'guicursor': Disable by default for unknown terminals.

User can still set guicursor explicitly in init.vim.

Closes #5990
Closes #6403

3 files changed, 26 insertions, 10 deletions

diff --git a/src/nvim/main.c b/src/nvim/main.c
index 33e1551351..7ad42d6776 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -283,7 +283,7 @@ int main(int argc, char **argv)
   cmdline_row = (int)(Rows - p_ch);
   msg_row = cmdline_row;
   screenalloc(false);           /* allocate screen buffers */
-  set_init_2();
+  set_init_2(params.headless);
   TIME_MSG("inits 2");
 
   msg_scroll = TRUE;
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 695d0edebf..458d80716c 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -939,11 +939,8 @@ void free_all_options(void)
 #endif
 
 
-/*
- * Initialize the options, part two: After getting Rows and Columns and
- * setting 'term'.
- */
-void set_init_2(void)
+/// Initialize the options, part two: After getting Rows and Columns.
+void set_init_2(bool headless)
 {
   int idx;
 
@@ -966,8 +963,12 @@ void set_init_2(void)
     p_window = Rows - 1;
   }
   set_number_default("window", Rows - 1);
-  parse_shape_opt(SHAPE_CURSOR);   /* set cursor shapes from 'guicursor' */
-  (void)parse_printoptions();       /* parse 'printoptions' default value */
+  if (!headless && !os_term_is_nice()) {
+    set_string_option_direct((char_u *)"guicursor", -1, (char_u *)"",
+                             OPT_GLOBAL, SID_NONE);
+  }
+  parse_shape_opt(SHAPE_CURSOR);   // set cursor shapes from 'guicursor'
+  (void)parse_printoptions();      // parse 'printoptions' default value
 }
 
 /*
@@ -2842,9 +2843,10 @@ did_set_string_option (
     }
   }
 
-  /* 'guicursor' */
-  else if (varp == &p_guicursor)
+  // 'guicursor'
+  else if (varp == &p_guicursor) {
     errmsg = parse_shape_opt(SHAPE_CURSOR);
+  }
 
   else if (varp == &p_popt)
     errmsg = parse_printoptions();
diff --git a/src/nvim/os/env.c b/src/nvim/os/env.c
index 1a97adfa21..839e0d1b51 100644
--- a/src/nvim/os/env.c
+++ b/src/nvim/os/env.c
@@ -889,3 +889,17 @@ bool os_setenv_append_path(const char *fname)
   }
   return false;
 }
+
+/// Returns true if the terminal can be assumed to silently ignore unknown
+/// control codes.
+bool os_term_is_nice(void)
+{
+#if defined(__APPLE__) || defined(WIN32)
+  return true;
+#else
+  const char *vte_version = os_getenv("VTE_VERSION");
+  return (vte_version && atoi(vte_version) >= 3900)
+    || NULL != os_getenv("KONSOLE_PROFILE_NAME")
+    || NULL != os_getenv("KONSOLE_DBUS_SESSION");
+#endif
+}