intro: don't tolerate drawing failures

src/demo/intro.c

@@ -244,9 +244,14 @@ int intro(struct notcurses* nc){
     if(!on){
       if(notcurses_check_pixel_support(nc) && notcurses_canopen_images(nc)){
         on = orcashow(nc, rows, cols);
+        if(on == NULL){
+          return -1;
+        }
       }
     }else{
-      orcaride(nc, on, expected_iter);
+      if(orcaride(nc, on, expected_iter)){
+        return -1;
+      }
     }
     int err;
     if( (err = animate(nc, ncp, &flipmode)) ){

src/demo/xray.c

@@ -180,7 +180,7 @@ int xray_demo(struct notcurses* nc){
   marsh.next_frame = 0;
   marsh.last_frame_rendered = -1;
   marsh.lplane = NULL;
-  marsh.dm = notcurses_check_pixel_support(nc) < 1 ? 0.5 * delaymultiplier : 0;
+  marsh.dm = notcurses_check_pixel_support(nc) ? 0 : 0.5 * delaymultiplier;
   int ret = -1;
   // FIXME need do something about SIGINT here, which can leave us locked up
   if(pthread_create(&tid1, NULL, xray_thread, NULL)){