Layout consistency

core/src/element.rs

@@ -6,7 +6,7 @@ use crate::renderer;
 use crate::widget;
 use crate::widget::tree::{self, Tree};
 use crate::{
-    Clipboard, Color, Layout, Length, Rectangle, Shell, Vector, Widget,
+    Clipboard, Color, Layout, Length, Rectangle, Shell, Size, Vector, Widget,
 };
 
 use std::any::Any;
@@ -296,12 +296,8 @@ where
         self.widget.diff(tree);
     }
 
-    fn width(&self) -> Length {
-        self.widget.width()
-    }
-
-    fn height(&self) -> Length {
-        self.widget.height()
+    fn size(&self) -> Size<Length> {
+        self.widget.size()
     }
 
     fn layout(
@@ -466,12 +462,8 @@ impl<'a, Message, Renderer> Widget<Message, Renderer>
 where
     Renderer: crate::Renderer,
 {
-    fn width(&self) -> Length {
-        self.element.widget.width()
-    }
-
-    fn height(&self) -> Length {
-        self.element.widget.height()
+    fn size(&self) -> Size<Length> {
+        self.element.widget.size()
     }
 
     fn tag(&self) -> tree::Tag {

core/src/layout.rs

@@ -7,7 +7,7 @@ pub mod flex;
 pub use limits::Limits;
 pub use node::Node;
 
-use crate::{Point, Rectangle, Size, Vector};
+use crate::{Length, Padding, Point, Rectangle, Size, Vector};
 
 /// The bounds of a [`Node`] and its children, using absolute coordinates.
 #[derive(Debug, Clone, Copy)]
@@ -71,12 +71,12 @@ pub fn next_to_each_other(
     left: impl FnOnce(&Limits) -> Node,
     right: impl FnOnce(&Limits) -> Node,
 ) -> Node {
-    let mut left_node = left(limits);
+    let left_node = left(limits);
     let left_size = left_node.size();
 
     let right_limits = limits.shrink(Size::new(left_size.width + spacing, 0.0));
 
-    let mut right_node = right(&right_limits);
+    let right_node = right(&right_limits);
     let right_size = right_node.size();
 
     let (left_y, right_y) = if left_size.height > right_size.height {
@@ -85,14 +85,106 @@ pub fn next_to_each_other(
         ((right_size.height - left_size.height) / 2.0, 0.0)
     };
 
-    left_node.move_to(Point::new(0.0, left_y));
-    right_node.move_to(Point::new(left_size.width + spacing, right_y));
-
     Node::with_children(
         Size::new(
             left_size.width + spacing + right_size.width,
             left_size.height.max(right_size.height),
         ),
-        vec![left_node, right_node],
+        vec![
+            left_node.move_to(Point::new(0.0, left_y)),
+            right_node.move_to(Point::new(left_size.width + spacing, right_y)),
+        ],
+    )
+}
+
+/// Computes the resulting [`Node`] that fits the [`Limits`] given
+/// some width and height requirements and no intrinsic size.
+pub fn atomic(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+
+    Node::new(limits.resolve(width, height, Size::ZERO))
+}
+
+/// Computes the resulting [`Node`] that fits the [`Limits`] given
+/// some width and height requirements and a closure that produces
+/// the intrinsic [`Size`] inside the given [`Limits`].
+pub fn sized(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    f: impl FnOnce(&Limits) -> Size,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+
+    let limits = limits.width(width).height(height);
+    let intrinsic_size = f(&limits);
+
+    Node::new(limits.resolve(width, height, intrinsic_size))
+}
+
+/// Computes the resulting [`Node`] that fits the [`Limits`] given
+/// some width and height requirements and a closure that produces
+/// the content [`Node`] inside the given [`Limits`].
+pub fn contained(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    f: impl FnOnce(&Limits) -> Node,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+
+    let limits = limits.width(width).height(height);
+    let content = f(&limits);
+
+    Node::with_children(
+        limits.resolve(width, height, content.size()),
+        vec![content],
+    )
+}
+
+/// Computes the [`Node`] that fits the [`Limits`] given some width, height, and
+/// [`Padding`] requirements and a closure that produces the content [`Node`]
+/// inside the given [`Limits`].
+pub fn padded(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    padding: impl Into<Padding>,
+    layout: impl FnOnce(&Limits) -> Node,
+) -> Node {
+    positioned(limits, width, height, padding, layout, |content, _| content)
+}
+
+/// Computes a [`padded`] [`Node`] with a positioning step.
+pub fn positioned(
+    limits: &Limits,
+    width: impl Into<Length>,
+    height: impl Into<Length>,
+    padding: impl Into<Padding>,
+    layout: impl FnOnce(&Limits) -> Node,
+    position: impl FnOnce(Node, Size) -> Node,
+) -> Node {
+    let width = width.into();
+    let height = height.into();
+    let padding = padding.into();
+
+    let limits = limits.width(width).height(height);
+    let content = layout(&limits.shrink(padding));
+    let padding = padding.fit(content.size(), limits.max());
+
+    let size = limits
+        .shrink(padding)
+        .resolve(width, height, content.size());
+
+    Node::with_children(
+        size.expand(padding),
+        vec![position(content.move_to((padding.left, padding.top)), size)],
     )
 }

