Introduce Widget::size_hint and fix further layout inconsistencies

widget/src/row.rs

@@ -21,26 +21,31 @@ pub struct Row<'a, Message, Renderer = crate::Renderer> {
     children: Vec<Element<'a, Message, Renderer>>,
 }
 
-impl<'a, Message, Renderer> Row<'a, Message, Renderer> {
+impl<'a, Message, Renderer> Row<'a, Message, Renderer>
+where
+    Renderer: crate::core::Renderer,
+{
     /// Creates an empty [`Row`].
     pub fn new() -> Self {
-        Self::with_children(Vec::new())
-    }
-
-    /// Creates a [`Row`] with the given elements.
-    pub fn with_children(
-        children: Vec<Element<'a, Message, Renderer>>,
-    ) -> Self {
         Row {
             spacing: 0.0,
             padding: Padding::ZERO,
             width: Length::Shrink,
             height: Length::Shrink,
             align_items: Alignment::Start,
-            children,
+            children: Vec::new(),
         }
     }
 
+    /// Creates a [`Row`] with the given elements.
+    pub fn with_children(
+        children: impl Iterator<Item = Element<'a, Message, Renderer>>,
+    ) -> Self {
+        children
+            .into_iter()
+            .fold(Self::new(), |column, element| column.push(element))
+    }
+
     /// Sets the horizontal spacing _between_ elements.
     ///
     /// Custom margins per element do not exist in iced. You should use this
@@ -80,12 +85,26 @@ impl<'a, Message, Renderer> Row<'a, Message, Renderer> {
         mut self,
         child: impl Into<Element<'a, Message, Renderer>>,
     ) -> Self {
-        self.children.push(child.into());
+        let child = child.into();
+        let size = child.as_widget().size_hint();
+
+        if size.width.is_fill() {
+            self.width = Length::Fill;
+        }
+
+        if size.height.is_fill() {
+            self.height = Length::Fill;
+        }
+
+        self.children.push(child);
         self
     }
 }
 
-impl<'a, Message, Renderer> Default for Row<'a, Message, Renderer> {
+impl<'a, Message, Renderer> Default for Row<'a, Message, Renderer>
+where
+    Renderer: crate::core::Renderer,
+{
     fn default() -> Self {
         Self::new()
     }