Test bottom-justified TrueType text with any common installed font

The test used Arial only, so it skipped on Linux and macOS CI. It now
uses the first of Arial, Helvetica, DejaVuSans, Verdana or Liberation
Sans that is installed (as the fonts crate's other TrueType tests do),
and keeps the Arial-specific checks for Arial.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/fonts/src/lib.rs

@@ -875,21 +875,25 @@ mod justify_tests {
 
     /// With a TrueType font, a bottom-justified text's alignment point is at the face's descent,
     /// where its descenders end, as AutoCAD places it (#2229: Arial's is 0.296 of the height).
-    /// Skips when Arial isn't installed.
+    /// Uses the first of these common fonts that is installed (Windows, macOS and Linux each have
+    /// one); skips without any.
     #[test]
     fn a_bottom_justified_truetype_text_sits_on_its_descent() {
-        let Some(face) = ttf::find("Arial") else { return };
+        let found = ["Arial", "Helvetica", "DejaVuSans", "Verdana", "LiberationSans-Regular"].into_iter().find_map(|n| ttf::find(n).map(|f| (n, f)));
+        let Some((name, face)) = found else { return };
         let ratio = ttf::descent_ratio(&face).unwrap();
-        assert!((ratio - 0.296).abs() < 0.01, "Arial's descent over cap height: {ratio}");
         let font = TextFont::Outline(face);
         let (sh, start) = placed(&font, "gjpqy", Align::Left, VAlign::Bottom);
-        assert!((start.y - ratio * H).abs() < 1e-9, "{start:?}");
-        // The descenders reach the alignment point's line: h/3 left them 0.1 above it.
-        let (lo, _) = ink_y(&sh);
-        assert!(lo.abs() < 0.02 * H, "descender bottom {lo} from the alignment point");
+        assert!((start.y - ratio * H).abs() < 1e-9, "{name}: {start:?}");
+        if name == "Arial" {
+            assert!((ratio - 0.296).abs() < 0.01, "Arial's descent over cap height: {ratio}");
+            // The descenders reach the alignment point's line: h/3 left them 0.1 above it.
+            let (lo, _) = ink_y(&sh);
+            assert!(lo.abs() < 0.02 * H, "descender bottom {lo} from the alignment point");
+        }
         // And Middle centres the ink, as with the stroke font.
         let (sh, _) = placed(&font, "Tg 1234 ABC", Align::Middle, VAlign::Baseline);
         let (lo, hi) = ink_y(&sh);
-        assert!(((lo + hi) / 2.0).abs() < 1e-9, "{lo}..{hi}");
+        assert!(((lo + hi) / 2.0).abs() < 1e-9, "{name}: {lo}..{hi}");
     }
 }