measure/
measure.rs

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::prelude::*;
8
9enum NodeContext {
10    Text(TextContext),
11    Image(ImageContext),
12}
13
14fn measure_function(
15    known_dimensions: taffy::geometry::Size<Option<f32>>,
16    available_space: taffy::geometry::Size<taffy::style::AvailableSpace>,
17    node_context: Option<&mut NodeContext>,
18    font_metrics: &FontMetrics,
19) -> Size<f32> {
20    if let Size { width: Some(width), height: Some(height) } = known_dimensions {
21        return Size { width, height };
22    }
23
24    match node_context {
25        None => Size::ZERO,
26        Some(NodeContext::Text(text_context)) => {
27            text_measure_function(known_dimensions, available_space, &*text_context, font_metrics)
28        }
29        Some(NodeContext::Image(image_context)) => image_measure_function(known_dimensions, image_context),
30    }
31}
32
33fn main() -> Result<(), taffy::TaffyError> {
34    let mut taffy: TaffyTree<NodeContext> = TaffyTree::new();
35
36    let font_metrics = FontMetrics { char_width: 10.0, char_height: 10.0 };
37
38    let text_node = taffy.new_leaf_with_context(
39        Style::default(),
40        NodeContext::Text(TextContext { text_content: LOREM_IPSUM.into(), writing_mode: WritingMode::Horizontal }),
41    )?;
42
43    let image_node = taffy
44        .new_leaf_with_context(Style::default(), NodeContext::Image(ImageContext { width: 400.0, height: 300.0 }))?;
45
46    let root = taffy.new_with_children(
47        Style {
48            display: Display::Flex,
49            flex_direction: FlexDirection::Column,
50            size: Size { width: length(200.0), height: auto() },
51            ..Default::default()
52        },
53        &[text_node, image_node],
54    )?;
55
56    // Compute layout and print result
57    taffy.compute_layout_with_measure(
58        root,
59        Size::MAX_CONTENT,
60        // Note: this closure is a FnMut closure and can be used to borrow external context for the duration of layout
61        // For example, you may wish to borrow a global font registry and pass it into your text measuring function
62        |known_dimensions, available_space, _node_id, node_context, _style| {
63            measure_function(known_dimensions, available_space, node_context, &font_metrics)
64        },
65    )?;
66    taffy.print_tree(root);
67
68    Ok(())
69}
measure/measure.rs

measure/
measure.rs
