Joincol is refused, as Newcol is, when the joined column cannot give each pane its tag and 2 rows

Joincol moved every pane of the keyboard's column into the next one
whether they fit or not. Two columns of two panes in a 12-row window
became one column of four, wanting 12 rows where 10 were free, a layout
that `size` then refused as it stood. Joincol now tries the join in place
first (layout.joinFits: the panes and width moved, minimaFit asked,
everything put back, nothing dropped or logged). A join that does not
fit is refused, "Joincol: no space: the joined column cannot give each
pane its tag and 2 rows".

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 26 insertions, 0 deletions

diff --git a/src/ninep/cols.zig b/src/ninep/cols.zig
index a1fe9ecc..7afcfbd8 100644
--- a/src/ninep/cols.zig
+++ b/src/ninep/cols.zig
@@ -232,6 +232,32 @@ test "New written to a column's exec makes its scratch in the session's director
     try testing.expectEqualStrings("/project/src/+New", p.panes[p.active].?.file.?.path);
 }
 
+test "Joincol is refused when the joined column cannot give each pane its tag and 2 rows" {
+    const p = try pardes.Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 160, .rows = 12 });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const ctl = @intFromEnum(tree.TopFile.ctl);
+    const focus = @intFromEnum(tree.TopFile.focus);
+    // Two panes in the first column, then a second column of two.
+    const a = try th.newPane(p);
+    _ = a;
+    try testing.expectEqual(tree.Status.ok, th.wr(p, ctl, "Newcol\n").reply.status);
+    const b = try th.newPane(p);
+    var digits: [16]u8 = undefined;
+    _ = th.wr(p, focus, try std.fmt.bufPrint(&digits, "{d}\n", .{b}));
+    _ = try th.newPane(p);
+    try testing.expectEqual(@as(usize, 2), p.ncol);
+    try testing.expect(p.col_n[0] >= 2 and p.col_n[1] >= 2);
+    // Focus in the left column: joined, four panes want 12 rows of 10.
+    const left = p.panes[p.col_panes[0][0]].?.serial;
+    _ = th.wr(p, focus, try std.fmt.bufPrint(&digits, "{d}\n", .{left}));
+    const r = th.wr(p, ctl, "Joincol\n");
+    try testing.expectEqual(tree.Status.err, r.reply.status);
+    try testing.expect(std.mem.indexOf(u8, r.reply.ename, "tag and 2 rows") != null);
+    try testing.expectEqual(@as(usize, 2), p.ncol);
+    try testing.expect(pardes.layout.minimaFit(p));
+}
+
 test "pane/new takes rows from a pane in another column before refusing ENOSPC" {
     const p = try pardes.Pardes.init(testing.allocator, .{ .tty_only = true, .cols = 160, .rows = 16 });
     defer p.deinit();