Shutdown gradually if not able to initialize display (#11)

Author: seriyps

src/drm.c

@@ -539,7 +539,7 @@ int modeset_prepare(int fd, struct modeset_output *output_list, uint16_t mode_wi
 
 		*output_list = *out;
 	}
-	if (!output_list) {
+	if (!out) {
 		fprintf(stderr, "couldn't create any outputs\n");
 		return -1;
 	}

src/main.cpp

@@ -685,7 +685,11 @@ int main(int argc, char **argv)
 	assert(drm_fd >= 0);
 	output_list = (struct modeset_output *)malloc(sizeof(struct modeset_output));
 	ret = modeset_prepare(drm_fd, output_list, mode_width, mode_height, mode_vrefresh);
-	assert(!ret);
+	if (ret) {
+        fprintf(stderr,
+                "cannot initialize display. Is display connected? Is --screen-mode correct?\n");
+		return -2;
+    }
 
 	////////////////////////////////// MPI SETUP
 	MppPacket packet;