core/src/layout/flex.rs

@@ -20,7 +20,7 @@ use crate::Element;
 
 use crate::layout::{Limits, Node};
 use crate::widget;
-use crate::{Alignment, Padding, Point, Size};
+use crate::{Alignment, Length, Padding, Point, Size};
 
 /// The main axis of a flex layout.
 #[derive(Debug)]
@@ -47,7 +47,7 @@ impl Axis {
         }
     }
 
-    fn pack(&self, main: f32, cross: f32) -> (f32, f32) {
+    fn pack<T>(&self, main: T, cross: T) -> (T, T) {
         match self {
             Axis::Horizontal => (main, cross),
             Axis::Vertical => (cross, main),
@@ -63,6 +63,8 @@ pub fn resolve<Message, Renderer>(
     axis: Axis,
     renderer: &Renderer,
     limits: &Limits,
+    width: Length,
+    height: Length,
     padding: Padding,
     spacing: f32,
     align_items: Alignment,
@@ -72,26 +74,64 @@ pub fn resolve<Message, Renderer>(
 where
     Renderer: crate::Renderer,
 {
-    let limits = limits.pad(padding);
+    let limits = limits.width(width).height(height).shrink(padding);
     let total_spacing = spacing * items.len().saturating_sub(1) as f32;
     let max_cross = axis.cross(limits.max());
 
-    let mut fill_sum = 0;
-    let mut cross = axis.cross(limits.min()).max(axis.cross(limits.fill()));
+    let mut fill_main_sum = 0;
+    let mut cross = match axis {
+        Axis::Horizontal => match height {
+            Length::Shrink => 0.0,
+            _ => max_cross,
+        },
+        Axis::Vertical => match width {
+            Length::Shrink => 0.0,
+            _ => max_cross,
+        },
+    };
+
     let mut available = axis.main(limits.max()) - total_spacing;
 
     let mut nodes: Vec<Node> = Vec::with_capacity(items.len());
     nodes.resize(items.len(), Node::default());
 
     for (i, (child, tree)) in items.iter().zip(trees.iter_mut()).enumerate() {
-        let fill_factor = match axis {
-            Axis::Horizontal => child.as_widget().width(),
-            Axis::Vertical => child.as_widget().height(),
+        let (fill_main_factor, fill_cross_factor) = {
+            let size = child.as_widget().size();
+
+            axis.pack(size.width.fill_factor(), size.height.fill_factor())
+        };
+
+        if fill_main_factor == 0 {
+            if fill_cross_factor == 0 {
+                let (max_width, max_height) = axis.pack(available, max_cross);
+
+                let child_limits =
+                    Limits::new(Size::ZERO, Size::new(max_width, max_height));
+
+                let layout =
+                    child.as_widget().layout(tree, renderer, &child_limits);
+                let size = layout.size();
+
+                available -= axis.main(size);
+                cross = cross.max(axis.cross(size));
+
+                nodes[i] = layout;
+            }
+        } else {
+            fill_main_sum += fill_main_factor;
         }
-        .fill_factor();
+    }
 
