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, 8 insertions, 3 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 98120555..e1dd3fc5 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -51,7 +51,7 @@ fn noteResult(p: *Pardes, serial: u32) void {
 /// Runs one look or exec from the pane `id`, then records the panes it
 /// created; failing that, a look records the pane it focused and an exec
 /// the pane it acted on (even one it closed).
-fn run(p: *Pardes, id: usize, exec: bool, text: []const u8) void {
+pub fn run(p: *Pardes, id: usize, exec: bool, text: []const u8) void {
     const context = p.panes[id].?.serial;
     // A pane an event reader holds hears its clicks instead of acting on
     // them (editors/acme/look.c:53 and exec.c:173 send them to winevent),
@@ -277,7 +277,12 @@ fn checkBuiltin(p: *Pardes, req: Req, line: []const u8, scope: builtins.Scope) ?
     };
     // Edit is the one pane word the root takes too: at the active pane.
     if (builtins.registry.scope(b) != scope and b != .Edit)
-        return refuseTo(p, req, if (scope == .pane) "not a window control message" else "not a session control message", line, if (scope == .pane) "/ctl" else "pane/<n>/ctl");
+        return refuseTo(p, req, if (scope == .pane) "not a window control message" else "not a session control message", line, if (scope == .pane)
+            "/ctl"
+        else if (b == .Delcol or b == .Joincol)
+            "col/<serial>/ctl" // a column's own ctl, the one /layout names
+        else
+            "pane/<n>/ctl");
     if (arg.len > 0 and !builtins.registry.takesArg(b)) return refuse(p, req, "wrong #args in control message", line);
     if (arg.len == 0 and builtins.registry.requiresArg(b)) return refuse(p, req, "wrong #args in control message", line);
     const setting = config.Runtime.find(word) orelse return null;
@@ -308,7 +313,7 @@ fn checkBuiltin(p: *Pardes, req: Req, line: []const u8, scope: builtins.Scope) ?
 /// would. Answers the refusal when it would have opened a prompt for an
 /// argument, which nobody writing to a file is there to type, or when it
 /// reported an error: `Mount: AlreadyMounted "Mount peer /tmp/s"`.
-fn runBuiltin(p: *Pardes, req: Req, id: usize, line: []const u8) ?Reply {
+pub fn runBuiltin(p: *Pardes, req: Req, id: usize, line: []const u8) ?Reply {
     p.fs.no_prompt = true;
     p.fs.refused = false;
     p.fs.failure_len = 0;