A command run from a pane gets acme's $winid, the serial of the pane it was run from; one from a column's or the workspace's tag gets none

PARDES_PANE names the command pane itself, so a script a click ran had
no way to address the pane it was run in, as acme's win scripts do with
$winid. The command pane now remembers that pane and its child gets
winid set to it; a header tag's command, which no pane owns, gets winid
unset. PARDES_PANE is unchanged.

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

4 files changed, 42 insertions, 0 deletions

diff --git a/src/exec.zig b/src/exec.zig
index e15ad12c..47484105 100644
--- a/src/exec.zig
+++ b/src/exec.zig
@@ -792,6 +792,7 @@ fn runCommand(p: *Pardes, from: usize, line: []const u8) ?usize {
         if (panes.terminal.onAlternateScreen(pane)) panes.terminal.feedOutput(p, pane, "\x1b[?1049l");
         panes.terminal.feedOutput(p, pane, "\x1b[?1000l\x1b[?1002l\x1b[?1003l\x1b[?1006l\x1b[?2004l\x1b[?25h\x1b[0m");
         echoCommand(p, pane, line);
+        pane.command_from = winid(p, src);
         p.emitSpawn(id, pane.serial, pane.cwdSlice());
         noteRun(p, pane, "run", line);
         return id;
@@ -804,12 +805,20 @@ fn runCommand(p: *Pardes, from: usize, line: []const u8) ?usize {
         p.reportError(from, "exec", err);
         return null;
     };
+    pane.command_from = winid(p, src);
     echoCommand(p, pane, line);
     placeNew(p, from, from, free, .command);
     noteRun(p, pane, "run", line);
     return free;
 }
 
+/// The serial a command's `$winid` names: the pane it was run from, none
+/// (0) from a column's or the workspace's tag.
+fn winid(p: *const Pardes, src: ?*Pane) u32 {
+    if (p.exec_header) return 0;
+    return if (src) |s| s.serial else 0;
+}
+
 /// `% line` above a command's output, every command, as a shell echoes
 /// what it was given; its newlines the terminal's, so a multi-line command
 /// does not staircase.
diff --git a/src/host_io.zig b/src/host_io.zig
index 1fab3729..8ddb0c90 100644
--- a/src/host_io.zig
+++ b/src/host_io.zig
@@ -1351,6 +1351,14 @@ test "the child environment replaces the launcher's terminal identity exactly on
 
 extern "c" fn unsetenv(name: [*:0]const u8) c_int;
 
+fn exportWinid(serial: u32) void {
+    var buf: [16]u8 = undefined;
+    if (serial != 0) if (std.fmt.bufPrintSentinel(&buf, "{d}", .{serial}, 0)) |text| {
+        if (Shell.setenv("winid", text, 1) == 0) return;
+    } else |_| {};
+    _ = unsetenv("winid");
+}
+
 /// The longest line a command pane runs (exec.zig refuses a longer one).
 pub const exec_command_max = pardes.exec.command_max;
 
@@ -1418,6 +1426,9 @@ pub fn forkShell(
         if (core) |c| (if (c.panes[pane]) |pn| pn.serial else 0) else 0,
         if (core) |c| !c.opts.nested else false,
     );
+    // acme's `$winid`: the pane a command was run from, so a script it runs
+    // can address that pane; unset for a shell and a header tag's command.
+    exportWinid(if (core) |c| (if (c.panes[pane]) |pn| (if (pn.command != null) pn.command_from else 0) else 0) else 0);
     if (helper) |path| {
         const c = core.?;
         const pn = c.panes[pane].?;
diff --git a/src/panes.zig b/src/panes.zig
index 0380f89f..a395d6ed 100644
--- a/src/panes.zig
+++ b/src/panes.zig
@@ -124,6 +124,10 @@ pub const Pane = struct {
     /// A command pane (exec.zig runCommand): the line its child runs as
     /// `$SHELL -c`, owned, where an interactive terminal has null.
     command: ?[]u8 = null,
+    /// The pane whose tag or text the command was run from, its child's
+    /// `$winid` (acme's name); 0 for one from a column's or the workspace's
+    /// tag, which no pane owns.
+    command_from: u32 = 0,
     /// The command's child has exited, and with what status (null: unknown,
     /// shown `exit ?`).
     command_done: bool = false,
diff --git a/test/fs.py b/test/fs.py
index 0821b117..23647b45 100644
--- a/test/fs.py
+++ b/test/fs.py
@@ -1306,6 +1306,24 @@ def test(binary, quic=False):
         # opened is deleted, as an $EDITOR must; one on a file already open
         # waits on that pane; a session that goes away ends it with 1.
         with session(binary, root, 'wait') as (client, address):
+            # A command run from a pane's tag gets acme's $winid, that pane;
+            # one from the workspace's tag, none.
+            def command_body(node, line):
+                client.write(node, line)
+                serial = int(client.read(node).split()[-1])
+                deadline = time.monotonic() + 10
+                while True:
+                    log = client.read('/log').decode()
+                    ran = log.rfind(f'\nrun {serial} ')
+                    if ran >= 0 and f'\nexit {serial} ' in log[ran:]:
+                        body = client.read(f'/pane/{serial}/body').decode().split('% echo winid')[-1]
+                        client.remove(f'/pane/{serial}')
+                        return body
+                    assert time.monotonic() < deadline, log[-400:]
+                    time.sleep(.05)
+            first_pane = min(int(row.split()[0]) for row in client.read('/index').splitlines())
+            assert f'winid={first_pane}\n' in command_body(f'/pane/{first_pane}/tagexec', b'echo winid=$winid\n')
+            assert 'winid=\n' in command_body('/tagexec', b'echo winid=$winid\n')
             # A second --detach of a name a live session holds: said, exit 1,
             # no Zig error trace.
             second_env = {k: v for k, v in os.environ.items() if not k.startswith('PARDES_')}