Add Float widget

examples/hello_world_widgets.rs

@@ -6,17 +6,20 @@ use toss::widgets::{BorderLook, Text};
 use toss::{Styled, Terminal, Widget, WidgetExt};
 
 fn widget() -> impl Widget<Infallible> {
-    Text::new(
-        Styled::new("Hello world!", ContentStyle::default().green())
-            .then_plain("\n")
-            .then(
-                "Press any key to exit",
-                ContentStyle::default().on_dark_blue(),
-            ),
-    )
-    .border()
-    .look(BorderLook::LINE_DOUBLE)
-    .style(ContentStyle::default().dark_red())
+    let styled = Styled::new("Hello world!", ContentStyle::default().green())
+        .then_plain("\n")
+        .then(
+            "Press any key to exit",
+            ContentStyle::default().on_dark_blue(),
+        );
+    Text::new(styled)
+        .padding()
+        .horizontal(1)
+        .border()
+        .look(BorderLook::LINE_DOUBLE)
+        .style(ContentStyle::default().dark_red())
+        .float()
+        .all(0.5)
 }
 
 fn render_frame(term: &mut Terminal) {

src/widget.rs

@@ -1,6 +1,6 @@
 use async_trait::async_trait;
 
-use crate::widgets::{Border, Padding};
+use crate::widgets::{Border, Float, Padding};
 use crate::{Frame, Size};
 
 // TODO Feature-gate these traits
@@ -33,6 +33,10 @@ pub trait WidgetExt: Sized {
         Border::new(self)
     }
 
+    fn float(self) -> Float<Self> {
+        Float::new(self)
+    }
+
     fn padding(self) -> Padding<Self> {
         Padding::new(self)
     }
@@ -45,6 +49,10 @@ pub trait AsyncWidgetExt: Sized {
         Border::new(self)
     }
 
+    fn float(self) -> Float<Self> {
+        Float::new(self)
+    }
+
     fn padding(self) -> Padding<Self> {
         Padding::new(self)
     }

src/widgets.rs

@@ -1,7 +1,9 @@
 mod border;
+mod float;
 mod padding;
 mod text;
 
 pub use border::*;
+pub use float::*;
 pub use padding::*;
 pub use text::*;

src/widgets/float.rs

@@ -0,0 +1,112 @@
+use async_trait::async_trait;
+
+use crate::{AsyncWidget, Frame, Pos, Size, Widget};
+
+pub struct Float<I> {
+    inner: I,
+    horizontal: Option<f32>,
+    vertical: Option<f32>,
+}
+
+impl<I> Float<I> {
+    pub fn new(inner: I) -> Self {
+        Self {
+            inner,
+            horizontal: None,
+            vertical: None,
+        }
+    }
+
+    pub fn horizontal(mut self, position: f32) -> Self {
+        self.horizontal = Some(position);
+        self
+    }
+
+    pub fn vertical(mut self, position: f32) -> Self {
+        self.vertical = Some(position);
+        self
+    }
+
+    pub fn all(self, position: f32) -> Self {
+        self.horizontal(position).vertical(position)
+    }
+
+    fn push_inner(&self, frame: &mut Frame, size: Size, mut inner_size: Size) {
+        inner_size.width = inner_size.width.min(size.width);
+        inner_size.height = inner_size.height.min(size.height);
+
+        let mut inner_pos = Pos::ZERO;
+
+        if let Some(horizontal) = self.horizontal {
+            let available = (size.width - inner_size.width) as f32;
+            // Biased towards the left if horizontal lands exactly on the
+            // boundary between two cells
+            inner_pos.x = (horizontal * available).floor().min(available) as i32;
+        }
+
+        if let Some(vertical) = self.vertical {
+            let available = (size.height - inner_size.height) as f32;
+            // Biased towards the top if vertical lands exactly on the boundary
+            // between two cells
+            inner_pos.y = (vertical * available).floor().min(available) as i32;
+        }
+
+        frame.push(inner_pos, inner_size);
+    }
+}
+
+impl<E, I> Widget<E> for Float<I>
+where
+    I: Widget<E>,
+{
+    fn size(
+        &self,
+        frame: &mut Frame,
+        max_width: Option<u16>,
+        max_height: Option<u16>,
+    ) -> Result<Size, E> {
+        self.inner.size(frame, max_width, max_height)
+    }
+
+    fn draw(self, frame: &mut Frame) -> Result<(), E> {
+        let size = frame.size();
+        let inner_size = self
+            .inner
+            .size(frame, Some(size.width), Some(size.height))?;
+
+        self.push_inner(frame, size, inner_size);
+        self.inner.draw(frame)?;
+        frame.pop();
+
+        Ok(())
+    }
+}
+
+#[async_trait]
+impl<E, I> AsyncWidget<E> for Float<I>
+where
+    I: AsyncWidget<E> + Send + Sync,
+{
+    async fn size(
+        &self,
+        frame: &mut Frame,
+        max_width: Option<u16>,
+        max_height: Option<u16>,
+    ) -> Result<Size, E> {
+        self.inner.size(frame, max_width, max_height).await
+    }
+
+    async fn draw(self, frame: &mut Frame) -> Result<(), E> {
+        let size = frame.size();
+        let inner_size = self
+            .inner
+            .size(frame, Some(size.width), Some(size.height))
+            .await?;
+
+        self.push_inner(frame, size, inner_size);
+        self.inner.draw(frame).await?;
+        frame.pop();
+
+        Ok(())
+    }
+}