NodeId, inputs: taffy::tree::LayoutInput) -> taffy::tree::LayoutOutput {
142        compute_cached_layout(self, node_id, inputs, |tree, node_id, inputs| {
143            let node = unsafe { node_from_id_mut(node_id) };
144            let font_metrics = FontMetrics { char_width: 10.0, char_height: 10.0 };
145
146            match node.kind {
147                NodeKind::Flexbox => compute_flexbox_layout(tree, node_id, inputs),
148                NodeKind::Grid => compute_grid_layout(tree, node_id, inputs),
149                NodeKind::Text => compute_leaf_layout(
150                    inputs,
151                    &node.style,
152                    Some(|known_dimensions, available_space| {
153                        text_measure_function(
154                            known_dimensions,
155                            available_space,
156                            node.text_data.as_ref().unwrap(),
157                            &font_metrics,
158                        )
159                    }),
160                ),
161                NodeKind::Image => compute_leaf_layout(
162                    inputs,
163                    &node.style,
164                    Some(|known_dimensions, _available_space| {
165                        image_measure_function(known_dimensions, node.image_data.as_ref().unwrap())
166                    }),
167                ),
168            }
169        })
170    }
171}
172
173impl LayoutTree for StatelessLayoutTree {
174    fn get_final_layout(&self, node_id: NodeId) -> &Layout {
175        unsafe { &node_from_id(node_id).final_layout }
176    }
177
178    fn get_final_layout_mut(&mut self, node_id: NodeId) -> &mut Layout {
179        unsafe { &mut node_from_id_mut(node_id).final_layout }
180    }
181}
182
183fn main() -> Result<(), taffy::TaffyError> {
184    let mut root = Node::new_column(Style::DEFAULT);
185
186    let text_node = Node::new_text(
187        Style::default(),
188        TextContext { text_content: LOREM_IPSUM.into(), writing_mode: WritingMode::Horizontal },
189    );
190    root.append_child(text_node);
191
192    let image_node = Node::new_image(Style::default(), ImageContext { width: 400.0, height: 300.0 });
193    root.append_child(image_node);
194
195    // Compute layout and print result
196    root.compute_layout(Size::MAX_CONTENT, true);
197    root.print_tree();
198
199    Ok(())
200}