iris: make span compaction explicit

examples/tabs/lib.rs

@@ -100,10 +100,12 @@ where
             rect(PaintId::PURPLE).sized((50, 50)).align(Align::TOP),
         )
             .span(Dir::RIGHT)
+            .compact()
             .center(),
         wtext("pretty cool right?").size(50),
     )
         .span(Dir::DOWN)
+        .compact()
         .add(rsc);
 
     let texts = Span::empty(Dir::DOWN).gap(10).add(rsc);

examples/text/lib.rs

@@ -38,24 +38,17 @@ where
         .add(Srgba8::new(53, 57, 66, 255).to_linear());
 
     let styled = "Bold, italic, underlined, and colored spans";
-    let styled = wtext(styled)
-        .size(20)
-        .spans(vec![
-            SpanStyle::new(0..4).bold(),
-            SpanStyle::new(6..12).italic(),
-            SpanStyle::new(14..24).underline(),
-            SpanStyle::new(30..37).color(PaintId::SKY),
-        ])
-        .width(rest(1));
+    let styled = wtext(styled).size(20).spans(vec![
+        SpanStyle::new(0..4).bold(),
+        SpanStyle::new(6..12).italic(),
+        SpanStyle::new(14..24).underline(),
+        SpanStyle::new(30..37).color(PaintId::SKY),
+    ]);
 
     let aligned = (
-        wtext("Left aligned")
-            .text_align(Align::CENTER_LEFT)
-            .width(rest(1)),
-        wtext("Centered").text_align(Align::CENTER).width(rest(1)),
-        wtext("Right aligned")
-            .text_align(Align::CENTER_RIGHT)
-            .width(rest(1)),
+        wtext("Left aligned").text_align(Align::CENTER_LEFT),
+        wtext("Centered").text_align(Align::CENTER),
+        wtext("Right aligned").text_align(Align::CENTER_RIGHT),
     )
         .span(Dir::DOWN)
         .gap(dp(4))
@@ -84,8 +77,7 @@ where
             .spans(vec![SpanStyle::new(0..9).bold()]),
         wtext("Drag across display text to select it. The overflow markers select hidden source text, but are never copied.")
             .overflow(TextOverflow::Wrap)
-            .color(PaintId::GRAY)
-            .width(rest(1)),
+            .color(PaintId::GRAY),
     )
         .span(Dir::DOWN)
         .gap(dp(6))

src/layout_tests.rs

@@ -204,6 +204,7 @@ fn a_span_reuses_unchanged_sibling_sizes_when_only_its_along_extent_changes() {
         children: vec![changed.any(), sibling.any()],
         dir: Dir::DOWN,
         gap: LayoutLen::ZERO,
+        compact_orthogonal: false,
     });
     let root = rsc
         .ui
@@ -231,6 +232,61 @@ fn a_span_reuses_unchanged_sibling_sizes_when_only_its_along_extent_changes() {
     );
 }
 
