feat(Paragraph): add alignment convenience functions (#866)

Added convenience functions left_aligned(), centered() and
right_aligned() plus unit tests. Updated example code.

Signed-off-by: Eelco Empting <me@eelco.de>

examples/colors_rgb.rs

@@ -143,8 +143,7 @@ impl Default for Fps {
 
 impl<'a> AppWidget<'a> {
     fn new(app: &'a App) -> Self {
-        let title =
+        let title = Paragraph::new("colors_rgb example. Press q to quit").centered();
-            Paragraph::new("colors_rgb example. Press q to quit").alignment(Alignment::Center);
         Self {
             title,
             fps_widget: FpsWidget { fps: &app.fps },

examples/constraints.rs

@@ -183,7 +183,7 @@ impl App {
             width = width - width_label.len() / 2
         );
         Paragraph::new(width_bar.dark_gray())
-            .alignment(Alignment::Center)
+            .centered()
             .block(Block::default().padding(Padding {
                 left: 0,
                 right: 0,
@@ -418,9 +418,7 @@ impl Example {
             .border_set(symbols::border::QUADRANT_OUTSIDE)
             .border_style(Style::reset().fg(color).reversed())
             .style(Style::default().fg(fg).bg(color));
-        Paragraph::new(text)
+        Paragraph::new(text).centered().block(block)
-            .alignment(Alignment::Center)
-            .block(block)
     }
 }
 

examples/demo2/root.rs

@@ -71,7 +71,7 @@ impl Root<'_> {
             })
             .collect_vec();
         Paragraph::new(Line::from(spans))
-            .alignment(Alignment::Center)
+            .centered()
             .fg(Color::Indexed(236))
             .bg(Color::Indexed(232))
             .render(area, buf);

examples/flex.rs

@@ -251,7 +251,7 @@ impl App {
         };
         let bar_width = width - 2; // we want to `<` and `>` at the ends
         let width_bar = format!("<{label:-^bar_width$}>");
-        Paragraph::new(width_bar.dark_gray()).alignment(Alignment::Center)
+        Paragraph::new(width_bar.dark_gray()).centered()
     }
 
     /// Render the demo content
@@ -416,9 +416,7 @@ impl Example {
             .border_set(symbols::border::QUADRANT_OUTSIDE)
             .border_style(Style::reset().fg(main_color).reversed())
             .style(Style::default().fg(fg_color).bg(main_color));
-        Paragraph::new(text)
+        Paragraph::new(text).centered().block(block)
-            .alignment(Alignment::Center)
-            .block(block)
     }
 }
 

examples/list.rs

@@ -173,7 +173,7 @@ impl App<'_> {
     fn render_title(&self, area: Rect, buf: &mut Buffer) {
         Paragraph::new("Ratatui List Example")
             .bold()
-            .alignment(Alignment::Center)
+            .centered()
             .render(area, buf);
     }
 
@@ -268,7 +268,7 @@ impl App<'_> {
         Paragraph::new(
             "\nUse ↓↑ to move, ← to unselect, → to change status, g/G to go top/bottom.",
         )
-        .alignment(Alignment::Center)
+        .centered()
         .render(area, buf);
     }
 }

examples/panic.rs

@@ -128,7 +128,7 @@ fn ui(f: &mut Frame, app: &App) {
         .title("Panic Handler Demo")
         .borders(Borders::ALL);
 
-    let p = Paragraph::new(text).block(b).alignment(Alignment::Center);
+    let p = Paragraph::new(text).block(b).centered();
 
     f.render_widget(p, f.size());
 }

examples/paragraph.rs

@@ -132,14 +132,14 @@ fn ui(f: &mut Frame, app: &App) {
     let paragraph = Paragraph::new(text.clone())
         .style(Style::default().fg(Color::Gray))
         .block(create_block("Right alignment, with wrap"))
-        .alignment(Alignment::Right)
+        .right_aligned()
         .wrap(Wrap { trim: true });
     f.render_widget(paragraph, layout[2]);
 
