fix(widgets/chart): remove panics with long axis labels

src/widgets/chart.rs

@@ -296,18 +296,8 @@ impl<'a> Chart<'a> {
             y -= 1;
         }
 
-        if let Some(ref y_labels) = self.y_axis.labels {
-            let mut max_width = y_labels.iter().map(Span::width).max().unwrap_or_default() as u16;
-            if let Some(ref x_labels) = self.x_axis.labels {
-                if !x_labels.is_empty() {
-                    max_width = max(max_width, x_labels[0].content.width() as u16);
-                }
-            }
-            if x + max_width < area.right() {
-                layout.label_y = Some(x);
-                x += max_width;
-            }
-        }
+        layout.label_y = self.y_axis.labels.as_ref().and(Some(x));
+        x += self.max_width_of_labels_left_of_y_axis(area);
 
         if self.x_axis.labels.is_some() && y > area.top() {
             layout.axis_x = Some(y);
@@ -362,6 +352,82 @@ impl<'a> Chart<'a> {
         }
         layout
     }
+
+    fn max_width_of_labels_left_of_y_axis(&self, area: Rect) -> u16 {
+        let mut max_width = self
+            .y_axis
+            .labels
+            .as_ref()
+            .map(|l| l.iter().map(Span::width).max().unwrap_or_default() as u16)
+            .unwrap_or_default();
+        if let Some(ref x_labels) = self.x_axis.labels {
+            if !x_labels.is_empty() {
+                max_width = max(max_width, x_labels[0].content.width() as u16);
+            }
+        }
+        // labels of y axis and first label of x axis can take at most 1/3rd of the total width
+        max_width.min(area.width / 3)
+    }
+
+    fn render_x_labels(
+        &mut self,
+        buf: &mut Buffer,
+        layout: &ChartLayout,
+        chart_area: Rect,
+        graph_area: Rect,
+    ) {
+        let y = match layout.label_x {
+            Some(y) => y,
+            None => return,
+        };
+        let labels = self.x_axis.labels.as_ref().unwrap();
+        let labels_len = labels.len() as u16;
+        if labels_len < 2 {
+            return;
+        }
+        let width_between_ticks = graph_area.width / (labels_len - 1);
+        for (i, label) in labels.iter().enumerate() {
+            let label_width = label.width() as u16;
+            let label_width = if i == 0 {
+                // the first label is put between the left border of the chart and the y axis.
+                graph_area
+                    .left()
+                    .saturating_sub(chart_area.left())
+                    .min(label_width)
+            } else {
+                // other labels are put on the left of each tick on the x axis
+                width_between_ticks.min(label_width)
+            };
+            buf.set_span(
+                graph_area.left() + i as u16 * width_between_ticks - label_width,
+                y,
+                label,
+                label_width,
+            );
+        }
+    }
+
+    fn render_y_labels(
+        &mut self,
+        buf: &mut Buffer,
+        layout: &ChartLayout,
+        chart_area: Rect,
+        graph_area: Rect,
+    ) {
+        let x = match layout.label_y {
+            Some(x) => x,
+            None => return,
+        };
+        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);
+            }
+        }
+    }
 }
 
 impl<'a> Widget for Chart<'a> {
@@ -390,33 +456,8 @@ impl<'a> Widget for Chart<'a> {
             return;
         }
 
-        if let Some(y) = layout.label_x {
-            let labels = self.x_axis.labels.unwrap();
-            let total_width = labels.iter().map(Span::width).sum::<usize>() as u16;
-            let labels_len = labels.len() as u16;
-            if total_width < graph_area.width && labels_len > 1 {
-                for (i, label) in labels.iter().enumerate() {
-                    buf.set_span(
-                        graph_area.left() + i as u16 * (graph_area.width - 1) / (labels_len - 1)
-                            - label.content.width() as u16,
-                        y,
-                        label,
-                        label.width() as u16,
-                    );
-                }
-            }
-        }
-
-        if let Some(x) = layout.label_y {
-            let labels = self.y_axis.labels.unwrap();
-            let labels_len = labels.len() as u16;
-            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);
-                }
-            }
-        }
+        self.render_x_labels(buf, &layout, chart_area, graph_area);
+        self.render_y_labels(buf, &layout, chart_area, graph_area);
 
