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89 lines
2.7 KiB
Rust
89 lines
2.7 KiB
Rust
type Coord = f32;
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#[derive(Debug, Default)]
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pub struct LayoutData {
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// inputs
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min: Coord,
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max: Coord,
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pref: Coord,
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stretch: f32,
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// outputs
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pos: Coord,
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size: Coord,
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}
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/// Layout the items within a specified size
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///
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/// This is quite a simple implementation for now
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pub fn layout_items(data: &mut [LayoutData], start_pos: Coord, size: Coord) {
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let (min, _max, perf, mut s) = data.iter().fold((0., 0., 0., 0.), |(min, max, pref, s), it| {
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(min + it.min, max + it.max, pref + it.pref, s + it.stretch)
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});
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if size >= perf {
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// bigger than the prefered size
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// distribute each item its prefered size
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let mut pos = start_pos;
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for it in data.iter_mut() {
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it.size = it.pref;
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it.pos = pos;
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pos += it.size;
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}
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// Allocate the space according to the stretch. Until all space is distributed, or all item
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// have reached their maximum size
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let mut extra_space = size - perf;
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while s > 0. && extra_space > 0. {
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let extra_per_stretch = extra_space / s;
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s = 0.;
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let mut pos = start_pos;
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for it in data.iter_mut() {
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let give = (extra_per_stretch * it.stretch).min(it.max - it.size);
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it.size += give;
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extra_space -= give;
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if give > 0. {
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s += it.stretch;
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}
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it.pos = pos;
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pos += it.size;
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}
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}
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} else
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/*if size < min*/
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{
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// We have less than the minimum size
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// distribute the difference proportional to the size (TODO: and stretch)
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let ratio = size / min;
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let mut pos = start_pos;
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for it in data {
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it.size = it.min * ratio;
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it.pos = pos;
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pos += it.size;
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}
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}
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}
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#[test]
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fn test_layout_items() {
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let my_items = &mut [
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LayoutData { min: 100., max: 200., pref: 100., stretch: 1., ..Default::default() },
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LayoutData { min: 50., max: 300., pref: 100., stretch: 1., ..Default::default() },
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LayoutData { min: 50., max: 150., pref: 100., stretch: 1., ..Default::default() },
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];
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layout_items(my_items, 100., 650.);
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assert_eq!(my_items[0].size, 200.);
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assert_eq!(my_items[1].size, 300.);
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assert_eq!(my_items[2].size, 150.);
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layout_items(my_items, 100., 200.);
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assert_eq!(my_items[0].size, 100.);
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assert_eq!(my_items[1].size, 50.);
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assert_eq!(my_items[2].size, 50.);
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layout_items(my_items, 100., 300.);
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assert_eq!(my_items[0].size, 100.);
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assert_eq!(my_items[1].size, 100.);
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assert_eq!(my_items[2].size, 100.);
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}
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