?1004 Focus Events

Have the terminal tell the program when its window gains or loses the keyboard focus.

CSI ? 1004 h/l

xterm: Mouse Tracking

With CSI ? 1004 h set, the terminal sends CSI I to the program when its window gains the keyboard focus and CSI O when it loses it, so that an editor can, for instance, reload a file that changed while it was in the background. CSI ? 1004 l stops the reports. It is xterm’s, listed with the mouse tracking modes, but it can be set with or without any of them (dpmodes, SendFocusButton). It is off to begin with, and RIS turns it off.

Focus changes come from the window, not from the data a case writes, so the cases check what DECRQM says and that setting the mode sends nothing on its own. libghostty-vt passes them.

Support

Terminal	Version	Support	Notes
VT220	manual, 2nd ed., 1984	No	not in the manual
VT510	manual, 1st ed., 1993	No	not in the manual; not in Table 5-6
xterm	patch 412, xterm-411a	Yes
libghostty-vt	0f171f6	Yes
kitty	0.49.1, run in a VM	Yes	passes the 3 cases that show it working
foot	1.28.0, run in a VM	Partly	fails FOCUS-3, FOCUS-4 of the 3 cases that show it working
xterm.js headless	6.0.0, run as a library	Yes	passes the 3 cases that show it working
alacritty_terminal	0.26.0, run as a library	Yes	passes the 3 cases that show it working
ConEmu	build 230724, its documentation	Yes	listed among the mouse modes, as `FOCUS_EVENT_MOUSE`; ANSI escape codes
rxvt-unicode	9.31, run in a VM	Partly	fails FOCUS-4 of the 3 cases that show it working
VTE	0.84.1, run as a library	Partly	fails FOCUS-3, FOCUS-4 of the 3 cases that show it working

Validation

FOCUS-1: Off to begin with

\e[?1004$p

|____|
reply \e[?1004;2$y

FOCUS-2: Setting it sends nothing

A
\e[?1004h
B

|AB__|
cursor 1,3
reply none

FOCUS-3: Set and reset

\e[?1004h
\e[?1004$p
\e[?1004l
\e[?1004$p

|____|
reply \e[?1004;1$y\e[?1004;2$y

FOCUS-4: RIS turns it off

\e[?1004h
\ec
\e[?1004$p

|____|
reply \e[?1004;2$y