A focus moved over 9P tells the programs that asked for focus reports, as a click does

A program that set DECSET 1004 heard `CSI O` and `CSI I` when the keyboard
moved by a click, a key or the window's focus, because update() checks
after each event. A /focus write went through serveFs, which never did,
so the program kept believing it had focus until the next input event.
serveFs now runs the same check once a request has settled.

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

2 files changed, 29 insertions, 0 deletions

diff --git a/src/ninep/ctl.zig b/src/ninep/ctl.zig
index 66fa22ab..aebd07e2 100644
--- a/src/ninep/ctl.zig
+++ b/src/ninep/ctl.zig
@@ -2563,6 +2563,32 @@ test "a 9P look keeps its leading blanks, a blank-only look included, and exec s
     try testing.expect(th.logHas(p, "blanks trimmed"));
 }
 
+test "a focus moved over 9P tells the programs that asked for focus reports, as a click does" {
+    const p = try Pardes.init(testing.allocator, .{ .cols = 90, .rows = 30, .shells = 2 });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const first = for (p.panes) |slot| {
+        if (slot) |pane| if (pane.isTerminal()) break pane.serial;
+    } else return error.NoShell;
+    try testing.expectEqual(Status.ok, wr(p, Node.of(first, .exec), "Tty\n").reply.status);
+    var shells: [2]usize = undefined;
+    var n: usize = 0;
+    for (p.panes, 0..) |slot, id| if (slot) |pane| if (pane.isTerminal() and n < 2) {
+        shells[n] = id;
+        n += 1;
+    };
+    try testing.expectEqual(@as(usize, 2), n);
+    p.active = shells[0];
+    p.update(.{ .output = .{ .pane = @intCast(shells[0]), .bytes = "\x1b[?1004h" } });
+    p.update(.{ .output = .{ .pane = @intCast(shells[1]), .bytes = "\x1b[?1004h" } });
+    while (p.nextEffect()) |_| {}
+    var digits: [16]u8 = undefined;
+    const moved = wr(p, @intFromEnum(tree.TopFile.focus), try std.fmt.bufPrint(&digits, "{d}\n", .{p.panes[shells[1]].?.serial}));
+    try testing.expectEqual(Status.ok, moved.reply.status);
+    try testing.expectEqual(shells[1], p.active);
+    try testing.expectEqualStrings("\x1b[O\x1b[I", moved.pty_buf[0..moved.pty_len]);
+}
+
 test "a line starting with # runs as nothing at an exec or a ctl, silently" {
     const p = try withFile(testing.allocator, "x\n");
     defer p.deinit();
diff --git a/src/pardes.zig b/src/pardes.zig
index 402b3cd8..3a6e154a 100644
--- a/src/pardes.zig
+++ b/src/pardes.zig
@@ -5733,6 +5733,9 @@ pub const Pardes = struct {
         // the end of whatever the editor does next.
         p.sync();
         p.fsReport();
+        // A /focus write moves the keyboard as a click does: the programs
+        // that asked (DECSET 1004) hear it now, as after update().
+        p.reportFocus();
         ctlfs.events.announce(p);
         return reply;
     }