ui: Test for abstract_ui whenever a minimal t_colors value is required

t_colors should not be checked when abstract_ui is active, because nvim UI is
not limited to a terminal.

src/nvim/edit.c

@@ -2294,8 +2294,7 @@ static int pum_wanted(void)
     return FALSE;
 
   /* The display looks bad on a B&W display. */
-  if (t_colors < 8
+  if (!abstract_ui && t_colors < 8)
-      )
     return FALSE;
   return TRUE;
 }

src/nvim/eval.c

@@ -14440,7 +14440,7 @@ static void f_synIDattr(typval_T *argvars, typval_T *rettv)
     if (modec != 't' && modec != 'c' && modec != 'g')
       modec = 0;        /* replace invalid with current */
   } else {
-    if (t_colors > 1)
+    if (abstract_ui || t_colors > 1)
       modec = 'c';
     else
       modec = 't';

src/nvim/main.c

@@ -281,9 +281,7 @@ int main(int argc, char **argv)
 
   event_init();
 
-  if (abstract_ui) {
+  if (!abstract_ui) {
-    t_colors = 256;
-  } else {
     // Print a warning if stdout is not a terminal TODO(tarruda): Remove this
     // check once the new terminal UI is implemented
     check_tty(&params);

src/nvim/screen.c

@@ -5971,7 +5971,7 @@ void screen_stop_highlight(void)
  */
 void reset_cterm_colors(void)
 {
-  if (t_colors > 1) {
+  if (abstract_ui || t_colors > 1) {
     /* set Normal cterm colors */
     if (cterm_normal_fg_color > 0 || cterm_normal_bg_color > 0) {
       out_str(T_OP);
@@ -6150,8 +6150,7 @@ void screen_fill(int start_row, int end_row, int start_col, int end_col, int c1,
     return;
 
   /* it's a "normal" terminal when not in a GUI or cterm */
-  norm_term = (
+  norm_term = (!abstract_ui && t_colors <= 1);
-    t_colors <= 1);
   for (row = start_row; row < end_row; ++row) {
     if (has_mbyte
         ) {
@@ -6675,7 +6674,7 @@ static void linecopy(int to, int from, win_T *wp)
  */
 int can_clear(char_u *p)
 {
-  return *p != NUL && (t_colors <= 1
+  return *p != NUL && ((!abstract_ui && t_colors <= 1)
                        || cterm_normal_bg_color == 0 || *T_UT != NUL);
 }
 
@@ -7702,8 +7701,7 @@ static void draw_tabline(void)
   int attr_fill = hl_attr(HLF_TPF);
   char_u      *p;
   int room;
-  int use_sep_chars = (t_colors < 8
+  int use_sep_chars = !abstract_ui && t_colors < 8;
-                       );
 
   redraw_tabline = FALSE;
 

src/nvim/syntax.c

@@ -5984,7 +5984,7 @@ init_highlight (
    * With 8 colors brown is equal to yellow, need to use black for Search fg
    * to avoid Statement highlighted text disappears.
    * Clear the attributes, needed when changing the t_Co value. */
-  if (t_colors > 8)
+  if (abstract_ui || t_colors > 8)
     do_highlight(
         (char_u *)(*p_bg == 'l'
                    ? "Visual cterm=NONE ctermbg=LightGrey"
@@ -6449,7 +6449,7 @@ do_highlight (
                     HL_TABLE()[idx].sg_cterm &= ~HL_BOLD;
                 }
                 color &= 7;             /* truncate to 8 colors */
-              } else if (t_colors == 16 || t_colors == 88
+              } else if (abstract_ui || t_colors == 16 || t_colors == 88
                          || t_colors == 256) {
                 /*
                  * Guess: if the termcap entry ends in 'm', it is
@@ -6497,7 +6497,7 @@ do_highlight (
                 if (color >= 0) {
                   if (termcap_active)
                     term_bg_color(color);
-                  if (t_colors < 16)
+                  if (!abstract_ui && t_colors < 16)
                     i = (color == 0 || color == 4);
                   else
                     i = (color < 7 || color == 8);
@@ -6873,7 +6873,7 @@ int hl_combine_attr(int char_attr, int prim_attr)
   if (char_attr <= HL_ALL && prim_attr <= HL_ALL)
     return char_attr | prim_attr;
 
-  if (t_colors > 1) {
+  if (abstract_ui || t_colors > 1) {
     if (char_attr > HL_ALL)
       char_aep = syn_cterm_attr2entry(char_attr);
     if (char_aep != NULL)
@@ -6937,7 +6937,7 @@ int syn_attr2attr(int attr)
 {
   attrentry_T *aep;
 
-  if (t_colors > 1)
+  if (abstract_ui || t_colors > 1)
     aep = syn_cterm_attr2entry(attr);
   else
     aep = syn_term_attr2entry(attr);
@@ -7364,7 +7364,7 @@ int syn_id2attr(int hl_id)
   hl_id = syn_get_final_id(hl_id);
   sgp = &HL_TABLE()[hl_id - 1];             /* index is ID minus one */
 
-  if (t_colors > 1)
+  if (abstract_ui || t_colors > 1)
     attr = sgp->sg_cterm_attr;
   else
     attr = sgp->sg_term_attr;