A column can be empty, as acme's can; new panes go where acme's makenewwindow puts them

Newcol makes an empty column; closing a column's last pane leaves it empty with
the keyboard on its tag; Delcol and Joincol alone take a column away; the
session's last pane closing quits. The +New stand-in and replaceStillborn /
stillborn_joiner are gone. Every new pane goes through exec.placeNew, which
follows acme's makenewwindow (active column, empty column whole, blank space,
halving the biggest) or, with Placement pardes, the old rules. ColumnTags is
gone: column tags are always shown. A grip drag shows acme's box cursor.

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

3 files changed, 12 insertions, 13 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 18068ab1..b4ae7231 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -308,6 +308,7 @@ fn writeSettings(p: *Pardes, w: *std.Io.Writer) !void {
             .tagline_size => try w.print("{s} {d}\n", .{ word, s.font.tagline_percent }),
             .window_opacity => try w.print("{s} {d}\n", .{ word, s.window_opacity }),
             .window_blur => try w.print("{s} {d}\n", .{ word, s.window_blur }),
+            .placement => try w.print("{s} {s}\n", .{ word, @tagName(s.placement) }),
             .message_ms => |which| try w.print("{s} {d}\n", .{ word, @field(s, "message_" ++ @tagName(which) ++ "_ms") }),
             // Bare, it names the default directory.
             .dump_dir => if (s.dump_dir.len > 0) try w.print("{s} {s}\n", .{ word, s.dump_dir.get() }) else try w.print("{s}\n", .{word}),
@@ -1120,7 +1121,7 @@ test "Joincol with no column to the right and Theme with no such theme say so" {
     try testing.expect(std.mem.indexOf(u8, pane.msg[0..pane.msg_len], "no theme \"drak\"") != null);
 }
 
-test "a look that fills a column's stillborn scratch is answered with the scratch already gone" {
+test "a look after Newcol fills the empty column the keyboard is on" {
     const gpa = testing.allocator;
     const p = try withFile(gpa, "x\n");
     defer p.deinit();
@@ -1130,14 +1131,12 @@ test "a look that fills a column's stillborn scratch is answered with the scratc
     var dir: [4096]u8 = undefined;
     const at = dir[0..try tmp.dir.realPath(testing.io, &dir)];
     var line: [4200]u8 = undefined;
-    // Newcol makes a column of one empty +New; a file looked from it
-    // joins that column and takes the scratch's place.
+    // Newcol makes an empty column and gives its tag the keyboard; no pane
+    // has it, so focus reads empty.
     try testing.expectEqual(tree.Status.ok, wr(p, @intFromEnum(tree.TopFile.ctl), "Newcol\n").reply.status);
-    const scratch = p.panes[p.active].?.serial;
-    try testing.expectEqual(tree.Status.ok, wr(p, Node.of(scratch, .look), try std.fmt.bufPrint(&line, "{s}/f.txt\n", .{at})).reply.status);
-    try testing.expect(p.paneBySerial(scratch) == null);
-    var want: [32]u8 = undefined;
-    const gone = try std.fmt.bufPrint(&want, "{d} ", .{scratch});
-    var rows = std.mem.splitScalar(u8, rd(p, @intFromEnum(tree.TopFile.index), 0, 4096).bytes, '\n');
-    while (rows.next()) |row| try testing.expect(!std.mem.startsWith(u8, row, gone));
+    try testing.expectEqual(@as(usize, 0), p.col_n[p.ncol - 1]);
+    try testing.expectEqualStrings("", rd(p, @intFromEnum(tree.TopFile.focus), 0, 64).bytes);
+    try testing.expectEqual(tree.Status.ok, wr(p, @intFromEnum(tree.TopFile.look), try std.fmt.bufPrint(&line, "{s}/f.txt\n", .{at})).reply.status);
+    try testing.expectEqual(@as(usize, 1), p.col_n[p.ncol - 1]);
+    try testing.expectEqual(p.active, p.col_panes[p.ncol - 1][0]);
 }
diff --git a/src/ninep/pane.zig b/src/ninep/pane.zig
index 714a2566..99acf24b 100644
--- a/src/ninep/pane.zig
+++ b/src/ninep/pane.zig
@@ -593,11 +593,11 @@ pub fn appendErrors(p: *Pardes, id: usize, text: []const u8) ?usize {
     }
     const free = p.freeSlot() orelse return null;
     const content = p.gpa.dupe(u8, text) catch return null;
-    const np = panes.Output.open(p, free, dir, .errors, "", content) catch {
+    _ = panes.Output.open(p, free, dir, .errors, "", content) catch {
         p.gpa.free(content);
         return null;
     };
-    exec.placeDoc(p, id, free, np);
+    exec.placeNew(p, id, id, free, .errors);
     return text.len;
 }
 
diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index b3f3dde6..5ef69bb4 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -577,7 +577,7 @@ fn open(p: *Pardes, req: Req, target: Target) Reply {
             // closing it leaves the pane alone.
             .new => {
                 const slot = p.freeSlot() orelse return Reply.fail(req.tag, E.NFILE);
-                p.newScratchBelow(p.active);
+                p.newScratchFor(p.active, .fs);
                 const made = p.panes[slot] orelse return Reply.fail(req.tag, E.NFILE);
                 return .{ .tag = req.tag, .handle = made.serial };
             },