test(layout): add visual buffer tests for Rect methods (#2124)

ratatui-core/tests/rect.rs

@@ -0,0 +1,148 @@
+//! Integration tests for Rect operations visualized with buffers.
+
+use ratatui_core::buffer::Buffer;
+use ratatui_core::layout::{Margin, Offset, Rect};
+use ratatui_core::widgets::Widget;
+
+/// A minimal widget that fills its entire area with the given symbol.
+struct Filled<'a> {
+    symbol: &'a str,
+}
+
+impl Widget for Filled<'_> {
+    fn render(self, area: Rect, buf: &mut Buffer) {
+        for y in area.top()..area.bottom() {
+            for x in area.left()..area.right() {
+                if let Some(cell) = buf.cell_mut((x, y)) {
+                    cell.set_symbol(self.symbol);
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn inner() {
+    let base = Rect::new(2, 2, 10, 6);
+    let inner = base.inner(Margin::new(2, 1));
+
+    let mut buf = Buffer::empty(Rect::new(0, 0, 15, 10));
+    Filled { symbol: "█" }.render(base, &mut buf);
+    Filled { symbol: "░" }.render(inner, &mut buf);
+
+    let expected = Buffer::with_lines([
+        "               ",
+        "               ",
+        "  ██████████   ",
+        "  ██░░░░░░██   ",
+        "  ██░░░░░░██   ",
+        "  ██░░░░░░██   ",
+        "  ██░░░░░░██   ",
+        "  ██████████   ",
+        "               ",
+        "               ",
+    ]);
+    assert_eq!(buf, expected);
+}
+
+#[test]
+fn outer() {
+    let base = Rect::new(4, 3, 6, 4);
+    let outer = base.outer(Margin::new(2, 1));
+
+    let mut buf = Buffer::empty(Rect::new(0, 0, 15, 10));
+    Filled { symbol: "░" }.render(outer, &mut buf);
+    Filled { symbol: "█" }.render(base, &mut buf);
+
+    let expected = Buffer::with_lines([
+        "               ",
+        "               ",
+        "  ░░░░░░░░░░   ",
+        "  ░░██████░░   ",
+        "  ░░██████░░   ",
+        "  ░░██████░░   ",
+        "  ░░██████░░   ",
+        "  ░░░░░░░░░░   ",
+        "               ",
+        "               ",
+    ]);
+    assert_eq!(buf, expected);
+}
+
+#[test]
+fn offset() {
+    let base = Rect::new(2, 2, 5, 3);
+    let moved = base.offset(Offset { x: 4, y: 2 });
+
+    let mut buf = Buffer::empty(Rect::new(0, 0, 15, 10));
+    Filled { symbol: "░" }.render(base, &mut buf);
+    Filled { symbol: "█" }.render(moved, &mut buf);
+
+    let expected = Buffer::with_lines([
+        "               ",
+        "               ",
+        "  ░░░░░        ",
+        "  ░░░░░        ",
+        "  ░░░░█████    ",
+        "      █████    ",
+        "      █████    ",
+        "               ",
+        "               ",
+        "               ",
+    ]);
+    assert_eq!(buf, expected);
+}
+
+#[test]
+fn intersection() {
+    let a = Rect::new(2, 2, 6, 4);
+    let b = Rect::new(5, 3, 6, 4);
+    let inter = a.intersection(b);
+
+    let mut buf = Buffer::empty(Rect::new(0, 0, 15, 10));
+    Filled { symbol: "░" }.render(a, &mut buf);
+    Filled { symbol: "▒" }.render(b, &mut buf);
+    Filled { symbol: "█" }.render(inter, &mut buf);
+
+    let expected = Buffer::with_lines([
+        "               ",
+        "               ",
+        "  ░░░░░░       ",
+        "  ░░░███▒▒▒    ",
+        "  ░░░███▒▒▒    ",
+        "  ░░░███▒▒▒    ",
+        "     ▒▒▒▒▒▒    ",
+        "               ",
+        "               ",
+        "               ",
+    ]);
+    assert_eq!(buf, expected);
+}
+
+#[test]
+fn clamp() {
+    let area = Rect::new(2, 2, 10, 6);
+    let rect = Rect::new(8, 5, 8, 4);
+    let clamped = rect.clamp(area);
+
+    let mut buf = Buffer::empty(Rect::new(0, 0, 20, 12));
+    Filled { symbol: "█" }.render(area, &mut buf);
+    Filled { symbol: "▒" }.render(rect, &mut buf);
+    Filled { symbol: "░" }.render(clamped, &mut buf);
+
+    let expected = Buffer::with_lines([
+        "                    ",
+        "                    ",
+        "  ██████████        ",
+        "  ██████████        ",
+        "  ██░░░░░░░░        ",
+        "  ██░░░░░░░░▒▒▒▒    ",
+        "  ██░░░░░░░░▒▒▒▒    ",
+        "  ██░░░░░░░░▒▒▒▒    ",
+        "        ▒▒▒▒▒▒▒▒    ",
+        "                    ",
+        "                    ",
+        "                    ",
+    ]);
+    assert_eq!(buf, expected);
+}