feat(chart): allow custom alignment of Y-Axis labels

src/widgets/chart.rs

@@ -78,8 +78,8 @@ impl<'a> Axis<'a> {
 
     /// Defines the alignment of the labels of the axis.
     /// The alignment behaves differently based on the axis:
-    /// - Y-Axis: The labels are aligned in the area on the left of the axis
-    /// - X-Axis: The first label is aligned relative to the Y-axis
+    /// - Y-Axis: The labels are aligned within the area on the left of the axis
+    /// - X-Axis: The first X-axis label is aligned relative to the Y-axis
     pub fn label_alignment(mut self, alignment: Alignment) -> Axis<'a> {
         self.label_alignment = alignment;
         self
@@ -310,7 +310,7 @@ impl<'a> Chart<'a> {
         }
 
         layout.label_y = self.y_axis.labels.as_ref().and(Some(x));
-        x += self.max_width_of_labels_left_of_y_axis(area);
+        x += self.max_width_of_labels_left_of_y_axis(area, self.y_axis.labels.is_some());
 
         if self.x_axis.labels.is_some() && y > area.top() {
             layout.axis_x = Some(y);
@@ -366,7 +366,7 @@ impl<'a> Chart<'a> {
         layout
     }
 
-    fn max_width_of_labels_left_of_y_axis(&self, area: Rect) -> u16 {
+    fn max_width_of_labels_left_of_y_axis(&self, area: Rect, has_y_axis: bool) -> u16 {
         let mut max_width = self
             .y_axis
             .labels
@@ -377,7 +377,10 @@ impl<'a> Chart<'a> {
             if !x_labels.is_empty() {
                 let mut first_label_width = x_labels[0].content.width() as u16;
                 first_label_width = match self.x_axis.label_alignment {
-                    Alignment::Left => first_label_width,
+                    Alignment::Left => {
+                        let y_axis_offset = if has_y_axis { 1 } else { 0 };
+                        first_label_width.saturating_sub(y_axis_offset)
+                    }
                     Alignment::Center => first_label_width / 2,
                     Alignment::Right => 0,
                 };
@@ -482,11 +485,16 @@ impl<'a> Chart<'a> {
         };
         let labels = self.y_axis.labels.as_ref().unwrap();
         let labels_len = labels.len() as u16;
-        let label_width = graph_area.left().saturating_sub(chart_area.left());
         for (i, label) in labels.iter().enumerate() {
             let dy = i as u16 * (graph_area.height - 1) / (labels_len - 1);
             if dy < graph_area.bottom() {
-                buf.set_span(x, graph_area.bottom() - 1 - dy, label, label_width as u16);
+                let label_area = Rect::new(
+                    x,
+                    graph_area.bottom() - 1 - dy,
+                    graph_area.left() - chart_area.left() - 1,
+                    1,
+                );
+                Self::render_label(buf, label, label_area, self.y_axis.label_alignment);
             }
         }
     }

tests/widgets_chart.rs

@@ -169,16 +169,13 @@ fn widgets_chart_handles_x_axis_labels_alignments() {
         let mut terminal = Terminal::new(backend).unwrap();
         terminal
             .draw(|f| {
-                let datasets = vec![Dataset::default()
-                    .marker(symbols::Marker::Braille)
-                    .style(Style::default().fg(Color::Magenta))
-                    .data(&[(2.0, 2.0)])];
                 let x_axis = Axis::default()
-                    .bounds([0.0, 1.0])
                     .labels(vec![Span::from("AAAA"), Span::from("B"), Span::from("C")])
                     .label_alignment(alignment);
-                let y_axis = Axis::default().bounds([0.0, 1.0]);
-                let chart = Chart::new(datasets).x_axis(x_axis).y_axis(y_axis);
+
+                let y_axis = Axis::default();
+
+                let chart = Chart::new(vec![]).x_axis(x_axis).y_axis(y_axis);
                 f.render_widget(chart, f.size());
             })
             .unwrap();
@@ -217,6 +214,58 @@ fn widgets_chart_handles_x_axis_labels_alignments() {
     );
 }
 
+#[test]
+fn widgets_chart_handles_y_axis_labels_alignments() {
+    let test_case = |y_alignment, lines| {
+        let backend = TestBackend::new(20, 5);
+        let mut terminal = Terminal::new(backend).unwrap();
+        terminal
+            .draw(|f| {
+                let x_axis = Axis::default().labels(create_labels(&["AAAAA", "B"]));
+
+                let y_axis = Axis::default()
+                    .labels(create_labels(&["C", "D"]))
+                    .label_alignment(y_alignment);
+
+                let chart = Chart::new(vec![]).x_axis(x_axis).y_axis(y_axis);
+                f.render_widget(chart, f.size());
+            })
+            .unwrap();
+        let expected = Buffer::with_lines(lines);
+        terminal.backend().assert_buffer(&expected);
+    };
+    test_case(
+        Alignment::Left,
+        vec![
+            "D   │               ",
+            "    │               ",
+            "C   │               ",
+            "    └───────────────",
+            "AAAAA              B",
+        ],
+    );
+    test_case(
+        Alignment::Center,
+        vec![
+            "  D │               ",
+            "    │               ",
+            "  C │               ",
+            "    └───────────────",
+            "AAAAA              B",
+        ],
+    );
+    test_case(
+        Alignment::Right,
+        vec![
+            "   D│               ",
+            "    │               ",
+            "   C│               ",
+            "    └───────────────",
+            "AAAAA              B",
+        ],
+    );
+}
+
 #[test]
 fn widgets_chart_can_have_axis_with_zero_length_bounds() {
     let backend = TestBackend::new(100, 100);