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