perf(rect)!: Rect::inner takes Margin directly instead of reference

Also, adds `Rect::ZERO` and `Rect::inner` is now `const`.

BREAKING CHANGE: `Margin` needs to be passed without reference now.

BREAKING-CHANGES.md

@@ -47,6 +47,22 @@ This is a quick summary of the sections below:
   - MSRV is now 1.63.0
   - `List` no longer ignores empty strings
 
+## Unreleased
+
+### `Rect::inner` takes `Margin` directly instead of reference ([#1008])
+
+[#1008]: https://github.com/ratatui-org/ratatui/pull/1008
+
+`Margin` needs to be passed without reference now.
+
+```diff
+-let area = area.inner(&Margin {
++let area = area.inner(Margin {
+     vertical: 0,
+     horizontal: 2,
+ });
+```
+
 ## [v0.26.0](https://github.com/ratatui-org/ratatui/releases/tag/v0.26.0)
 
 ### `Flex::Start` is the new default flex mode for `Layout` ([#881])

examples/demo2/tabs/about.rs

@@ -64,20 +64,16 @@ impl Widget for AboutTab {
 }
 
 fn render_crate_description(area: Rect, buf: &mut Buffer) {
-    let area = area.inner(
-        &(Margin {
-            vertical: 4,
-            horizontal: 2,
-        }),
-    );
+    let area = area.inner(Margin {
+        vertical: 4,
+        horizontal: 2,
+    });
     Clear.render(area, buf); // clear out the color swatches
     Block::new().style(THEME.content).render(area, buf);
-    let area = area.inner(
-        &(Margin {
-            vertical: 1,
-            horizontal: 2,
-        }),
-    );
+    let area = area.inner(Margin {
+        vertical: 1,
+        horizontal: 2,
+    });
     let text = "- cooking up terminal user interfaces -
 
     Ratatui is a Rust crate that provides widgets (e.g. Paragraph, Table) and draws them to the \
@@ -108,7 +104,7 @@ pub fn render_logo(selected_row: usize, area: Rect, buf: &mut Buffer) {
     } else {
         THEME.logo.rat_eye_alt
     };
-    let area = area.inner(&Margin {
+    let area = area.inner(Margin {
         vertical: 0,
         horizontal: 2,
     });

examples/demo2/tabs/email.rs

@@ -59,7 +59,7 @@ impl EmailTab {
 impl Widget for EmailTab {
     fn render(self, area: Rect, buf: &mut Buffer) {
         RgbSwatch.render(area, buf);
-        let area = area.inner(&Margin {
+        let area = area.inner(Margin {
             vertical: 1,
             horizontal: 2,
         });

examples/demo2/tabs/recipe.rs

@@ -105,7 +105,7 @@ impl RecipeTab {
 impl Widget for RecipeTab {
     fn render(self, area: Rect, buf: &mut Buffer) {
         RgbSwatch.render(area, buf);
-        let area = area.inner(&Margin {
+        let area = area.inner(Margin {
             vertical: 1,
             horizontal: 2,
         });
@@ -124,7 +124,7 @@ impl Widget for RecipeTab {
         };
         render_scrollbar(self.row_index, scrollbar_area, buf);
 
-        let area = area.inner(&Margin {
+        let area = area.inner(Margin {
             horizontal: 2,
             vertical: 1,
         });

examples/demo2/tabs/traceroute.rs

@@ -26,7 +26,7 @@ impl TracerouteTab {
 impl Widget for TracerouteTab {
     fn render(self, area: Rect, buf: &mut Buffer) {
         RgbSwatch.render(area, buf);
-        let area = area.inner(&Margin {
+        let area = area.inner(Margin {
             vertical: 1,
             horizontal: 2,
         });

examples/demo2/tabs/weather.rs

@@ -28,14 +28,14 @@ impl WeatherTab {
 impl Widget for WeatherTab {
     fn render(self, area: Rect, buf: &mut Buffer) {
         RgbSwatch.render(area, buf);
-        let area = area.inner(&Margin {
+        let area = area.inner(Margin {
             vertical: 1,
             horizontal: 2,
         });
         Clear.render(area, buf);
         Block::new().style(THEME.content).render(area, buf);
 
-        let area = area.inner(&Margin {
+        let area = area.inner(Margin {
             horizontal: 2,
             vertical: 1,
         });

examples/scrollbar.rs

@@ -186,7 +186,7 @@ fn ui(f: &mut Frame, app: &mut App) {
             .begin_symbol(None)
             .track_symbol(None)
             .end_symbol(None),
-        chunks[2].inner(&Margin {
+        chunks[2].inner(Margin {
             vertical: 1,
             horizontal: 0,
         }),
@@ -204,7 +204,7 @@ fn ui(f: &mut Frame, app: &mut App) {
         Scrollbar::new(ScrollbarOrientation::HorizontalBottom)
             .thumb_symbol("🬋")
             .end_symbol(None),
-        chunks[3].inner(&Margin {
+        chunks[3].inner(Margin {
             vertical: 0,
             horizontal: 1,
         }),
@@ -222,7 +222,7 @@ fn ui(f: &mut Frame, app: &mut App) {
         Scrollbar::new(ScrollbarOrientation::HorizontalBottom)
             .thumb_symbol("░")
             .track_symbol(Some("─")),
-        chunks[4].inner(&Margin {
+        chunks[4].inner(Margin {
             vertical: 0,
             horizontal: 1,
         }),