-        if fill_factor == 0 {
-            let (max_width, max_height) = axis.pack(available, max_cross);
+    for (i, (child, tree)) in items.iter().zip(trees.iter_mut()).enumerate() {
+        let (fill_main_factor, fill_cross_factor) = {
+            let size = child.as_widget().size();
+
+            axis.pack(size.width.fill_factor(), size.height.fill_factor())
+        };
+
+        if fill_main_factor == 0 && fill_cross_factor != 0 {
+            let (max_width, max_height) = axis.pack(available, cross);
 
             let child_limits =
                 Limits::new(Size::ZERO, Size::new(max_width, max_height));
@@ -101,34 +141,47 @@ where
             let size = layout.size();
 
             available -= axis.main(size);
-            cross = cross.max(axis.cross(size));
+            cross = cross.max(axis.cross(layout.size()));
 
             nodes[i] = layout;
-        } else {
-            fill_sum += fill_factor;
         }
     }
 
-    let remaining = available.max(0.0);
+    let remaining = match axis {
+        Axis::Horizontal => match width {
+            Length::Shrink => 0.0,
+            _ => available.max(0.0),
+        },
+        Axis::Vertical => match height {
+            Length::Shrink => 0.0,
+            _ => available.max(0.0),
+        },
+    };
 
     for (i, (child, tree)) in items.iter().zip(trees).enumerate() {
-        let fill_factor = match axis {
-            Axis::Horizontal => child.as_widget().width(),
-            Axis::Vertical => child.as_widget().height(),
-        }
-        .fill_factor();
+        let (fill_main_factor, fill_cross_factor) = {
+            let size = child.as_widget().size();
+
+            axis.pack(size.width.fill_factor(), size.height.fill_factor())
+        };
+
+        if fill_main_factor != 0 {
+            let max_main =
+                remaining * fill_main_factor as f32 / fill_main_sum as f32;
 
-        if fill_factor != 0 {
-            let max_main = remaining * fill_factor as f32 / fill_sum as f32;
             let min_main = if max_main.is_infinite() {
                 0.0
             } else {
                 max_main
             };
 
-            let (min_width, min_height) =
-                axis.pack(min_main, axis.cross(limits.min()));
+            let max_cross = if fill_cross_factor == 0 {
+                max_cross
+            } else {
+                cross
+            };
 
+            let (min_width, min_height) = axis.pack(min_main, 0.0);
             let (max_width, max_height) = axis.pack(max_main, max_cross);
 
             let child_limits = Limits::new(
@@ -154,18 +207,18 @@ where
 
         let (x, y) = axis.pack(main, pad.1);
 
-        node.move_to(Point::new(x, y));
+        node.move_to_mut(Point::new(x, y));
 
         match axis {
             Axis::Horizontal => {
-                node.align(
+                node.align_mut(
                     Alignment::Start,
                     align_items,
                     Size::new(0.0, cross),
                 );
             }
             Axis::Vertical => {
-                node.align(
+                node.align_mut(
                     align_items,
                     Alignment::Start,
                     Size::new(cross, 0.0),
@@ -178,8 +231,12 @@ where
         main += axis.main(size);
     }
 
-    let (width, height) = axis.pack(main - pad.0, cross);
-    let size = limits.resolve(Size::new(width, height));
+    let (intrinsic_width, intrinsic_height) = axis.pack(main - pad.0, cross);
+    let size = limits.resolve(
+        width,
+        height,
+        Size::new(intrinsic_width, intrinsic_height),
+    );
 
-    Node::with_children(size.pad(padding), nodes)
+    Node::with_children(size.expand(padding), nodes)
 }