+ fprintf(f, "Begins executing continuously.\n"
+ "May be interrupted with SIGINT.\n");
+}
+
+static const char * const display_filename_default_ =
+#ifdef HAVE_LIBPNG
+ "dcpu16-display.png"
+#else /* HAVE_LIBPNG */
+ "dcpu16-display.pnm"
+#endif /* HAVE_LIBPNG */
+;
+COMMAND_IMPL(display) {
+ static DCPU16_DISPLAY *display = NULL;
+ const char *filename = display_filename_default_;
+
+ if (arg_count == 2) {
+ filename = arg_vector[1];
+ }
+
+ if (display) {
+ printf("display already enabled..\n");
+ return 0;
+ }
+
+ display = display_new(filename);
+
+ if (display == NULL) {
+ fprintf(stderr, "failed to initialize display buffer\n");
+ return 0;
+ }
+
+ if (dcpu16_acct_add(vm, DCPU16_ACCT_EV_WRITE, display_fn, display)) {
+ fprintf(stderr, "failed to register display update callback\n");
+ return 0;
+ }
+
+ if (dcpu16_acct_add(vm, DCPU16_ACCT_EV_RESET, display_reset_fn, display)) {
+ fprintf(stderr, "failed to register display reset callback\n");
+ return 0;
+ }
+
+ if (dcpu16_acct_add(vm, DCPU16_ACCT_EV_CYCLE, display_cycle_fn, display)) {
+ fprintf(stderr, "failed to register display cycle callback\n");
+ return 0;
+ }
+
+ /* init display as if reset occurred */
+ display_reset_fn(vm, DCPU16_ACCT_EV_RESET, 0, display);
+
+ return 0;
+}
+COMMAND_HELP(display) {
+ fprintf(f, "\tdisplay [file]\n");
+ if (summary) return;
+
+ fprintf(f, "Attaches display interface, begins updating an image file of display contents...\n"
+ "Image filename may be specified, defaults to '%s'\n",
+ display_filename_default_
+ );