feat(widgets): implement Widget for Widget refs (#833)

Many widgets can be rendered without changing their state.

This commit implements The `Widget` trait for references to
widgets and changes their implementations to be immutable.

This allows us to render widgets without consuming them by passing a ref
to the widget when calling `Frame::render_widget()`.

```rust
// this might be stored in a struct
let paragraph = Paragraph::new("Hello world!");

let [left, right] = area.split(&Layout::horizontal([20, 20]));
frame.render_widget(&paragraph, left);
frame.render_widget(&paragraph, right); // we can reuse the widget
```

Implemented for all widgets except BarChart (which has an implementation
that modifies the internal state and requires a rewrite to fix.

Other widgets will be implemented in follow up commits.

Fixes: https://github.com/ratatui-org/ratatui/discussions/164
Replaces PRs: https://github.com/ratatui-org/ratatui/pull/122 and
https://github.com/ratatui-org/ratatui/pull/16
Enables: https://github.com/ratatui-org/ratatui/issues/132
Validated as a viable working solution by:
https://github.com/ratatui-org/ratatui/pull/836

examples/colors_rgb.rs

@@ -23,7 +23,7 @@ use crossterm::{
     ExecutableCommand,
 };
 use palette::{convert::FromColorUnclamped, Okhsv, Srgb};
-use ratatui::{prelude::*, widgets::*};
+use ratatui::prelude::*;
 
 #[derive(Debug, Default)]
 struct App {

examples/demo2/colors.rs

@@ -1,5 +1,5 @@
 use palette::{IntoColor, Okhsv, Srgb};
-use ratatui::{prelude::*, widgets::*};
+use ratatui::prelude::*;
 
 /// A widget that renders a color swatch of RGB colors.
 ///

src/layout/layout.rs

@@ -1172,7 +1172,7 @@ mod tests {
             assert_buffer_eq,
             layout::flex::Flex,
             prelude::{Constraint::*, *},
-            widgets::{Paragraph, Widget},
+            widgets::Paragraph,
         };
 
         /// Test that the given constraints applied to the given area result in the expected layout.

src/prelude.rs

@@ -31,4 +31,5 @@ pub use crate::{
     symbols::{self, Marker},
     terminal::{CompletedFrame, Frame, Terminal, TerminalOptions, Viewport},
     text::{self, Line, Masked, Span, Text},
+    widgets::{block::BlockExt, StatefulWidget, Widget},
 };

src/terminal/frame.rs

@@ -1,7 +1,4 @@
-use crate::{
+use crate::prelude::*;
-    prelude::*,
-    widgets::{StatefulWidget, Widget},
-};
 
 /// A consistent view into the terminal state for rendering a single frame.
 ///
@@ -74,10 +71,7 @@ impl Frame<'_> {
     /// ```
     ///
     /// [`Layout`]: crate::layout::Layout
-    pub fn render_widget<W>(&mut self, widget: W, area: Rect)
+    pub fn render_widget<W: Widget>(&mut self, widget: W, area: Rect) {
-    where
-        W: Widget,
-    {
         widget.render(area, self.buffer);
     }
 

src/text/line.rs

@@ -407,6 +407,22 @@ impl<'a> From<Line<'a>> for String {
 }
 
 impl Widget for Line<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Widget::render(&self, area, buf);
+    }
+}
+
+/// Implement [`Widget`] for [`Option<Line>`] to simplify the common case of having an optional
+/// [`Line`] field in a widget.
+impl Widget for &Option<Line<'_>> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        if let Some(line) = self {
+            line.render(area, buf);
+        }
+    }
+}
+
+impl Widget for &Line<'_> {
     fn render(self, area: Rect, buf: &mut Buffer) {
         let area = area.intersection(buf.area);
         buf.set_style(area, self.style);
@@ -418,7 +434,7 @@ impl Widget for Line<'_> {
             None => 0,
         };
         let mut x = area.left().saturating_add(offset);
-        for span in self.spans {
+        for span in self.spans.iter() {
             let span_width = span.width() as u16;
             let span_area = Rect {
                 x,

src/text/span.rs

@@ -299,6 +299,22 @@ impl<'a> Styled for Span<'a> {
 }
 
 impl Widget for Span<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Widget::render(&self, area, buf);
+    }
+}
+
+/// Implement [`Widget`] for [`Option<Span>`] to simplify the common case of having an optional
+/// [`Span`] field in a widget.
+impl Widget for &Option<Span<'_>> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        if let Some(span) = self {
+            span.render(area, buf);
+        }
+    }
+}
+
+impl Widget for &Span<'_> {
     fn render(self, area: Rect, buf: &mut Buffer) {
         let Rect {
             x: mut current_x,

src/text/text.rs

@@ -414,10 +414,26 @@ impl std::fmt::Display for Text<'_> {
     }
 }
 
-impl<'a> Widget for Text<'a> {
+impl Widget for Text<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Widget::render(&self, area, buf);
+    }
+}
+
+/// Implement [`Widget`] for [`Option<Text>`] to simplify the common case of having an optional
+/// [`Text`] field in a widget.
+impl Widget for &Option<Text<'_>> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        if let Some(text) = self {
+            text.render(area, buf);
+        }
+    }
+}
+
+impl Widget for &Text<'_> {
     fn render(self, area: Rect, buf: &mut Buffer) {
         buf.set_style(area, self.style);
-        for (line, row) in self.lines.into_iter().zip(area.rows()) {
+        for (line, row) in self.lines.iter().zip(area.rows()) {
             let line_width = line.width() as u16;
 
             let x_offset = match (self.alignment, line.alignment) {

src/widgets.rs

@@ -53,7 +53,59 @@ pub use self::{
 };
 use crate::{buffer::Buffer, layout::Rect};
 
