lightweight_pdf_layout/
list.rs

1//! `List` layout (Phase 6): sugar over `Row`/`Column` — a fixed-width
2//! marker column beside each item's content, stacked vertically. Reuses
3//! Row/Column's existing measure/layout entirely rather than duplicating
4//! that logic; see `lightweight_pdf_core::list` for why `List` is still its own
5//! element (builder ergonomics) despite delegating like this.
6
7use crate::geometry::{Constraints, Rect, Size};
8use crate::layoutable::{LayoutCtx, LayoutResult, Layoutable};
9use crate::warnings::{LayoutWarning, LayoutWarningKind};
10use lightweight_pdf_core::{Align, Column, List, Marker, Row, Text};
11
12fn marker_text(marker: &Marker) -> String {
13    match marker {
14        Marker::Bullet => "\u{2022}".to_string(),
15        Marker::Number(n) => format!("{n}."),
16    }
17}
18
19/// Translates a `List` into an equivalent `Column` of `Row`s (marker +
20/// content). Item content that has no explicit width gets `flex(1.0)` so
21/// it fills the remaining row width instead of shrink-wrapping to its own
22/// natural size (`Element::common_mut`, added for exactly this).
23fn to_column(list: &List) -> Column {
24    let mut col = Column::new().gap(list.gap);
25    for item in &list.items {
26        let mut content = item.content.clone();
27        if let Some(common) = content.common_mut() {
28            if common.width.is_none() && common.flex.is_none() {
29                common.flex = Some(1.0);
30            }
31        }
32        let row = Row::new()
33            .gap(list.gap)
34            .child(Text::new(marker_text(&item.marker)).width(list.marker_width).align(Align::End))
35            .child(content);
36        col = col.child(row);
37    }
38    col.common = list.common;
39    col
40}
41
42impl Layoutable for List {
43    fn measure(&self, ctx: &LayoutCtx, constraints: Constraints) -> Size {
44        to_column(self).measure(ctx, constraints)
45    }
46
47    fn layout(&self, ctx: &LayoutCtx, area: Rect, warnings: &mut Vec<LayoutWarning>, page: usize) -> LayoutResult {
48        // Lists don't paginate in V1 (same "atomic, no Split" contract as
49        // Row) — if the translated Column would need to split, keep what
50        // fits and clip+warn on the rest instead of silently dropping it.
51        match to_column(self).layout(ctx, area, warnings, page) {
52            LayoutResult::Fit(node) => LayoutResult::Fit(node),
53            LayoutResult::Split { current, .. } => {
54                warnings.push(LayoutWarning {
55                    kind: LayoutWarningKind::ContentOverflow,
56                    page,
57                    element_hint: "List content exceeds available space".to_string(),
58                });
59                LayoutResult::Fit(current)
60            }
61        }
62    }
63}
64
65#[cfg(test)]
66mod tests {
67    use super::*;
68    use crate::font_resolver::{FontMetrics, FontResolver};
69    use crate::render_node::RenderNode;
70    use lightweight_pdf_core::{FontKey, Text as TextEl};
71
72    struct FixedMetrics;
73    impl FontMetrics for FixedMetrics {
74        fn advance(&self, ch: char) -> f32 {
75            if ch == ' ' {
76                300.0
77            } else {
78                600.0
79            }
80        }
81        fn ascent(&self) -> f32 {
82            800.0
83        }
84        fn descent(&self) -> f32 {
85            -200.0
86        }
87    }
88    struct FixedResolver;
89    impl FontResolver for FixedResolver {
90        fn metrics(&self, _key: FontKey) -> &dyn FontMetrics {
91            &FixedMetrics
92        }
93    }
94    fn ctx() -> LayoutCtx<'static> {
95        LayoutCtx { resolver: &FixedResolver }
96    }
97
98    #[test]
99    fn bullet_and_numbered_items_get_distinct_markers() {
100        let list = List::new()
101            .bullet(TextEl::new("Erstens"))
102            .numbered(TextEl::new("Zweitens"))
103            .numbered(TextEl::new("Drittens"));
104        let c = ctx();
105        let mut warnings = Vec::new();
106        let area = Rect {
107            x: 0.0,
108            y: 0.0,
109            width: 300.0,
110            height: 300.0,
111        };
112        let LayoutResult::Fit(RenderNode::Group { children: rows, .. }) = list.layout(&c, area, &mut warnings, 1) else {
113            panic!("expected Fit");
114        };
115        assert_eq!(rows.len(), 3);
116
117        fn marker_of(row: &RenderNode) -> String {
118            let RenderNode::Group { children: cells, .. } = row else {
119                panic!("expected row group")
120            };
121            let RenderNode::Group { children: wrap, .. } = &cells[0] else {
122                panic!("expected clip wrapper")
123            };
124            let RenderNode::TextLines { lines, .. } = &wrap[0] else {
125                panic!("expected TextLines")
126            };
127            lines.join("")
128        }
129        assert_eq!(marker_of(&rows[0]), "\u{2022}");
130        assert_eq!(marker_of(&rows[1]), "1.");
131        assert_eq!(marker_of(&rows[2]), "2.");
132    }
133
134    #[test]
135    fn item_content_fills_remaining_row_width() {
136        let list = List::new().bullet(TextEl::new("x"));
137        let c = ctx();
138        let mut warnings = Vec::new();
139        let area = Rect {
140            x: 0.0,
141            y: 0.0,
142            width: 200.0,
143            height: 100.0,
144        };
145        let LayoutResult::Fit(RenderNode::Group { children: rows, .. }) = list.layout(&c, area, &mut warnings, 1) else {
146            panic!("expected Fit");
147        };
148        let RenderNode::Group { children: cells, .. } = &rows[0] else {
149            panic!("expected row group")
150        };
151        let RenderNode::Group { area: content_area, .. } = &cells[1] else {
152            panic!("expected clip wrapper for content cell")
153        };
154        // marker_width (16) + row gap (6) = 22; content should claim the
155        // rest of the 200pt row, not shrink to "x"'s own tiny width.
156        assert!(
157            content_area.width > 150.0,
158            "expected content to fill remaining width, got {}",
159            content_area.width
160        );
161    }
162}
lightweight_pdf_layout/list.rs

lightweight_pdf_layout/
list.rs
