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

use crate::dom;
use crate::geom::flow_relative::{Rect, Sides, Vec2};
use crate::geom::Length;
use crate::style::values::*;
use crate::style::{style_for_element, ComputedValues};
use std::convert::TryInto;
use std::sync::Arc;

mod dom_traversal;
mod element_data;
mod flow;
mod fragments;
mod positioned;
mod replaced;

use dom_traversal::*;
use flow::*;
use positioned::*;
use replaced::*;

pub use element_data::*;
pub use fragments::*;

/// <https://drafts.csswg.org/css-display/#independent-formatting-context>
#[derive(Debug)]
pub enum IndependentFormattingContext {
    Flow(BlockFormattingContext),

    // Not called FC in specs, but behaves close enough
    Replaced(ReplacedContent),
    // Other layout modes go here
}

enum NonReplacedIFC<'a> {
    Flow(&'a BlockFormattingContext),
}

impl IndependentFormattingContext {
    fn construct<'a>(
        context: &'a Context<'a>,
        style: &'a Arc<ComputedValues>,
        display_inside: DisplayInside,
        contents: Contents,
    ) -> Self {
        match contents.try_into() {
            Ok(non_replaced) => match display_inside {
                DisplayInside::Flow | DisplayInside::FlowRoot => {
                    IndependentFormattingContext::Flow(BlockFormattingContext::construct(
                        context,
                        style,
                        non_replaced,
                    ))
                }
            },
            Err(replaced) => IndependentFormattingContext::Replaced(replaced),
        }
    }

    fn as_replaced(&self) -> Result<&ReplacedContent, NonReplacedIFC> {
        match self {
            IndependentFormattingContext::Replaced(r) => Ok(r),
            IndependentFormattingContext::Flow(f) => Err(NonReplacedIFC::Flow(f)),
        }
    }

    fn layout<'a>(
        &'a self,
        containing_block: &ContainingBlock,
        tree_rank: usize,
        absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
    ) -> FlowChildren {
        match self.as_replaced() {
            Ok(replaced) => match *replaced {},
            Err(ifc) => ifc.layout(containing_block, tree_rank, absolutely_positioned_fragments),
        }
    }
}

impl<'a> NonReplacedIFC<'a> {
    fn layout(
        &self,
        containing_block: &ContainingBlock,
        tree_rank: usize,
        absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
    ) -> FlowChildren {
        match self {
            NonReplacedIFC::Flow(bfc) => {
                bfc.layout(containing_block, tree_rank, absolutely_positioned_fragments)
            }
        }
    }
}

pub struct ContainingBlock {
    inline_size: Length,
    block_size: LengthOrAuto,
    mode: (WritingMode, Direction),
}

pub struct DefiniteContainingBlock {
    size: Vec2<Length>,
    mode: (WritingMode, Direction),
}

/// https://drafts.csswg.org/css2/visuren.html#relative-positioning
fn relative_adjustement(
    style: &ComputedValues,
    inline_size: Length,
    block_size: LengthOrAuto,
) -> Vec2<Length> {
    if !style.box_.position.is_relatively_positioned() {
        return Vec2::zero();
    }
    fn adjust(start: LengthOrAuto, end: LengthOrAuto) -> Length {
        match (start, end) {
            (LengthOrAuto::Auto, LengthOrAuto::Auto) => Length::zero(),
            (LengthOrAuto::Auto, LengthOrAuto::Length(end)) => -end,
            (LengthOrAuto::Length(start), _) => start,
        }
    }
    let block_size = block_size.auto_is(Length::zero);
    let box_offsets = style.box_offsets().map_inline_and_block_axes(
        |v| v.percentage_relative_to(inline_size),
        |v| v.percentage_relative_to(block_size),
    );
    Vec2 {
        inline: adjust(box_offsets.inline_start, box_offsets.inline_end),
        block: adjust(box_offsets.block_start, box_offsets.block_end),
    }
}

// FIXME: use std::mem::take when it’s stable
// https://github.com/rust-lang/rust/issues/61129
fn take<T>(x: &mut T) -> T
where
    T: Default,
{
    std::mem::replace(x, Default::default())
}