-/// Base requirements for a Widget
+/// A `Widget` is a type that can be drawn on a [`Buffer`] in a given [`Rect`].
+///
+/// Prior to Ratatui 0.26.0, widgets generally were created for each frame as they were consumed
+/// during rendering. This meant that they were not meant to be stored but used as *commands* to
+/// draw common figures in the UI.
+///
+/// Starting with Ratatui 0.26.0, the `Widget` trait was more universally implemented on &T instead
+/// of just T. This means that widgets can be stored and reused across frames without having to
+/// clone or recreate them.
+///
+/// # Examples
+///
+/// ```rust,no_run
+/// use ratatui::{backend::TestBackend, prelude::*, widgets::*};
+/// # let backend = TestBackend::new(5, 5);
+/// # let mut terminal = Terminal::new(backend).unwrap();
+///
+/// terminal.draw(|frame| {
+///     frame.render_widget(Clear, frame.size());
+/// });
+/// ```
+///
+/// Rendering a widget by reference:
+///
+/// ```rust
+/// # use ratatui::{backend::TestBackend, prelude::*, widgets::*};
+/// # let backend = TestBackend::new(5, 5);
+/// # let mut terminal = Terminal::new(backend).unwrap();
+/// // this variable could instead be a value stored in a struct and reused across frames
+/// let paragraph = Paragraph::new("Hello world!");
+///
+/// terminal.draw(|frame| {
+///     frame.render_widget(&paragraph, frame.size());
+/// });
+/// ```
+///
+/// It's common to render widgets inside other widgets:
+///
+/// ```rust
+/// use ratatui::{prelude::*, widgets::*};
+///
+/// struct MyWidget;
+///
+/// impl Widget for &MyWidget {
+///     fn render(self, area: Rect, buf: &mut Buffer) {
+///         Block::default()
+///             .title("My Widget")
+///             .borders(Borders::ALL)
+///             .render(area, buf);
+///         // ...
+///     }
+/// }
+/// ```
 pub trait Widget {
     /// Draws the current state of the widget in the given buffer. That is the only method required
     /// to implement a custom widget.

src/widgets/barchart.rs

@@ -1,5 +1,5 @@
 #![warn(missing_docs)]
-use crate::prelude::*;
+use crate::{prelude::*, widgets::Block};
 
 mod bar;
 mod bar_group;
@@ -7,8 +7,6 @@ mod bar_group;
 pub use bar::Bar;
 pub use bar_group::BarGroup;
 
-use super::{Block, Widget};
-
 /// A chart showing values as [bars](Bar).
 ///
 /// Here is a possible `BarChart` output.
@@ -36,6 +34,9 @@ use super::{Block, Widget};
 /// The chart can have a [`Direction`] (by default the bars are [`Vertical`](Direction::Vertical)).
 /// This is set using [`BarChart::direction`].
 ///
+/// Note: this is the only widget that doesn't implement `Widget` for `&T` because the current
+/// implementation modifies the internal state of self. This will be fixed in the future.
+///
 /// # Examples
 ///
 /// The following example creates a `BarChart` with two groups of bars.  
@@ -391,15 +392,6 @@ impl<'a> BarChart<'a> {
         }
     }
 
-    /// renders the block if there is one and updates the area to the inner area
-    fn render_block(&mut self, area: &mut Rect, buf: &mut Buffer) {
-        if let Some(block) = self.block.take() {
-            let inner_area = block.inner(*area);
-            block.render(*area, buf);
-            *area = inner_area
-        }
-    }
-
     fn render_horizontal(self, buf: &mut Buffer, area: Rect) {
         // get the longest label
         let label_size = self
@@ -586,19 +578,20 @@ impl<'a> BarChart<'a> {
     }
 }
 
-impl<'a> Widget for BarChart<'a> {
+impl Widget for BarChart<'_> {
-    fn render(mut self, mut area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
         buf.set_style(area, self.style);
 
-        self.render_block(&mut area, buf);
+        self.block.render(area, buf);
+        let inner = self.block.inner_if_some(area);
 
