iris/tests/layout.rs

//! Where a frame puts things, with no window to put them in.

use iris::harness::{Harness, assert_corners};
use iris::prelude::*;

/// A fixed 100 wide, and the rest of the 400 to its neighbour.
fn two_rects(h: &mut Harness) -> (WidgetId, WidgetId) {
    let left = rect(Color::RED).width(100).add(&mut h.rsc);
    let right = rect(Color::BLUE).add(&mut h.rsc);
    h.set_root((left, right).span(Dir::RIGHT));
    (left.id(), right.id())
}

#[test]
fn a_span_gives_each_child_the_width_it_asked_for() {
    let mut h = Harness::new((400, 200));
    let (left, right) = two_rects(&mut h);

    assert_corners!(h, left, (0, 0), (100, 200));
    assert_corners!(h, right, (100, 0), (400, 200));
}

#[test]
fn resizing_relays_out_against_the_new_output() {
    let mut h = Harness::new((400, 200));
    let (left, right) = two_rects(&mut h);

    h.resize((800, 100));
    assert!(h.needs_redraw());
    h.frame();

    assert_corners!(h, left, (0, 0), (100, 100));
    assert_corners!(h, right, (100, 0), (800, 100));
}

#[test]
fn an_empty_widget_takes_a_share_of_a_span() {
    let mut h = Harness::new((400, 200));
    let gap = ().add(&mut h.rsc);
    let right = rect(Color::BLUE).width(100).add(&mut h.rsc);
    h.set_root((gap, right).span(Dir::RIGHT));

    assert_corners!(h, gap, (0, 0), (300, 200));
    assert_corners!(h, right, (300, 0), (400, 200));
}

#[test]
fn a_child_drawn_twice_moves_once() {
    let mut h = Harness::new((400, 200));
    // `Aligned` draws its child twice; listing it twice would move it twice.
    let inner = rect(Color::BLUE).add(&mut h.rsc);
    let centered = inner.center().width(200).add(&mut h.rsc);
    let left = rect(Color::RED).width(100).add(&mut h.rsc);
    h.set_root((left, centered).span(Dir::RIGHT));
    assert_corners!(h, inner, (100, 0), (300, 200));

    h.rsc[left].x = Some(Len::px(150));
    h.frame();

    assert_corners!(h, inner, (150, 0), (350, 200));
}

#[test]
fn a_resize_lands_where_a_cold_start_would() {
    let build = |h: &mut Harness| {
        let para = wtext(
            "Wrapping shapes one source into as many lines as its container leaves room \
             for, so the height of a paragraph is an answer rather than a setting.",
        )
        .size(20)
        .wrap(true)
        .pad(16)
        .add(&mut h.rsc);
        let below = rect(Color::RED).add(&mut h.rsc);
        let root = (para, below).span(Dir::DOWN).pad(12);
        h.set_root(root);
        (para, below)
    };

    let mut cold = Harness::new((900, 1200));
    let (cold_para, cold_below) = build(&mut cold);

    let mut resized = Harness::new((1920, 1200));
    let (para, below) = build(&mut resized);
    resized.resize((900, 1200));
    resized.frame();

    assert_eq!(resized.region(&para), cold.region(&cold_para), "paragraph");
    assert_eq!(resized.region(&below), cold.region(&cold_below), "below");
}

#[test]
fn a_fixed_box_is_drawn_again_rather_than_stretched() {
    let mut h = Harness::new((400, 400));
    // The panel fills a stack sized by its sibling, so it is drawn in the
    // whole box and then placed in the shorter one. Reusing it in that fixed
    // box afterwards would leave it whatever height it happened to have.
    let panel = rect(Color::BLUE).add(&mut h.rsc);
    let leaf = rect(Color::RED).height(100).add(&mut h.rsc);
    let stack = (panel, leaf)
        .stack()
        .size(StackSize::Child(1))
        .add(&mut h.rsc);
    h.set_root(stack.align(Align::TOP));
    assert_corners!(h, panel, (0, 0), (400, 100));

    h.rsc[leaf].y = Some(Len::px(250));
    h.frame();

    assert_corners!(h, panel, (0, 0), (400, 250));
}

#[test]
fn a_moved_subtree_takes_its_children_with_it() {
    let mut h = Harness::new((400, 400));
    let first = rect(Color::RED).height(40).add(&mut h.rsc);
    let inner = rect(Color::BLUE).add(&mut h.rsc);
    let row = inner.pad(10).height(40).add(&mut h.rsc);
    h.set_root((first, row).span(Dir::DOWN));
    assert_corners!(h, inner, (10, 50), (390, 70));

    h.rsc[first].y = Some(Len::px(80));
    h.frame();