examples/table.rs

@@ -318,7 +318,7 @@ fn render_scrollbar(f: &mut Frame, app: &mut App, area: Rect) {
             .orientation(ScrollbarOrientation::VerticalRight)
             .begin_symbol(None)
             .end_symbol(None),
-        area.inner(&Margin {
+        area.inner(Margin {
             vertical: 1,
             horizontal: 1,
         }),

src/layout/layout.rs

@@ -608,7 +608,7 @@ impl Layout {
         // This is equivalent to storing the solver in `Layout` and calling `solver.reset()` here.
         let mut solver = Solver::new();
 
-        let inner_area = area.inner(&self.margin);
+        let inner_area = area.inner(self.margin);
         let (area_start, area_end) = match self.direction {
             Direction::Horizontal => (
                 f64::from(inner_area.x) * FLOAT_PRECISION_MULTIPLIER,

src/layout/rect.rs

@@ -47,6 +47,14 @@ impl fmt::Display for Rect {
 }
 
 impl Rect {
+    /// A zero sized Rect at position 0,0
+    pub const ZERO: Self = Self {
+        x: 0,
+        y: 0,
+        width: 0,
+        height: 0,
+    };
+
     /// Creates a new `Rect`, with width and height limited to keep the area under max `u16`. If
     /// clipped, aspect ratio will be preserved.
     pub fn new(x: u16, y: u16, width: u16, height: u16) -> Self {
@@ -112,12 +120,12 @@ impl Rect {
     ///
     /// If the margin is larger than the `Rect`, the returned `Rect` will have no area.
     #[must_use = "method returns the modified value"]
-    pub fn inner(self, margin: &Margin) -> Self {
+    pub const fn inner(self, margin: Margin) -> Self {
         let doubled_margin_horizontal = margin.horizontal.saturating_mul(2);
         let doubled_margin_vertical = margin.vertical.saturating_mul(2);
 
         if self.width < doubled_margin_horizontal || self.height < doubled_margin_vertical {
-            Self::default()
+            Self::ZERO
         } else {
             Self {
                 x: self.x.saturating_add(margin.horizontal),
@@ -385,7 +393,7 @@ mod tests {
     #[test]
     fn inner() {
         assert_eq!(
-            Rect::new(1, 2, 3, 4).inner(&Margin::new(1, 2)),
+            Rect::new(1, 2, 3, 4).inner(Margin::new(1, 2)),
             Rect::new(2, 4, 1, 0)
         );
     }

src/widgets/canvas/rectangle.rs

@@ -98,7 +98,7 @@ mod tests {
             "██████████",
         ]);
         expected.set_style(buffer.area, Style::new().red());
-        expected.set_style(buffer.area.inner(&Margin::new(1, 1)), Style::reset());
+        expected.set_style(buffer.area.inner(Margin::new(1, 1)), Style::reset());
         assert_buffer_eq!(buffer, expected);
     }
 
@@ -132,8 +132,8 @@ mod tests {
             "█▄▄▄▄▄▄▄▄█",
         ]);
         expected.set_style(buffer.area, Style::new().red().on_red());
-        expected.set_style(buffer.area.inner(&Margin::new(1, 0)), Style::reset().red());
-        expected.set_style(buffer.area.inner(&Margin::new(1, 1)), Style::reset());
+        expected.set_style(buffer.area.inner(Margin::new(1, 0)), Style::reset().red());
+        expected.set_style(buffer.area.inner(Margin::new(1, 1)), Style::reset());
         assert_buffer_eq!(buffer, expected);
     }
 
@@ -176,8 +176,8 @@ mod tests {
             "⣇⣀⣀⣀⣀⣀⣀⣀⣀⣸",
         ]);
         expected.set_style(buffer.area, Style::new().red());
-        expected.set_style(buffer.area.inner(&Margin::new(1, 1)), Style::new().green());
-        expected.set_style(buffer.area.inner(&Margin::new(2, 2)), Style::reset());
+        expected.set_style(buffer.area.inner(Margin::new(1, 1)), Style::new().green());
+        expected.set_style(buffer.area.inner(Margin::new(2, 2)), Style::reset());
         assert_buffer_eq!(buffer, expected);
     }
 }

src/widgets/scrollbar.rs

@@ -58,7 +58,7 @@ use crate::{prelude::*, symbols::scrollbar::*};
 /// // and the scrollbar, those are separate widgets
 /// frame.render_stateful_widget(
 ///     scrollbar,
-///     area.inner(&Margin {
+///     area.inner(Margin {
 ///         // using an inner vertical margin of 1 unit makes the scrollbar inside the block
 ///         vertical: 1,
 ///         horizontal: 0,