-        if area.is_empty() || self.data.is_empty() || self.bar_width == 0 {
+        if inner.is_empty() || self.data.is_empty() || self.bar_width == 0 {
             return;
         }
 
         match self.direction {
-            Direction::Horizontal => self.render_horizontal(buf, area),
+            Direction::Horizontal => self.render_horizontal(buf, inner),
-            Direction::Vertical => self.render_vertical(buf, area),
+            Direction::Vertical => self.render_vertical(buf, inner),
         }
     }
 }

src/widgets/barchart/bar.rs

@@ -115,24 +115,21 @@ impl<'a> Bar<'a> {
     /// bar width, then the value is split into 2 parts. the first part is rendered in the bar
     /// using value_style. The second part is rendered outside the bar using bar_style
     pub(super) fn render_value_with_different_styles(
-        self,
+        &self,
         buf: &mut Buffer,
         area: Rect,
         bar_length: usize,
         default_value_style: Style,
         bar_style: Style,
     ) {
-        let text = if let Some(text) = self.text_value {
+        let value = self.value.to_string();
-            text
+        let text = self.text_value.as_ref().unwrap_or(&value);
-        } else {
-            self.value.to_string()
-        };
 
         if !text.is_empty() {
             let style = default_value_style.patch(self.value_style);
             // Since the value may be longer than the bar itself, we need to use 2 different styles
             // while rendering. Render the first part with the default value style
-            buf.set_stringn(area.x, area.y, &text, bar_length, style);
+            buf.set_stringn(area.x, area.y, text, bar_length, style);
             // render the second part with the bar_style
             if text.len() > bar_length {
                 let (first, second) = text.split_at(bar_length);

src/widgets/barchart/bar_group.rs

@@ -1,9 +1,5 @@
 use super::Bar;
-use crate::{
+use crate::prelude::*;
-    prelude::{Alignment, Buffer, Rect},
-    style::Style,
-    text::Line,
-};
 
 /// A group of bars to be shown by the Barchart.
 ///

src/widgets/block.rs

@@ -8,11 +8,7 @@
 
 use strum::{Display, EnumString};
 
-use crate::{
+use crate::{prelude::*, symbols::border, widgets::Borders};
-    prelude::*,
-    symbols::border,
-    widgets::{Borders, Widget},
-};
 
 mod padding;
 pub mod title;
@@ -520,7 +516,35 @@ impl<'a> Block<'a> {
         self.padding = padding;
         self
     }
+}
 
+impl Widget for Block<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Widget::render(&self, area, buf);
+    }
+}
+
+/// Implement [`Widget`] for [`Option<Block>`] to simplify the common case of having an optional
+/// [`Block`] field in a widget.
+impl Widget for &Option<Block<'_>> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        if let Some(block) = self {
+            block.render(area, buf);
+        }
+    }
+}
+
+impl Widget for &Block<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        if area.is_empty() {
+            return;
+        }
+        self.render_borders(area, buf);
+        self.render_titles(area, buf);
+    }
+}
+
+impl Block<'_> {
     fn render_borders(&self, area: Rect, buf: &mut Buffer) {
         buf.set_style(area, self.style);
         let symbols = self.border_set;
@@ -703,13 +727,20 @@ impl<'a> Block<'a> {
     }
 }
 
-impl<'a> Widget for Block<'a> {
+/// An extension trait for [`Block`] that provides some convenience methods.
-    fn render(self, area: Rect, buf: &mut Buffer) {
+///
-        if area.area() == 0 {
+/// This is implemented for [`Option<Block>`](Option) to simplify the common case of having a
-            return;
+/// widget with an optional block.
-        }
+pub trait BlockExt {
-        self.render_borders(area, buf);
+    /// Return the inner area of the block if it is `Some`. Otherwise, returns `area`.
-        self.render_titles(area, buf);
+    ///
+    /// This is a useful convenience method for widgets that have an `Option<Block>` field
+    fn inner_if_some(&self, area: Rect) -> Rect;
+}
+
+impl BlockExt for Option<Block<'_>> {
+    fn inner_if_some(&self, area: Rect) -> Rect {
+        self.as_ref().map_or(area, |block| block.inner(area))
     }
 }
 

src/widgets/calendar.rs

@@ -12,10 +12,7 @@ use std::collections::HashMap;
 
 use time::{Date, Duration, OffsetDateTime};
 
-use crate::{
+use crate::{prelude::*, widgets::Block};
-    prelude::*,
-    widgets::{Block, Widget},
-};
 
 /// Display a month calendar for the month containing `display_date`
 #[derive(Debug, Clone, Eq, PartialEq, Hash)]
@@ -117,36 +114,42 @@ impl<'a, DS: DateStyler> Monthly<'a, DS> {
     }
 }
 
-impl<'a, DS: DateStyler> Widget for Monthly<'a, DS> {
+impl<DS: DateStyler> Widget for Monthly<'_, DS> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        // Block is used for borders and such
+        Widget::render(&self, area, buf);
-        // Draw that first, and use the blank area inside the block for our own purposes
+    }
-        let mut area = match self.block.take() {
+}
-            None => area,
+
-            Some(b) => {
+impl<DS: DateStyler> Widget for &Monthly<'_, DS> {
-                let inner = b.inner(area);
+    fn render(self, area: Rect, buf: &mut Buffer) {
-                b.render(area, buf);
+        self.block.render(area, buf);
-                inner
+        let inner = self.block.inner_if_some(area);
-            }
+        self.render_monthly(inner, buf);
-        };
+    }
+}
+
+impl<DS: DateStyler> Monthly<'_, DS> {
+    fn render_monthly(&self, area: Rect, buf: &mut Buffer) {
+        let layout = Layout::vertical([
+            Constraint::Length(self.show_month.is_some().into()),
+            Constraint::Length(self.show_weekday.is_some().into()),
+            Constraint::Proportional(1),
+        ]);
+        let [month_header, days_header, days_area] = area.split(&layout);
 
