Position Menu layer based on available space

examples/combo_box/src/main.rs

@@ -60,10 +60,6 @@ impl Sandbox for Example {
             .push(Text::new("Which is your favorite language?"))
             .push(combo_box);
 
-        if self.selected_language == Language::Javascript {
-            content = content.push(Text::new("You are wrong!"));
-        }
-
         content = content
             .push(button)
             .push(Space::with_height(Length::Units(800)));

native/src/layer/menu.rs

@@ -1,6 +1,7 @@
 use crate::{
     container, layout, mouse, scrollable, Clipboard, Container, Element, Event,
-    Hasher, Layer, Layout, Length, Point, Rectangle, Scrollable, Size, Widget,
+    Hasher, Layer, Layout, Length, Point, Rectangle, Scrollable, Size, Vector,
+    Widget,
 };
 use std::borrow::Cow;
 
@@ -8,6 +9,7 @@ pub struct Menu<'a, Message, Renderer: self::Renderer> {
     container: Container<'a, Message, Renderer>,
     is_open: &'a mut bool,
     width: u16,
+    target_height: f32,
 }
 
 #[derive(Default)]
@@ -38,6 +40,7 @@ where
         options: impl Into<Cow<'a, [T]>>,
         on_selected: Box<dyn Fn(T) -> Message>,
         width: u16,
+        target_height: f32,
         text_size: u16,
         padding: u16,
     ) -> Self
@@ -60,6 +63,7 @@ where
             container,
             is_open: &mut state.is_open,
             width,
+            target_height,
         }
     }
 }
@@ -75,15 +79,29 @@ where
         bounds: Size,
         position: Point,
     ) -> layout::Node {
+        let space_below = bounds.height - (position.y + self.target_height);
+        let space_above = position.y;
+
         let limits = layout::Limits::new(
             Size::ZERO,
-            Size::new(bounds.width - position.x, bounds.height - position.y),
+            Size::new(
+                bounds.width - position.x,
+                if space_below > space_above {
+                    space_below
+                } else {
+                    space_above
+                },
+            ),
         )
         .width(Length::Units(self.width));
 
         let mut node = self.container.layout(renderer, &limits);
 
-        node.move_to(position);
+        node.move_to(if space_below > space_above {
+            position + Vector::new(0.0, self.target_height)
+        } else {
+            position - Vector::new(0.0, node.size().height)
+        });
 
         node
     }

native/src/widget/combo_box.rs

@@ -1,7 +1,7 @@
 use crate::{
     layer::{self, menu},
     layout, mouse, scrollable, text, Clipboard, Element, Event, Hasher, Layout,
-    Length, Overlay, Point, Rectangle, Size, Vector, Widget,
+    Length, Overlay, Point, Rectangle, Size, Widget,
 };
 use std::borrow::Cow;
 
@@ -210,14 +210,16 @@ where
 
         if is_open {
             if let Some(Internal { menu, on_selected }) = self.internal.take() {
+                let bounds = layout.bounds();
+
                 Some(Overlay::new(
-                    layout.position()
-                        + Vector::new(0.0, layout.bounds().height),
+                    layout.position(),
                     Box::new(layer::Menu::new(
                         menu,
                         self.options.clone(),
                         on_selected,
-                        layout.bounds().width.round() as u16,
+                        bounds.width.round() as u16,
+                        bounds.height,
                         self.text_size.unwrap_or(20),
                         self.padding,
                     )),