         if let Some(y) = layout.axis_x {
             for x in graph_area.left()..graph_area.right() {

src/widgets/list.rs

@@ -5,7 +5,6 @@ use crate::{
     text::Text,
     widgets::{Block, StatefulWidget, Widget},
 };
-use std::iter::{self, Iterator};
 use unicode_width::UnicodeWidthStr;
 
 #[derive(Debug, Clone)]
@@ -185,9 +184,7 @@ impl<'a> StatefulWidget for List<'a> {
         state.offset = start;
 
         let highlight_symbol = self.highlight_symbol.unwrap_or("");
-        let blank_symbol = iter::repeat(" ")
-            .take(highlight_symbol.width())
-            .collect::<String>();
+        let blank_symbol = " ".repeat(highlight_symbol.width());
 
         let mut current_height = 0;
         let has_selection = state.selected.is_some();

src/widgets/table.rs

@@ -10,10 +10,7 @@ use cassowary::{
     WeightedRelation::*,
     {Expression, Solver},
 };
-use std::{
-    collections::HashMap,
-    iter::{self, Iterator},
-};
+use std::collections::HashMap;
 use unicode_width::UnicodeWidthStr;
 
 /// A [`Cell`] contains the [`Text`] to be displayed in a [`Row`] of a [`Table`].
@@ -427,9 +424,7 @@ impl<'a> StatefulWidget for Table<'a> {
         let has_selection = state.selected.is_some();
         let columns_widths = self.get_columns_widths(table_area.width, has_selection);
         let highlight_symbol = self.highlight_symbol.unwrap_or("");
-        let blank_symbol = iter::repeat(" ")
-            .take(highlight_symbol.width())
-            .collect::<String>();
+        let blank_symbol = " ".repeat(highlight_symbol.width());
         let mut current_height = 0;
         let mut rows_height = table_area.height;
 

tests/widgets_chart.rs

@@ -47,6 +47,78 @@ fn widgets_chart_can_render_on_small_areas() {
     test_case(2, 2);
 }
 
+#[test]
+fn widgets_chart_handles_long_labels() {
+    let test_case = |x_labels, y_labels, lines| {
+        let backend = TestBackend::new(10, 5);
+        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 mut x_axis = Axis::default().bounds([0.0, 1.0]);
+                if let Some((left_label, right_label)) = x_labels {
+                    x_axis = x_axis.labels(vec![Span::from(left_label), Span::from(right_label)]);
+                }
+                let mut y_axis = Axis::default().bounds([0.0, 1.0]);
+                if let Some((left_label, right_label)) = y_labels {
+                    y_axis = y_axis.labels(vec![Span::from(left_label), Span::from(right_label)]);
+                }
+                let chart = Chart::new(datasets).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(
+        Some(("AAAA", "B")),
+        None,
+        vec![
+            "          ",
+            "          ",
+            "          ",
+            "   ───────",
+            "AAA      B",
+        ],
+    );
+    test_case(
+        Some(("A", "BBBB")),
+        None,
+        vec![
+            "          ",
+            "          ",
+            "          ",
+            " ─────────",
+            "A     BBBB",
+        ],
+    );
+    test_case(
+        Some(("AAAAAAAAAAA", "B")),
+        None,
+        vec![
+            "          ",
+            "          ",
+            "          ",
+            "   ───────",
+            "AAA      B",
+        ],
+    );
+    test_case(
+        Some(("A", "B")),
+        Some(("CCCCCCC", "D")),
+        vec![
+            "D  │      ",
+            "   │      ",
+            "CCC│      ",
+            "   └──────",
+            "   A     B",
+        ],
+    );
+}
+
 #[test]
 fn widgets_chart_can_have_axis_with_zero_length_bounds() {
     let backend = TestBackend::new(100, 100);