         // Draw the month name and year
         if let Some(style) = self.show_month {
-            let line = Span::styled(
+            Line::styled(
                 format!("{} {}", self.display_date.month(), self.display_date.year()),
                 style,
-            );
+            )
-            // cal is 21 cells wide, so hard code the 11
+            .alignment(Alignment::Center)
-            let x_off = 11_u16.saturating_sub(line.width() as u16 / 2);
+            .render(month_header, buf);
-            buf.set_line(area.x + x_off, area.y, &line.into(), area.width);
-            area.y += 1
         }
 
         // Draw days of week
         if let Some(style) = self.show_weekday {
-            let days = String::from(" Su Mo Tu We Th Fr Sa");
+            Span::styled(" Su Mo Tu We Th Fr Sa", style).render(days_header, buf);
-            buf.set_string(area.x, area.y, days, style);
-            area.y += 1;
         }
 
         // Set the start of the calendar to the Sunday before the 1st (or the sunday of the first)
@@ -154,6 +157,7 @@ impl<'a, DS: DateStyler> Widget for Monthly<'a, DS> {
         let offset = Duration::days(first_of_month.weekday().number_days_from_sunday().into());
         let mut curr_day = first_of_month - offset;
 
+        let mut y = days_area.y;
         // go through all the weeks containing a day in the target month.
         while curr_day.month() as u8 != self.display_date.month().next() as u8 {
             let mut spans = Vec::with_capacity(14);
@@ -168,8 +172,8 @@ impl<'a, DS: DateStyler> Widget for Monthly<'a, DS> {
                 spans.push(self.format_date(curr_day));
                 curr_day += Duration::DAY;
             }
-            buf.set_line(area.x, area.y, &spans.into(), area.width);
+            buf.set_line(days_area.x, y, &spans.into(), area.width);
-            area.y += 1;
+            y += 1;
         }
     }
 }

src/widgets/canvas.rs

@@ -16,14 +16,7 @@ pub use self::{
     points::Points,
     rectangle::Rectangle,
 };
-use crate::{
+use crate::{prelude::*, symbols, text::Line as TextLine, widgets::Block};
-    buffer::Buffer,
-    layout::Rect,
-    style::{Color, Style},
-    symbols,
-    text::Line as TextLine,
-    widgets::{Block, Widget},
-};
 
 /// Interface for all shapes that may be drawn on a Canvas widget.
 pub trait Shape {
@@ -694,19 +687,25 @@ where
     }
 }
 
-impl<'a, F> Widget for Canvas<'a, F>
+impl<F> Widget for Canvas<'_, F>
 where
     F: Fn(&mut Context),
 {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        let canvas_area = match self.block.take() {
+        Widget::render(&self, area, buf);
-            Some(b) => {
+    }
-                let inner_area = b.inner(area);
+}
-                b.render(area, buf);
+
-                inner_area
+impl<F> Widget for &Canvas<'_, F>
-            }
+where
-            None => area,
+    F: Fn(&mut Context),
-        };
+{
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        self.block.render(area, buf);
+        let canvas_area = self.block.inner_if_some(area);
+        if canvas_area.is_empty() {
+            return;
+        }
 
         buf.set_style(canvas_area, Style::default().bg(self.background_color));
 

src/widgets/canvas/line.rs

@@ -108,11 +108,7 @@ fn draw_line_high(painter: &mut Painter, x1: usize, y1: usize, x2: usize, y2: us
 #[cfg(test)]
 mod tests {
     use super::Line;
-    use crate::{
+    use crate::{assert_buffer_eq, prelude::*, widgets::canvas::Canvas};
-        assert_buffer_eq,
-        prelude::*,
-        widgets::{canvas::Canvas, Widget},
-    };
 
     #[track_caller]
     fn test(line: Line, expected_lines: Vec<&str>) {

src/widgets/canvas/map.rs

@@ -46,11 +46,7 @@ mod tests {
     use strum::ParseError;
 
     use super::*;
-    use crate::{
+    use crate::{assert_buffer_eq, prelude::*, widgets::canvas::Canvas};
-        assert_buffer_eq,
-        prelude::*,
-        widgets::{canvas::Canvas, Widget},
-    };
 
     #[test]
     fn map_resolution_to_string() {

src/widgets/canvas/rectangle.rs

@@ -54,11 +54,7 @@ impl Shape for Rectangle {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::{
+    use crate::{assert_buffer_eq, prelude::*, widgets::canvas::Canvas};
-        assert_buffer_eq,
-        prelude::*,
-        widgets::{canvas::Canvas, Widget},
-    };
 
     #[test]
     fn draw_block_lines() {

src/widgets/chart.rs

@@ -4,14 +4,14 @@ use std::cmp::max;
 use strum::{Display, EnumString};
 use unicode_width::UnicodeWidthStr;
 
+use super::block::BlockExt;
 use crate::{
-    buffer::Buffer,
     layout::Flex,
     prelude::*,
     symbols,
     widgets::{
         canvas::{Canvas, Line as CanvasLine, Points},
-        Block, Borders, Widget,
+        Block, Borders,
     },
 };
 
