sgr-direct PoC: use ncdirect_supported_styles() to guide output

src/poc/sgr-direct.c

@@ -14,11 +14,19 @@ int main(void){
   }
   int e = 0;
   for(unsigned i = 0 ; i < (NCSTYLE_STRUCK << 1u) ; ++i){
-    if(ncdirect_set_styles(nc, i)){
+    if((ncdirect_supported_styles(nc) & i) == i){
+      if(ncdirect_set_styles(nc, i)){
+        ncdirect_stop(nc);
+        return EXIT_FAILURE;
+      }
+      printf("%08x ", i);
+    }else{
+      printf("         ");
+    }
+    if(ncdirect_set_styles(nc, NCSTYLE_NONE)){
       ncdirect_stop(nc);
       return EXIT_FAILURE;
     }
-    printf("%08x ", i);
     if(++e % 8 == 0){
       printf("\n");
     }