layout-cat 0.1.0

Box-model layout: cascade + block layout over a dom-cat tree using css-cat stylesheets. Produces a LayoutBox tree with positions and dimensions. No mut, no Rc/Arc, no interior mutability, no panics, exhaustive matches. Fourth sub-crate of a Servo-replacement webview runtime targeting Tauri.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167

//! Integration tests covering the cascade + block layout path.

#![allow(clippy::float_cmp)]

use layout_cat::{Error, LayoutBox, Viewport, layout};

fn run(html: &str, css: &str) -> Result<layout_cat::LayoutTree, Error> {
    let html_doc = html_cat::parse(html).map_err(|_| fail("html parse"))?;
    let dom = dom_cat::Document::from_html_doc(&html_doc);
    let sheet = css_cat::parse(css)?;
    Ok(layout(&dom, &sheet, Viewport::new(800, 600)))
}

fn fail(msg: &'static str) -> Error {
    Error::Css(css_cat::Error::EmptySelectorList {
        at: css_cat::span::Span::new(
            css_cat::span::Position::new(1, 1, 0),
            css_cat::span::Position::new(1, 1, 0),
        ),
    })
    .ignore(msg)
}

trait ErrorTagged {
    fn ignore(self, _msg: &'static str) -> Self;
}

impl ErrorTagged for Error {
    fn ignore(self, _msg: &'static str) -> Self {
        self
    }
}

fn first_descendant(node: &LayoutBox, idx: usize) -> Option<&LayoutBox> {
    node.children().get(idx)
}

#[test]
fn root_box_present() -> Result<(), Error> {
    let tree = run("<html><body><p>hi</p></body></html>", "")?;
    tree.root_box()
        .map(|_| ())
        .ok_or_else(|| fail("expected root box"))
}

#[test]
fn body_fills_viewport_width_by_default() -> Result<(), Error> {
    let tree = run("<html><body><p>hi</p></body></html>", "")?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    (body.rect().width() == 800.0)
        .then_some(())
        .ok_or_else(|| fail("body width != viewport"))
}

#[test]
fn explicit_width_applied() -> Result<(), Error> {
    let tree = run("<html><body><p>hi</p></body></html>", "p { width: 200px; }")?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    (p.rect().width() == 200.0)
        .then_some(())
        .ok_or_else(|| fail("p width != 200"))
}

#[test]
fn padding_consumed() -> Result<(), Error> {
    let tree = run(
        "<html><body><p>hi</p></body></html>",
        "p { width: 100px; padding: 8px; }",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    (p.padding().left() == 8.0 && p.padding().right() == 8.0)
        .then_some(())
        .ok_or_else(|| fail("padding wrong"))
}

#[test]
fn vertical_stacking() -> Result<(), Error> {
    let tree = run(
        "<html><body><p>a</p><p>b</p></body></html>",
        "p { height: 50px; }",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let a = first_descendant(body, 0).ok_or_else(|| fail("no a"))?;
    let b = first_descendant(body, 1).ok_or_else(|| fail("no b"))?;
    (a.rect().origin().y() == 0.0 && b.rect().origin().y() == 50.0)
        .then_some(())
        .ok_or_else(|| fail("vertical stacking wrong"))
}

#[test]
fn margin_shorthand_four_sides() -> Result<(), Error> {
    let tree = run(
        "<html><body><p>x</p></body></html>",
        "p { margin: 10px 20px 30px 40px; }",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    let m = p.margin();
    (m.top() == 10.0 && m.right() == 20.0 && m.bottom() == 30.0 && m.left() == 40.0)
        .then_some(())
        .ok_or_else(|| fail("margin shorthand wrong"))
}

#[test]
fn padding_shorthand_two_values() -> Result<(), Error> {
    let tree = run(
        "<html><body><p>x</p></body></html>",
        "p { padding: 5px 10px; }",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    let pad = p.padding();
    (pad.top() == 5.0 && pad.right() == 10.0 && pad.bottom() == 5.0 && pad.left() == 10.0)
        .then_some(())
        .ok_or_else(|| fail("padding two-value wrong"))
}

#[test]
fn display_none_skipped() -> Result<(), Error> {
    let tree = run(
        "<html><body><p>shown</p><p class=\"hidden\">gone</p></body></html>",
        ".hidden { display: none; }",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    (body.children().len() == 1)
        .then_some(())
        .ok_or_else(|| fail("display:none should drop child"))
}

#[test]
fn color_resolved_from_hex() -> Result<(), Error> {
    let tree = run(
        "<html><body><p>x</p></body></html>",
        "p { color: #ff0000; }",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    let c = p.style().color();
    (c.red() > 0.99 && c.green() < 0.01 && c.blue() < 0.01)
        .then_some(())
        .ok_or_else(|| fail("color wrong"))
}

#[test]
fn percentage_width_resolved() -> Result<(), Error> {
    let tree = run("<html><body><p>x</p></body></html>", "p { width: 50%; }")?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    (p.rect().width() == 400.0)
        .then_some(())
        .ok_or_else(|| fail("percentage width wrong"))
}

#[test]
fn inline_style_attribute() -> Result<(), Error> {
    let tree = run(
        "<html><body><p style=\"width: 123px;\">x</p></body></html>",
        "",
    )?;
    let body = tree.root_box().ok_or_else(|| fail("no root"))?;
    let p = first_descendant(body, 0).ok_or_else(|| fail("no p"))?;
    (p.rect().width() == 123.0)
        .then_some(())
        .ok_or_else(|| fail("inline style ignored"))
}