@@ -809,7 +809,7 @@ impl<'a> Chart<'a> {
     }
 
     fn render_x_labels(
-        &mut self,
+        &self,
         buf: &mut Buffer,
         layout: &ChartLayout,
         chart_area: Rect,
@@ -892,7 +892,7 @@ impl<'a> Chart<'a> {
     }
 
     fn render_y_labels(
-        &mut self,
+        &self,
         buf: &mut Buffer,
         layout: &ChartLayout,
         chart_area: Rect,
@@ -916,26 +916,27 @@ impl<'a> Chart<'a> {
     }
 }
 
-impl<'a> Widget for Chart<'a> {
+impl Widget for Chart<'_> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        if area.area() == 0 {
+        Widget::render(&self, area, buf);
+    }
+}
+
+impl Widget for &Chart<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        buf.set_style(area, self.style);
+
+        self.block.render(area, buf);
+        let chart_area = self.block.inner_if_some(area);
+        if chart_area.is_empty() {
             return;
         }
-        buf.set_style(area, self.style);
+
         // Sample the style of the entire widget. This sample will be used to reset the style of
         // the cells that are part of the components put on top of the grah area (i.e legend and
         // axis names).
         let original_style = buf.get(area.left(), area.top()).style();
 
-        let chart_area = match self.block.take() {
-            Some(b) => {
-                let inner_area = b.inner(area);
-                b.render(area, buf);
-                inner_area
-            }
-            None => area,
-        };
-
         let layout = self.layout(chart_area);
         let graph_area = layout.graph_area;
         if graph_area.width < 1 || graph_area.height < 1 {
@@ -996,7 +997,7 @@ impl<'a> Widget for Chart<'a> {
         }
 
         if let Some((x, y)) = layout.title_x {
-            let title = self.x_axis.title.unwrap();
+            let title = self.x_axis.title.as_ref().unwrap();
             let width = graph_area
                 .right()
                 .saturating_sub(x)
@@ -1010,11 +1011,11 @@ impl<'a> Widget for Chart<'a> {
                 },
                 original_style,
             );
-            buf.set_line(x, y, &title, width);
+            buf.set_line(x, y, title, width);
         }
 
         if let Some((x, y)) = layout.title_y {
-            let title = self.y_axis.title.unwrap();
+            let title = self.y_axis.title.as_ref().unwrap();
             let width = graph_area
                 .right()
                 .saturating_sub(x)
@@ -1028,7 +1029,7 @@ impl<'a> Widget for Chart<'a> {
                 },
                 original_style,
             );
-            buf.set_line(x, y, &title, width);
+            buf.set_line(x, y, title, width);
         }
 
         if let Some(legend_area) = layout.legend_area {

src/widgets/clear.rs

@@ -1,4 +1,4 @@
-use crate::{buffer::Buffer, layout::Rect, widgets::Widget};
+use crate::prelude::*;
 
 /// A widget to clear/reset a certain area to allow overdrawing (e.g. for popups).
 ///
@@ -25,6 +25,12 @@ use crate::{buffer::Buffer, layout::Rect, widgets::Widget};
 pub struct Clear;
 
 impl Widget for Clear {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Widget::render(&self, area, buf);
+    }
+}
+
+impl Widget for &Clear {
     fn render(self, area: Rect, buf: &mut Buffer) {
         for x in area.left()..area.right() {
             for y in area.top()..area.bottom() {

src/widgets/gauge.rs

@@ -1,12 +1,6 @@
 #![deny(missing_docs)]
-use crate::{
+
-    buffer::Buffer,
+use crate::{prelude::*, widgets::Block};
-    layout::Rect,
-    style::{Color, Style, Styled},
-    symbols,
-    text::{Line, Span},
-    widgets::{Block, Widget},
-};
 
 /// A widget to display a progress bar.
 ///
@@ -161,28 +155,33 @@ impl<'a> Gauge<'a> {
     }
 }
 
-impl<'a> Widget for Gauge<'a> {
+impl Widget for Gauge<'_> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        Widget::render(&self, area, buf);
+    }
+}
+
+impl Widget for &Gauge<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
         buf.set_style(area, self.style);
-        let gauge_area = match self.block.take() {
+        self.block.render(area, buf);
-            Some(b) => {
+        let inner = self.block.inner_if_some(area);
-                let inner_area = b.inner(area);
+        self.render_gague(inner, buf);
-                b.render(area, buf);
+    }
-                inner_area
+}
-            }
+
-            None => area,
+impl Gauge<'_> {
-        };
+    fn render_gague(&self, gauge_area: Rect, buf: &mut Buffer) {
-        buf.set_style(gauge_area, self.gauge_style);
+        if gauge_area.is_empty() {
-        if gauge_area.height < 1 {
             return;
         }
 
