ui: Add update_fg/update_bg methods

It is necessary to notify the UI when the default background/foreground colors
change in order to render correctly.

src/nvim/msgpack_rpc/remote_ui.c

@@ -67,6 +67,8 @@ Object remote_ui_attach(uint64_t channel_id, uint64_t request_id, Array args,
   ui->put = remote_ui_put;
   ui->bell = remote_ui_bell;
   ui->visual_bell = remote_ui_visual_bell;
+  ui->update_fg = remote_ui_update_fg;
+  ui->update_bg = remote_ui_update_bg;
   ui->flush = remote_ui_flush;
   ui->suspend = remote_ui_suspend;
   pmap_put(uint64_t)(connected_uis, channel_id, ui);
@@ -266,6 +268,20 @@ static void remote_ui_visual_bell(UI *ui)
   push_call(ui, "visual_bell", args);
 }
 
+static void remote_ui_update_fg(UI *ui, int fg)
+{
+  Array args = ARRAY_DICT_INIT;
+  ADD(args, INTEGER_OBJ(fg));
+  push_call(ui, "update_fg", args);
+}
+
+static void remote_ui_update_bg(UI *ui, int bg)
+{
+  Array args = ARRAY_DICT_INIT;
+  ADD(args, INTEGER_OBJ(bg));
+  push_call(ui, "update_bg", args);
+}
+
 static void remote_ui_flush(UI *ui)
 {
   UIData *data = ui->data;

src/nvim/syntax.c

@@ -45,6 +45,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax_defs.h"
 #include "nvim/term.h"
+#include "nvim/ui.h"
 #include "nvim/os/os.h"
 #include "nvim/os/time.h"
 
@@ -6528,6 +6529,7 @@ do_highlight (
 
         if (is_normal_group) {
           normal_fg = HL_TABLE()[idx].sg_rgb_fg;
+          ui_fg_updated();
         }
       } else if (STRCMP(key, "GUIBG") == 0)   {
         if (!init || !(HL_TABLE()[idx].sg_set & SG_GUI)) {
@@ -6546,6 +6548,7 @@ do_highlight (
 
         if (is_normal_group) {
           normal_bg = HL_TABLE()[idx].sg_rgb_bg;
+          ui_bg_updated();
         }
       } else if (STRCMP(key, "GUISP") == 0)   {
         // Ignored

src/nvim/ui.c

@@ -113,6 +113,18 @@ void ui_write(uint8_t *s, int len)
     free(tofree);
 }
 
+void ui_fg_updated(void)
+{
+  UI_CALL(update_fg, normal_fg);
+  UI_CALL(flush);
+}
+
+void ui_bg_updated(void)
+{
+  UI_CALL(update_bg, normal_bg);
+  UI_CALL(flush);
+}
+
 /*
  * If the machine has job control, use it to suspend the program,
  * otherwise fake it by starting a new shell.
@@ -167,6 +179,8 @@ void ui_cursor_shape(void)
 
 void ui_resize(int width, int height)
 {
+  ui_fg_updated();
+  ui_bg_updated();
   sr.top = 0;
   sr.bot = height - 1;
   sr.left = 0;

src/nvim/ui.h

@@ -32,6 +32,8 @@ struct ui_t {
   void (*bell)(UI *ui);
   void (*visual_bell)(UI *ui);
   void (*flush)(UI *ui);
+  void (*update_fg)(UI *ui, int fg);
+  void (*update_bg)(UI *ui, int bg);
   void (*suspend)(UI *ui);
 };
 

test/functional/ui/screen.lua

@@ -278,6 +278,14 @@ function Screen:_handle_visual_bell()
   self._visual_bell = true
 end
 
+function Screen:_handle_update_fg(fg)
+  self._fg = fg
+end
+
+function Screen:_handle_update_bg(bg)
+  self._bg = bg
+end
+
 function Screen:_handle_suspend()
   self._suspended = true
 end