1 files changed, 59 insertions, 0 deletions
diff --git a/src/terminal.zig b/src/terminal.zig
index 63c5479f..af540202 100644
--- a/src/terminal.zig
+++ b/src/terminal.zig
@@ -380,6 +380,13 @@ pub fn reportsMouse(pane: *const Pane) bool {
     return state.vt.flags.mouse_event != .none;
 }
 
+/// DECSET 1004: the program wants to hear when it gains and loses focus.
+pub fn reportsFocus(pane: *const Pane) bool {
+    if (comptime !enabled) return false;
+    const state = pane.terminal orelse return false;
+    return state.vt.modes.get(.focus_event);
+}
+
 /// ...every move of it, a button down or not (1003).
 pub fn tracksAllMotion(pane: *const Pane) bool {
     if (comptime !enabled) return false;
@@ -2738,3 +2745,55 @@ const DeviceAttrs = @typeInfo(@typeInfo(@typeInfo(
 pub fn ptyDeviceAttrs(_: *ghostty_vt.TerminalStream.Handler) DeviceAttrs {
     return .{};
 }
+
+/// Every byte the core wrote to each pane's pty since the last call, `\n`
+/// between panes' shares: "0:<bytes>\n1:<bytes>\n" for panes that got any.
+fn ptyWritesByPane(p: *Pardes, out: *std.ArrayList(u8)) ![]const u8 {
+    out.clearRetainingCapacity();
+    var per: [pardes.MAX_PANES]std.ArrayList(u8) = @splat(.empty);
+    defer for (&per) |*b| b.deinit(p.gpa);
+    while (p.nextEffect()) |effect| {
+        if (effect == .write) try per[effect.write.pane].appendSlice(p.gpa, effect.write.bytes.slice());
+    }
+    for (per, 0..) |b, id| if (b.items.len > 0) try out.print(p.gpa, "{d}:{s}\n", .{ id, b.items });
+    return out.items;
+}
+
+test "a program that asked for focus reports hears CSI I and CSI O as its pane takes and gives up the keyboard, and as the window does" {
+    if (comptime !enabled) return error.SkipZigTest;
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .cols = 90, .rows = 30, .shells = 3 });
+    defer p.deinit();
+    var frame = std.heap.ArenaAllocator.init(gpa);
+    defer frame.deinit();
+    _ = try p.render(frame.allocator());
+    var out: std.ArrayList(u8) = .empty;
+    defer out.deinit(gpa);
+    _ = try ptyWritesByPane(p, &out);
+    p.active = 0;
+    // Asking while its pane has the keyboard: told at once that it has.
+    p.update(.{ .output = .{ .pane = 0, .bytes = "\x1b[?1004h" } });
+    try std.testing.expectEqualStrings("0:\x1b[I\n", try ptyWritesByPane(p, &out));
+    p.update(.{ .output = .{ .pane = 1, .bytes = "\x1b[?1004h" } });
+    try std.testing.expectEqualStrings("", try ptyWritesByPane(p, &out));
+    // A click into the other pane moves the keyboard: out of one, into the
+    // other.
+    const r = p.rects[1];
+    const at_col = r.x + config.GUTTER + 2;
+    const at_row = p.bodyTop(p.panes[1].?, r) + 1;
+    p.update(.{ .mouse = .{ .button = .left, .kind = .press, .col = at_col, .row = at_row } });
+    p.update(.{ .mouse = .{ .button = .left, .kind = .release, .col = at_col, .row = at_row } });
+    try std.testing.expectEqual(@as(usize, 1), p.active);
+    try std.testing.expectEqualStrings("0:\x1b[O\n1:\x1b[I\n", try ptyWritesByPane(p, &out));
+    // The window: away and back.
+    p.update(.{ .focus = false });
+    try std.testing.expectEqualStrings("1:\x1b[O\n", try ptyWritesByPane(p, &out));
+    p.update(.{ .focus = false });
+    try std.testing.expectEqualStrings("", try ptyWritesByPane(p, &out));
+    p.update(.{ .focus = true });
+    try std.testing.expectEqualStrings("1:\x1b[I\n", try ptyWritesByPane(p, &out));
+    // A program that did not ask hears nothing: pane 2.
+    p.active = 2;
+    p.update(.tick);
+    try std.testing.expectEqualStrings("1:\x1b[O\n", try ptyWritesByPane(p, &out));
+}