direct mode: write sprixel with posix i/o for strength

src/lib/direct.c

@@ -417,7 +417,12 @@ ncdirect_dump_plane(ncdirect* n, const ncplane* np, int xoff){
         return -1;
       }
     }
-    if(ncfputs(np->sprite->glyph, n->ttyfp) == EOF){
+    // flush our FILE*, as we're about to use UNIX I/O (since we can't rely on
+    // stdio to transfer large amounts at once).
+    if(ncdirect_flush(n)){
+      return -1;
+    }
+    if(blocking_write(fileno(n->ttyfp), np->sprite->glyph, np->sprite->glyphlen) < 0){
       return -1;
     }
     return 0;