A Newcol refused because the panes' tags would not fit logs its err alone and spends no column serial

Newcol tries its column before keeping it: the new column is inserted,
the panes' rows are shared out again, and where a pane would be left
under its tag and two rows the column is taken back. The trial showed.
insertColumn logged `newcol N` and the take-back `delcol N`, so a
follower saw a column come and go around the err. Laying the column out
also gave it a serial, so the next column made skipped one. The trial is
now unannounced, since insert and drop have unlogged forms. A refusal puts
the serial counter back where it was, after first giving every existing
column its serial so the trial's is the only one spent. Only a column
that stays is logged, and it gets the next serial.

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

1 files changed, 16 insertions, 4 deletions

diff --git a/src/layout.zig b/src/layout.zig
index 28f3d270..4aebcf28 100644
--- a/src/layout.zig
+++ b/src/layout.zig
@@ -325,8 +325,14 @@ pub fn removePane(p: *Pardes, id: usize) void {
 /// Close column `c` once its panes are gone, its width to the one left of
 /// it (the first column's to its right), as acme's rowclose gives it.
 pub fn dropColumn(p: *Pardes, c: usize) void {
-    std.debug.assert(p.col_n[c] == 0);
     const serial = columnSerial(p, c);
+    dropColumnUnannounced(p, c);
+    noteColumn(p, "delcol", serial);
+}
+
+/// dropColumn with no `delcol`, for a column never announced.
+pub fn dropColumnUnannounced(p: *Pardes, c: usize) void {
+    std.debug.assert(p.col_n[c] == 0);
     tagline.exitHeader(p);
     if (p.ncol > 1) p.col_weight[if (c > 0) c - 1 else c + 1] +|= p.col_weight[c];
     p.col_tags[c].deinit(p.gpa);
@@ -341,12 +347,11 @@ pub fn dropColumn(p: *Pardes, c: usize) void {
     p.ncol -= 1;
     p.col_tags[p.ncol] = .{ .what = .column, .gpa = p.gpa };
     p.col_serial[p.ncol] = 0;
-    noteColumn(p, "delcol", serial);
 }
 
 /// `newcol <serial>` or `delcol <serial>` in the log: the column's serial,
 /// as /layout and /col name it.
-fn noteColumn(p: *Pardes, what: []const u8, serial: u32) void {
+pub fn noteColumn(p: *Pardes, what: []const u8, serial: u32) void {
     var buf: [16]u8 = undefined;
     pardes.ctlfs.events.notePath(p, what, std.fmt.bufPrint(&buf, "{d}", .{serial}) catch return);
 }
@@ -649,6 +654,14 @@ pub fn firstColumn(p: *Pardes) ?usize {
 }
 
 pub fn insertColumn(p: *Pardes, col: usize, before: bool) ?usize {
+    const c = insertColumnUnannounced(p, col, before) orelse return null;
+    noteColumn(p, "newcol", columnSerial(p, c));
+    return c;
+}
+
+/// insertColumn with no serial given and no `newcol`: a column that may
+/// yet be taken back (Newcol's trial), which then leaves no trace.
+pub fn insertColumnUnannounced(p: *Pardes, col: usize, before: bool) ?usize {
     if (!canSplitCol(p, col)) return null;
     var old_weight = p.col_weight[col];
     if (old_weight < 2 or old_weight % 2 != 0) {
@@ -672,7 +685,6 @@ pub fn insertColumn(p: *Pardes, col: usize, before: bool) ?usize {
     p.col_serial[c] = 0;
     p.col_n[c] = 0;
     p.ncol += 1;
-    noteColumn(p, "newcol", columnSerial(p, c));
     return c;
 }