terminal: add test for pagelist to clear styles

src/terminal/PageList.zig

@@ -4765,6 +4765,56 @@ test "PageList clone partial trimmed left" {
     try testing.expectEqual(@as(usize, 40), s2.totalRows());
 }
 
+test "PageList clone partial trimmed left reclaims styles" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    var s = try init(alloc, 80, 20, null);
+    defer s.deinit();
+    try testing.expectEqual(@as(usize, s.rows), s.totalRows());
+    try s.growRows(30);
+
+    // Style the rows we're trimming
+    {
+        try testing.expect(s.pages.first == s.pages.last);
+        const page = &s.pages.first.?.data;
+
+        const style: stylepkg.Style = .{ .flags = .{ .bold = true } };
+        const style_id = try page.styles.add(page.memory, style);
+
+        var it = s.rowIterator(.left_up, .{ .screen = .{} }, .{ .screen = .{ .y = 9 } });
+        while (it.next()) |p| {
+            const rac = p.rowAndCell();
+            rac.row.styled = true;
+            rac.cell.* = .{
+                .content_tag = .codepoint,
+                .content = .{ .codepoint = 'A' },
+                .style_id = style_id,
+            };
+            page.styles.use(page.memory, style_id);
+        }
+
+        // We're over-counted by 1 because `add` implies `use`.
+        page.styles.release(page.memory, style_id);
+
+        // Expect to have one style
+        try testing.expectEqual(1, page.styles.count());
+    }
+
+    var s2 = try s.clone(.{
+        .top = .{ .screen = .{ .y = 10 } },
+        .memory = .{ .alloc = alloc },
+    });
+    defer s2.deinit();
+    try testing.expectEqual(@as(usize, 40), s2.totalRows());
+
+    {
+        try testing.expect(s2.pages.first == s2.pages.last);
+        const page = &s2.pages.first.?.data;
+        try testing.expectEqual(0, page.styles.count());
+    }
+}
+
 test "PageList clone partial trimmed both" {
     const testing = std.testing;
     const alloc = testing.allocator;

src/terminal/ref_counted_set.zig

@@ -339,10 +339,7 @@ pub fn RefCountedSet(
 
             assert(item.meta.ref > 0);
             item.meta.ref -= 1;
-
+            if (item.meta.ref == 0) self.living -= 1;
-            if (item.meta.ref == 0) {
-                self.living -= 1;
-            }
         }
 
         /// Release a specified number of references to an item by its ID.