+        buf.set_style(gauge_area, self.gauge_style);
+
         // compute label value and its position
         // label is put at the center of the gauge_area
-        let label = {
+        let default_label = Span::raw(format!("{}%", f64::round(self.ratio * 100.0)));
-            let pct = f64::round(self.ratio * 100.0);
+        let label = self.label.as_ref().unwrap_or(&default_label);
-            self.label.unwrap_or_else(|| Span::from(format!("{pct}%")))
-        };
         let clamped_label_width = gauge_area.width.min(label.width() as u16);
         let label_col = gauge_area.left() + (gauge_area.width - clamped_label_width) / 2;
         let label_row = gauge_area.top() + gauge_area.height / 2;
@@ -217,7 +216,7 @@ impl<'a> Widget for Gauge<'a> {
             }
         }
         // render the label
-        buf.set_span(label_col, label_row, &label, clamped_label_width);
+        buf.set_span(label_col, label_row, label, clamped_label_width);
     }
 }
 
@@ -351,32 +350,25 @@ impl<'a> LineGauge<'a> {
     }
 }
 
-impl<'a> Widget for LineGauge<'a> {
+impl Widget for LineGauge<'_> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        buf.set_style(area, self.style);
+        Widget::render(&self, area, buf);
-        let gauge_area = match self.block.take() {
+    }
-            Some(b) => {
+}
-                let inner_area = b.inner(area);
-                b.render(area, buf);
-                inner_area
-            }
-            None => area,
-        };
 
-        if gauge_area.height < 1 {
+impl Widget for &LineGauge<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        buf.set_style(area, self.style);
+        self.block.render(area, buf);
+        let gauge_area = self.block.inner_if_some(area);
+        if gauge_area.is_empty() {
             return;
         }
 
         let ratio = self.ratio;
-        let label = self
+        let default_label = Line::from(format!("{:.0}%", ratio * 100.0));
-            .label
+        let label = self.label.as_ref().unwrap_or(&default_label);
-            .unwrap_or_else(move || Line::from(format!("{:.0}%", ratio * 100.0)));
+        let (col, row) = buf.set_line(gauge_area.left(), gauge_area.top(), label, gauge_area.width);
-        let (col, row) = buf.set_line(
-            gauge_area.left(),
-            gauge_area.top(),
-            &label,
-            gauge_area.width,
-        );
         let start = col + 1;
         if start >= gauge_area.right() {
             return;

src/widgets/list.rs

@@ -4,7 +4,7 @@ use unicode_width::UnicodeWidthStr;
 
 use crate::{
     prelude::*,
-    widgets::{Block, HighlightSpacing, StatefulWidget, Widget},
+    widgets::{Block, HighlightSpacing},
 };
 
 /// State of the [`List`] widget
@@ -812,21 +812,37 @@ impl<'a> List<'a> {
     }
 }
 
-impl<'a> StatefulWidget for List<'a> {
+impl Widget for List<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        let mut state = ListState::default();
+        StatefulWidget::render(&self, area, buf, &mut state);
+    }
+}
+
+impl Widget for &List<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        let mut state = ListState::default();
+        StatefulWidget::render(self, area, buf, &mut state);
+    }
+}
+
+impl StatefulWidget for List<'_> {
     type State = ListState;
 
-    fn render(mut self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
+    fn render(self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
-        buf.set_style(area, self.style);
+        StatefulWidget::render(&self, area, buf, state);
-        let list_area = match self.block.take() {
+    }
-            Some(b) => {
+}
-                let inner_area = b.inner(area);
-                b.render(area, buf);
-                inner_area
-            }
-            None => area,
-        };
 
-        if self.items.is_empty() || list_area.is_empty() {
+impl StatefulWidget for &List<'_> {
+    type State = ListState;
+
+    fn render(self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
+        buf.set_style(area, self.style);
+        self.block.render(area, buf);
+        let list_area = self.block.inner_if_some(area);
+
+        if list_area.is_empty() || self.items.is_empty() {
             return;
         }
 
@@ -846,7 +862,7 @@ impl<'a> StatefulWidget for List<'a> {
         let selection_spacing = self.highlight_spacing.should_add(state.selected.is_some());
         for (i, item) in self
             .items
-            .iter_mut()
+            .iter()
             .enumerate()
             .skip(state.offset)
             .take(last_visible_index - first_visible_index)
@@ -911,13 +927,6 @@ impl<'a> StatefulWidget for List<'a> {
     }
 }
 
-impl<'a> Widget for List<'a> {
-    fn render(self, area: Rect, buf: &mut Buffer) {
-        let mut state = ListState::default();
-        StatefulWidget::render(self, area, buf, &mut state);
-    }
-}
-
 impl<'a> Styled for List<'a> {
     type Item = List<'a>;
 
@@ -961,7 +970,7 @@ mod tests {
         prelude::Alignment,
         style::{Color, Modifier, Stylize},
         text::{Line, Span},
-        widgets::{Borders, StatefulWidget, Widget},
+        widgets::Borders,
     };
 
     #[test]

src/widgets/paragraph.rs

@@ -1,12 +1,10 @@
 use unicode_width::UnicodeWidthStr;
 
+use super::block::BlockExt;
 use crate::{
     prelude::*,
     text::StyledGrapheme,
-    widgets::{
+    widgets::{reflow::*, Block},
-        reflow::{LineComposer, LineTruncator, WordWrapper, WrappedLine},
-        Block, Widget,
-    },
 };
 
 fn get_line_offset(line_width: u16, text_area_width: u16, alignment: Alignment) -> u16 {
@@ -325,19 +323,24 @@ impl<'a> Paragraph<'a> {
     }
 }
 
