feat(api): ui options relevant for remote TUI

runtime/doc/ui.txt

@@ -49,6 +49,9 @@ with these (optional) keys:
 				'wildmenu'. |ui-popupmenu|
 	`ext_tabline`		Externalize the tabline. |ui-tabline|
 	`ext_termcolors`	Use external default colors.
+	`term_name`		Sets the name of the terminal 'term'.
+	`term_colors`		Sets the number of supported colors 't_Co'.
+	`term_background`	Sets the default value of 'background'.
 
 Specifying an unknown option is an error; UIs can check the |api-metadata|
 `ui_options` key for supported options.

src/nvim/api/ui.c

@@ -14,6 +14,7 @@
 #include "nvim/map.h"
 #include "nvim/memory.h"
 #include "nvim/msgpack_rpc/channel.h"
+#include "nvim/option.h"
 #include "nvim/popupmnu.h"
 #include "nvim/screen.h"
 #include "nvim/ui.h"
@@ -255,6 +256,33 @@ static void ui_set_option(UI *ui, bool init, String name, Object value, Error *e
     return;
   }
 
+  if (strequal(name.data, "term_name")) {
+    if (value.type != kObjectTypeString) {
+      api_set_error(error, kErrorTypeValidation, "term_name must be a String");
+      return;
+    }
+    set_tty_option("term", xstrdup(value.data.string.data));
+    return;
+  }
+
+  if (strequal(name.data, "term_colors")) {
+    if (value.type != kObjectTypeInteger) {
+      api_set_error(error, kErrorTypeValidation, "term_colors must be a Integer");
+      return;
+    }
+    t_colors = (int)value.data.integer;
+    return;
+  }
+
+  if (strequal(name.data, "term_background")) {
+    if (value.type != kObjectTypeString) {
+      api_set_error(error, kErrorTypeValidation, "term_background must be a String");
+      return;
+    }
+    set_tty_background(value.data.string.data);
+    return;
+  }
+
   // LEGACY: Deprecated option, use `ext_cmdline` instead.
   bool is_popupmenu = strequal(name.data, "popupmenu_external");
 

src/nvim/option.c

@@ -4914,6 +4914,23 @@ bool set_tty_option(const char *name, char *value)
   return false;
 }
 
+void set_tty_background(const char *value)
+{
+  if (option_was_set("bg") || strequal((char *)p_bg, value)) {
+    // background is already set... ignore
+    return;
+  }
+  if (starting) {
+    // Wait until after startup, so OptionSet is triggered.
+    do_cmdline_cmd((value[0] == 'l')
+                   ? "autocmd VimEnter * ++once ++nested set bg=light"
+                   : "autocmd VimEnter * ++once ++nested set bg=dark");
+  } else {
+    set_option_value("bg", 0L, value, 0);
+    reset_option_was_set("bg");
+  }
+}
+
 /// Find index for an option
 ///
 /// @param[in]  arg  Option name.

src/nvim/tui/input.c

@@ -442,18 +442,7 @@ static HandleState handle_bracketed_paste(TermInput *input)
 static void set_bg_deferred(void **argv)
 {
   char *bgvalue = argv[0];
-  if (!option_was_set("bg") && !strequal((char *)p_bg, bgvalue)) {
-    // Value differs, apply it.
-    if (starting) {
-      // Wait until after startup, so OptionSet is triggered.
-      do_cmdline_cmd((bgvalue[0] == 'l')
-                     ? "autocmd VimEnter * ++once ++nested set bg=light"
-                     : "autocmd VimEnter * ++once ++nested set bg=dark");
-    } else {
-      set_option_value("bg", 0L, bgvalue, 0);
-      reset_option_was_set("bg");
-    }
-  }
+  set_tty_background(bgvalue);
 }
 
 // During startup, tui.c requests the background color (see `ext.get_bg`).