DECHCCM, DECVCCM, DECPCCM Cursor Coupling Modes
Choose whether the window follows the cursor around a page larger than the screen.
DECHCCM Horizontal Cursor Coupling Mode
CSI ? 60 h/l
DECVCCM Vertical Cursor Coupling Mode
CSI ? 61 h/l
DECPCCM Page Cursor Coupling Mode
CSI ? 64 h/l
In DEC’s windowing extension, the screen is a window onto a page of display memory that can be wider, taller, or one of several pages. These three modes decide whether the window follows the cursor when it moves out of view:
| Mode | Name | Set (coupled) | DEC STD 070 default |
|---|---|---|---|
60 | DECHCCM, horizontal | the page moves sideways in the window to keep the cursor visible | reset |
61 | DECVCCM, vertical | the page moves up or down in the window | set |
64 | DECPCCM, page | the window switches to the cursor’s page | set |
DECVCCM is on p. 5-86 and DECPCCM on p. 5-87, both in §5.5, Windowing Extension, at levels 3 and 4. The VT510 manual has DECVCCM and DECPCCM, but no page for DECHCCM.
A terminal whose page is the size of its screen has nothing to couple. xterm recognizes all three modes and ignores them (charproc.c); DECRQM reports each as permanently reset, 4, at level 3 and up, and xterm is a VT420 by default (do_dec_rqm). esctest2 expects DECHCCM to be permanently reset, and DECVCCM and DECPCCM to be changeable, listing xterm as not supporting those two; the cases follow xterm.
libghostty-vt does not have the modes: none is in its table in modes.zig, so DECRQM reports each as not recognized, 0. Both cases are known differences.
Support
| Terminal | Version | Support | Notes |
|---|---|---|---|
| VT220 | manual, 2nd ed., 1984 | No | not in the manual |
| VT510 | manual, 1st ed., 1993 | Partly | DECVCCM and DECPCCM; DECHCCM only in Table 5-6, always reset |
| xterm | patch 412, xterm-411a | No | recognized and ignored; DECRQM reports each as permanently reset |
| libghostty-vt | 0f171f6 | No | none is in its mode table; DECRQM reports 0 (DECHCCM-1, DECHCCM-2) |
| ConEmu | build 230724, its documentation | No | not in ConEmu’s list, ANSI escape codes |
Validation
DECHCCM-1: All three permanently reset
\e[?60$p\e[?61$p\e[?64$p
|_____|
reply \e[?60;4$y\e[?61;4$y\e[?64;4$y
DECHCCM-2: Even after they are set
\e[?60h\e[?61h\e[?64h
\e[?60$p\e[?61$p\e[?64$p
|_____|
reply \e[?60;4$y\e[?61;4$y\e[?64;4$y