-impl<'a> Widget for Paragraph<'a> {
+impl Widget for Paragraph<'_> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        buf.set_style(area, self.style);
+        Widget::render(&self, area, buf);
-        let text_area = match self.block.take() {
+    }
-            Some(b) => {
+}
-                let inner_area = b.inner(area);
-                b.render(area, buf);
-                inner_area
-            }
-            None => area,
-        };
 
-        if text_area.height < 1 {
+impl Widget for &Paragraph<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        buf.set_style(area, self.style);
+        self.block.render(area, buf);
+        let inner = self.block.inner_if_some(area);
+        self.render_paragraph(inner, buf);
+    }
+}
+
+impl Paragraph<'_> {
+    fn render_paragraph(&self, text_area: Rect, buf: &mut Buffer) {
+        if text_area.is_empty() {
             return;
         }
 

src/widgets/sparkline.rs

@@ -3,10 +3,7 @@ use std::cmp::min;
 
 use strum::{Display, EnumString};
 
-use crate::{
+use crate::{prelude::*, widgets::Block};
-    prelude::*,
-    widgets::{Block, Widget},
-};
 
 /// Widget to render a sparkline over one or more lines.
 ///
@@ -156,18 +153,23 @@ impl<'a> Styled for Sparkline<'a> {
     }
 }
 
-impl<'a> Widget for Sparkline<'a> {
+impl Widget for Sparkline<'_> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        let spark_area = match self.block.take() {
+        Widget::render(&self, area, buf);
-            Some(b) => {
+    }
-                let inner_area = b.inner(area);
+}
-                b.render(area, buf);
-                inner_area
-            }
-            None => area,
-        };
 
-        if spark_area.height < 1 {
+impl Widget for &Sparkline<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        self.block.render(area, buf);
+        let inner = self.block.inner_if_some(area);
+        self.render_sparkline(inner, buf);
+    }
+}
+
+impl Sparkline<'_> {
+    fn render_sparkline(&self, spark_area: Rect, buf: &mut Buffer) {
+        if spark_area.is_empty() {
             return;
         }
 

src/widgets/table/cell.rs

@@ -1,4 +1,4 @@
-use crate::{prelude::*, widgets::Widget};
+use crate::prelude::*;
 
 /// A [`Cell`] contains the [`Text`] to be displayed in a [`Row`] of a [`Table`].
 ///

src/widgets/table/table.rs

@@ -4,7 +4,7 @@ use super::*;
 use crate::{
     layout::{Flex, SegmentSize},
     prelude::*,
-    widgets::{Block, StatefulWidget, Widget},
+    widgets::Block,
 };
 
 /// A widget to display data in formatted columns.
@@ -610,16 +610,32 @@ impl Widget for Table<'_> {
     }
 }
 
+impl Widget for &Table<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        let mut state = TableState::default();
+        StatefulWidget::render(self, area, buf, &mut state);
+    }
+}
+
 impl StatefulWidget for Table<'_> {
     type State = TableState;
 
-    fn render(mut self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
+    fn render(self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
-        buf.set_style(area, self.style);
+        StatefulWidget::render(&self, area, buf, state);
+    }
+}
 
-        let table_area = self.render_block(area, buf);
+impl StatefulWidget for &Table<'_> {
+    type State = TableState;
+
+    fn render(self, area: Rect, buf: &mut Buffer, state: &mut Self::State) {
+        buf.set_style(area, self.style);
+        self.block.render(area, buf);
+        let table_area = self.block.inner_if_some(area);
         if table_area.is_empty() {
             return;
         }
+
         let selection_width = self.selection_width(state);
         let columns_widths = self.get_columns_widths(table_area.width, selection_width);
         let (header_area, rows_area, footer_area) = self.layout(table_area);
@@ -663,16 +679,6 @@ impl Table<'_> {
         (header_area, rows_area, footer_area)
     }
 
-    fn render_block(&mut self, area: Rect, buf: &mut Buffer) -> Rect {
-        if let Some(block) = self.block.take() {
-            let inner_area = block.inner(area);
-            block.render(area, buf);
-            inner_area
-        } else {
-            area
-        }
-    }
-
     fn render_header(&self, area: Rect, buf: &mut Buffer, column_widths: &[(u16, u16)]) {
         if let Some(ref header) = self.header {
             buf.set_style(area, header.style);

src/widgets/tabs.rs

@@ -1,8 +1,5 @@
 #![deny(missing_docs)]
-use crate::{
+use crate::{prelude::*, widgets::Block};
-    prelude::*,
-    widgets::{Block, Widget},
-};
 
 const DEFAULT_HIGHLIGHT_STYLE: Style = Style::new().add_modifier(Modifier::REVERSED);
 
@@ -249,25 +246,30 @@ impl<'a> Styled for Tabs<'a> {
     }
 }
 
-impl<'a> Widget for Tabs<'a> {
+impl Widget for Tabs<'_> {
-    fn render(mut self, area: Rect, buf: &mut Buffer) {
+    fn render(self, area: Rect, buf: &mut Buffer) {
-        buf.set_style(area, self.style);
+        Widget::render(&self, area, buf);
-        let tabs_area = match self.block.take() {
+    }
-            Some(b) => {
+}
-                let inner_area = b.inner(area);
-                b.render(area, buf);
-                inner_area
-            }
-            None => area,
-        };
 
