A root focus file names the pane with the keyboard and moves it; a pane's ctl says whether it is current

Scripts had no way to ask which pane has the keyboard or to give it one.
rio answers both through a window's wctl: its read ends with current or
notcurrent, and a write of current takes the keyboard (rio(4)). A pane's
ctl line now ends the same way, and since there is one keyboard for the
whole tree, /focus reads the focused pane's serial and takes a serial to
move the keyboard there, off any header that had it; a serial no pane has
fails with "no such window". fs-bench's stale readdir check is fixed too.

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

2 files changed, 15 insertions, 3 deletions

diff --git a/test/fs.py b/test/fs.py
index fe7e4c13..ccf3eb89 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -234,6 +234,17 @@ def discovery(binary, embedded=False):
                 assert locked, 'a lock waiting on another open goes once it unlocks'
                 client.close(mine)
                 other.close(theirs)
+            # /focus names the pane with the keyboard and moves it, as rio's
+            # wctl `current` does; a pane's ctl line ends saying which it is.
+            client.write('/focus', f'{first}\n'.encode())
+            assert client.read('/focus') == f'{first}\n'.encode()
+            assert client.read(f'/pane/{first}/ctl').endswith(b' current ')
+            assert client.read(f'/pane/{second}/ctl').endswith(b' notcurrent ')
+            try:
+                client.write('/focus', b'99999\n')
+                raise AssertionError('focus took a serial no pane has')
+            except OSError as refused:
+                assert 'no such window' in str(refused), refused
             assert set(client.list('/pane')) == {'new', str(fixture), str(first), str(second)}
             client.write(f'/pane/{first}/body', b'first pane', truncate=True)
             assert client.read(f'/pane/{first}/body') == b'first pane'
@@ -304,7 +315,7 @@ def discovery(binary, embedded=False):
                 assert client.read('/src/pardes.zig').startswith(b'const std')
                 assert client.stat('/src/pardes.zig')['mode'] == 0o444
                 assert b'pub const Pardes' in client.read(f'/pane/{look(client, "/virtual/src/pardes.zig")}/body')
-    print('9P discovery: listing/stat/find are inert; new, remove, look, exec, name, sel, log and ctl lock behave')
+    print('9P discovery: listing/stat/find are inert; new, remove, look, exec, name, sel, log, ctl lock and focus behave')
 
 
 def run_file(binary):
diff --git a/test/fs_bench.zig b/test/fs_bench.zig
index da9da47c..75b2eb11 100644
--- a/test/fs_bench.zig
+++ b/test/fs_bench.zig
@@ -123,7 +123,8 @@ fn checkReply(s: *Session, req: ctlfs.Req, reply: ctlfs.Reply) !void {
                 if (req.node == s.node(.ctl)) {
                     const tail = try checkNumbers(rest, &.{pane.cols});
                     if (!std.mem.startsWith(u8, tail, "default ")) return error.IncorrectReply;
-                    if ((try checkNumbers(tail[8..], &.{pardes.config.tab_width})).len != 0)
+                    const current = try checkNumbers(tail[8..], &.{pardes.config.tab_width});
+                    if (!std.mem.eql(u8, current, "current ") and !std.mem.eql(u8, current, "notcurrent "))
                         return error.IncorrectReply;
                 } else return error.UnmeasuredOperation;
             }
@@ -143,7 +144,7 @@ fn checkReply(s: *Session, req: ctlfs.Req, reply: ctlfs.Reply) !void {
                 const size: usize = bytes[off + 9];
                 off += 10;
                 if (dir > 1 or size == 0 or size > bytes.len - off) return error.IncorrectReply;
-                if (entry < names.len and (node != nodes[entry] or dir != @intFromBool(entry >= 7) or
+                if (entry < names.len and (node != nodes[entry] or dir != @intFromBool(entry >= 8) or
                     !std.mem.eql(u8, names[entry], bytes[off..][0..size]))) return error.IncorrectReply;
                 off += size;
             }