     let paragraph = Paragraph::new(text)
         .style(Style::default().fg(Color::Gray))
         .block(create_block("Center alignment, with wrap, with scroll"))
-        .alignment(Alignment::Center)
+        .centered()
         .wrap(Wrap { trim: true })
         .scroll((app.scroll, 0));
     f.render_widget(paragraph, layout[3]);

examples/popup.rs

@@ -73,7 +73,7 @@ fn ui(f: &mut Frame, app: &App) {
         "Press p to show the popup"
     };
     let paragraph = Paragraph::new(text.slow_blink())
-        .alignment(Alignment::Center)
+        .centered()
         .wrap(Wrap { trim: true });
     f.render_widget(paragraph, instructions);
 

examples/table.rs

@@ -313,7 +313,7 @@ fn render_scrollbar(f: &mut Frame, app: &mut App, area: Rect) {
 fn render_footer(f: &mut Frame, app: &mut App, area: Rect) {
     let info_footer = Paragraph::new(Line::from(INFO_TEXT))
         .style(Style::new().fg(app.colors.row_fg).bg(app.colors.buffer_bg))
-        .alignment(Alignment::Center)
+        .centered()
         .block(
             Block::default()
                 .borders(Borders::ALL)

src/widgets/paragraph.rs

@@ -194,7 +194,7 @@ impl<'a> Paragraph<'a> {
     /// Set the text alignment for the given paragraph
     ///
     /// The alignment is a variant of the [`Alignment`] enum which can be one of Left, Right, or
-    /// Center.
+    /// Center. If no alignment is specified, the text in a paragraph will be left-aligned.
     ///
     /// # Example
     ///
@@ -208,6 +208,51 @@ impl<'a> Paragraph<'a> {
         self
     }
 
+    /// Left-aligns the text in the given paragraph.
+    ///
+    /// Convenience shortcut for `Paragraph::alignment(Alignment::Left)`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use ratatui::{prelude::*, widgets::*};
+    /// let paragraph = Paragraph::new("Hello World").left_aligned();
+    /// ```
+    #[must_use = "method moves the value of self and returns the modified value"]
+    pub fn left_aligned(self) -> Self {
+        self.alignment(Alignment::Left)
+    }
+
+    /// Center-aligns the text in the given paragraph.
+    ///
+    /// Convenience shortcut for `Paragraph::alignment(Alignment::Center)`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use ratatui::{prelude::*, widgets::*};
+    /// let paragraph = Paragraph::new("Hello World").centered();
+    /// ```
+    #[must_use = "method moves the value of self and returns the modified value"]
+    pub fn centered(self) -> Self {
+        self.alignment(Alignment::Center)
+    }
+
+    /// Right-aligns the text in the given paragraph.
+    ///
+    /// Convenience shortcut for `Paragraph::alignment(Alignment::Right)`.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// # use ratatui::{prelude::*, widgets::*};
+    /// let paragraph = Paragraph::new("Hello World").right_aligned();
+    /// ```
+    #[must_use = "method moves the value of self and returns the modified value"]
+    pub fn right_aligned(self) -> Self {
+        self.alignment(Alignment::Right)
+    }
+
     /// Calculates the number of lines needed to fully render.
     ///
     /// Given a max line width, this method calculates the number of lines that a paragraph will
@@ -922,4 +967,22 @@ mod test {
         let paragraph = paragraph.wrap(Wrap { trim: true });
         assert_eq!(paragraph.line_width(), 1200);
     }
+
+    #[test]
+    fn left_aligned() {
+        let p = Paragraph::new("Hello, world!").left_aligned();
+        assert_eq!(p.alignment, Alignment::Left);
+    }
+
+    #[test]
+    fn centered() {
+        let p = Paragraph::new("Hello, world!").centered();
+        assert_eq!(p.alignment, Alignment::Center);
+    }
+
+    #[test]
+    fn right_aligned() {
+        let p = Paragraph::new("Hello, world!").right_aligned();
+        assert_eq!(p.alignment, Alignment::Right);
+    }
 }