-        if tabs_area.height < 1 {
+impl Widget for &Tabs<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        buf.set_style(area, self.style);
+        self.block.render(area, buf);
+        let inner = self.block.inner_if_some(area);
+        self.render_tabs(inner, buf);
+    }
+}
+
+impl Tabs<'_> {
+    fn render_tabs(&self, tabs_area: Rect, buf: &mut Buffer) {
+        if tabs_area.is_empty() {
             return;
         }
 
         let mut x = tabs_area.left();
         let titles_length = self.titles.len();
-        for (i, title) in self.titles.into_iter().enumerate() {
+        for (i, title) in self.titles.iter().enumerate() {
             let last_title = titles_length - 1 == i;
             let remaining_width = tabs_area.right().saturating_sub(x);
 
@@ -284,7 +286,7 @@ impl<'a> Widget for Tabs<'a> {
             }
 
             // Title
-            let pos = buf.set_line(x, tabs_area.top(), &title, remaining_width);
+            let pos = buf.set_line(x, tabs_area.top(), title, remaining_width);
             if i == self.selected {
                 buf.set_style(
                     Rect {

tests/widgets_calendar.rs

@@ -11,6 +11,7 @@ use ratatui::{
 };
 use time::{Date, Month};
 
+#[track_caller]
 fn test_render<W: Widget>(widget: W, expected: Buffer, size: (u16, u16)) {
     let backend = TestBackend::new(size.0, size.1);
     let mut terminal = Terminal::new(backend).unwrap();
@@ -63,7 +64,7 @@ fn show_month_header() {
     )
     .show_month_header(Style::default());
     let expected = Buffer::with_lines(vec![
-        "     January 2023    ",
+        "    January 2023     ",
         "  1  2  3  4  5  6  7",
         "  8  9 10 11 12 13 14",
         " 15 16 17 18 19 20 21",
@@ -101,7 +102,7 @@ fn show_combo() {
     .show_month_header(Style::default())
     .show_surrounding(Style::default());
     let expected = Buffer::with_lines(vec![
-        "     January 2023    ",
+        "    January 2023     ",
         " Su Mo Tu We Th Fr Sa",
         "  1  2  3  4  5  6  7",
         "  8  9 10 11 12 13 14",

tests/widgets_chart.rs

@@ -8,6 +8,7 @@ use ratatui::{
     widgets::{Axis, Block, Borders, Chart, Dataset, GraphType::Line},
     Terminal,
 };
+use rstest::rstest;
 
 fn create_labels<'a>(labels: &'a [&'a str]) -> Vec<Span<'a>> {
     labels.iter().map(|l| Span::from(*l)).collect()
@@ -30,38 +31,36 @@ where
     terminal.backend().assert_buffer(&expected);
 }
 
-#[test]
+#[rstest]
-fn widgets_chart_can_render_on_small_areas() {
+#[case(0, 0)]
-    let test_case = |width, height| {
+#[case(0, 1)]
-        let backend = TestBackend::new(width, height);
+#[case(1, 0)]
-        let mut terminal = Terminal::new(backend).unwrap();
+#[case(1, 1)]
-        terminal
+#[case(2, 2)]
-            .draw(|f| {
+fn widgets_chart_can_render_on_small_areas(#[case] width: u16, #[case] height: u16) {
-                let datasets = vec![Dataset::default()
+    let backend = TestBackend::new(width, height);
-                    .marker(symbols::Marker::Braille)
+    let mut terminal = Terminal::new(backend).unwrap();
-                    .style(Style::default().fg(Color::Magenta))
+    terminal
-                    .data(&[(0.0, 0.0)])];
+        .draw(|f| {
-                let chart = Chart::new(datasets)
+            let datasets = vec![Dataset::default()
-                    .block(Block::default().title("Plot").borders(Borders::ALL))
+                .marker(symbols::Marker::Braille)
-                    .x_axis(
+                .style(Style::default().fg(Color::Magenta))
-                        Axis::default()
+                .data(&[(0.0, 0.0)])];
-                            .bounds([0.0, 0.0])
+            let chart = Chart::new(datasets)
-                            .labels(create_labels(&["0.0", "1.0"])),
+                .block(Block::default().title("Plot").borders(Borders::ALL))
-                    )
+                .x_axis(
-                    .y_axis(
+                    Axis::default()
-                        Axis::default()
+                        .bounds([0.0, 0.0])
-                            .bounds([0.0, 0.0])
+                        .labels(create_labels(&["0.0", "1.0"])),
-                            .labels(create_labels(&["0.0", "1.0"])),
+                )
-                    );
+                .y_axis(
-                f.render_widget(chart, f.size());
+                    Axis::default()
-            })
+                        .bounds([0.0, 0.0])
-            .unwrap();
+                        .labels(create_labels(&["0.0", "1.0"])),
-    };
+                );
-    test_case(0, 0);
+            f.render_widget(chart, f.size());
-    test_case(0, 1);
+        })
-    test_case(1, 0);
+        .unwrap();
-    test_case(1, 1);
-    test_case(2, 2);
 }
 
 #[test]