A column has a ctl, an exec and an rmdir over 9P, and Restore maps its serial

A script could read and write a column's tag but not act on the column.
col/<serial>/ctl takes Delcol, Joincol, New and Tty, each acting on that
column as from its tag; col/<serial>/exec runs a word as a middle click in
the tag; rmdir col/<serial> closes an empty column and refuses one with
panes (ENOTEMPTY, an err record saying why). The root ctl's refusal of
Delcol and Joincol points at col/<serial>/ctl. A dump keeps each column's
serial and Restore logs restoredcol <old> <new>; the dump golden gains
them. Documented: Joincol's survivor, the column on the right, keeps its
serial and tag.

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

1 files changed, 20 insertions, 5 deletions

diff --git a/src/dump.zig b/src/dump.zig
index 61aeabbf..5b0983ad 100644
--- a/src/dump.zig
+++ b/src/dump.zig
@@ -180,6 +180,9 @@ pub const Pane = struct {
 };
 
 pub const Column = struct {
+    /// Its serial when dumped (0 in older dumps): a Restore logs
+    /// `restoredcol <old> <new>` for it.
+    serial: u32 = 0,
     tag: ?[]const u8 = null,
     weight: f32 = 1,
     panes: []const usize = &.{},
@@ -665,6 +668,7 @@ pub fn dumpState(p: *Pardes) !void {
             ids_len += 1;
         };
         columns[columns_len] = .{
+            .serial = layout.columnSerial(p, c),
             .tag = p.col_tags[c].own,
             .weight = @as(f32, @floatFromInt(p.col_weight[c])) / @as(f32, @floatFromInt(column_weight_unit)),
             .panes = column_ids[c][0..ids_len],
@@ -733,14 +737,18 @@ pub fn restore(p: *Pardes, zon_bytes: []const u8, from: []const u8) !*Pardes {
     var opts = p.opts;
     opts.cols = p.screen_w;
     opts.rows = p.screen_h;
-    var old: [MAX_PANES]u32 = @splat(0);
+    var old: OldSerials = .{};
     const replacement = try initDump(p.gpa, opts, zon_bytes, p, &old);
     pardes.ctlfs.events.notePath(replacement, "restore", from);
-    // Which serial each pane had, for a script that held the old ones.
-    for (replacement.panes, old) |slot, was| if (slot) |pane| if (was != 0) {
+    // Which serial each pane and column had, for a script that held them.
+    for (replacement.panes, old.panes) |slot, was| if (slot) |pane| if (was != 0) {
         var rec: [32]u8 = undefined;
         pardes.ctlfs.events.notePath(replacement, "restored", std.fmt.bufPrint(&rec, "{d} {d}", .{ was, pane.serial }) catch continue);
     };
+    for (old.cols[0..replacement.ncol], 0..) |was, c| if (was != 0) {
+        var rec: [32]u8 = undefined;
+        pardes.ctlfs.events.notePath(replacement, "restoredcol", std.fmt.bufPrint(&rec, "{d} {d}", .{ was, layout.columnSerial(replacement, c) }) catch continue);
+    };
     return replacement;
 }
 
@@ -748,7 +756,13 @@ pub fn initFromDump(gpa: std.mem.Allocator, opts: Options, zon_bytes: []const u8
     return initDump(gpa, opts, zon_bytes, null, null);
 }
 
-fn initDump(gpa: std.mem.Allocator, opts: Options, zon_bytes: []const u8, previous: ?*const Pardes, old_serials: ?*[MAX_PANES]u32) !*Pardes {
+/// The serials a dump's panes and columns had, read as it is restored.
+const OldSerials = struct {
+    panes: [MAX_PANES]u32 = @splat(0),
+    cols: [MAX_COLS]u32 = @splat(0),
+};
+
+fn initDump(gpa: std.mem.Allocator, opts: Options, zon_bytes: []const u8, previous: ?*const Pardes, old_serials: ?*OldSerials) !*Pardes {
     const image_gpa = opts.image_allocator orelse gpa;
     const pdf_gpa = opts.pdf_allocator orelse gpa;
     const tree_sitter_gpa = opts.tree_sitter_allocator orelse gpa;
@@ -799,7 +813,7 @@ fn initDump(gpa: std.mem.Allocator, opts: Options, zon_bytes: []const u8, previo
     }
     for (st.panes, 0..) |src, i| {
         if (i >= MAX_PANES) break;
-        if (old_serials) |o| o[i] = src.serial;
+        if (old_serials) |o| o.panes[i] = src.serial;
         const pane: *pardes.panes.Pane = switch (src.kind) {
             .terminal => terminal: {
                 const t = src.terminal.?;
@@ -869,6 +883,7 @@ fn initDump(gpa: std.mem.Allocator, opts: Options, zon_bytes: []const u8, previo
     p.col_serial = @splat(0);
     if (st.topbar_custom) |bar| p.global_tag.own = try p.gpa.dupe(u8, bar);
     for (st.columns[0..p.ncol], 0..) |col, c| {
+        if (old_serials) |o| o.cols[c] = col.serial;
         if (col.tag) |bar| p.col_tags[c].own = try p.gpa.dupe(u8, bar);
         const scaled = @as(f64, @floatCast(col.weight)) * @as(f64, @floatFromInt(column_weight_unit));
         const bounded = @min(scaled, @as(f64, @floatFromInt(max_column_weight)));