+#[test]
+fn a_span_leaves_children_in_its_offered_orthogonal_axis_by_default() {
+    let mut rsc = TestRsc { ui: Ui::default() };
+    let short = wtext("short").add(&mut rsc);
+    let root = (short, wtext("a much wider line"))
+        .span(Dir::DOWN)
+        .add_strong(&mut rsc);
+    let root_id = root.id();
+    let root = root.any();
+    let mut render = UiRenderState::new();
+    render.resize((200.0, 100.0));
+    render.update(&root, &mut rsc);
+
+    let width = render.active[&root_id].size.x;
+    assert_eq!(width.rel, 0.0);
+    assert_eq!(width.rest, 0.0);
+    assert!(width.abs > 0.0 && width.abs < 200.0);
+    assert_eq!(
+        render.active[&short.id()]
+            .region
+            .to_px(vec2(200.0, 100.0))
+            .size()
+            .x,
+        200.0,
+    );
+}
+
+#[test]
+fn a_compact_span_shrinks_its_orthogonal_axis_to_its_widest_child() {
+    let mut rsc = TestRsc { ui: Ui::default() };
+    let short = wtext("short").add(&mut rsc);
+    let root = (short, wtext("a much wider line"))
+        .span(Dir::DOWN)
+        .compact()
+        .add_strong(&mut rsc);
+    let root_id = root.id();
+    let root = root.any();
+    let mut render = UiRenderState::new();
+    render.resize((200.0, 100.0));
+    render.update(&root, &mut rsc);
+
+    let width = render.active[&root_id].size.x;
+    assert_eq!(width.rel, 0.0);
+    assert_eq!(width.rest, 0.0);
+    assert!(width.abs > 0.0 && width.abs < 200.0);
+    assert_eq!(
+        render.active[&short.id()]
+            .region
+            .to_px(vec2(200.0, 100.0))
+            .size()
+            .x,
+        width.abs,
+    );
+}
+
 #[test]
 fn a_child_coordinate_offset_moves_only_the_child_subtree() {
     let mut rsc = TestRsc { ui: Ui::default() };
@@ -1077,6 +1133,7 @@ fn a_span_of_padded_children_inside_a_span_draws_each_where_its_box_is() {
         children: vec![header.any(), inner.any()],
         dir: Dir::DOWN,
         gap: LayoutLen::ZERO,
+        compact_orthogonal: false,
     });
     let mut list = LazySpan::new(Dir::DOWN, Pin::End);
     list.push_back(LazyItem::new(0, outer.any()));

src/widget/layout/span.rs

@@ -5,6 +5,7 @@ pub struct Span {
     pub children: Vec<StrongWidget>,
     pub dir: Dir,
     pub gap: LayoutLen,
+    pub compact_orthogonal: bool,
 }
 
 impl Widget for Span {
@@ -85,7 +86,7 @@ impl Widget for Span {
         }
         if ortho_mixed {
             ortho_len = LayoutLen::default();
-        } else {
+        } else if self.compact_orthogonal {
             let ortho = ortho_len
                 .apply_rest(painter.density())
                 .align(AxisAlign::Neg);
@@ -111,9 +112,18 @@ impl Span {
             children: Vec::new(),
             dir,
             gap: LayoutLen::ZERO,
+            compact_orthogonal: false,
         }
     }
 
+    /// Shrink the span and its children to the widest orthogonal child
+    /// instead of leaving children in the orthogonal space offered by its
+    /// parent.
+    pub fn compact(mut self) -> Self {
+        self.compact_orthogonal = true;
+        self
+    }
+
     pub fn gap(mut self, gap: impl Into<LayoutLen>) -> Self {
         self.gap = gap.into();
         self
@@ -132,6 +142,7 @@ pub struct SpanBuilder<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Ta
     pub children: Wa,
     pub dir: Dir,
     pub gap: LayoutLen,
+    pub compact_orthogonal: bool,
     _pd: PhantomData<(State, Tag)>,
 }
 
@@ -146,6 +157,7 @@ impl<Rsc, const LEN: usize, Wa: WidgetArrLike<Rsc, LEN, Tag>, Tag> WidgetFnTrait
             children: self.children.add(rsc).arr.into_iter().collect(),
             dir: self.dir,
             gap: self.gap,
+            compact_orthogonal: self.compact_orthogonal,
         }
     }
 }
@@ -158,6 +170,7 @@ impl<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag>
             children,
             dir,
             gap: LayoutLen::ZERO,
+            compact_orthogonal: false,
             _pd: PhantomData,
         }
     }
@@ -166,6 +179,13 @@ impl<State, const LEN: usize, Wa: WidgetArrLike<State, LEN, Tag>, Tag>
         self.gap = gap.into();
         self
     }
+
+    /// Shrink the span and its children to the widest orthogonal child
+    /// instead of filling the orthogonal space offered by its parent.
+    pub fn compact(mut self) -> Self {
+        self.compact_orthogonal = true;
+        self
+    }
 }
 
 impl std::ops::Deref for Span {