TUI: detect BSD vt console

FreeBSD console sets TERM=xterm, but it does not support xterm features
like cursor-shaping. GUI terminals typically set TERM=xterm-256color, so
on FreeBSD we can guess that TERM=xterm is the degraded vt.

OpenBSD console sets TERM=vt220
https://github.com/openbsd/src/blob/master/etc/etc.amd64/ttys

NetBSD console sets TERM=vt100
https://github.com/NetBSD/src/blob/trunk/etc/etc.amd64/ttys

closes #8644

3 files changed, 28 insertions, 7 deletions

diff --git a/src/nvim/os/pty_process_unix.c b/src/nvim/os/pty_process_unix.c
index bafbfe1e4b..bcf57e1b5b 100644
--- a/src/nvim/os/pty_process_unix.c
+++ b/src/nvim/os/pty_process_unix.c
@@ -12,7 +12,7 @@
 #include <sys/ioctl.h>
 
 // forkpty is not in POSIX, so headers are platform-specific
-#if defined(__FreeBSD__) || defined (__DragonFly__)
+#if defined(__FreeBSD__) || defined(__DragonFly__)
 # include <libutil.h>
 #elif defined(__OpenBSD__) || defined(__NetBSD__) || defined(__APPLE__)
 # include <util.h>
diff --git a/src/nvim/tui/terminfo.c b/src/nvim/tui/terminfo.c
index ad86dd928b..ad57f0af7f 100644
--- a/src/nvim/tui/terminfo.c
+++ b/src/nvim/tui/terminfo.c
@@ -13,6 +13,7 @@
 #include "nvim/memory.h"
 #include "nvim/message.h"
 #include "nvim/option.h"
+#include "nvim/os/os.h"
 #include "nvim/tui/terminfo.h"
 #include "nvim/tui/terminfo_defs.h"
 
@@ -33,6 +34,24 @@ bool terminfo_is_term_family(const char *term, const char *family)
     && ('\0' == term[flen] || '-' == term[flen]);
 }
 
+bool terminfo_is_bsd_console(const char *term)
+{
+#if defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) \
+  || defined(__DragonFly__)
+  if (strequal(term, "vt220")         // OpenBSD
+      || strequal(term, "vt100")) {   // NetBSD
+    return true;
+  }
+# if defined(__FreeBSD__)
+  // FreeBSD console sets TERM=xterm, but it does not support xterm features
+  // like cursor-shaping. Assume that TERM=xterm is degraded. #8644
+  return strequal(term, "xterm") && !!os_getenv("XTERM_VERSION");
+# endif
+#else
+  return false;
+#endif
+}
+
 /// Loads a built-in terminfo db when we (unibilium) failed to load a terminfo
 /// record from the environment (termcap systems, unrecognized $TERM, …).
 /// We do not attempt to detect xterm pretenders here.
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 26896a141d..405d853148 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -1468,7 +1468,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
                                 long konsolev, bool iterm_env)
 {
   unibi_term *ut = data->ut;
-  const char * xterm_version = os_getenv("XTERM_VERSION");
+  const char *xterm_version = os_getenv("XTERM_VERSION");
 #if 0   // We don't need to identify this specifically, for now.
   bool roxterm = !!os_getenv("ROXTERM_ID");
 #endif
@@ -1477,6 +1477,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
     || terminfo_is_term_family(term, "nsterm");
   bool kitty = terminfo_is_term_family(term, "xterm-kitty");
   bool linuxvt = terminfo_is_term_family(term, "linux");
+  bool bsdvt = terminfo_is_bsd_console(term);
   bool rxvt = terminfo_is_term_family(term, "rxvt");
   bool teraterm = terminfo_is_term_family(term, "teraterm");
   bool putty = terminfo_is_term_family(term, "putty");
@@ -1497,7 +1498,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
     && strstr(colorterm, "gnome-terminal");
   bool mate_pretending_xterm = xterm && colorterm
     && strstr(colorterm, "mate-terminal");
-  bool true_xterm = xterm && !!xterm_version;
+  bool true_xterm = xterm && !!xterm_version && !bsdvt;
 
   char *fix_normal = (char *)unibi_get_str(ut, unibi_cursor_normal);
   if (fix_normal) {
@@ -1670,7 +1671,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
   if (-1 == data->unibi_ext.set_cursor_style) {
     // DECSCUSR (cursor shape) is widely supported.
     // https://github.com/gnachman/iTerm2/pull/92
-    if ((!konsolev || konsolev >= 180770)
+    if ((!bsdvt && (!konsolev || konsolev >= 180770))
         && ((xterm && !vte_version)  // anything claiming xterm compat
             // per MinTTY 0.4.3-1 release notes from 2009
             || putty
@@ -1684,7 +1685,7 @@ static void patch_terminfo_bugs(TUIData *data, const char *term,
             || rxvt       // per command.C
             // per analysis of VT100Terminal.m
             || iterm || iterm_pretending_xterm
-            || teraterm    // per TeraTerm "Supported Control Functions" doco
+            || teraterm   // per TeraTerm "Supported Control Functions" doco
             || alacritty  // https://github.com/jwilm/alacritty/pull/608
             // Some linux-type terminals implement the xterm extension.
             // Example: console-terminal-emulator from the nosh toolset.
@@ -1755,6 +1756,7 @@ static void augment_terminfo(TUIData *data, const char *term,
 {
   unibi_term *ut = data->ut;
   bool xterm = terminfo_is_term_family(term, "xterm");
+  bool bsdvt = terminfo_is_bsd_console(term);
   bool dtterm = terminfo_is_term_family(term, "dtterm");
   bool rxvt = terminfo_is_term_family(term, "rxvt");
   bool teraterm = terminfo_is_term_family(term, "teraterm");
@@ -1769,8 +1771,8 @@ static void augment_terminfo(TUIData *data, const char *term,
   // None of the following work over SSH; see :help TERM .
   bool iterm_pretending_xterm = xterm && iterm_env;
 
-  const char * xterm_version = os_getenv("XTERM_VERSION");
-  bool true_xterm = xterm && !!xterm_version;
+  const char *xterm_version = os_getenv("XTERM_VERSION");
+  bool true_xterm = xterm && !!xterm_version && !bsdvt;
 
   // Only define this capability for terminal types that we know understand it.
   if (dtterm         // originated this extension