add fps reporting

1 files changed, 20 insertions, 0 deletions

diff --git a/drm-legacy.c b/drm-legacy.c
index 56a0fed..e136c8a 100644
--- a/drm-legacy.c
+++ b/drm-legacy.c
@@ -51,6 +51,7 @@ static int legacy_run(const struct gbm *gbm, const struct egl *egl)
 	struct gbm_bo *bo;
 	struct drm_fb *fb;
 	uint32_t i = 0;
+	int64_t start_time, report_time, cur_time;
 	int ret;
 
 	eglSwapBuffers(egl->display, egl->surface);
@@ -69,10 +70,19 @@ static int legacy_run(const struct gbm *gbm, const struct egl *egl)
 		return ret;
 	}
 
+	start_time = report_time = get_time_ns();
+
 	while (1) {
 		struct gbm_bo *next_bo;
 		int waiting_for_flip = 1;
 
+		/* Start fps measuring on second frame, to remove the time spent
+		 * compiling shader, etc, from the fps:
+		 */
+		if (i == 1) {
+			start_time = report_time = get_time_ns();
+		}
+
 		egl->draw(i++);
 
 		eglSwapBuffers(egl->display, egl->surface);
@@ -114,6 +124,16 @@ static int legacy_run(const struct gbm *gbm, const struct egl *egl)
 			drmHandleEvent(drm.fd, &evctx);
 		}
 
+		cur_time = get_time_ns();
+		if (cur_time > (report_time + 2 * NSEC_PER_SEC)) {
+			double elapsed_time = cur_time - start_time;
+			double secs = elapsed_time / (double)NSEC_PER_SEC;
+			unsigned frames = i - 1;  /* first frame ignored */
+			printf("Rendered %u frames in %f sec (%f fps)\n",
+				frames, secs, (double)frames/secs);
+			report_time = cur_time;
+		}
+
 		/* release last buffer to render on again: */
 		gbm_surface_release_buffer(gbm->surface, bo);
 		bo = next_bo;