Show available key bindings with F1/?

src/ui/input.rs

@@ -1,4 +1,20 @@
+use std::convert::Infallible;
+
 use crossterm::event::{KeyCode, KeyModifiers};
+use crossterm::style::{ContentStyle, Stylize};
+use toss::styled::Styled;
+
+use super::widgets::background::Background;
+use super::widgets::border::Border;
+use super::widgets::empty::Empty;
+use super::widgets::float::Float;
+use super::widgets::join::{HJoin, Segment};
+use super::widgets::layer::Layer;
+use super::widgets::list::{List, ListState};
+use super::widgets::padding::Padding;
+use super::widgets::resize::Resize;
+use super::widgets::text::Text;
+use super::widgets::BoxedWidget;
 
 /// A key event data type that is a bit easier to pattern match on than
 /// [`crossterm::event::KeyEvent`].
@@ -46,3 +62,62 @@ macro_rules! key {
     (   Alt + $key:ident ) => { KeyEvent { code: KeyCode::$key, shift: false, ctrl: false, alt: true,  } };
 }
 pub(crate) use key;
+
+/// Helper wrapper around a list widget for a more consistent key binding style.
+pub struct KeyBindingsList(List<Infallible>);
+
+impl KeyBindingsList {
+    pub fn new(state: &ListState<Infallible>) -> Self {
+        Self(state.widget())
+    }
+
+    fn binding_style() -> ContentStyle {
+        ContentStyle::default().cyan()
+    }
+
+    pub fn widget(self) -> BoxedWidget {
+        let binding_style = Self::binding_style();
+        Float::new(Layer::new(vec![
+            Border::new(Background::new(Padding::new(self.0).horizontal(1))).into(),
+            Float::new(
+                Padding::new(Text::new(
+                    Styled::new("jk/↓↑", binding_style)
+                        .then_plain(" to scroll, ")
+                        .then("esc", binding_style)
+                        .then_plain(" to close"),
+                ))
+                .horizontal(1),
+            )
+            .horizontal(0.5)
+            .into(),
+        ]))
+        .horizontal(0.5)
+        .vertical(0.5)
+        .into()
+    }
+
+    pub fn empty(&mut self) {
+        self.0.add_unsel(Empty::new());
+    }
+
+    pub fn heading(&mut self, name: &str) {
+        self.0
+            .add_unsel(Text::new((name, ContentStyle::default().bold())));
+    }
+
+    pub fn binding(&mut self, binding: &str, description: &str) {
+        let widget = HJoin::new(vec![
+            Segment::new(Resize::new(Text::new((binding, Self::binding_style()))).min_width(16)),
+            Segment::new(Text::new(description)),
+        ]);
+        self.0.add_unsel(widget);
+    }
+
+    pub fn binding_ctd(&mut self, description: &str) {
+        let widget = HJoin::new(vec![
+            Segment::new(Resize::new(Empty::new()).min_width(16)),
+            Segment::new(Text::new(description)),
+        ]);
+        self.0.add_unsel(widget);
+    }
+}