    // The row is the same shape somewhere else, so one slot moved it and
    // `inner`'s own region was never rewritten.
    assert_corners!(h, inner, (10, 90), (390, 110));
}

#[test]
fn a_fixed_length_child_keeps_it_when_the_box_around_it_grows() {
    let mut h = Harness::new((400, 200));
    let fixed = rect(Color::BLUE).width(50).add(&mut h.rsc);
    let rest = rect(Color::GREEN).add(&mut h.rsc);
    let panel = (fixed, rest).span(Dir::RIGHT).add(&mut h.rsc);
    // Changing the bar's width is the only thing that changes the box the
    // panel and everything under it was drawn for.
    let bar = rect(Color::RED).width(100).add(&mut h.rsc);
    h.set_root((bar, panel).span(Dir::RIGHT));
    assert_corners!(h, fixed, (100, 0), (150, 200));
    assert_corners!(h, rest, (150, 0), (400, 200));

    h.rsc[bar].x = Some(Len::px(200));
    h.frame();

    // The panel's box is 100 shorter, so the fixed child is the same 50 wide
    // against its new start and the one taking the rest absorbs the change.
    assert_corners!(h, fixed, (200, 0), (250, 200));
    assert_corners!(h, rest, (250, 0), (400, 200));
}

#[test]
fn a_box_with_a_fixed_length_can_be_stretched_on_its_other_axis() {
    let mut h = Harness::new((400, 200));
    // The row is 40 tall whatever happens, which used to make its drawing
    // impossible to take out of: recovering a fraction of a box needs a
    // relative extent, and it has none on that axis.
    let inner = rect(Color::BLUE).add(&mut h.rsc);
    let row = inner.pad(10).height(40).add(&mut h.rsc);
    let filler = rect(Color::GREEN).add(&mut h.rsc);
    let column = (row, filler).span(Dir::DOWN).add(&mut h.rsc);
    let bar = rect(Color::RED).width(100).add(&mut h.rsc);
    h.set_root((bar, column).span(Dir::RIGHT));
    assert_corners!(h, inner, (110, 10), (390, 30));

    h.rsc[bar].x = Some(Len::px(200));
    h.frame();

    assert_corners!(h, inner, (210, 10), (390, 30));
}

#[test]
fn only_a_container_that_places_its_children_lengthens_the_chain() {
    let mut h = Harness::new((400, 200));
    let leaf = rect(Color::BLUE).add(&mut h.rsc);
    // Four widgets between the span and the leaf, none of which places what
    // it draws, so all of them share the span's slot.
    let buried = leaf.pad(4).pad(4).pad(4).pad(4).add(&mut h.rsc);
    let bar = rect(Color::RED).width(100).add(&mut h.rsc);
    h.set_root((bar, buried).span(Dir::RIGHT));

    let slot = h.render.active[&leaf.id()].parent_move;
    assert_eq!(
        h.render.moves.depth(slot),
        2,
        "the span above the leaf, and the root the window is held in"
    );
}

/// A span that sizes from its children passes their `rest` weight up rather
/// than collapsing it to one share, so nesting divides the same space instead
/// of re-dividing a share of it.
#[test]
fn nested_spans_divide_the_space_once_however_deep_the_nesting_is() {
    let mut h = Harness::new((400, 200));
    let (a, b, c, d) = (
        rect(Color::RED).add(&mut h.rsc),
        rect(Color::BLUE).add(&mut h.rsc),
        rect(Color::GREEN).add(&mut h.rsc),
        rect(Color::WHITE).add(&mut h.rsc),
    );
    let left = (a, b).span(Dir::RIGHT).add(&mut h.rsc);
    let right = (c, d).span(Dir::RIGHT).add(&mut h.rsc);
    h.set_root((left, right).span(Dir::RIGHT));

    for (i, id) in [a, b, c, d].into_iter().enumerate() {
        let x = i as f32 * 100.0;
        assert_corners!(h, id, (x, 0), (x + 100.0, 200));
    }
}

/// The same space, unevenly nested: weights carried up mean a share is a
/// share of the whole, not of whatever branch a widget happens to sit in.
#[test]
fn an_uneven_nesting_still_gives_every_share_the_same_length() {
    let mut h = Harness::new((400, 200));
    let (a, b, c, d) = (
        rect(Color::RED).add(&mut h.rsc),
        rect(Color::BLUE).add(&mut h.rsc),
        rect(Color::GREEN).add(&mut h.rsc),
        rect(Color::WHITE).add(&mut h.rsc),
    );
    let one = (a,).span(Dir::RIGHT).add(&mut h.rsc);
    let three = (b, c, d).span(Dir::RIGHT).add(&mut h.rsc);
    h.set_root((one, three).span(Dir::RIGHT));

    for (i, id) in [a, b, c, d].into_iter().enumerate() {
        let x = i as f32 * 100.0;
        assert_corners!(h, id, (x, 0), (x + 100.0, 200));
    }
}

/// Where the shader puts an edge: the two parts of a scalar are floored
/// apart, so a fraction and a pixel offset snap independently.
fn drawn_edges(h: &Harness, id: WidgetId, axis: Axis) -> (f32, f32) {
    let active = &h.render.active[&id];
    let region = h.render.moves.resolve(active.parent_move, active.region);
    let dim = h.size().axis(axis);
    let edge = |s: UiScalar| (s.rel * dim).floor() + s.px.floor();
    let span = region.axis(axis);
    (edge(span.start), edge(span.end))
}

fn hairline(h: &mut Harness, marks: &mut Vec<WidgetId>) -> StrongWidget {
    let inner = rect(Color::RED).add_strong(&mut h.rsc);
    let mark = SetSize {
        inner,
        x: Some(Len::px(1.0)),
        y: None,
    }
    .add_strong(&mut h.rsc);
    marks.push(mark.id());
    mark
}

fn share(h: &mut Harness, inner: StrongWidget, ratio: f32) -> StrongWidget {
    SetSize {
        inner,
        x: Some(Len::rest(ratio)),
        y: None,
    }
    .add_strong(&mut h.rsc)
}

/// Shares in weights no binary fraction lands on, a padding on one branch
/// and not the other, so an edge falls near an integer as often as it can.
fn hairlines(h: &mut Harness, depth: usize, marks: &mut Vec<WidgetId>) -> StrongWidget {
    let mut span = Span::empty(Dir::RIGHT);
    if depth == 0 {
        let left = rect(Color::BLUE).add_strong(&mut h.rsc);
        let left = share(h, left, 3.0);
        span.push(left);
        let mark = hairline(h, marks);
        span.push(mark);
        let right = rect(Color::BLUE).add_strong(&mut h.rsc);
        let right = share(h, right, 7.0);
        span.push(right);
        return span.add_strong(&mut h.rsc);
    }
    let first = hairlines(h, depth - 1, marks);
    let first = share(h, first, 3.0);
    span.push(first);
    let second = hairlines(h, depth - 1, marks);
    let second = Pad {
        padding: Padding {
            left: 3.0,
            right: 7.0,
            top: 0.0,
            bottom: 0.0,
        },
        inner: second,
    }
    .add_strong(&mut h.rsc);
    let second = share(h, second, 5.0);
    span.push(second);
    span.add_strong(&mut h.rsc)
}

/// A one-pixel line is a pixel wherever it is drawn. Both edges of a fixed
/// length share their box's fraction, so composing the chain moves them
/// together and the shader's `floor` cannot round the pixel between them
/// away -- only shift it. A separator that disappeared at one window size
/// would be a defect no size comparison catches.
#[test]
fn a_one_pixel_line_keeps_its_pixel_through_a_chain() {
    let mut h = Harness::new((1920, 1200));
    let mut marks = Vec::new();
    let root = hairlines(&mut h, 4, &mut marks);
    h.state.set_root(root);
    h.frame();
    assert_eq!(marks.len(), 16);

    for size in [(1920, 1200), (1919, 1201), (997, 1003), (1367, 733)] {
        h.resize(size);
        h.frame();
        for mark in &marks {
            let (start, end) = drawn_edges(&h, *mark, Axis::X);
            assert_eq!(end - start, 1.0, "at {size:?}, mark {mark:?}");
        }
    }
}

/// A span short of room takes it from its shares, which go to nothing and
/// then to nothing wider; the fixed lengths between them keep their pixels.
/// Collapsing those to make room would delete a separator the caller asked
/// for, which is worse than overflowing.
#[test]
fn a_span_out_of_room_shrinks_its_shares_and_not_its_fixed_lengths() {
    let mut h = Harness::new((400, 20));
    let mut marks = Vec::new();
    let mut span = Span::empty(Dir::RIGHT);
    for _ in 0..3 {
        let share_of = rect(Color::BLUE).add_strong(&mut h.rsc);
        let share_of = share(&mut h, share_of, 1.0);
        span.push(share_of);
        let mark = hairline(&mut h, &mut marks);
        span.push(mark);
    }
    let root = span.add_strong(&mut h.rsc);
    h.state.set_root(root);
    h.frame();

    for width in [400, 10, 3, 1] {
        h.resize((width, 20));
        h.frame();
        for mark in &marks {
            let (start, end) = drawn_edges(&h, *mark, Axis::X);
            assert_eq!(end - start, 1.0, "at {width} wide, mark {mark:?}");
        }
    }
}